Sedimentary environments in the Paleozoic rocks of northwest Georgia

I
. I

SEDIMENTARY ENVIRONMENTS IN THE PALEOZOIC ROCKS OF NORTHWEST GEORGIA
Compiled by T.M. CHOWNS
Guidebook 11
Published by the Geological Survey for the 7th Annual Field Trip of the
Georgia Geological Society
GEORGIA DEPARTMENT OF NATURAL RESOURCES
Joe D. Tanner, Commissioner
DIVISON OF EARTH AND WATER RESOURCES THE GEOLOGICAL SURVEY OF GEORGIA
Sam M. Pickering, Jr.. State Geologist
ATLANTA 1972

GEORGIA GEOLOGICAL SOCIETY

President Secretary Treasurer Councilor Councilor

Officers 1971-72

Robert C. Vorhis J. Marion Wampler Joseph B. Murray J. Marion Wampler Howard R. Cramer

President President-Elect Secretary Treasurer Councilor Councilor

Officers 1972-73

Robert E. Carver J. Marion Wampler Roger Austin Joseph B. Murray Howard R. Cramer Norman Herz

1972 Field Trip Committee
Howard R. Cramer, Chairman T. M. Chowns Lewis Lipps William H. McLemore Doral Mills Joseph B. Murray Robert C. Vorhis

ii

CONTENTS

Introduction

1

Depositional Environments in the Upper Ordovician of Northwest Georgia and

Southeast Tennessee, T. M. Chowns . . . . . . . . . . . .

3

Molasse Sedimentation in the Silurian Rocks of Northwest Georgia, T. M.

Chowns . . . . . . . . . . . . . . . . . . . . . . .

13

Trace Fossils from the Ringgold Road Cut (Ordovician and Silurian), Georgia,

Robert W. Frey and T. M. Chowns . . . . . . . . . . . . . . .

25

Sedimentary Environment of the Armuchee Chert, Northwest Georgia, W. E.

Nunan . . . . . . . . . . . . . . . . . . . . . . . . .

57

Depositional Environments of the Tuscumbia-Monteagle-Floyd Interval in

Northwest Georgia and Southeast Tennessee, William H. McLemore

69

Road Log.

75

Appendix .

95

iii

Acknowledgments This guidebook was prepared for the 7th annual field trip of the Georgia Geological Society, 13-14 October, 1972. The Georgia Geological Society gratefully acknowledges the assistance of the Georgia Geological Survey, under the direction of S.M. Pickering, Jr., in the publication of the guidebook. Special thanks are due to Lynda Stafford who edited the manuscripts for publication, and to Ron Owens who assisted in draughting the figures. J. E. Elkins prepared the photographs for the road log. We also thank the Southern Railway System for generously underwriting the Friday evening smoker.
iv

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Introduction
T. M. Chowns
This guidebook is intended as a summary and progress report of recent research into some of the sedimentary environments encountered in the Paleozoic succession in northwest Georgia. It does not attempt an overall review of the stratigraphy of the area for which the reader is referred to the work of Butts and Gildersleeve (1948), Cressler (1963; 1964a; 1964b; 1970) and Croft (1964).
In particular attention is directed towards strata of Upper Ordovician, Silurian, Devonian and Mississippian age. Studies have been mainly restricted to the northwestern part of the Valley and Ridge Province because of poor exposure southeast of the Rome Fault, and as a result details of the lowermost strata (Cambrian, Rome and Conasauga formations; Cambro-Ordovician, Knox Group) are still poorly known. Studies have commenced on the Middle Ordovician, Chickamauga Limestone in Alabama (Wilson, 1971 ), but the various facies of the equivalent Taconic mollasse wedge to the east remain to be unraveled. For completeness the reader should consult Ferro, et al. (1972) for a stimulating reappraisal of Mississippian and Pennsylvania sedimentary environments.
Table 1 summarizes the stratigraphy in the northwest part of the Valley and Ridge Province and indicates the major sedimentary environments. The stratigraphic column reflects the shifting interface between cratonic carbonate sequences and terrigenous molasse facies derived from the Appalachian orogen. An appreciation of the importance of transitional tidal flat, tidal marsh, barrier island and lagoonal environments in these miogeoclinal sediments is one of the main results of recent research into ancient sedimentary environments.
References
Butts, C., Gildersleeve, B., 1948, Geology and mineral resources of the Paleozoic area in northwest Georgia: Georgia Geol. Surv. Bull. 54, 176 p.
Cressler, C. W., 1963, Geology and ground-water resources of Catoosa County, Georgia: Georgia Geol. Surv. Inf. Circ. 28, 19 p.
Cressler, C. W., 1964a, Geology and ground-water resources of the Paleozoic rock area, Chattooga County, Georgia: Georgia Geol. Surv. Inf. Circ. 27, 14 p.
Cressler, C. W., 1964b, Geology and ground-water resources of Walker County, Georgia: Georgia Geol. Surv. Inf. Circ. 29, 95 p.
Croft, M.G. 1964, Geology and ground-water resources of Dade County, Georgia: Georgia Geol. Surv. Inf. Circ. 26, 17 p.
Ferm, J. C., Milici, R. C., Eason, J. E., 1972, Carboniferous depositional environments in the Cumberland Plateau of southern Tennessee and northern Alabama: Tennessee Div. Geol. Report of Investigations 33, 32 p.
Wilson, A. 0., 1971, Petrology of parts of the Black River age strata of the Chickamauga Limestone, Etowah and DeKalb Counties, Alabama: in Drahovzal, J. A., and Neathery, T. L., eds., The Middle and Upper Ordovician of the Alabama Appalachians : Alabama Geol. Soc. Guidebook, p. 79-100.
1

System Pennsylvanian
Mississippian
Devonian Silurian Ordovician
CambroOrdovician Cambrian

Stratigraphic units Crab Orchard Mountains Fm. 1,100+' Gizzard Fm. 200-350'
Pennington Fm. Bangor Limestone Hartselle Fm. Monteagle Limestone Tuscumbia Limestone Fort Payne Fm.
1000-2,700'
Chattanooga Shale 10-25'
Red Mountain Fm. 150-1,300'
Sequatchie Fm. 150-250'
Chickamauga Ls . 1,400-2,300'
Knox Group 3,500-3,650'
Weisner, Shady, Rome, and Conasauga fms.

Sedimentary Environments
Humid, terrigenous, tidal marsh, lagoon and barrier island sediments (Molasse facies)
Shallow marine shelf and semi-arid tidal flat carbonates with pro-molasse terrigenous wedges.
Arid tidal flat, carbonate deposits passing upwards into shallow marine shelf carbonate sediments. Terrigenous promolasse sediments to the south and east.
Terrigenous, shallow, euxinic sea.
Terrigenous, promolasse slope and platform deposits with barrier islands and lagoons.
Shallow marine carbonates passing eastwards into terrigenous tidal flat and alluvial deposits (molasse facies).
Shallow marine and tidal flat carbonates.

Table 1. Stratigraphy of the Valley and Ridge Province

2

DEPOSITIONAL ENVIRONMENTS IN THE UPPER ORDOVICIAN OF
NORTHWEST GEORGIA AND SOUTHEAST TENNESSEE
T. M. Chowns
University of Georgia
Introduction
In northwest Georgia the Sequatchie Formation (Upper Ordovician) is a group of gray and red calcareous sandstones, siltstones and shales with subordinate limestones, which occupies the interval between the Chickamauga Limestone (Middle Ordovician) and the Red Mountain Formation (Lower Silurian) (Butts and Gildersleeve, 1948, p. 33; Milici and Smith 1 969, p. 25). The unit is between 150 and 200 feet thick and has always been mapped as part of the Red Mountain Formation although it could probably be mapped separately, as it is in the Valley and Ridge of Tennessee (Fig. 1 ).
When traced northwestwards across the Vall y and Ridge Province into Sequatchie Valley the formation undergoes a spectacular facies change (see for example Thompson, 1970a, 1971 , p. 71; Drahovzal and Neathery , 1971, p. 18-25, 50-52). While red sandstones and siltst ones predominate in t he east (Rocky Face Mountain, Whiteoak Mountain), gray sandy and silty limestones predominate in the west (Lookout Valley , Southern Sequatchie Valley), and the Sequatchie Formation passes into the Inman, Leipers and Shellmound 1 formations (Fig. 2). The red-bed facies which is the most distinctive feature of the Sequatchie Formation, is highly diachronous. In the northern part of Sequatchie Valley red beds are restricted to the Shellmound Formation, while in the southern part they occur in th e Inman F ormation (Milici and Wedow, in preparation). SimHarly, in Lookout Valley red beds occur only in the lower part of the Sequatchie (Inman Member), but to the east they are foun d at higher an d higher horizons as first Leipers, and then Shellmo und members pass into red beds .
The Sequatchie Formation is in fact merely the youngest of a series of red-bed t ongues (near-shore facies), which prograded westwards across the southern Appalachian basin into gray marine limestones during Middle and Late Ordovician times (Allen and Lester, 1957).
Age of the Sequatchie Formation
Ulrich (1 914 p. 614) first proposed the name Sequatchie for dep sits of Richmond age in t he Southern Appalachians, apparently having in mind a type section at Inman
Tennessee2 (Ulrich, 1914, p . 612, 647; Burchard, 1913 , p. 39). However, it is clearly
erroneous to prescribe rigid time boundaries to a diachronous red-bed sequence, and it now seems probable that rocks which have been mapped as Sequatchie in Tennessee and Georgia include strata of Edenian, Maysvillian and Richmondian age.
The contacts of the formation, both with the Catheys Formation below and the Red Mountain Formation above, appear to be completely conformable so that there is pro bably an unbroken succession of sediments ranging in age from Middle Ordovician to Early Silurian in the study area.
1 The Shellmound is a new formational name proposed by Milici and Wedow (in preparation) for gray calcareous shales and siltstones, with limestones which occur between the top of the Leipers Limestone and the base of the Red Mountain Formation in southeast Tennessee.
2 Ulrich never published a formal description of the Sequatchie Formation and thus his intentions must be interpreted from some oblique references made in a paper read before the 12th International Geological Congress in 1913 (Ulrich 1914, p. 614, 612, 647) and from some short notes published by Burchard (1913, p. 32-43).
3

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l
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MADDOX GA~::::::::::::::::~
IJI~!~}~~~I~~t:~

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0 Measured Sections

e Measured Sections with Probable Outcrops of

Hooker Seams

Hooker Seams (McCallie.l908)

Fig. 1. Location map for measured sections in the Sequatchie Formation, showing the distribution of the Hooker ironstone

seams. Stippled area: Silurian- Pennsylvanian r ocks; blank: Cambrian- Ordovician.

Correlation
In the complex problem of interpreting Middle and Upper Ordovician facies changes correlation is critical. Figure 3 which provides the framework for the following environmental interpretations is based on measured sections spaced as closely as possible. The correlations shown are lithologic rather than biostratigraphic but approximate time equivalence is inferred.
The top of the Sequatchie Formation is drawn beneath the first ledges of Red Mountain sandstone (barrier-sandstone facies), the base above the last calcarenites and calcirudites of the Catheys Limestone. Within the formation correlations are based on gross lithology and sedimentary structures rather than on color variations. In western outcrops the distinctive lithology of the Leipers Limestone serves to divide the succession while in the east it is the argillaceous character of the Shellmound Member which allows it to be differentiated from the more arenaceous Inman-Leipers equivalents. Correlation at the base of the Shellmound is also facilitated by a bed of chamosite-hematite oolite which may be recognized in several strike belts. It occurs in southern Sequatchie Valley, throughout Lookout Valley, and can be traced as far east as Pigeon Mountain; a total distance of 25 miles across strike (Fig. 1 ).
Lithofacies
"Juniata" Facies
In the most easterly exposures where Ordo-Silurian strata are exposed (Rocky Face Mountain, Horn Mountain) the Red Mountain Formation passes gradationally downwards into dark red unfossiliferous siltstones and sandstones which are approximately equivalent to the Sequatchie Formation further west (Zone+ 5 of Allen and Lester, 1957, p. 16). In detail these beds may be divided into a series of fining-upward cycles, with massive, coarse-grained, poorly sorted sandstones passing upwards into siltstones and shales with thin sandstone interbeds. The overall appearance of these beds, therefore, suggests alluvial sedimentation; the massive sandstones being laid down as meandering stream deposits and the siltstones and shales as overbank deposits.
The name "Juniata" facies is used for these alluvial beds to emphasize a similarity to the fluviatile Juniata Formation of the central Appalachians which is stratigraphically equivalent to the Sequatchie Formation (Woodward, 1951, p. 387-408; Rogers, 1953, p. 98; Thompson, 1970b).
Red Sequatchie Facies
Ulrich (1914, p. 614) described the Sequatchie Formation as red shale and argillaceous limestone and it is clear from his notes (in Burchard, 1913, p. 32-43) that, although he defined the formation on the basis of a Richmond age he considered red beds to be a principle lithology. These red beds include fine grained calcareous sandstones, siltstones and shales, grading into impure fine grained pelmicrites
The red color is of primary origin and arises from the presence of thin hematite coatings on the grains. Thus the finer the grain size the darker the red coloration. Chemical analyses carried out by Weidemann (unpublished manuscript) suggest values for Fe+++ ranging from 2 or 3 percent in the sandstones to 4 or 5 percent in shaly siltstones. Although in some areas reddening is concordant with primary sedimentary structures, in many places localized bleaching during diagenesis has tended to blur color boundaries. In particular, Wiedemann draws attention to the bleached halos and Liesegang rings which develop around burrows in bioturbated red beds, as well as to bleached zones along extension fractures. In both cases bleaching resulted from the reduction and removal of the hematite stain; in the first case during early diagenesis, in the second at a later stage.
The red Sequatchie facies is characterized by a very distinctive suite of sedimentary structures including graded beds, laminations, ripple cross-laminations and desiccation structures. Graded units are thin to medium bedded with scoured bases and consist of fine sandstone or pelmicrite passing upward into shale. Desiccation structures include mudcracks, breccias and birdseyes. Many of the shale units at the top of the graded beds show polygonal mud cracks, and fragments of these polygons occur commonly in the sandstones.
5

LLANDOVERIAN BRASSFIELD ROCKWOOD RED MOUNTAIN

RICHMONDIAN? SHELLMOUND SHELL MOUND

MAYSVILLIAN?

LEIPERS

LEIPERS VsEQUATCHIE

(.0

EDENIAN?

< INMAN

SHERMAN IAN?

CAT-HEYS

CATHEYS

CATHEYS

CENTRAL BASIN SEQUATCHIE

VALLEY AND

EAST

VALLEY

RIDGE

Fig. 2. Schematic diagram showing the stratigraphic relationship between Upper Ordovician rocks in southeastern Tennessee and northwest Georgia. Stippled area: littoral facies; blank: open marine facies.

Body fossils are rare, although some thin beds of ostracod biomicrite occur in places. Otherwise skeletal remains are restricted to abraded fragments of bryozoans and brachiopods, which occur with scattered limestone pebbles in tenuous lenses at some intervals. Trace fossil markings are common and include Skolithos, Tigillites, Teichichnus and Chondrites.
Considered overall the evidence is overwhelming that the red Sequatchie facies was deposited in a supratidal (high-tidal-flat) environment. In particular, the coincidence of graded beds with desiccation structures indicates periods of rapid suspension sedimentation separated by long intervals of subaerial exposure. Such is the case on supratidal flats which undergo only periodic flooding during spring tides and storms. In the intervals between inundations, during dry periods, fine grained tidal muds may be subjected to intense desiccation and provide resiliant mud polygons which are readily eroded and redistributed pn the next flood tide. During storm tides lime clasts and skeletal debris may be transported from intertidal or subtidal areas and left stranded on the supratidal flats. Beds of ostracod biomicrite were probably deposited in shallow ponds temporarily impounded on the flats. Vertical burrows like Skolithos and Tigillites are characteristic of littoral sediments.
Since the dominant direction of sediment transport on tidal flats is landwards the red Sequatchie facies must have been supplied with sediment from gray beds offshore (to the west). The red color of the facies was therefore produced on the supratidal flats as a result of subaerial oxidation.
Gray Sequatchie Facies
This facies includes not only calcareous sandstones, siltstones and shales similar to those .in the red facies (except for color), but also a variety of pellet and skeletal limestone lithologies. The gray Sequatchie facies is therefore more calcareous than the red facies, shows a greater range of lithologies, and was deposited in a greater variety of environments. In general, the facies passes eastwards into supratidal sediments and westwards into marine deposits (Fig. 3) so that transitional environments may be expected.
Intervals of flaser bedded, fine grained sandstone, siltstone and shale are characteristic and show the same combination of graded beds and desiccation structures noted in the previous facies. However, in the absence of hematite staining the sandstones are medium gray and the shales greenish gray (total iron 1-4 percent according to Weidemann).
These also appear to be tidal-flat sediments, but in contrast to the supratidal facies, bedding is thinner, desiccation cracks and breccias are less well developed and skeletal debris is more abundant. The rarity of burrow structures and the presence of massive convoluted load casts on the bases of some sandstones suggest rapid sedimentation. Thin beds of finely laminated calcareous siltstone and calcilutite possibly represent algal mats. The evidence is therefore consistent with deposition on intertidal flats (low-tidal-flats) where flooding took place daily and prevented subaerial reddening. Repeated scouring and deposition produced thin bedding except in local depressions (e.g. abandoned tidal channels) where thicker beds of waterlogged sandstone accumulated and foundered on underlying substrates.
Closely associated with these sediments are units of poorly sorted, cross-bedded, sandy, skeletal calcarenite and calcirudite which are interpreted as the lag deposits of migrating tidal channels. Basal contacts are sharp and calcirudites pass gradationally upward into normal tidal-flat lithologies. Skeletal fragments, mainly bryozoans and brachiopods, are usually broken and abraded, but in some places branching bryozoan colonies occur in growth position. Obviously, these animals were able to establish themselves in the more protected reaches of the tidal distributary system. Rounded intraclasts of shale and dolostone, sometimes imbricated, are a common occurrence. Cross-bedding is in the form of shallow troughs, which mark the passage of low amplitude, curvedcrested megaripples. The thickness of these units varies from less than a foot up to 30 feet, and generally increases in the western part of the study area where the main arteries of the tidal distributary system are exposed.
7

ANDERSON HILL

HOOKER

RINGGOLD

GREEN GAP
=

SHELLMOUND

~
LEIPERS

INMAN

J...-. --J....

r=:=:::=1 Red Sequatchie t=:::l Facies

r,:t ~ - - - - - - - -

- - - - - - - ::_-_ -_::

~ Gray Sequatchie ~ Facies

nmlLeipers
~Facies

== w

:r:

-0
. 1-

C()

<!

::J

0
ewn

-

c=::J Mannie Shale Facies r=:l (with ironstone seams)

a ~ Fernvale Facies underlying

~channel limestones

0

5

Fig. 3. Regional facies relationships in the Upper Ordovician of southeast Tennessee and northwest Georgia. For location of section line see Figure 1.

Tidal-flat and tidal-channel facies of the red and gray Sequatchie facies are invariably dolomitic, the grain size of the dolomite being approximately proportional to the grain size of the host rock. They also contain vugs and veins of gypsum which suggest that evaporation on the supratidal flats produced residual brines comparable to those found in modern arid tidal flats (sabkhas) (Illing et al., 1965).
Fernvale Facies
Lithologies dominated by mature, well sorted, calcarenites and calcirudites are referred to as the Fernvale facies, because they predominate in the Fervale member of the Shellmound Formation (Milici and Wedow, in preparation). The Fernvale consists of red and gray, ripple marked, bryozoan-crinoid biosparites (grainstones and packstones) with occasional cross-bedded units. It represents the highest energy environment encountered in these rocks and is interpreted as a barrier-beach deposit. Red and gray lithologies probably indicate relative degrees of subaerial oxidation and may therefore be used to distinguish upper and lower beach deposits. Since the hematite coatings, which are responsible for the red color of the facies, often show geopetal structures, the iron must have been introduced in particulate form rather than in solution. The most likely source was red dust blown from neighbouring supratidal flats.
Amongst other differences, red Fernvale limestones reveal a diagenetic history which is distinctly different from other calcarenites and calcirudites in the Sequatchie. In the majority of limestones the definition of carbonate fabrics is obscured by recrystallization and dolomitization but in the red Fernvale facies grain-cement contacts remain sharp, recrystallization and dolomitization occurring only on a minor scale. Up to three generations of calcite cement, characterized by different amounts of iron in solid solution (as determined by staining), may be identified. Significantly, the hematite coatings were superposed on the first generation cement. Because the hematite is itself of very early diagenetic origin, cementation must have commenced on the beach before final burial took place. It is concluded, therefore, that the red Fernvale is a beachrock facies. Apparently for some reason these beachrocks resisted later recrystalli:?:ation and homogenization.
Although Fernvale calcarenites and calcirudites occur mainly at the top of the Shellmound, mature, well sorted, cross-bedded limestones of similar origin occur at one or two horizons lower down in the same interval. It would not be surprising to find that the Fernvale Limestone of central Tennessee were highly diachronous in the same fashion as the previous facies (see Wilson, 1949, p. 214).
Mannie Facies
The Fernvale facies passes eastwards into a group of dark gray to reddish gray, fissile shales which resemble the Mannie Shale of central Tennessee (Wilson, 1949, p. 215 ). They rest on Fernvale calcarenites or tidal flat sediments below, and are overlain by transgressive barrier sandstones at the base of the Red Mountain Formation. Followed from outcrop to outcrop lithologies and thicknesses change considerably. Near contacts with the Fernvale facies thin interbeds of skeletal limestone occur, but otherwise the facies is rather unfossiliferous. There are also intervals of massive, poorly sorted, coarse grained quartz sandstone and bioturbated shaly sandstone with very coarse grained quartz grains and black phosphate pebbles and granules. In places these sandstones are strongly hematitic and contain small chamosite-hematite ooids.
On the basis of stratigraphic position and overall lithology the Mannie facies is interpreted as a lagoonal sequence impounded behind the Fernvale barriers. Limestone interbeds probably represent washover deposits derived from this barrier during storms, while the coarse grained sandstones are probably reworked fluviatile sands trapped in sluggish tidal channels. Most of the skeletal debris within these beds appears to have been transported into the lagoon but the presence of Modiolopsis in growth position indicates a small indigenous fauna. Phosphatic debris was derived locally within the lagoon by the erosion of thin phosphate crusts which occurred on some of the sandstones.
The presence of oolitic ironstones within these lagoonal beds is particularly significant in the light of evidence that the Clinton-type ores of the Red Mountain Formation formed in back-barrier tidal-channel and lagoonal environments.
9

A similar sequence of shales and sandy limestones with oolitic ironstones occurs near the base of the Shellmound Formation. However, this unit contains a more varied fauna including brachiopods, branching and encrusting bryozoans and bivalves (Modiolopsis, Byssonychia), suggesting a less restricted environment (a marine embayment, or open lagoon).

This unit may be traced westwards from Ringgold (Taylor Ridge) through Pigeon Mountain and Lookout Valley into the southern part of Sequatchie Valley. In the west it is underlain by marine sediments (Leipers Limestone), but elsewhere the beds above and below are tidal-flat deposits. Although the sequence is capped by a thin Fernvale limestone at a couple of localities (lagoon beach) there is no evidence of a major barrier unless it lies further west in Fernvale lithologies of the southeastern part of the Central Basin of Tennessee (see Wilson, 1949, p. 238, fig. 73).

There are two ironstone beds associated with these lagoonal deposits where they outcrop near Hooker, in Lookout Valley, and these or similar beds may be found as far east as Pigeon Mountain and to the west in the southern part of Sequatchie Valley. McCallie (1908, p. 60, 75, 81-85) was able to follow the Hooker seams southwards through Lookout Valley into Johnson Crook, and noted that the ore was workable in places. Apparently the same ironstones were also worked further west in Sequatchie Valley, Jackson County, Alabama (R. L. Wilson, 1972, personal communication).

In general these ironstones may be described as argillaceous, oolitic, chamosite-hematite

mudstones, with lesser units of ripple marked or cross-bedded hematite oolite. Green

chamosite (approximately 2Si0?. as delicately laminated discoidal

oAo1io2s0,3as

3Fe0 aq.) is the primary iron mineral and occurs a replacement of skeletal debris and as a con-

stituent of the matrix. The hematite is secondary, all stages between laminated chamosite

ooids, and structureless pseudomorphs of hematite (flaxseed grains) being observed. The

ratio of hematite to chamosite is directly related to the degree of current sorting to which

the ironstones have been subjected, indicating that replacement took place on the sea floor.

The flaxseed shape appears to be diagnostic of chamosite so that wherever flaxseed hematite

grains occur they may be attributed to primary chamosite (Chowns, 1970.).

Leipers Facies
The Leipers Formation in Sequatchie Valley, Tennessee consists of bioturbate, silty, dolomitic biomicrites (packstones and wackestones) and corresponds to the massive argillaceous limestone subfacies of Wilson (1949, p. 182). Any sedimentary structures which may originally have been present in these rocks were destroyed by burrowing. The fauna includes a somewhat restricted collection of brachiopods (especially Platystrophia ponderosa), gastropods and encrusting bryozoans.
Mainly on the basis of stratigraphic position the Leipers facies is ascribed to a shallow marine environment (open marine embayment).
Some interbeds of nodular argillaceous biomicrite (wackestones) referred to as "Pseudo-Leipers" by Milici and Wedow (in preparation) occur near the base of the Shellmound Formation in Sequatchie and Lookout Valleys and are tentatively included in the same environment. However, they contain small nodular masses of anhydrite of the type normally associated with supratidal sediments.

Catheys Facies
The Catheys Formation is the highest formation in the Nashville Group at the top of the Chickamauga Supergroup (Milici and Smith, 1969, p. 7), and is traditionally Middle Ordovician in age. Throughout the study area the formation consists of thin bedded calcirudites, and fine grained calcarenites interstratified with shales (nodular facies of Wilson, 1949, p. 148). The limestones are abundantly fossiliferous with brachiopods, bryozoans, bivalves, gastropods, orthoceratids, and trilobites, and were clearly deposited in an open marine (subtidal) environment.
The writer rejects the suggestion of Wilson (1949, p. 156) and previous authors that the contact between the Catheys and younger formations is unconformable. Everywhere the contact between the Catheys and Sequatchie formations is exposed in the study area, it is found to be gradational and Wilson admits "no phenomena indicative of a physical

10

break" in the Central Basin. Rather it appears that the Inman and Leipers formations pass westwards into Catheys lithologies and that missing faunas and formations are to be ascribed to facies changes rather than unconformities. Lithologically the Catheys and Leipers formations of the Central Basin are identical (Wilson loc. cit.) and at least in part represent marine equivalents of tidal-flat sediments in Sequatchie Valley and the Valley and Ridge Province.
Regional Synthesis A cross section drawn from south-east to north-west across the Valley and Ridge Province into the Central Basin of Tennessee, approximately normal to the strike of the Appalachian Basin, reveals the regional relationships of many of the facies which constitute the marginal deposits of the Upper Ordovician molasse in the central and southern Appalachians. Red alluvial sandstones and shales in the east ("Juniata" facies) pass westwards into transitional, tidal-flat (Sequatchie facies), barrier-island (Fernvale facies) and lagoonal sediments (Mannie facies), and finally into open marine deposits (Leipers-Catheys facies). These facies are therefore part of a continuum in which local erosional breaks occur but no major unconformities. With transgressions and regressions facies shift east and west across time lines, disappear at one period and recur at another. Precisely how these facies are related in time however, must await a modern biostratigraphic zonation based on conodonts or brachiopod and bryozoan lineages.
Acknowledgment It is a pleasure to acknowledge the help of Robert C. Milici, who first introduced the writer to the Sequatchie Formation and provided generous advice arid opportunity for discussion.
11

References
Allen, A. T. and Lester, J. G., 1957, Zonation of the Middle and Upper Ordovician strata in northwestern Georgia: Georgia Geol. Surv. Bull. 66, 110 p.
Burchard, E. F., 1913, The red iron ores of east Tennessee: Tennessee Div. Geol. Bull. 16, 173 p. (Reprinted 1962).
Butts, C. and Gildersleeve, B., 1948, Geology and mineral resources of the Paleozoic area in northwest Georgia: Georgia Geol. Surv. Bull. 54, 176 p.
Chowns, T. M., 1970, A chamosite-hematite oolite from the Sequatchie Formation in
northwest Georgia (abs.): Georgia Acad. Sci. Bull. 28, p. s19.
Drahovzal, J. A. and Neathery, T. L., 1971, Middle and Upper Ordovician stratigraphy of the Alabama Appalachians in Drahovzal, J. A., and Neathery, T. L., eds., The Middle and Upper Ordovician of the Alabama Appalachians: Ala. Geol. Soc. p. 1-62.
llling, L. V., Wells, A. J., and Taylor, J. M. C., 1965, Penecontemporary dolomite in the Persian Gulf, in Pray, L. C., Murray, R. C., ed., Dolomitization and limestone diagenesis: Soc. Econ. Paleontologists and Mineralogists Special Publication 13, p. 89-111.
McCallie, S. W., 1908, Report on the fossil iron ores of Georgia: Georgia Geol. Surv. Bull. 17,199 p.
Milici, R. C., and Smith, J. W., 1969, Stratigraphy of the Chickamauga Supergroup in its type area: Georgia Geol. Surv. Bull. 80, p. 1-35.
Milici, R. C., and Wedow H., (in preparation), Upper Ordovician and Silurian stratigraphy in Sequatchie Valley and parts of the adjacent Valley and Ridge, Tennessee.
Rogers, J., 1953, Geologic map of east Tennessee with explanatory text: Tennessee Div. Geol. Bull. 58, pt. 2, 168 p.
Thompson, A.M., 1970a, Tidal-flat deposition and early dolomitization in Upper Ordovician rocks southern Appalachian Valley and Ridge: Jour. Sedimentary Petrology 40, p. 1271-1286.
Thompson, A.M., 1970b, Geochemistry of color genesis in red-bed sequence, Juniata and Bald Eagle formations, Pennsylvania: Jour. Sedimentary Petrology 40, p. 599-615.
Thompson, A.M., 1971, Clastic-carbonate facies relationships and paleoenvironments in Upper Ordovician rocks of Northeast Alabama, in Drahovzal, J. A., and Neathery, T. L., eds., The Middle and Upper Ordovician of the Alabama Appalachians: Ala. Geol. Soc. p. 63-78.
Ulrich, E. 0., 1914, The Ordovician-Silurian boundary: XII International Geol. Congress, Canada, p. 593-667.
Wilson, C. W., 1949, Pre-Chattanooga stratigraphy in Central Tennessee: Tennessee Div. Geol. Bull. 56, 407 p.
Woodward, H. P., 1951, Ordovician System of West Virginia: West Virginia Geol. Surv.. Vol. 21, 627 p.
12

MOLASSE SEDIMENTATION IN THE SILURIAN ROCKS OF NORTHWEST GEORGIA
T. M. Chowns University of Georgia
Regional Setting
The Silurian system in northwest Georgia consists of a single formation, the Red Mountain Formation, which extends into the State as a series of northeast-southwest trending ridges, from its type area in Alabama. All outcrops occur west of the Rome Fault, where the formation rests conformably on Ordovician strata below and is overlain unconformably by Devonian rocks.
Within thl.s area Appalachian folding has provided a repetition of outcrop belts which allow a three dimensional interpretation of Silurian sedimentary environments. The formation thickens progressively in a southeasterly direction, the isopachs striking northeast-southwest approximately parallel to the Appalachian fold axes (Fig. 1 ). Variations in thickness are mainly depositional, no major truncation being apparent beneath the Devonian unconformity. East of the Rome fault, however, the Devonian Frog Mountain Sandstone lies unconformably on various Ordovician formations (Cressler, 1970, p. 36), the Red Mountain Formation having been entirely removed.
In general massive sandstones predominate in the east (cf. the Clinch Sandstone in Tennessee) and pass westwards through an intermediate alternating sandstone-shale facies (cf. the Rockwood Formation .in Tennessee) into limestones and shales (cf. the Brassfield Limestone in Tennessee). Sedimentation on the Appalachian miogeocline was clearly dominated by a terrigenous source to the east, and sections drawn east-west through northwest Georgia reveal the marginal sediments of a large wedge of clastic molasse deposited following the Taconian orogenic phase (Figs. 2 3).
This molasse wedge extends continuously along the eastern margin of the Appalac chian miogeocline from New York to Alabama (Colton, 1970, p. 30; Berry and Boucot, 1970, p. 52) and consists of an assemblage of recurring lithofacies similar to those developed in Georgia (Hunter, 1970; Zenger, 1971). The persistance of these lithofacies is illustrated by the recurrence of Clinton-type iron ores throughout the outcrop belt.
It is the purpose of this paper to interpret the environment of deposition of some of these lithofacies in Georgia. Special attention is focussed on the section at Ringgold (Fig. 4) which is the best single exposure of the formation in the State at the present time, and provides key data for the interpretation of these rocks elsewhere.
Age of the Red Mountain Formation
The age of the Red Mountain Formation in Georgia bas been established as lower middle and upper Llandoverian on the basis of brachiopod zonation (Butts and Gildersleeve, 1948, p. 37; Berry and Boucot, 1970, p. 29). In particular, species oJ Pentamerus and Eocoelia first make their appearance in the upper part of the formation. The formation therefore includes lower strata than in the type area where only upper Llandoverian rocks are present. Whereas at Birmingham, Alabama, a distinct angular unconformity separates the Silurian and Ordovician systems, in Georgia the boundary appears completely conformable.
Lithofacies
Quartz Sandstone Facies (littoral sand facies)
This facies is best developed in Rocky Face Mountain and other eastern strike belts, but tongues extend westwards into Taylor Ridge and Whiteoak Mountain (e.g. Whiteoak . Mountain Sandstone; Butts and Gildersleeve, 1948, p. 36) (Fig. 3). The sandstones show considerable variation. They may be medium to coarse grained or conglomeratic, thin to thick bedded, with colors ranging from very light gray to medium gray or dusky red. Sorting varies, but medium to well sorted sandstones predominate.
13



f0 20

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o Reference Sections

Fig. 1. a) Principal Silurian outcrops in the southern Appalachians (shown in black) and b) isopachs for Silurian System.

The writer's observations support the conclusions of Sheldon (1970, p. 109), who interpreted similar sandstones in Alabama as barrier island sequences on the basis of sedimentary structures and overall geometry. The facies combines a complex of littoral subfacies including beach, tidal channel, tidal delta and washover deposits (Fig. 5). No dune sandstones have been recognized so far.
Beach sandstones are medium to coarse grained and medium to thick bedded. In favourable exposures they may show bimodal cross-bedding with low-angle accretion beds dipping to the west (seawards) and high-angle cross-beds, of the type developed during the migration of ridge and runnel structures, dipping to the east (landwards). Basal contacts with adjacent facies may be gradational by interbedding, or sharp, but never scoured. Skolithos is abundant in some sandstones. Body fossils may or may not occur.
Thick bedded, tidal-channel sandstones are characterized by pronounced scouring at their basal contacts and are usually coarser grained than beach sandstones. Crossbedding is also more pronounced with high angle cross-beds dipping both eastwards and westwards. This bimodality is t hought to record t he migration of sand waves driven by ebb and flood tidal currents. They often contain pebble sized shale clasts derived by the erosion of local lagoonal deposits.
These sandstones are incised, and pass laterally into thin bedded ripple-laminated sandstones and siltstones which represent the sand flats of tidal deltas fed by earlier tidal channels. The sand flats, like the tidal channels, contain abundant shale clasts.
Washover deposits, formed by the landward transport of barrier sands by storm tides, may form cross-bedded sand flats or if they debouch into lagoons they may occur as thin graded beds.
Both the sand flats of tidal deltas and washovers contain an abundant trace fauna dominated by a Skolithos assemblage. By contrast channel sandstones are usually barren.
Two types of barrier sandstone are recognized depending on the relative succession of these subfacies. In transgressive sand sheets the beach sandstone overlies tidal-delta and washover deposits, while in regressive sand sheets the reverse applies. Certain other differences may also be recognised. Regressive barrier sequences, built along prograding shorelines, are thicker and better developed than transgressive sequences, built during the destruction and reworking of the shoreline. They are also extremely ferruginous while transgressive sand sheets are not. Apparently reworking and marine groundwater circulation during a transgression removes any ferric iron coatings which may be present.
Wherever hematitic sandstones of the regressive barrier facies outcrop, and where structure, topography and access permit, these beds have been tried for iron ore either for the blast furnace or paint industry. The two most important ironstone mining centers in Georgia were at Rising Fawn in J ohnson Crook and at Estelle on the west side of Pigeon Moun tain (McCallie, 1908, p . 55, 96) (Fig. 2 ). Much of the stone was too lean to be worked as ore but individual beds and lenses sometimes ran up to 57 percent Fe203 (40 percent Fe) before weathering, with soft weathered ores running up to 85 percent Fe203 (60 percent Fe) (McCallie, 1908).
Many of the principal occurrences appear to have been in tidal channels and associated tidal-delta deposits. Apparently, some channels trapped large amounts of abraded skeletal debris which underwent coating and replacement by iron minerals; mainly hematite but some chamosite (approximately 2Si02 Al203 3Fe0 aq.) . Whereas eastern barriers were built entirely of sandstone, western barriers further from the source of terrigenous sediment contained larger quantities of skeletal debris and therefore provided ironstones which were more amenable as iron ores.
Alternating Sandstone and Shale Facies (Promolasse slope and platform facies)
This lithofacies is particularly well developed in the Taylor Ridge strike belt and consists of very thin to medium bedded, dolomitic sandstones and siltstones interbedded with shales (Fig. 3). Colors range from light gray (medium sorted) to medium dark gray (poorly sorted), weathering to shades of orange and brown as a result of ferroan dolomite. The facies passes eastwards into the quartz sandstone facies and westwards into the carbonate facies. It recurs twice in the succession, at the top and bottom of the formation.
15

(!)

0' miles 1I

rl

l

0 Meaured Sections

Ironstone Mines

Blast Furnaces

Fig. 2. Location map for measured sections in the Red Mountain (Rockwood) Formation , showing the distribution of ironstone mines and blast furnaces.

~Carbonate Facies
8 Red Shale Facies ( Promolasse Platform)
DGray Shale Facies (Lagoon)
~Alternating Sandstone-Shale Facies ( Promolasse Slope)
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A close examination of the lower unit as exposed at Ringgold is particularly instructive . The sequence may be divided into three subfacies as follows; a) The base of the succession consists predominantly of shale with inter beds of siltstoue and fine grained sandstone (30 percent). Approximately 40 percent of these interbeds are graded with sharp bottom contacts and gradational tops. The remaining beds show both gradational tops and bottoms. Although shells are poorly preserved, the interval is fossilifero us throughout, and contains traces assigned to a mixed Cruziana-Zoop hycos assemblage. b) In the overlying subfacies sandstones increase in importance, making up approximately 35 percent of the succession. The sandstones are fine to very fine grained and nearly all are graded (90 percent). Sharp basal contacts are frequently scoured with abundant tool marks as well as some flutes and grooves. An analysis of sedimentary structures within the sandstones reveals that while the lower parts were deposited in the upper flow regime (parallel laminations), the upper parts were deposited in the lower flow regime. Sole marks, and sedimentary structures of this kind , known as Bouma sequences (see Fig. 6), are characteristic of sandstones laid down as sheet deposits by periodic currents of waning velocity (e.g. t urbidites, tidalites and storm deposits). The sole marks suggest currents flowing towards the west (i.e. seawards) normal to the depositi onal strike (Fig. 4). Again this interval is fossiliferous throughout with lebensspuren of a mixed Cruziana-Zoophycos assemblage. c) In the upper part of the alternating sandstone and shale facies only about 50 percent of the sandstones are graded, the remainder have sharp contacts top and bottom and resemble the hematitic beach sands of the barrier sandstone facies. They are often crossbedded and were deposited as migrating sand waves or ripples rather than as periodic sand sheets . This suggests that this subfacies was deposited above wave-base while the lower subfacies were deposited beneath. The shales associated with these sandstones are distinctly more fissile than those associated with the graded sandstones indicating that the winnowing of fine and coarse sediment is more complete. The overall percentage of sandstones in this unit fluctuates between 24 percent and 62 percent in a series of cycles.
A distinctive feature of this subfacies is the occurrence of massive load casts or flow rolls on the bases of some of the thicker sandstones. Such structures indicate heavy loading of waterlogged sediments and hence rapid sedimentation. They also suggest gravitational instability.
This unit is fossiliferous like those below, but whereas shells are restricted to the bases of the graded sandstones they occur throughout the cross-bedded sandstones in this interval. Like the sediments the trace fossils are of mixed origin with representatives of both the Cruziana and Skolithos assemblages.
Taken as a unit the alternating sandstone and shale facies reveals a coarsening-upward cycle which culminates in the hematitic sandstones of a regressive barrier sequence. The combined evidence of periodic currents and gravitational instability strongly suggests that the graded sandstones are turbidites. A closer examination of the Bouma sequences shows .that the turbidites. become increasingly proximal towards the top of the succession (see Appendix and Fig. 4). Both sole markings and load casts suggest a westerly dipping paleoslope. These observations are interpreted to indicate that the lower alternating sandstone and shale unit at Ringgold represents the deposits of a westward prograding slope, referred to here as a promolasse slope. The three subfacies described above are then interpreted as:
a) Promolasse and lower promolasse slope deposits b) Middle and upper promolasse slope deposits c) Slope break and promolasse platform deposits in front of a barrier island.
Similar sequences have been described in Devonian and Cretaceous shelf and slope sediments by Walker (1971) and Hubert et al. (1972).
Turbidity currents appear to have been initiated by gravitational instability and slumping at the slope break, the cyclic development of shales and sandstones immediately above and below this level being the result of successive phases of slumping and rebuilding:
By contrast with the sandstones of the overlying barrier facies, the turbidite sandstones are finer grained, less well sorted and without hematite grain coatings. Apparently the barrier system was extremely effective in retaining coarse grained terrigenous sediment
18

Fig. 4. Columnar section of Ordovician and Silurian rocks exposed in the road cuts on I-75 at Ringgold Gap, Georgia.

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which never appeared at the edge of the pro molasse platform where it might have undergone slumping. Although the cross-bedded sandstones of the promolasse platform are sometimes hematitic, there is only one ferruginous bed amongst the lower turbidites. It is therefore concluded that oxidation potentials were lower on the slope and ferric iron coatings were removed from the turbidite sands upon burial.
Because these sediments were deposited on a prograding platform and slope, it is possible to make some estimates regarding water depths. Assuming a minimum of subsidence during deposition the depth of water at the slope break is given by the thickness of subfacies c, approximately 60 feet, while t he depth at the foot of the slope is given by the combined thickness of facies a, b and c, approximately 180 feet. Allowing for syndepositional subsidence these figures must be regarded as maximum depths. However, a glance at Figure 3 shows that, whatever the absolute rate of subsidence, differential subsidence between eastern and western parts of the miogeocline, exposed in northwest Georgia, was at a minimum during lower and middle Llandoverian times.
The upper group of alternating sandstones and shales at Ringgold shares many of the attributes described above. The sandstones are graded-bedded with similar sole markings and sedimentary structures and are once again interpreted as turbidites. However, it is noi p ssible to demonstrate a complete regressive cycle. These beds were probably deposited seawards of littoral deposits which never prograded westwards as far as Taylor Ridge during the interval of time represented by the sedimentary record.
Carbonate Facies
Rocks of the alternating sandstone-shale facies and the quartz sandstone facies pass westwards into carbonate sands which make up the Brassfield Limestone in central Tennessee (Fig. 3) (Wilson, 1949, p. 240). Only the roargjns of this facies are exposed in Georgia, mainly in the extreme northwest in Lookout and Chattanooga Valleys. In this belt carbonate sands interfinger with promolasse shales and distal turbidites. Some limestones are hematitic in varying degrees due to the presence of hematite coated fossil grains and there were once workable ironstones along Walden Ridge and in Sequatchie Valley (Tennessee). However, precisely bow these ferrugin ous beds are related to the hematitic barrier sands described previously has yet to be determined. They may represent extem~ions of the same unit or they may have been derived by longshore drift from barriers to the north near Rockwood, Tennessee.
The Brassfield Limestone is regarded as a part of the Lower Silurian shallow water, cratonic carbonate facies.
Shale Facies
Shale sequences occur interbedded with each of the facies outlined on the previous pages. Regionally, however, they tend to predominate in a middle belt between quartz sandstones in the east and carbonate .rocks in the west. They may be expected to form in any of a number of quiet water environments dominated by terrigenous sedimentation. For example:
a) as promolasse deposits b) in protected bays on molasse platforms c) in lagoons behind barrier islands.
Such shale units are difficult to interp t from individual outcrops, especially where exposures are poor . Sedimentary structures, skeletal debris, and trace fossil assemblages may be absent, or provide ambiguous data, so that these facies are best interpreted by their relationship to other facies of known environment.
a) Promolasse Shales
Promolasse shales lie at the western limits of the molasse facies. They pass eastwards into alternating sandstones and shales of the promolasse slope facies and westwards into the shelf carbonate facies. Thin interbeds of limestone and fine grained sandstone or siltstone (distal turbidites) may therefore be expected. Shale colors range from medium dark grey to light olive grey with increasing carbonate. Western exposures (e.g. Estelle, Pigeon Mountain) are richly fossiliferous.
20

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The ABC index (Walker 1967) is a measure of the proximality of a group of turbidites to their source. It is calculated on the basis of the proportion of beds in the group beginning with divisions a, b and c of the ideal Bouma sequence (Bouma 1962). Thus:
ABC index ~ A,+'h!3 percent A+B+C
where A, B and C are the percentages of beds in each group beginning with divisions a, b and c respectively. Prox imal turbidites are charac terized by large numbers of beds commencing with a and therefore give high values for the ABC index, while distal turbidites, with more beds commencing with b and c, give low values.

Fig. 6. The interpretation of Bouma sequences in turbidites (see Bouma, 1962 and Walker, 1967).

b) Protected Platform Shales
The red shale facies, which forms a prominant feature of the Taylor Ridge strike belt, appears to pass eastwards into barrier sandstones without intervening slope deposits and is therefore interpreted as a protected platform facies. It rests on a transgressive barrier sandstone at the base and passes upwards into promolasse slope deposits indicative of deeper water. The red color of the shales shows that the environment of deposition was sufficiently oxidizing to prevent reduction of iron coatings on the clay micelles during early diagenesis. Interbedded with the shales are a series of fining-upward cycles consisting of alternating shale and fine-grained sandstone, which probably represent the feather edges of barrier sands to the east. The unit contains a restricted marine fauna consisting of crinoid columnals and the brachiopod Eocoelia.
c) Lagoonal Shales The gray shale unit with thin ironstone seams, best exposed in the Estelle section,
lies between two barrier sandstones, the lower developed during a marine regression, the upper during a transgression. It is therefore seen to lie landward of the barriers and is interpreted as a lagoonal deposit. The unit may be traced westward from Rocky Face Mountain as far as the southern part of Chattanooga Valley but pinches out west of Chattanooga. Thin ironstone seams (1-8 inches thick) are characteristic of the subfacies, but occur only as far east as Taylor Ridge. Hematite is again the principal iron mineral and occurs with accessory chamosite both as coated grains and fossil replacements. The ironstones are clearly related in origin to the ironstones of the littoral sand facies. They are cross-bedded and ripple marked and probably represent lag deposits formed on migrating shoals or shallow tidal channels.
Care is sometimes necessary in distinguishing this subfacies from the promolasse shale subfacies, because thin graded sandstone beds resembling turbidites may occur, particularly in the vicinity of barrier sandstones. Although the depositional process is similar these sandstones appear to be washovers derived from the barriers during storms.
Aside from the abraded skeletal debris which occurs in the ironstones, taken as a
whole this facies is rather unfossiliferous.
Conclusions
It is concluded that the Silurian Red Mountain Formation in Georgia was deposited in a spectrum of sedimentary environments ranging from littoral (lagoon and barrier) to open marine (platform and slope). Together these environments comprise the marginal domains of a large wedge of clastic molasse which spread westwards across the southern part of the Appalachian miogeocline following the Taconian orogeny. Depositional facies strike in an approximately north-north-easterly direction with littoral deposits to the east and marine sediments to the west. Terrigenous sediment was transported both longshore in the littoral zone and seawards down the promolasse slope. Isopachs strike approximately north-east and show that sedimentation and subsidence increased landwards.
Because facies and isopachs strike approximately parallel to Appalachian structures, crustal shortening especially along thrust faults tends to accentuate depositional variations. However, there is no evidence that the Appalachian folds exerted an influence on Silurian sedimentation in Georgia.
Acknowledgments During the course of work on the Red Mountain Formation the writer has received help from numerous individuals. In particular J. Hatten Howard III, Charles D. Masters, Richard P. Sheldon, Robert C. Milici, Dale Cummings, E. A. Chowns, Marith J. Reheis, and Jan D. Smith assisted the author with measurements and discussions in the field.
22

References
Berry, W. B. N., and Boucot, A. J., 1970, Correlation of the North American Silurian rocks: Geol. Soc. Amer. Spec. Paper 102, 289 p.
Bouma , A. H., 1962, Sedimentology of some flysch deposits; A graphic approach to facies interpretation: Elsevier, Amsterdam, Netherlands, 168 p.
Butts, C., and Gildersleeve, B., 1948, Geology and mineral resources of the Paleozoic area in northwest Georgia: Georgia Geol. Surv. Bull. 54, 176 p.
Colton, G. W., 1970, The Appalachian Basin- its depositional sequences and their geologic relationships: in Fisher, G. W., Pettijohn, F. J., Reed, J. C., Weaver, K. N., eds. Studies of Appalachian geology: central and southern: New York, John Wiley and Sons, p. 5-47.
Cressler, C. W., 1970, Geology and ground-water resources of Floyd and Polk Counties, Georgia: Georgia Geol. Surv., Information Circular 39, 95 p.
Hubert J. F., Butera, J. G., Rice, R. F., 1972, Sedimentology of Upper Cretaceous CodyParkman delta, southwestern Powder River Basin, Wyoming: Geol. Soc. Amer. Bull. 83, p. 1649-1670.
Hunter, R. E., 1970, Facies of iron sedimentation in the Clinton Group: in Fisher, G. W., Pettijohn, F. J., Reed, J. C., Weaver, K. N., eds. Studies of Appalachian geology: central and southern: New York, John Wiley & Sons, p. 101-121.
McCallie, S. W., 1908, Report on the fossil iron ores of Georgia: Georgia Geol. Surv. Bull. 17, 199 p.
Sheldon, R. P., 1970, Sedimentation of iron-rich rocks of Llandovery age (Lower Silurian) in the Southern Appalachian Basin: in Berry, W. B. N., Boucot, A. J ., eds., Correlation of the North American Silurian rocks: Geol. Soc. Amer. Spec. Paper 102, p. 107-112.
Walker, R. G., 1967, Turbidite sedimentary structures and their relationship to proximal and distal depositional environments: Jour. Sed. Pet. v. 37, p. 25-43.
Walker, R. G., 1971, Nondeltaic depositional environments in the Catskill clastic wedge (Upper Devonian) of central Pennsylvania: Geol. Soc. Amer. Bull. 82, p. 1305-1326.
Whitlow, J. W., 1962, Red iron-ore beds of Silurian age in northeastern Alabama, Georgia and eastern Tennessee: U.S. Geol. Surv. Mineral Investigations Field Studies Map MF-175, 2 sheets.
Wilson, G. W., 1949, Pre-Chattanooga stratigraphy in central Tennessee: Tennessee Div. Geol. Bull. 56, 407 p.
Zenger, D. H., 1971, Uppermost Clinton (Middle Silurian) stratigraphy and petrology eastcentral New York: New York State Museum and Science Service Bull. 417, 57 p.
23

TRACE FOSSILS FROM THE RINGGOLD ROAD CUT (ORDOVICIAN AND SILURIAN), GEORGIA

Robert W. Frey and T. M. Chowns Department of Geology University of Georgia Athens, Georgia
Abstract
A survey of trace fossils from parts of the Catheys, Sequatchie, and Red Mountain Formations at Ringgold, Georgia, yielded 25 species representing 18 genera: Arenicolites, ?Arthrophycus, ?Asterosoma, Aulichnites, Chondrites, Cruziana, Curvolithus, Dictyodora, Diplocraterion, "Fraena," Gyrochorte, ?Hormosiroidea, Monocraterion, Palaeophycus, Planolites, Skolithos, Tigillites, and Trichophycus. Those from the Red Mountain are referred mainly to the Skolithos and Cruziana assemblages, suggesting (1) shallow turbulent waters and shifting, unstable substrates, and (2) somewhat deeper, less agitated waters and more stable substrates, respectively.

Introduction

Trace fossils constitute a significant but oft-ignored record of ancient life and

depositional conditions. They provide valuable information on soft-bodied animals that

otherwise might not become fossilized, and they reflect behavioral patterns among hard-

bodied animals that otherwise might not be decipherable from functional morphology.

Because the distribution and abundance of trace-making animals are governed by particular

environmental conditions, their traces are also related to these conditions. Furthermore,

the traces ordinarily cannot be reworked or transported, and they are generally improved

rather than destroyed by diagenesis. If studied adequately, trace fossils can thus become

major lines of evidence bolstering other kinds of paleontologic, paleoecologic, stratigraphic

and sedimentologic data.



Fossil and recent traces along the Georgia coast have received considerable study (e.g., Weimer and Hoyt, 1964; Frey and Howard, 1969, 1972; Howard and Elders, 1970; Frey and Mayou, 1971; and Hertweck, 1972), but virtually nothing has been done with Paleozoic trace fossils (see Allen and Lester, 1953).

Our main purpose in this study has been (a) to document the major kinds of trace fossils present in the Ringgold cut, a "standard" reference section for the Red Mountain
Formation, and (b) to place these data in a stratigraphic framework that would shed additional light on facies relationships within the formation. We hope that this reconnaissance study will serve as a background and stimulus for further work on trace fossils of the Red Mountain Formation and other Paleozoic rocks in Georgia and adjacent states.

Classification of Trace Fossils
Trace fossils may be classified in a variety of ways, but one of the most useful systems is that devised by Seilacher (1964a; Frey, 1971, p. 97-99, Table 3). The scheme is based upon salient behavioral traits of organisms:
resting traces - shallow depressions made by animals that temporarily settle onto or dig into the substrate.
crawling traces- trackways, trails, and ephemeral intrastratal traces made by animals traveling from one point to another.
grazing traces - grooves, pits, and lacy furrows made by mobile deposit feeders at or very near the substrate surface.
feeding structures- ephemeral burrows or intrastratal feeding probes made by hemisessile deposit feeders; burrows also provide shelter.
dwelling structures- burrows or tubes providing "permanent" domiciles, mostly for hemisessile suspension feeders.
These categories overlap, of course, and they by no means embrace the spectrum of possible behavioral patterns. But these five have proven to be consistently most useful in the study of trace fossils. These behavioral terms are indicated in our descriptions of individual trace fossils.
25

To enhance the usefulness of this paper as a field guide, however, we have adopted a rather arbitrary classification of the trace fossils, based upon morphology and configuration: (1) vertical cylindrical burrows, (2) U-shaped burrows, (3) inclined burrows and burrow systems, (4) horizontal burrows, and (5) trails and trackways.
Preservation of Trace Fossils
Preservation includes two important aspects : (1) modes of occurrence and the mechanical-sedimentological processes of alteration and preservation, called toponomy, and (2) physio-chemical processes of alteration and preservation (see Frey, 1971, p. 99102).
Diagenesis is always a factor in trace fossil preservation, but the most obvious examples at Ringgold are burrows that are partly to wholly replaced by pyrite or limonite. These are discussed in a subsequent part of the paper.
A useful toponomic classification of trace fossils, devised by Martinsson (1965, 1970), is given in Figure 1. The scheme is based upon relationships between trace fossils and the casting medium (sandstone bed in Fig. 1), as follows:
endichnion - a trace fossil preserved within the main body of the casting medium. exichnion- a trace fossil preserved outside the main body of the casting medium.
epichnion -a trace fossil preserved at the upper surface of the main body of the casting medium; may appear as a ridge or a groove.
hypichnion- a trace fossil preserved at the lower surface of the main body of the casting medium; may appear as a ridge or a groove.
Endichnia and exichnia are approximately equivalent to "endogenic full reliefs," by Seilacher's (1964a, b) classification, and epichnia and hypichnia to "exogenic semireliefs." Martinsson's scheme avoids the use of parallel descriptive and genetic terms, however.
Hypichnia and exichnia were observed most commonly among trace fossils at Ringgold. Hypichnia are "sole marks," and one must bear in mind that-while examining such specimens in the field, or in reading the following descriptions-the specimens are normally viewed up-side-down and in mirror image of the original structure created by the animal.
TRACE FOSSILS FROM THE RED MOUNTAIN FORMATION (SILURIAN)
We have examined the ichnofauna in detail only in the lower part of the Red Mountain at Ringgold. This part of the section corresponds to the main road cut, where the major depositional units are best developed. The observed stratigraphic distribution of these trace fossils is illustrated in Figure 4.
Vertical Cylindrical Burrows
Most vertical cylindrical burrows represent dwellings constructed by sessile or hemisessile suspension-feeding animals, although some are produced by predaceous and deposit-feeding animals. In unstable substrates, whether shifting sands or incoherent muds, the walls of such burrows tend to be thicker, more distinct, and better constructed than those in more stable sediments, where structural reinforcement by the animal is less critical.
The vertical cylindrical burrows observed by us at Ringgold may be assigned to one of three genera: Tigillites, Skolithos, and Monocraterion. Not all specialists agree upon the distinguishing characteristics of the three burrows (e.g., Hantzschel, 1962, 1965; Goldring, 1962; Boyd, 1966; Hallam and Swett, 1966). Most of the confusion results from inadequate original descriptions and illustrations, giving rise to arguments over such things as "degree of crowding" of burrows (which is clearly not a taxonomic matter) and the presence or absence of a "funnel" capping the burrow (which does have taxonomic significance). The following informal diagnoses are adopted here: Tigillites tends to be relatively squat or stumpy, generally 1.5 em or more in diameter; Skolithos tends to be more slender and elongate-like a soda straw-generally less than 1 em in diameter; and
26

. :-.

.

...(j .-: .

.e .." .
. . ..

Epichnia Endichnia Hypichnia Exichnia

Fig. 1. Toponomic classification of trace fossils, by Martinsson (1965, 1970). (Drawing by A. Hallam, unpublished)

27

Monocraterion has a flared, funnel-like top, whether the main burrow stem resembles Tigillites or Skolithos. (See Figure 2).
Tigillites Fig. 2A; Pl. 1A, B; Pl. 5J,
Simple cylindrical shafts, 1 to 2.5 em in diameter, having fairly smooth, distinct walls; maximum length observed, about 8 em. Diameter nearly constant within a given specimen. Annulations and funnel-like apertures not observed (cf. Ha:ntzschel, 1962, p. W218; 1965, p. 92-93). Preserved as exichnia; interpreted as dwelling structures.
Tigillites is similar to Cylindricum (Hantzschel, 1962, p. W189-W190; 1965, p. 28-29), but the latter is generally smaller in diameter and has a rounded base, like a test tube. Future work may nevertheless show that Tigillites and Cylindricum should be consolidated with Skolithos, the "senior synonym."
Skolithos Fig. 2B; Pl. 1C, D.
Unbranched, straight to slightly sinuous cylindrical shafts, 2 to 8 mm in diameter, having smooth, distinct walls; maximum length observed, about 5 em. ~iameter ~early constant within a given specimen. Not annulated and not closely crowded (cf. Hantzschel, 1962, p. W215; 1965, p. 85). Preserved as exichnia; interpreted as dwelling structures.
These burrows are somewhat short and sparse relative to numerous other occurrences of the genus (Howell, 1943; cf. Osgood, 1970, p. 327-328); but this condition may be due in part to original substrate characteristics and subsequent burrow preservation, i.e., thinbedded sandstones and abundant scour zones. Skolithos has not been observed in the massive quartz sandstones at Ringgold but crowded burrows, up to 30 em long and 5 to 10 em apart, have been seen in this facies at Dry Gap, Whiteoak Mountain.
.. The name Sabellari{ex has been applied to gently curving Skolithos-like burrows (Hantzschel, 1962, p. W214-W215; 1965, p. 81), but slight curvation is seen even in plesiotypes of Skolithos (Howell, 1945, Pl. 1, fig. 3); indeed, there is a complete gradation between the two burrow forms (Osgood, 1970, p. 326). Certain markedly sinuous burrows observed at Ringgold should perhaps be called Sabellarifex, however. (See Pl. 5K).
Monocraterion Fig. 2C; Pl. 1E, F.
Vertical, more or less cylindrical shafts having a broad, funnel-like opening at the upper end; walls of burrow and funnel moderately distinct but slightly irregular. Shafts 3 to 4 mm in diameter; maximum length observed, about 8 em. Funnels 1.5 to 2.5 em deep and 3.5 to 4.5 em wide. Annulations not observed. Endichnia and exichnia; burrow fill may or may not be conspicuously different from host rock. Interpreted as a feeding structure or as a combined feeding-dwelling structure (cf. Hantzschel, 1965, p. 57).
Funnels such as those associated with the Monocraterion structure may be formed in a variety of ways, especially by an animal migrating through the substrate-an "escape structure" (Hallam and Swett, 1966), or adjusting a dwelling tube within the substrate (Frey and Howard, 1972, Fig. 8). However, the funnels seen by us are more like those associated with certain Arenicolites (Frey and Howard, 1970, Fig. 7i), which are feeding structures. Characteristics of Ringgold specimens argue against the passive fill of a dwelling structure.
U-Shaped Burrows
Vertical U-shaped burrows of various kinds are common at places in the Ringgold cut. Very distinctive among these is the "U-in-U" burrow, which resembles a set of nested chevrons. Most such structures originate as a simple U-shaped burrow, modified subsequently by the animal either to accomodate new growth-as from a juvenile to an adult stage (Hertweck, 1970)-or to maintain a constant position relative to the substrate surface despite increased deposition or erosion of sediments (Goldring, 1964, Fig. 1 ). The animal's prime objective is simply to maintain the basic U-shaped burrow in which he dwells-whether by enlarging it, or by shifting it upward or downward in the substrate. But the displaced or abandoned individual U-burrows are commonly preserved in the rock record, giving the total structure a nested, U-in-U appearance.
28

The only other common origin of such burrows is by the activity of sediment-ingesting animals that " mine " the substrate, systematically probing first one sediment level and then another (e.g., Frey, 1970; Fig. 4D). In general, these feeding burrows are broader, less consistent (but no less complex) in structural plan, and less commonly oriented vertically than the burrows discussed above.
All U-in-U burrows constitute spreiten structures (Frey, 1971, Table 1). They are termed retrusive if extended upward, or protrusive if extended downward; either way, the last-formed U generally remains discernible. (Dictyodora-Fig. 2M- is also a spreite ).
The trace fossil Trichophycus is not strictly a simple U-shaped burrow, but because it shares certain traits of this "group," it is included here. More representative members of the "group" are Diplocraterion and Arenicolites. These are illustrated in Figure 2.
Diplocraterion Fig. 2D; Pl. 1G, H.
Elongate, vertical, U-shaped spreiten burrows having distinct walls; limbs of U closely appressed and parallel. Overall structure 1 to 1.5 em in width; maximum length observed., about 10 em. Individual burrows 2.5 to 3 mm in diameter, virtually constant within a given specimen. Apertural funnels not observed (cf. Hantzschel, 1962, p. W192; 1965, p. 32), but apertures are poorly preserved among our specimens. Preserved as exichnia; interpreted as dwelling structures.
In all specimens examined, the spreiten are protrusive. In some specimens the individual U-in-U burrows are closely spaced whereas in most specimens they are not. The latter type has been designatedPolyupsilon (Howell, 1957; Hantzschel, 1965, p. 73), but we agree with Goldring (1962, p. 238) that the two structures are completely intergradational and that Poly upsilon is a junior synonym ofDiplocraterion. Specimens of Corophioides and D iplocraterion are also intergradational, but the arms of Corophioides are less constant in diameter and are not persistently parallel (Osgood, 1970, p. 314-318).
Particular configurations of these spreiten are good indicators of. depositional history (Goldring, 1962 Text-fig. 3; 1964, Fig. 1. 7). Our specimens suggest emplacement of the burrows in erodjng rather than aggrading substrates, although intense bioturbation near the top of beds (Pl. 1H) indicates that the substrates eventually became stable.
Arenicolites Fig. 2E-G; Pl. 11-L.
Vertical U-shaped burrows having distinct walls and lacking spreiten. Burrow walls in our specimens are unornamented (cf. Hantzschel, 1962, p. W183-W184 ; 1965, p. 9), but some are lined. Three species were observed; all preserved as ex.ichnia and interpreted as dwelling structures (certain species of this genus are feeding structures, e.g., Frey and Howard, 1970, Fig. 7i).
Species A (Fig. 2E; Pl. 11)-Broadly U-shaped limbs. Overall structure 4 to 6 em in width and 2.5 to 3.5 em in depth. Burrows 3 to 4 mm in diameter, more or less constant within a given specimen. Possibly intergradational with species B.
Species B (Fig. 2F; Pl. 1K, L)-Broad, shallow, crescentric limbs. Overall structure 3 to 6 em in width and 0.5 to 1.5 em in depth; burrows 3 to 10 mm in diameter, more or less constant within a given specimen. Shallowness of these burrows is attributed mainly to (1) thinness of host beds and (2) possible erosion of originally longer U-shaped burrows (cf. Dubois and Lessertisseur, 1964, Fig. 5). Suggestion of spreiten among certain specimens (Pl. 1L) is interpreted as a physio-chemical rather than a biogenic feature (see Bather, 1925; Frey and Cowles, 1969, Pl. 4, fig. 6; Osgood, 1970, p. 317).
Species C (Fig. 2G; Pl. 1J)-closely appressed, parallel limbs; diameter of burrow increases with depth. Overall structure 1.5 to 2 em across and about 2.5 em in depth; arms about 2 mm in diameter at upper ends and about 5 mm in diameter at base.
Trichophycus Fig. 2H, I; Pl. 1M-P; Pl. 2A-D; Pl. 3C, D, G; Pl. 51.
Broad, irregular U-shaped burrows, branched or unbranched, some having spreiten; walls distinct, typically ornamented with scratch marks. Two species observed. Preserved
29

as hypichnia and exichnia; interpreted as dwelling structures or combined feeding-dwelling structures (Hantzschel, 1962, p. W219, and 1965, p. 94-95; Osgood, 1970, p. 346-350). The stria-tions are thought to be scratch marks made by the claws of arthropods or polychaete&.
Various "external molds" of horizontal cylindrical burrows at Ringgold (Pl. 3F) are possibly associated with this genus (cf. Osgood, 1970, Pl. 60, fig. 7). Poorly preserved specimens of this trace fossil probably cannot be consistently distinguished from Planolites. Species A (Fig. 2H; Pl. lM-P; Pl. 30, D, G; Pl. 51)- Straight to gently sinuou or undulating, rarely branched, dominantly horizontal burrows having upturned ends ornamented with conspicuous longitudinal striations. Some specimens exhibit prominent irregularly spaced transverse constrictions (Pls. lN, 3G). Burrows 0.5 to 1.2 em in diam ter branches not necessarily 'the same diameter as parent trunk; maximum length observed, about 15 em. Our specimens do not closely resemble any known species of Trichophycus but are somewhat similar toT. uenosum (Osgood, 1970, Pl. 68, figs. 1, 3-7). Species B (Fig. 21, Pl. 2A-D)- Broad, shallow, vertically crescentric spreiten burrows having distinct walls; spreiten may branch, and some bear scratch marks . (Cf. Seilacher and Meiscbner, 1964, Fig. 11). Overall structure 15 to 40 em in length and 3 to 5 em in depth; individual urrows 2 to 3 em in diameter. This species is very similar to Teichichnus (llii'ntzschel, 1962, p. W218 1965,p. 91-92), a genus that embraces a diversity of forms (Chisholm, 1970; Frey, 1970 p. 17) and which needs taxonomic reevaluation; even scratch marks have been seen among trace fossils assigned to Teichichnus (Martinsson, 1965, Fig. 27).
Inclined Burrows and Burrow Systems Trace fossils within this category are made chiefly by mobile deposit- or suspensionfeeding animals as either dwelling or feeding structures. The feeding stru tures generally reflect (1) efficient utilization of resources (feeding space, etc.) by the animals involved and (2) reduced water agitation, permitting the settlement from suspension of sufficient organic detritus to sustain the deposit-feeding animals (Purdy, 1964). Red Mountain representatives of this "group' include Chondrites and Dictyodora (Fig. 2).
Chondrites Fig. 2J-L; Pl. 2E-I.
Small burrows branched in dendritic patterns, generally regular in appearance but lacking true symmetry~ burrow system includes vertical, horizontal, and inclined components, all more or less the same diameter within a given specimen. Fecal fillings of burrows not observed (cf. Hantzschel, 1962, p. Wl87-W188; 1965, p. 21-22). At least three species ar present ; preserved as hypichnia and exichnia, and interpreted as feeding structures (Simpson, 1957 Frey, 1970 p. 14-15; Osgood, 1970, p. 328-340). In general vertical burrow components predominate in sandstones and horizontal components at lithologic interfaces, at Ringgold; the latter are considered to be the main feeding probes, concentrated along horizons richer in organic detritus. Burrows ar xtremely d nse locally (Pl. 2H).
Species A (Fig. 2J; Pl. 2E, I)-Burrow syst m in radial fashion, the respective fronds having crude appearances of bilateral symmetry. Individual burrows 2 to 4 mm in diameter; maximum lateral spread of a single frond along a bedding plane, about 10 em.
Species B (Fig. 2K; Pl. 2F)-Burrow system without consistent pattern, but individual burrows more or less regular in appearance. Burrows 1 to 1.5 mm in diameter; maximum lateral spread of a single frond along a bedding plane, about 5 em.
30

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Fig. 2. Burrows from the Red MoWltain Formation. (Reconstructions not to scale.) A, Tigillites. B, Skolithos. C, Monocraterion. D, Diptocraterion. E, Arenicolites sp. A. F, Arenicolites sp. B. G, Arenicolites sp. C. H, Trichophycus sp. A. I, Trichophycus sp. B. J, Chondrites sp. A. K, Chondrites sp. B. L, Chondrites sp. C. M. Dictyodora. N , Palaeophycus. 0, Planolites sp. A. P, Planolites sp. B.

Species C (Fig. 2L ; Pl. 2G)-Burrow system without consistent pattern; individual burrows ll'regularly sinuous. Burrows 2 to 2.5 mm in diameter; maximum lateral spread of a single frond along a bedding plane, about 4 em.
Dictyodora Fig. 2M; Pl. 3A-C.
Complex spreiten structures consisting of irregularly winding, fence-like bands of closely j uxtaposed, gently inclined individual burrows. Spreiten frequ ntly cut t hr ough previously co nstructed parts . Individual burro ws about 1 .5 mm in diameter; structures observed are as much as 20 em across. Observed parts preserved as exichnia, although original structure (Hlintzsch el , 1962, Fig. 119.2, 4; 1965, p . 31) may also have included endichnial parts. Interpreted as a feeding structure (Se ilacher , 19617a, p. 78).
Our specimens exhibit less ' infolding" than numerous other species of.Dictyo dora (e. g. , Milller, 1962, Pis . 1-4). The repeated truncations within certain spreiten neverth less resuJ ted in very intense bi oturbation of t he substrate (Pl. 3C; cf. Ruchhol z, 1967, Pl. 4, fig. 2).
Horizontal Burrows
Horizontal burrows embrace a wide array of trace fossils. Most represent dwelling or foraging structures made by mobile predaceous animals and suspension or deposit feeders.
Unfortunately, the taxonomy of tra e fossils within this group is badly in ne d of overhaul. T he burrows o bserved by us have been assigned to two genera: Palaeop hycus and Planolites. As presently defined, however, some of the d istinctions between them are nebulous (see Hantzschel, 1962 1965; Osgood, 1970, p . 373-378 Frey and Howard, 1972). For example, the original description of Planolites specified a burrow filled with sediment having passed through the gut of the burrowing animal. This statement in effect requires an interpretation of the burrow's function and formation prior to establishing the burrow's identity. Taxonomy should of course be based upon burrow morphology and configuration, not burrow fill or animal behavior. But if such interpretations are removed from consideration, the genus is reduced to a "catch-all" taxon until su ch time as it and otherwise similar genera are restudied and redefined taxonomically.
By our conventions, Palaeophycus refers to irregularly walled subcylindrical burrows, many specimens exh ibiting the collapse of originally open cavities, and Planolites r efers simply to smooth-walled cylindrical burrows lacking collapse features (Fig. 2) . Whether or not the names are entirely appropriate, the two types of burrows are important. (Isolated parts of Trichophycus may also appear as "horizontal burrows.")
Palaeophycus Fig. 2N; Pl. 3D-F.
Straight to gently curved, horizontal, branched or unbranched burrows having distinct, lined, but somewhat in:eguJar walls. Burrows may be collapsed; elliptical in cross section, 3 to 8 mm wide and 1 t o 4 mm thick; maximum length observed, about 20 em. Preserved as hypichnia; interpreted as dwelling structures or dwelling-foraging structures (cf. Frey and Howard, 1972, Fig. 7). (See Hiintzschel, 1962, p. W208; 1965, p. 65.) Colla pse features show that parts of the burrows were preserved for a while as open tunnels, finally
giving way to weight of overlying sediment; subcylindrical parts were evjdently pas ively
filled with sediment. True branching is present but is less common than crowded burrows at first suggest (Pl. 3E).
32

Our specimens generally resemble the type species, P. tubulare (Osgood, 1970, p. 37 3-374; Pl. 76, Fig. 8; Pl. 77, Figs. 4, 7). This trace fossil is also similar to Siphonites (Gardet et al. 1956; Hantzschel, 1962, p. W215, and 1965, p. 85), which consists of collapsed and reworked dwelling tubes.
Planolites Fig. 20, P; Pl. 3H-K; Pl. 4A, B.
Straight to gently sinuous, horizontal to slightly undulatory, infrequently branched burrows having smooth, distinct walls (cf. Heinberg, 1970, Fig. 3d). Two species seem to be present, although intergradational specimens were observed. Preserved as hypichnia; interpreted as dwelling structures or combined feeding-dwelling structures (certain other species of this group are feeding structures; cf. Hantzschel, 1962, p. W210, and 1965, p. 72; Frey, 1970, p. 16-17).
Species A (Fig. 20, Pl. 3H, I)- Small subhorizontal burrows, more undulatory than sinuous; 1 to 3 mm in diameter; maximum length observed, about 8 em. Poorly
preserved specimens (Pl. 31) resemble certain other poorly preserved burrows attributed to Palaeophycus by Osgood (1970, Pl. 83, Fig. 1).
Species B (Fig. 2P; Pl. 3J, K; Pl. 4A, B)-Large horizontal burrows, more sinuous than undulatory; 4 to 15 nun in diameter; maximum length observed, about 20 em. The structure shown in Plate SF is possibly a "mold" of such burrows. Branching characteristics in some specimens (Pl. 4B) are somewhat reminiscent of Thalassinoides (Hantzschel,l962, Fig. 136.6; Frey , 1970, Fig. 3E).
Trails and Trackways
Trackways and 1;rails are ordinarily made by predaceous or mobile deposit-feeding animals traveling from place to place, whether epistratally or intrastratally. Such traces are fairly common in many thin-bedded Paleozoic sandstones, siltstones, and shales, especially in flysch-molasse sequences (e. g., Chamberlain, 1971a, b).
No trackways were observed by us, although they are probably present. Several trilobite species are known from the Red Mountain Formation (Allen and Lester, 1954), s0tne of which were capable of leaving delicate "toe prints" in sediment (cf. Martinsson, 1965 Figs. 13-19; Osgood, 1970, Pis. 72-75).
A variety of trails were encountered at Ringgold. Few were observed in abundance but are more common in certain parts of the section than in others. Some of the trails are smooth or "structureless" throughout their extent, whereas others are lobed, annulated, or otherwise patterned (Fig. 3). These traces have been assigned to Curuolithus, Gyrochorte, Cruziana, Aulichnites, and "Fraena, "the last one being another "catch-all" taxon. (Cruziana was not seen at Ringgold, but a specimen from the Red Mountain was noted elsewhere and is included here because of its potential importance.)
Curvolithus Fig. 3A; Pl. 4F.
Trilobate, sinuous to meandering, horizontal trails; the broad central lobe is flanked by narrower lateral lobes (see Heinberg, 1970, Fig. .Sa). Trails 1.5 to 1.7 em across, extending many decimeters through tortuous paths. Faint irregular, oblique annulations observed in places along lateral parts of central lobe (cf. Hantzschel, 1962, p. W189; 1965, p. 28). Sharp median ridge or groove not observed (cf. Hiintzschel, 1962, Fig. 119:3;Heinberg, 1970, Fig. 3b). Preserved as hypichnia; interpreted as combined crawling-grazing traces (cf. Bandel, 1967, p. 4 Pl. 2, Fig. 5, in discussion of similarly meandering Aulichnites).
33

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Fig. 3. Trails and miscellaneous burrows from the Red Mountain and Catheys Formations. (Reconsturctions not to scale.) A, Curvolithus. B, Gyrochorte. C, Cruziana. D, Aulichnites. E, "Fraena" sp. A. F, "Fraena" sp. B. G, "Secondary burrows" in Tigillites. H, ?Hormosiroidea, cast and mold, from the Catheys.

Gyrochorte Fig. 3B; Pl. 4C, D.
Bilobate, straight to sinuous, gently undulatory trails having a distinct median furrow; lobes consist of prominently annulated segments that are oriented slightly obliquely. Trails 3 to 6 mm wide; maximum length observed, about 10 em. Plaited or zipp~r-like "Zopf" pattern not well developed (cf. Hantzschel, 1962, p . W196-W200; 1965, p. 41). Preserved as hypichnia; interpreted as crawling traces (see Hallam, 1970, p. 190-195; Heinberg, 1970, Fig. 4a).
A poorly preserved specimen of a similar trace fossil (Pl. 4E) may be a varient of those illustrated in Plate 4C, D, but it also resembles the "Cruziana-like" trails illustrated by Osgood (1970, Pl. 65, Fig. 7; Pl. 75, Fig. 1). Our specimens also resemble Crossopodia (Hiintzschel, 1962, p. W189, and 1965, p. 27; Hattin and Frey 1969).
Cruziana Fig. 3C; Pl. 4!.
Bilobate, sinuous trail, 8 to 10 rnm in width; lobes marked by delicate, irregular, very
slightly oblique, transverse striations. Only one specimen observed (from the Red Mountain at Summerville). In this specimen the trail adjoins a bulbous enlargement surrounded by thin nanges of sediment. Preserved as a hypichnion; interpreted as a combined crawlingresting trace. The flanges evidently reflect the carapace of the trace-making animal; another such "scrape" is seen in lower part of photo.
This specimen is not typical of CT?Jziana in some respects (see Hiintzschel, 1962, p. Wl89, and 1965., p. 27-28; Crimes, 1970) but it is comparable to Cruziana made by trilobites ploughing 'head down" through the substrate (Seilacher, 1970, Fig. 4).
Aulichnites Fig. 3D; Pl. 4G, H.
Bilobate, straight to slightly sinuous trails having a prominent median furrow and smooth, unornamented lobes (cf. Heinberg, 1970, Fig. 3c). Trails 3 to 4 mm in width; maximum length observed, about 8 em. Preserved as hypichnia interpreted as crawling traces.
Our specimens. are generally smaller and have greater relative relief than t hose pictured by Hantzschel (1962, Fig.l10.4) and Bandel (1967, Pl. 2, Fig. 3). This trace fossil form is similar to Rouaultia, as discussed by Hantzschel (1962, p. W212), but that name is now considered to be invalid (Hantzschel, 1965, p. 80). Aulichnites may be intergradational with Scolicia (Hantzschel, 1962, p. W185, W215; 1965, p. 13, 83), but our specimens bear none of the main attributes of that genus.
"Fraena" Fig. 3E, F; Pl. 4J-L; Pl. 5A.
Simple sinuous trails consisting of a broad central furrow and smaller lateral ridges. Branching is rare, although the trails may cross or intersect. Preserved as hypichnia; interpreted as crawling traces.
Our specimens generally resemble those illustrated by Osgood (1970, Pl. 79, Fig. 4). Most such traces have not been given formal trace fossil names and are therefore not cited by Hiintzschel (1962, 1965, 1966). If rigorously redefined, the name Fraena (Hantzschel, 1962, p. W193; 1965, p. 36) might be useful in describing "nonlobate" trails.
Two distinct species were observed.
35

BARRIER ISLAND (BEACH I TIDAL
DELTA &TIDAL CHANNEL}

I 40 39

PRO MOLASSE PLATFORM
38

Ql'lll{

q,.q,_

c:: c:: II) ,

,

()
.....

~ ( )

,

,

,

:::.

\)

, Cb ,

, ... ... ~ 1:)
..C..,.b....c...:.;,.:.
::::- ..... 1:)
~41::
~tl)

~..""bca(\...)).~''.,.:.'.-~.:.~"_.I~:.'.l,'..l:.1"c-:~::.,')::{::,.~.-:Cu.c~(q~ .:!:.),:.:..!-:--c(\~ ~:c:~:))::...~-~,..("Cc.c....).b:'.(.:,5~...:""(~u.!.c.).'l~-toc'~(1CC,Q::)b)~.l.....t.....(Cc,.........).b.:.:...::::~.-:.:.~..1:c...:t,..::'.~:..). '--.!.((c":\.:'.:.)))..I':...-t..-.C\:cc:.'.:,:):b..::.=.".!~.'."cC.(.:.b.':

Mixed Cruriono Skolifllos assemblaQe

Cruriono assembloQe

c:.o

"'

PROMOLASSE

SLOPE

37

a

BASIN

Cruziono assemblaQe possibly with some Zoophycos components

uu_l__ 35

M==~M L3~4J~~~~~~:~~~~:~~{~~~~~~~s~;L______

L_

(BEACH,TIDAL DELTA~3-3..::-:~::-::.::.:.::.::::~:-::::.:::.: ...~.-....~~~II~=

8 WASHOVER}

~

Skolifllos assemblaQe with some Cruziono components

Fig. 4. Stratigraphic section, environmental interpretations, and distribution of trace fossils and other sedimentary parameters in lower part of Red Mountain Formation at Ringgold.

Species A (Fig. 3E; Pl. 4J, K)-Small trails, 2 to 4 mm in width; maximum length observed, about 20 em.
Species B (Fig. 3F; Pl. 4L; Pl. 5A)-Large trails, 8 to 12 mm in width; maximum length observed, about 25 em. Trails commonly exhibit subdued, irregular, transverse annulations suggestive of peristaltic movement by the trace-making animal. Where curved, ofle side of the trail is generally more pronounced than the other.
Miscellaneous Trace Fossils
The trace fossils included here are either (1) nondiagnostic specimens suggestive of distinct, important genera, for which additional specimens should be sought and studied, or (2) general kinds of trace fossils that do not require formal names.
?Asterosoma (Pl. 5B)-Large, striated, horizontally radiating, tuberform burrows; branches expand in diameter away from point of origin, (cf. Hantzschel, 1962, Fig. 111.2; MUller, 1971, Fig. 1, Pl. 1; and Chamberlain, 1971a, Pl. 29, Fig. 14.)
?Arthrophycus (Pl. 5C)- Branched horizontal burrows having more or less regular annulations, generally separated by a median groove. lf these characteristics are found
to be more distinct and consistent among additional specimens, Arthrophycus (=Harlania)
would be the correct name (see Desio, 1940, Pl. 6, Fig. 1, Pl. 7; Hantzschel, 1962, Fig. 111.3; Selly, 1970, Pl. 2b). H not the assignment might be Palaeophycus arthrophycoides (Wilckens, 1947, p. 48, PL 9, Fig. 3 ).
"Secondary burrows" (Fig. 3G; Pl. 5D)- Sinuous Planolites-like burrows, 2 to 3 mm in diameter, oriented at various angles but consistently penetrating or associated with pre-existing burrows of other kinds. Tigillites, for example, is commonly obscured by as many as three or four of these burrows and accompanying bioturbation, imparting to the overall structure an appearance similar to the basal part of Rosselia (lf"antzschel, 1962, p. W211). The secondary burrowers evidently either (1) coursed along structural weaknesses in the substrate created by the primary burrower, or (2) were scavenging or coprophagous animals that fed upon organic secretions or defecations left by the primary burrowers (cf. Frey, 1970, p. 26).
"Mineral-filled burrows" (Pl. 5E, F)-Small Plan.olites-like burrows, 1.5 to 3 mm in diameter, partly to wholly replaced by pyrite, commonly oxidized to limonite. Concentration of the pyrite was evidently related to the partial decay and reduction of organic residues left by the burrowing animal (cf. Frey, 1970, p. 25-26; 1971, p. 101-102).
TRACE FOSSILS FROM THE CATHEYS AND SEQUATCHIE FORMATIONS (ORDOVICIAN)
We have devoted relatively little attention to trace fossils in the Ordovician at Ringgold. Bioturbate textures are prominent in places, and we have observed such fossils as Chondrites, Tigillites, and Trichophycus in the Sequatchie; these are not described herein. One unusual specimen from the Catheys (collected by Michael R. Voorhies University of Georgia) warrants further study, however, and is therefore described below.
?Hormosiroidea Fig. 3H; Pl. 5G, H.
Straight, horizontal, rosary-like burrow, 14 em in length. Slightly elliptical in transverse view. Individual beads 8 to 9 mm in diameter separated by nodes 5 to 7 mm in diameter. Constrictions regularly spaced, averaging 1.3 nod s per centimeter. Nodes are aligned slightly obliquely, imparting the appearance (albeit false) of a spiral twist. Apparently preserved as an endichnion.
37

This sp imen is very similar to Honnosiroidea florentia Schu(fer (in Osg d, 1970, p. 369-370 Pl. 78, Fig. 7) ex: p that th latter exhibits small conn ting rods between b ad , rath r than simple nodes. Furthermore, no one has ye established whether the "b ads in H. florentia are truly spherical or are merely h mi pheres adjoining a bedding surfa e. Our specimen also bears some resembl n to Neonereite, wtiseria/is (Seilacher, 1960, Fig. 3: Pl. 2, Fig. 1 ), but the latter is evidently much less perfect in geometric plan.
Hormosiroidea was interpreted originally as an alga, although this interpretation is nowuntenable . Osgood (1970, caption fox Pl. 78, Fig. 7) interpreted it as a crawling trace his int rpretation is plausible, but we suggest that our simple-noded specimen might represent a feeding structure (cf. Bandel, 1967, p. 6-7).
ENVIRONMENTAL SIGNIFICANCE OF RED MOUNTAIN TRACE FOSSILS
Individually and collectively trac fossils have considerable application in paleoecology and environmental reconstrlt tion (Frey 1971 p. 104-116). 1n ur reconnaissan e study at Ringgold we have necessarily d voted mm attention to characteristic a semblages of tra e fossils and their implications than to d tail d analyses of individual traces or b dding units.
From the standpoint of characteristic assemblages of trace fossils, one of the most useful approaches is that by 8 ilacher (1967b Frey, 1971 p. 109-113 Tab! 4). This scheme is ba ed upon the obs rvation Lhat particular kinds of trace-making animal
t nd l.o congregate uncl(,!r particular sets of environmental conditions. Especially
important are sucb things as wat r currents or turbulence susp nd d or deposited food materials substrate consistency , o.>>ygenation and salinity, all of which r late (ideally at least) to water depth 0r distance from shore (e. g., Farrow, 1966).
Seilacher's scheme consists of the following "assemblages" and their salient (but intergradational) environment implications.
Scoyenia-nonmarine clastics, such as continental "red beds."
Glossifungites--stable, coherent substrates; appreciable water turbulence; generally in the littoral or shallow infralittoral zones. Such conditions are not found commonly; one example from our present Georgia coast is the ancient salt marsh mud cropping out on the oceanward side of Cabretta Island (Frey and Howard, 1969, p. 434-435, Pl. 1, Fig. 2; Pl. 4, Fig. 3).
Skolithos-unstable, shifting sediments; comparatively rapid deposition or erosion; appreciable currents or water turbulence; generally in the littoral or shallow infralittoral zones.
Cruz iana-well-sorted silts or sands, commonly thinly interbedded; moderately stable substrat s; intermediate water turbulence; generally in the infralittoral and cir alittoral zones.
Zoophycos-impure silts and sands; stable substrates; little water turbulence; generally in the circalittoral to bathyal zones, in places free of turbidites.
Nereites-pelagic sedimentation, mostly mud; substrates oridinarily stable, with virtually no water agitation, except for periodic turbiclity flows generally in the bathyal to abyssal zones, commonly developed between turbidite deposits.
Although these assemblages ar nam d for characteristic genera of trace fossils, individual genera rarely have inequivocaJ significance (Frey and Howard, 1970); varieties of both Sholitho and Zoophycos have been found in the Cruziana assemblage, for example, and Skolithos assemblages in the Pleistocene of Georgia and Florida are d minated by Ophiomorpha (Weimer and Hoyt, 1964; Frey and Mayou, 1971).
38

Furthermore, Cruziana-the crawling trace of trilobites-can hardly be dominant in the Cruziana assemblages of Mesozoic and Cenozoic rocks! Therefore, these assemblages must be approached in terms of such things as trace fossil abundances, behavioral patterns represented, and substrate interrelationships, rather than by simply consulting 'checklists' of generic names. Thus, whatever the variations among them, vertical dwelling structures predominate in the Glossi{ungites and Skolithos assemblages, and horizontal or inclined dwelling and feeding structures and crawling traces predominate in the Cruziana assemblage. Dwelling structures of any kind are rare in the Zoophycos and Nereites assemblages, which are dominated by horizontal feeding structures and grazing traces.
The Scoyenia, G/ossifungites, and Nereites assemblages definitely are not present at Ringgold. Tbe SJwlithos and Cruziana assemblages are best developed, although certain of the genera have also been reported from the Zoophycos assemblage. Based purely upon characteristics of individual genera, a typological approach to differentiating thes assemblages is indicated below; however, our final interpretation of the assemblages is illustrated in Figure 4.

TRACE FOSSILS
Tigillites Skolithos Monocraterion Diplocra terion Arenicolites sp. A Arenicolites sp. B Arenicolites sp. C Trichophycus sp. A Trichophycus sp. B Chondrites sp. A Chondrites sp. B Chondrites sp. C Dictyodora Palaeophycus Planolites sp. A Planolites sp. B Curvolithus Gyrochorte Cruziana Aulichnites "Fraena" sp. A "Fraena" sp. B

CHARACTERISTIC ASSEMBLAGES

Skolithos

Cruziana Zoophycos

X

X

X

X

X

X

X

x

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Planolites, being a "catch-all" taxon , is ambiguous in meaning; it occurs even in the Scoyenia and Nereites assemblages. Chondrite , a more distinctive trace fossil, is also a notorious facies-crossing type, although Chamberlain (1971 b, Fig. 6) attached speciaJ significance to it in the Carboniferous of Oklahoma. Dictyodora could well occur in the Zoophycos assemblage but is by no means uniquely indicative of it.
In spite of such difficulties, however, the overall aspect of trace fossil distributions at Ringgold agrees favorably with environmental conclusions drawn from sedimentological and stratigraphic data (Fig. 4). In Unit 32, for exampl , the ratio of dwelling structures to feeding structures is about 5:1, whereas in Unit 38 the ratio is about 1:1 , with crawling traces also present; these distributions of behavioral patterns might be expected under the

39

postulated current-energy regimes. A thorough study of the trace fossils, especially from the standpoint of animal-sediment relationships, etc., would undoubtedly yield more refined data.
SUGGESTIONS FOR FURTHER STUDY Our survey of trace fossils from the Ringgold road cut should obviously be followed by a comprehensive investigation, not only with respect to this classic stratigraphic section but also through the Catheys, Sequatchie, and Red Mountain Formations elsewhere in Georgia, Alabama, and Tennessee. Only with this kind of information at hand may we evaluate the real facies relationships and the behavioral and paleoecological significance of the trace fossils. Perhaps less exciting but equally important is the need for concerted studies on interrelated trace fossil genera, with a view toward resolving the numerous taxonomical ambiguities noted on previous pages.
40

REFERENCES
Allen, A. T., Jr., and Lester, J. G., 1953, Animal tracks in an Ordovician rock of northwest Georgia, in Short contributions to the geology, geography, and archaeology of Georgia: Georgia Geol. Survey Bull. 60, p. 205-214.
___ 1954, Contributions to the paleontology of northwest Georgia: Georgia Geol. Survey Bull. 62, 167 p.
Bandel, Klaus, 1967, Trace fossils from two Upper Pennsylvanian sandstones in Kansas: Univ. of Kansas Paleont. Contr., Paper 18, 13 p.
Bather, F. A., 1925, U-shaped markings on estuarine sandstone near Bleawyke: Yorkshire Geol. Soc., Proc., n. s., v. 20, p. 185-199.
Boyd, D. W., 1966, Lamination deformed by burrowers in Flathead Sandstone (Middle Cambrian) of central Wyoming: Univ. Wyoming Contr. Geology, v. 5, p. 45-53.
Chamberlain, C. K., 1971a, Morphology and ethology of trace fossils from the Ouachita Mountains, southeast Oklahoma: Jour. Paleontology, v. 45, p. 212-246.
1971b, Bathymetry and paleoecology of Ouachita geosyncline of southeastern Oklahoma as determined from trace fossils: Amer. Assoc. Petrol. Geol., Bull., v. 55, p. 34-50.
Chisholm, J. 1., 1970, Teichichnus and related trace-fossils in the Lower Carboniferous at St. Monance, Scotland: Geol. Surv. Great Britain, Bull. 32, p. 21-51.
Crimes, T. P., 1970, The significance of trace fossils in sedimentology, stratigraphy, and palaeoecology, with examples from Lower Palaeozoic strata, in Crimes, T_ P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 101-126.
Desio, Ardito, 1940, Vestigia problematiche paleozoiche della Libia: Universitil Milano, Instituto Geologia, Paleontologia, Geografia fisica, ser. P., No. 20, p. 47-92.
Dubois, Paul, and Lessertisseur, Jacques, 1964, Note sur Bifungites, trace problematique du Dlvonien du Sahara: Soc. geol. de France, Bull. (7}, VI, p. 626-634.
Farrow, G. E., 1966, Bathymetric zonation of Jurassic trace fossils from the coast of Yorkshire, England: Palaeogeogr., Palaeoclimatol., Palaeoecol., v. 2, p. 103-151.
Frey, R. W., 1970, Trace fossils of Fort Hays Limestone Member of Niobrara Chalk (Upper Cretaceous), west-central Kansas: Univ. Kansas Paleont. Contr., Article 53,41 p.
1971, Ichnology-the study of fossil and Recent lebensspuren, in B. F. Perkins (ed.), Trace fossils, a field guide to selected localities in Pennsylvanian, Permian, Cretaceous, and Tertiary rocks of Texas, and related papers: Louisiana State Univ., School Geosci., Misc. Publ. 71-1, p. 91-125.
Frey, R. W., and Cowles, John, 1969, New observations on Tisoa, a trace fossil from the Lincoln Creek Formation (mid-Tertiary) of Washington: The Compass, v. 47, p. 10-22.
Frey, R. W. and Howard, J.D., 1969, A profile of biogenic sedimentary structures in a Holocene barrier island-salt marsh complex, Georgia: Gulf Coast Assoc. Geol. Sacs., Trans., v. 19, p. 427-444.
41

1970, Comparison of Upper Cretaceous ichnofaunas from siliceous sandstones and chalk, western interior region, U.S.A., in Crimes, T. P., and Harper, J . C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 141-166.
1972, Georgia coastal region, Sapelo Island, U.S.A.: Sedimentology and biology. VI. Radiographic study of sedimentary structures made by beach and offshore animals in aquaria: Senckenbergiana maritima, v. 4 (in press).
Frey, R. W., and Mayou, T.V., 1971, Decapod burrows in Holocene barrier island beaches and washover fans, Georgia: Senckenbergiana maritima, v. 3, p. 53-77.
Gardet, Gustave, et al., 1956, Sur un Problematicum du Lias infe'rieur de la Haute-Marne: Siphonites heberti de Sap.: Soc. G~ol. de France, Bull. (6), VI, p. 997-1000.
Goldring, Roland, 1962, The trace fossils of the Baggy Beds (Upper Devonian) of North Devon, England: PaHi.ont. Zeitschr., v. 36, p. 232-251.
1964, Trace-fossils and the sedimentary surface in shallow-water marine sediments, in van Straaten, L. M. J. U. (ed.), Deltaic and shallow marine sedimentation: Develop. Sedimentology, v. 1, p. 136-143.
Hallam, Anthony, 1970, Gyrochorte and other trace fossils in the Forest Marble (Bathonian) of Dorset, England, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 189-200.
Hallam, Anthony, and Swett, K., 1966, Trace fossils from the Lower Cambrian Pipe Rock of the northwest Highlands: Scottish Jour. Geol., v. 2, p. 101-106.
Hlintzschel, Walter, 1962, Trace fossils and problematica, in Moore, R. C. (ed.), Treatise on invertebrate paleontology, Pt. W, Miscellanea: Geol. Soc. Amer. and Univ. Kansas Press, p. W177-W245.
1965, Vestigia Invertebratorum et Problematica; Fossilium Catalogus. I: Animalia, pars 108, 142 p.
1966, Recent contributions to knowledge of trace fossils and problematica, in Rhodes, F. H. T., etal., Treatise on invertebrate paleontology, Part W, Conodonts, conoidal shells, worms, trace fossils: comments and additions: Univ. Kansas Paleont. Contr., Paper 9, p. 10-17.
Hattin, D. E., and Frey, R. W., 1969, Facies relations of Crossopodia sp., a trace fossil from the Upper Cretaceous of Kansas, Iowa, and Oklahoma: Jour. Paleontology, v. 43, p. 1435-1440.
Heinberg, C., 1970, Some Jurassic trace fossils from Jameson Land (east Greenland), in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 227-234.
Hertweck, GUnther, 1970, The animal community of a muddy environment and the development of biofacies as effected by the life cycle of the characteristic species, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 235-242.
1972, Georgia coastal region, Sapelo Island, U.S.A.: Sedimentology and biology. V. Distribution and environmental significance of lebensspuren and in-situ skeletal remains: Senckenbergiana maritima, v. 4 (in press).
42

Howard, J.D., and Elders, C. A., 1970, Burrowing patterns of haustoriid amphipods from Sapelo Island, Georgia, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 243-262.
Howell, B. F., 1943, Burrows of Skolithos and Planolites in the Cambrian Hardyston Sandstone at Reading, Pennsylvania: Publ. Wagner Free Inst. Sci., v. 3, p. 3-33.
1945, Skolithos, Diplocraterion, and Sabellidites in the Cambrian Antietam Sandstone of Maryland: Publ. Wagner Free Inst. Sci., v. 20, p. 33-40.
1957, New Cretaceous scoleciform annelid from Colorado: Palaeontological Soc. India, D. N. Wadia Jubilee No., v. 2, p. 149-152.
Martinsson, Anders, 1965, Aspects of a Middle Cambrian thanatotope on Oland: Geol. Foreningens I Stockholm Forhandlingar, v. 87, p. 181-230.
1970, Toponomy of trace fossils, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 323-330.
MUller, A. H., 1962, Zur Ichnologie, Taxiologie und Okologie fossiler Tiere: Freiberger Forschungshefte, Heft C 151, p. 5-49.
1971, Zur Kenntnis von Asterosoma (Vestigia invertebratorum): Freiberger Forschungshefte, Heft C 267, p. 7-17.
Osgood, R. G., Jr., 1970, Trace fossils of the Cincinnati area: Palaeontographica Americana, v. 6(41), p. 281-444.
Purdy, E. G., 1964, Sediments as substrates, in Imbrie, J., and Newell, N.D. (eds.), Approaches to paleoecology: New York, John Wiley & Sons, p ..238-271.
Ruchholz, Kurt, 1967, Zur Ichnologie und Fazies des Devons und Unterkarbons im Harz: Geologie, v. 16, p. 503-527.
Seilacher, Adolf, 1960, Lebensspuren als Leitfossilien: Geologisch. Rundschau, v. 49, p. 41-50.
1964a, Biogenic sedimentary structures, in Imbrie, J., and Newell, N.D. (eds.), Approaches to paleoecology: New York, John Wiley & Sons, p. 296-316.
1964b, Sedimentological classification and nomenclature of trace fossils: Sedimentology, v. 3, p. 253-256.
1967a, Fossil behavior: Scientific American, v. 217, p. 72-80.
1967b, Bathymetry of trace fossils: Marine Geology, v. 5, p. 413-428.
1970, Cruziana stratigraphy of "non-fossiliferous" Palaeozoic sandstones, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 447-476.
Seilacher, Adolf, and Meischner, D., 1964, Fazies-Analyse im PaUiozoikum des OsloGebietes: Geologisch. Rundschau, v. 54, p. 596-619.
Selley, R. C., 1970, Ichnology of Palaeozoic sandstones in the southern desert of Jordon: a study of trace fossils in their sedimentologic context, in Crimes, T. P., and Harper, J. C. (eds.), Trace fossils: Geol. Jour., Special Issue 3, p. 477-488.
Simpson, Scott, 1957, On the trace-fossil Chondrites: Geol. Soc. London, Quart. Jour., v. 112, p. 475-499.
43

Weimer, R. J., and Hoyt, J. H., 1964, Burrows of Callianassa major Say, geologic indicators of littoral and shallow neritic environments: Jour. Paleontology, v. 38, p. 761-767.
Wilckens, Otto, 1947, PaHiontologische und geologische Ergebnisse der Reise von KohlLarsen (1928-29) nach SUd-Georgien: Abhandl. Senckenberg. Naturf. Gesellschaft, No. 474, 75 p.
44

Plate 1. Trace fossils from the Red Mountain Formation at Ringgold. A, B. Tigillites, vertical exposures. C,D. Skolithos, vertical exposures. E,F. Monocraterion, vertical exposures. G,H. Diplocraterion, vertical exposures. Shallow, intense bioturbation at top of H. I- L. Arenicolites; I and J vertical exposures, K and L sole views. I. Species A. J. Species C. K, L. Species B. M - P. Trichophycus sp. A, sole views.
46

Plate 1 - Trace Fossils 47

Plate 2. Trace fossils from the Red Mountain Formation at Ringgold. A-D . Trichophycus sp. B. A. Bottom of spreite bearing radial scratch marks (scale in em). B. Cross section through spreite (scale as in A). C. End view of specimen having three branches. D. Latero-ventral view of specimen in C, illustrating upward turn of top branch and oblique, elongate scratch marks. E - I. Chondrites, sole views. E, I. Species A. F. Species B. G. Species C. H. Profusion of Chondrites and other small burrows on ripple marks.
48

Plate 2 - Trace Fossils 49

Plate 3. Trace fossils from the Red Mountain Formation at Ringgold. A - C . Dictyodora, sole views. Sequence of photos illustrates progressively more intense bioturbation. (Specimen in A collected by Norman King:) Trichophycus sp. A in middle and lower part of C. D- F. Palaeophycus, sole views. D. Slightly collapsed burrow, crossed at left by Trichophycus sp. A. E. Partly to wholly collapsed burrows, some branched. F. Collapsed burrow, near penny. Large burrow at bottom is "external mold" of either Trichophycus or Planolites; such "molds" seen commonly at Ringgold. G. Trichophycus sp. A, sole view. H - K. Planolites, sole views. H, I. Species A; poorly preserved and slightly iron stained in I. J, K. Species B.
50

J

K

Plate 3 - Trace Fos~ih
51

Plate 4. Trace fossils from the Red Mountain Formation at Ringgold and Summerville. A, B. Planolites sp. B, sole views. Those in A associated with a priel (=washout) cast.
c,n. Gyrochorte, sole views.
E. Gyrochorte-like trail, sole view. F. Curuolithus, sole view.
G,H. Aulichnites, sole view. I. Cruziana, sole view (scale in inches). From Summerville.
J- L .. "Fraena ", sole views. J, K. Species A. L. Species B.
52

53

Plate 5.
A. B. c. D.
E, F. G,H.
I.
J.
K.

Trace fossils from the Red Mountain and Catheys Formations at Ringgold. "Fraena" sp. B, sole view. ?Asterosoma, sole view. ?Arthrophycus, sole view. "Secondary burr~<>ws," probably in Tigillites; vertical exposure. "Mineral-filled" burrows, possibly Planolites sp. A; sole views. ?Hormosiroidea, ?sole view. From the Catheys. G. Burrow cast. H. Burrow mold. Trichophycus sp. A, showing upward-turning ends of burrows (cf. Fig. 2H); sole view.
Tigillites, sole view. ?Sabellarifex; these irregular burrows otherwise resemble Skolithos. Vertical exposure.

54

c
Plate 5 -Trace Fossils
55

SEDIMENTARY ENVIRONMENT OF THE ARMUCHEE CHERT,
NORTHWEST GEORGIA
W. E. Nunan Department of Geology University of North Carolina at Chapel Hill
Abstract
The Lower Devonian Armuchee Chert was deposited on a shallow marine shelf as thick accumulations of sponge spicules and spiculitic micrite. Chertification of the rocks occurred very' early in diagenesis, commencing immediately after deposition. Processes of chertification followed two courses which were related to the unstable opaline silica of the sponge spicules. "Felted" mats of sponge spicules inverted from opal into chalcedony and microcrystalline quartz, while the spiculitic micrite was repla ed by silica from enriched interstitial waters to form chert. The source for the silica in these rocks is attributed to the solution and inversion of abundant spicules "freed" upon death of profuse sponge populations on the shelf. Rosenfeld's (1954) suggestion that the Chattanooga Shale served as a source for the silica in the Armuchee rocks is disputed.
Introduction
The Armuchee Chert is a body of siliceous sedimentary rocks which is present in a limited area in the folded Appalachians of northwestern Georgia and northeastern Alabama (Fig. 1). Exposures of the Armuchee occur on many of the ridges between the Cartersville Fault southwest of Cedartown (Cressler, 1970) and Taylor Ridge up to the vicinity of Maddox Gap in the northern part of Walker County, Georgia. In Alabama, the formation is exposed on the southeast flank of Bogan Mountain in Cherokee County.
The Armuchee is Onesquethaw in age (Nunan and Lipps, 1968) and is considered by many to be a facies equivalent of part of the Frog Mountain Sandstone of Alabama (Hayes, 1902; Rosenfeld, 1954; Kiefer, 1970; Cressler, 1970; Nunan, 1971). In northwestern Georgia, the Armuchee unconformably overlies the Middle Silurian Red Mountain Formation. The chert is everywhere overlain by a thin section of Frog Mountain Sandstone except possibly in some areas of Polk County. In this area, Cressler (1970) suggested that the Frog Mountain is present only locally as thin sand interbeds within the Armuchee and that the chert is in direct contact with Mississippian rocks. The upper part of the Armuchee is interbedded with the Frog Mountain at most exposures (Nunan, 1971).
The purpose of this report is to suggest a possible origin for the silica of the Armuchee Chert and to propose a sedimentary environment for the accumulation of the sediments.
The origin of the many varieties of chert has been much disputed in the past. Several schools of thought have developed concerning the origin of the silica and the time of introduction of silica into siliceous rocks. Some workers have contended that many cherts were formed by the direct precipitation of silica into siliceous oozes on the ocean floors and were subsequently lithified. Others have suggested organic processes participate in the sequence of chert formation. Elsewhere t he evidence suggests that limestones have been replaced by silica leacl'led from adjacent sedimentary units, for example,overlying volcanic ashes (Allen and Lester, 1957).
In 1946, Bramlette discussed possible processes for the alteration of diatomaceous sediments into chert. One of the mechanisms is the dissolution of relatively unstable, abundant, opaline skeletons of diatoms and the re-precipitation of the silica in the more stable mineralogical varieties of chalcedony and microcrystalline quartz in close proximity to the source diatoms. He observed that remains of siliceous skeletal elements of microfossils in rocks as old as pre-Cambrian are commonly preserved only in cherty rocks.
57

Jackson

I \
(
(
/
~ )
-.~;._~ ~ ~
_ __ ~ \~ _}

~ ~0
<:;;/"

0)_: D ::----."'>- .--- -
,..r

_ ..

I I

Cherokee

IJ

Floyd

.

I

- -'___,;:.."- --LI --,

I

. _/L~ - Po lk ,~_ .

,_...} I

/

_,-J

....-. - - - I

Haralson

1

1 Cleburne
-\

I

~

~

/

OUTCROP TRACE OF DEVONIAN STRATA

1..0

-N-

OUTCROP AREA OF

~

. ARMUCHEE CHERT

0

10

20

30

40

MILES

0

10 20 30 40 50 60

I

I

I

I

I

I

I

KILOMETERS

NUNAN 1972
Fig. 1. Location map of outcrop pattern of Devonian strata in northwestern Georgia and northeastern Alabama (after Kiefer and Dennison, 1971; and Cressler, 1970).

The origin of the silica in the Armuchee Chert was investigated by Rosenfeld (1954) who attributed it to leaching of the overlying Chattanooga Shale and subsequent replacement of an original sandy rock by the silica. I present evidence that argues for another hypothesis on the origin of the Armuchee Chert.
Stratigraphy
The Armuchee Chert was named by Hayes (1902) for exposures near the community of Armuchee, Georgia in northern Floyd County. He believed that the chert represented an offshore sediment equivalent in age to the Frog Mountain Sandstone of Alabama.
The lower contact of the Armuchee Chert is apparently paraconformable to the underlying Middle Silurian Red Mountain Formation (Oliver and others, 1961). The contact is sharp and marked by an abrupt change in lithology from the sandstone and shale of the Red Mountain into the light grey chert of the Armuchee.
The upper contact of the Armuchee Chert is variable in position due to an intertonguing relationship with the Frog Mountain Sandstone (Nunan, 1971). The Armuchee is conformably overlain by a few meters of Frog Mountain at all exposures known to me. Cressler (1970) suggested that there are places in Polk County, Georgia, where the Armuchee may be in direct contact with Mississippian rocks.
The Frog Mountain Sandstone is unconformably overlain by the Chattanooga Shale of Late Devonian age (Conant and Swanson, 1961) in most of the area northwest of the Rome Fault. It is possible that the Floyd Shale rests on the Frog Mountain Sandstone in parts of southwestern Floyd County with the Chattanooga Shale being absent (Nunan, 1971 ).
In Polk County, the Chattanooga is not present and Cressler (1970) showed the Frog Mountain and Armuchee to be in contact with the Fort Payne Chert and the Floyd Shale.
The Armuchee Chert is variable in thickness throughout the outcrop area. The thinnest sections are along Taylor Ridge near Gore, Georgia, (approximately 7.8 meters thick), on Dick Ridge (about 4.7 meters thick) in the gap through which West Armuchee Creek flows (Nunan, 1971), and in Polk County where it is about 2 meters thick near Elders Lake (Cressler, 1970). The thickest sections are on Horn Mountain at Calhoun Gap (21.5 meters), along the northern end of Lavender Mountain near O'Brian Gap (15.6 meters), and on Turkey Mountain (15.5 meters). The chert is interbedded in its upper portions with tongues of the Frog Mountain Sandstone at most exposures northwest of the Rome Fault (Nunan, 1971).
At several localities in the lower part of the Armuchee, the bedding in the chert is accentuated by thin, lense-shaped partings of sandstone and shale. Another very characteristic feature is the almost ubiquitous occurrence of knobby protuberances on bedding surfaces (Figs. 2A and B).
The sandstone-chert relationships described by Nunan (1971), the equivalent ages of at least parts of the two formations (Kiefer, 1970; Nunan and Lipps, 1968) and the reported occurrence of chert beds in the lower part of the Frog Mountain near Tannehill, Alabama (Kiefer, 1970) are strong evidence that the Armuchee Chert and Frog Mountain Sandstone are facies equivalents of each other.
Petrography
The chert rocks that comprise the Armuchee are recrystallized spiculites and chert which replace spiculitic micrites. The spiculites consist of "felted" masses of sponge spicules that have inverted from original opal chalcedony and microcrystalline quartz (Figs. 3A and B). The spicules are predominantly of the monaxon variety, or perhaps broken fragments of other types, but a few fish hook (Fig. 4), club (Fig. 5), cross (Fig. 6), and other shapes are present. Central canals are preserved in many of the spicules (Figs. 4 and 5).
Fine quartz sand and silt account for as much as 20 percent of some of the spiculites. Dolomite rhombs, replaced by silica, may comprise as much as 25 to 30 percent of the rock. These are commonly coated with limonite. Many of the thin-sections have scattered, rhomb-shaped holes which may be molds of dolomite crystals that have been removed during telogenetic weathering. Glauconite grains account for as much as 10 percent of the rock in places. Fossils, other than sponge spicules, are rare in the spiculites.
59

Fig. 2A. Cross-section of a sponge (?)individual showing influence on the bedding surface which is towards the top of the photograph.
Fig. 2B. "Knobby" protuberances common on bedding surfaces of the Armuchee Chert (two of these knobs have been planed off) .. 60

The silicified micrites are of two types, fossiliferous micrite (Figs. 6 and 7) and burrowed micrite (Fig. 8). Fine quartz sand and silt comprise up to 10 percent of these rocks. Glauconite grains may account for as much as five percent but is usually less. Fossils include bryozoan (Fig. 7), gastropod, and brachiopod fragments . Sponge spicules are scattered throughout (Figs. 6 and 7), but the original content may be higher than is now recognizable. Faint rod-shaped forms that may be inverted spicules are present in many of them (Fig. 7).
Chertified dolomite rhombs occur in the micrites, and they are usually limonite stained. In the fossiliferous micrites, these rhombs may be as large as 0.2 mm (Fig. 7). In the bioturbated micrites, rhombs are much smaller and are concentrated around peripheries of burrowed material (Fig. 8).
Paleogeography
The Armuchee Chert occurs in a northeast-southwest belt which semi-parallels the ' 0" isopach that Kiefer (1970) determined for the Frog Mountain. It is along strike with the Jemison Chert in Olin ton County Alabama, which occupies a position just south of where Kiefer (1970) shows the Frog Mountain to be absent, but also just south of where he shows the smallest grain sizes to be present in the Frog Mountain. The age of the Jemison is inaccurately known, but it is possible that it is contemporaneous with the Armuchee (Dennison, personal communication~ 1972). Between the Jemison and the Armuchee outcrop areas, Kiefer shows a significant thickening of the Frog Mountain (Fig. 10).
The author suggests that the Armuchee and Jemison cherts were deposited as shal1ow water shelf sediments, possibly contemporaneously, and that the extreme thicknesses of Frog Mountain Sandstone between the two chert bodies may be due to a rather weak delta development by the streams carrying debris off of the Nashville Dome to an Early Devonian sea.
Diagenesis
Diagenesis of the primary sediments which eventually became the rocks of the Armuchee Chert began almost simultaneously with sedimentation. Disaggregated opaline sponge spicules, disarmed of their protective organic coverings, would be very unstable in the water into which they fell. Solution may have begun almost immediately after death consequently increasing the amount of silica in the water.
Many of the spicules probably escaped solution by entrapment in micrite or by concentration of the spicules by the action of currents (Figs. 3A and 3B). In these cases, alteration of the opaline spicules to chalcedony and microcrystalline quartz (Fig. 9) became a process of inversion, analogous to the aragonite-calcite inversion so common in the shells of many invertebrate groups. Bramlette (1946) postulated a similar sequence of events for the evolution of siliceous rocks in the Monterey Formation in California.
Silicification of the micrite and their contained fossils probably result d from replacement of the calcite by silica from silica-enriched interstitial water. Fossils in the matrix have indistinct boundaries indicating that they may have been partially djssolved during the process of silicification (Fig. 7).
Scattered dolomite rhombs replaced portions of the siliceous sediments. Iron may have been introduced, or concentrated, at this time because most of the relict dolomite rhombs are rimmed with limonite . There is evidence that partial dolomitization occurred both prior to and after silicification, with perhaps more than one period of chel'tification.
Rosenfeld (1954) thought the silica in the Armuchee rocks was due to leaching of the overlying Chattanooga Shale, and concentration in the underlying Armuchee by replacement of an. original sandstone rock. There are a number of arguments against such a method for deriving the silica and formation of the cherty rock.
First, there is the ubiquitous presence of sponge spicules in the Armuchee rocks, thus providing a source for the silica in the primary sediments. Second, if the Armuchee
61

Fig. 3A. "Felted" mat of recrystallized sponge spicules, crossed nicols . O'Brian Gap, spiculite facies.
Fig. 3B. "Felted" mat of recrystallized sponge spicules, plain light. Calhoun Gap, spiculite facies. 62

Fig. 4. Fish hook-shaped spicule and associated spicules floating in a silicified silty micrite. Crossed nichols. Bogan Mountain, Alabama, micrite facies.
Fig. 5. Club-shaped spicule, crossed nicols, same thin-section as Figure 4 . 63

Fig. 6. Cross-shaped spicule, plain light. Same specimen as Figure 4.
Fig. 7. Bryozoan fragment, chertified dolomite rhombs, and several spicules in a chertified micrite matrix, plain light. Micrite facies. 64

was originally a sandstone, why would such leaching and replacement action effect only that sandstone, and not the underlying Red Mountain Formation (which is quite sandy) or the Armuchee's lateral equivalent, the Frog Mountain Sandstone? Third, there is no evidence that the rocks in the Armuchee Chert were ever sandy sediments. Fourth, the Chattanooga is not present in Polk County, and could not have been the source for the silica in that area.
Sedimentary Environment
Petrographic evidence suggests that the Armuchee Chert was deposited as thick concentrations of disaggregated sponge spicules and as layers of spiculitic micrite on a relatively shallow shelf. The sponges from which the spicules were derived must have been very abundant in ~he shallow sea. Bryozoans, brachiopods, gastropods, and other benthic sessile organisms lived on the ocean floor. While trilobites (Nunan and Lipps, 1968) crawled around scavenging for food, burrowing organisms disrupted many of the sediments.
Stratigraphic relationships of the Armuchee with the Frog Mountain Sandstone also make a shallow water interpretation for the sedimentary environment tenable. The Frog Mountain sands were considered by Kiefer (1970) to have been deposited in shallow marine water along the south edge of the Nashville Dome. Intertonguing sandstone and chert beds in the upper part of the Armuchee, and sandstone and shale lenses in the lower part of the formation strongly suggest that environments of deposition of the Frog Mountain and the Armuchee were contiguous and closely related.
Summary The Lower Devonian Armuchee Chert was deposited on a shallow marine shelf a few kilometers seaward from the strand line. The sediments were originally thick accumulations of sponge spicules and associated spiculitic, fossiliferous micrite. The terrigenous clastic content constituted less than 20 percent of these sediments and consisted of fine quartz sand and silt.
Chertification of the spiculitic sediments probably followed a course of inversion of opal to chalcedony and microcrystalline quartz soon after deposition. The micritic sediments were silicified shortly after deposition by a process of replacement of the micrite by silica derived from silica rich, interstitial water. The source of the silica in this water is due to an increase in silica in the ocean waters as a result of solution of "freed" sponge spicules in the immediate area, and entrapment of these silica rich ocean waters by the sediments at the time of sedimentation.
Dolomite, in the form of scattered rhombs, replaced as much as 25 percent of the rocks. Most of these rhombs were subsequently replaced by chert.
Acknowledgments
This study grew out of a study of the stratigraphy of the Lower Devonian rocks of northwestern Georgia which was completed as a Master's thesis as part of the requirements for a degree from Emory University. My special thanks go t o Dr. H. R. Cramer for introducing me to the Armuchee and for his patience and per~uasion as my advisor throughout my work on these rocks. The following people also deserve a note of appreciation for their help and encouragement : Dr. P. K. Birkhead , Clemson University, for first calling my attention to the presence of sponge spicules in these rocks; Dr. Lewis Lipps, Shorter College, for supplying many paleontologic specimens; Drs. J. M. Dennison and D. A. Textoris, University of North Carolina, for encouragement and many enlightening discussions; and Dr. Textoris, T. M. Gathright, Jr., Virginia Division of Mineral Resources, and L. B. Howell, University of North Carolina for photographic assistance. Dr. Textoris critically reviewed the manuscript. Special thanks are due my wife, Elizabeth, for clerical assistance and moral support during this study.
65

Fig. 8. Chertified bioturbated micrite, negative print. The white areas are concentrations of limonite-coated silicified dolomite rhombs. Plain light. O'Brian Gap.
Fig. 9. Chalcedony and microcrystalline quartz. Crossed nicols. O'Brian Gap, micrite facies. 66

TENNESSEE
I

\t.._,

I
t- '

_ _r-'

I----,

_J'-.._ --

0~
JEMISON
SEDIMENTS

'0' ISOPACH LINE OF FROG MOUNTAIN SANDSTONE
COARSEST FROG MOUNTAIN SEDIMENTS
ARMUCHEE SEDIMENTS

0

10 20 30 40

0 10 20 30 40 so 60

I

I

I

I

I

I

KILOMETERS

PALINSPASTIC BASE

NUNAN 1972

Fig. 10. Paleogeographic setting of the Armuchee sediments. (Frog Mountain and Jemison data after Kiefer, 1970; base after Kiefer and DE<nnison, 1971).

67

References Allen, A. T., and Lester, J. G., 1957, Zonation of the Middle and Upper Ordovician strata
in northwestern Georgia: Ga. Geol. Survey Bull. 66, 110 p. Bramlette, M. N., 1946, The Monterey Formation of California and the origin of its
siliceous rocks: U.S. Geol. Survey Prof. Paper 212, 57 p. Conant, L. C., and Swanson, V. E., 1961, Chattanooga Shale and related rocks of central
Tennessee and nearby areas: U. S. Geol. Survey Prof. Paper 357, 91 p. Cressler, C. W., 1970, Geology and ground-water resources of Floyd and Polk Counties,
Georgia: Ga. Geol. Survey Inf. Circ. No. 39, 93 p. Hayes, C. W., 1902, U.S. Geol. Survey Atlas, Rome Folio, no. 78. Kiefer, J.D., 1970, Pre-Chattanooga Devonian stratigraphy of Alabama and northwest
Georgia: Ph. D. thesis, Univ. of Illinois at Urbana-Champaign, 175 p. _ _ and Dennison, J. M., 1971, Palinspastic map of Devonian strata of Alabama and
northwest Georgia: Amer. Assoc. Petroleum Geologists Bull., v. 56, p. 161-166. Nunan, W. E., 1971, Stratigraphy of the Lower Devonian rocks of northwestern Georgia:
Master's thesis, Emory University, 78 p. _ _ and Lipps, E. L., 1968, A Devonian fauna from the Frog Mountain Sandstone,
Floyd County, Georgia: Ga. Acad. Sci. Bull., v. 26, p. 71. Oliver, W. A., and others, 1967, Devonian of the Appalachian Basin, United States: in
International Symposium on the Devonian System, Vol. 1, Alberta Soc. of Petroleum Geologists, Calgary, Canada, p. 1001-1040. Pettijohn, F. J., 1957, Sedimentary rocks: New York, Harper and Brothers, 2nd Ed., 718 p. Rosenfeld, S. J., 1954, An investigation of the relationship between the Armuchee Chert and the Frog Mountain Sandstone of Devonian age: Ga. Acad. Sci. Bull., v. 12, p. 31-32.
68

DEPOSITIONAL ENVIRONMENTS OF THE TUSCUMBIA-MONTEAGLE-FLOYD INTERVAL IN NORTHWEST GEORGIA AND SOUTHEAST TENNESSEE
by
William H. McLemore U. S. Forest Service Atlanta, Georgia
Mississippian rocks of northwest Georgia and southeast Tennessee are exposed in three distinct areas (Figure 1): (1) along the flanks of Sand and Lookout-Pigeon Mountain in Dade, Walker, and Chattooga Counties, Georgia and Marion and Hamilton Counties, Tennessee; (2) in a series of more or less interconnected synclines between Taylor Ridge-Whiteoak Mountain and the Rome-Saltville Fault in Floyd, Chattooga, Walker, Gordon, Whitfield, and Catoosa Counties, Georgia and Hamilton and Bradley Counties, Te1messee; and (3) in several isolated areas in Polk County, Georgia. These rocks can be divided into two distinct facies; the westernmost is predominantly limestone, whereas the eastern facies is mainly shale with intercalated beds of limestone and sandstone.
The change in facies from carbonates to clastics is most pronounced in one stratigraphic interval, the Tuscumbia-Monteagle-Floyd Interval. This paper discusses the depesitional environments of the sediments of the Tuscumbia-Monteagle-Floyd Interval.

Tuscumbia Limestone and Lower Tongue of Floyd Shale

Description

Description

The Tuscumbia Limestone of northwest Georgia and southeast Tennessee probably represents the Warsaw, Salem, and St. Louis formations of the upper Mississippi Valley. St. Louis equivalents definitely occur in the study area (Butts, 1948); but Warsaw and Salem rocks, known in the Tuscumbia of northern Alabama, have not been recognized in Georgia. Thin oolitic and echinoderm grainstones and packstones occur in the lower Tuscumbia of the study area, but no paleontological
evidence has been found that could be used to determine whether these rocks are Warsaw-Salem equivalents. The contact with the underlying Fort Payne Chert is exposed on Georgia Highway 143, 1.3 miles southeast of Trenton, and appears to be conformable. The upper boundary with the Monteagle Limestone is placed at the uppermost cherty mudstone below which there are no thick oolitic limestones. Where exposures are good, the uppermost Tuscumbia bed is typically characterized by the presence of large "cannonball" chert nodules.

In the western facies, the Tuscumbia is a light gray to bluish gray, thick bedded wackestone and dark gray mudstone. Chert is common. Interbedded with the limestone is pearl gray, cherty, finely crystalline dolostone. Calcite pseudomorphs after gypsum are recognizable in dolomitic mudstones of the upper Tuscumbia. The thickness of the Tuscumbia in the study area varies between 125 and 225 feet. To the south and southeast, the Tuscumbia is replaced by the lower tongue of the Floyd Shale. The shale iri the lower tongue of the Floyd is composed mainly
of illite with subordinate kaolinite.

The most striking fossils in the Tuscumbia are the Jithostrotionoid corals, and the most common ones are either the polygonal corallites of the common species of Lithostrotionella or the cylindrical corallites usually referred to as Lithostrotion proliferum. The latter, however, are not confined to the Tuscumbia. Crenulated beds of mudstone similar to beds described by McQueen, Hinchey, and Aid (1941) have been tentatively attributed to algal origin. Fenestrate bryozoa are the most abundant fauna at some exposures.

69

~
N
I
'
' . . SCALE IN MILES
Figure 1. Outcrop Map of Mississippian Rocks in Northwest Georgia and Southeast Tennessee. 70

Depositional Environment
Field and petrographic data for the Tuscumbia Limestone indicate that the formation is a transitional unit from the tidal flat environment of the Fort Payne to the Bahaman BankFlorida Bay environment of the Monteagle Limestone.
The environment in which the Fort Payne Formation and much of the Tuscumbia were deposited must have been one where large quantities of both silica and dolostone could accumulate. It must also have been an environment compatible with shallow marine organisms and algal mats.
The environment of dolomite deposition is no longer controversial (Friedman and Sanders, 196'1), and most syngenetic and early diagenetic dolostones are considered to have formed by the reaction of hypersaline brines with normal marine limestones. Such hypersaline brines are forming today in the Persian Gulf and in the Bahamas. The dolomite occurs in tidal flats where alternate flooding and drying together with capillary movement provide a continual supply of magnesium from sea water (Illing, 1.964).
The source of silica in the Fort Payne and Tuscumbia is at present unknown . T. M. Chowns (personal communication 1972) has suggested that sponge spicules are the ultimate source. Blatt, Middleton, and Murray (1972) note that organisms are the source of silica for most post-Precambrian cherts. Peterson and von der Borch (1965) report an interesting association of algae, carbonates, and inorganic silica pr cipitation in some Australian ephemeral lakes that seasonally develop pH values greater than 10 because of active photosynthesis by indigenous algae. At these high pH values, detrital quartz grains and possibly clay minerals are corroded, saturating the lake waters with respect to amorphous silica. The algal activity fluctuates seasonally and, in addition, the lake basins are dry part of the time. The decrease in pH and the decrease in volume of solvent (water) that result from these changes cause the silica to precipitate. Peterson and von der Barch suggest that much of the nodular chert in carbonates formed in this manner.
The depositional environment of the lower tongue of the Floyd Shale will be discussed with the main portion of the.Floyd Shale in the next section.
Monteagle Limestone and Floyd Shale
Description
The Monteagle Limestone (Ste. Genevieve Limestone and Gasper Formation of older Georgia literature) conformably overlies the Tuscumbia Limestone and can be distinguished by its oolitic and non-cherty character. Lithologically the Monteagle is a light gray or bluish gray, medium-grained, echinoderm or oolitic grainstone or packstone. Locally bryozoan limestones occur. Although mudstones, dolostones, and cherty beds occur in the Monteagle, they are rare and usually quite thin.
The Monteagle extends farther south than the Tuscumbia (Figure 2) and thus divides the Floyd Shale into an upper and lower tongue. The lower tongue is correlative with the Tuscumbia. East of Whiteoak Mountain and Taylor Ridge, the upper tongue of the Floyd Shale overlies the Monteagle, and appears to be recipr cally related in thiclmess. However, the combined thickness of the two formations increases to the south. The Monteagle disappea1s in Floyd County, and almost the entire sequence of rocks between the Fort Payne Chert and the Hartselle Formation is composed of fine clastics.
Fossils recognized in the Monteagle of the study area include: Platy crinus penicillus, Campophyllum gasperense, and Productus inflatus. A wide variety of bryozoa, corals, blastoids, crinoids, pelecypods, gastropods, and trilobites were found in the Monteagle,
71

A

Base of Pennsylvanian

t:.

Pennington Fmn.

!DRJ1J II_ f: iii!i!ii iiiBOn86r.Janie~t~n~ !:ii:i:!::i :ITITl i!j j

!iiiII

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--

uscumbio Lfmestone

1
c=zF- ort

Payne

Fmn.

1 f 1 \ i:;;i@ ;~ s..._--~~ ; :T?r:!>,.~

-o-

1,000

N.......
~ ~ (9

-~
(D

0 .....LI--:M7:ii:le:;s-- I

0

25

Figure 2. Cross-Section A-A'. Cross-Section of the Tuscumbia-Monteagle-Floyd Interval in northwest Georgia and southeast Tennessee. Section A-A' is expanded 25 miles to accomodate thrust faulting.

but they were not identified by genus. Lycopsid type plant fossils (Edward Stanley, personal communication, 1969) were found by the author in the uppermost Monteagle Limestone two miles east of Ringgold, Ga.
The Floyd Shale is predominantly a brown to black, fissile, silty, carbonaceous, calcareous shale with intercalated beds of siltstone and limestone. lllite is the main clay mineral, with some kaolinite(+ 10%). Fossils are generally rare, and those that do occur are generally fenestrate bryozoa.
Depositional Environment
Because of numerous similarities (oolites, lime muds, dolomitization, cross-bedding, carbonate banks and reefs, etc.) between the rocks of the Monteagle and modern sediments of the Bahama Banks and Florida Bays, the Monteagle is interpreted to have formed in a similar environment. Many of the Mississippian carbonate rocks have direct analogues in the modern sediments.
Ferm and Ehrlich (1967) say that the Floyd Shale probably represents deltaic front and pro-delta deposits . The aut hor is in agreement wit h t his in terpretation , but would like to qualify it somewhat. The great thickness and lack of shallo w water sedimentary structures (ripple marks , mud cracks, etc.} see m to indicat e t hat the Floyd was deposited rat her rapidly in deeper waters . The carbonaceous material and paucity of f ossils appear t o indicate that the general dep ositional environment was unfavorable to bent honic life and probably reducing. A modern environment showing several similar features is the offshore area of the Texas and Louisana Gulf Coast.
References
Blatt, H., Middleton, G., and Murray, R., 1972, Origin of sedimentary rocks: Prentice-Hall, Inc., Englewood Cliffs, N. J., 634 p.
Butts, C., and Gildersleeve, B., 1948, Geology and mineral resources of the Paleozoic area in northwest Georgia: Georgia Geological Survey Bull. 54, 176 p.
Ferm, J. C., and Eh rlich, R., 1967 , Petrology and stratigraphy of the Alabama coal fields, in Ferm, J. C. , Ehrlich , Rober t , and Neathery , T. C., ed ., A field guide to Carboniferous detrital rocks in north ern Alabama : Geol. Soc. America Guidebook for the 1967 Annual Field Trip of the Coal Division, University, Alabama, p. 11-15.
Friedman, G. M., and Sanders, J. E., 1967, Origin and occurence of dolostones, in Chilingar, G. V., Bissell, H. J., and Fairbridge, R. W., ed., Carbonate Rocks, Volume I: Elsevier, Amsterdam, p. 267-317.
Tiling, L. V., 1964, Penecontemporary dolomite in the Persian Gulf: Am. Assoc. Petrol. Geologists, v. 48, p. 532-533.
McQueen, H. S., Hinchey, N. S., and Aid, K., 1941, The Lincoln Fold in Lincoln, Pike, and Ralls Counties, northeastern Missouri: Kansas Geol. Soc. Guidebook, 15th Ann. Field Conf., p. 99-110.
Peterson, M. N. A., and von der Borch, C. C., 1965, Chert : Modern inorganic deposition in a carbonate-precipitating locality: Science, v. 149, p. 1501-1503.
73

ITINERARY 74

ROAD LOG - FIRST DAY

Mileage

Between Points

Cumulative

0.0

0.0

0.3

0.3

0.4

0.7

0.3

1.0

6.4

7.4

1.6

9.0

8.3

17.3

Remarks . Leave the Albert Pick Motor Inn, Chattanooga,
Tennessee on U.S. 41, driving south. Chattanooga Creek. Turn right onto 26th Street. Turn onto the entrance ramp of 1-24 South. Junction with 1-75. Head south on 1-75. Georgia-Tennessee boundary. Stop 1 - Ringgold road cut.

STOP ONE -RINGGOLD ROAD CUT (T. M. Chowns and Robert W. Frey)

The road cuts on 1-75 at Ringgold expose strata from Middle Ordovician (Chickamauga Limestone) to Mississippian (Floyd Shale) in age and provide the best section of the Silurian Red Mountain Formation in the state. Part of the section is scheduled as a geologic monument (Chowns, 1971).

The Red Mountain Formation is one of the principaLridge formers in the western part of the Valley and Ridge Pwvince. Here, at Ringgold Gap, the formation_dips at about 15 and strikes approximately N 10 E. The Silurian cuesta is in two parts with a main escarpment to the west,.capped by the Whiteoak Mountain Sandstone, and a lesser escarpment to the east, consisting of alternating sandstones and shales at the top of the formation (Fig. 1 ).

The complete section is given in Figure 4 and in the appendix, but may be summarized as follows:

Red Mountain Formation (968')
Sequatchie Formation (184')
Catheys Formation

Chattanooga Shale

4th road cut (east)

Alternating sandstones and shales (21 7 ) - 3rd road cut

i ll Red shales with thin sandstones (288')- 2nd road cut Gray shales with thin ironstones (158 ') - gap Massive crossbedded, red, quartz sandstones (73') Alternating sandstones and shales (232') Gray shales, siltstones and limestones- 1st road cut (west)
Shellmound Member (104') Fine grained red sandstones-Inman-
Leipers Member (80')

Alternating fossiliferous limestones and

shales (188' seen)

75

CHATTANOOGA SH. MISSISSIPPIAN

RED MOUNTAIN FM .

SEQUATCHIE FM.
CHICKAMAUGA LS.

!jjjj!jj!f!f!;::- ~::;-::"?:!j:::~ :=- ..- --~ /~ ~ ~~~z~

INTERSTATE 75
I

\0

r--.

I

ONE

MILE

I

VERTICAL EXAGGERATION 2

E::::)Aiternating Sandstone
I:::::::J Shale Facies

r:-1 Red Shale
L:_JFacies

D Gray Shale Facies

r:D Qua~tz Sandstone
WillFoc1es

~ Gray Sequatchie
~Facies

~Red Sequatchie
~Facies

Figure 1. Geologic cross-section of strata exposed in the Ringgold road cuts.

-..J -..J
Figure 2. Alternating limestones and shales of the Catheys Formation, Ringgold (scale in feet).

00
r-

Figure 3. Contact between the Catheys Formation and the Sequatchie Formation, Ringgold; a) Reddened catheys limest<:mes; b) Catheys limestone interbedded with red siltstones; c) Sequatchie red siltstones with rolled bryozoan fragments; d) Unfossiliferous Sequatchie red siltstones (scale in feet) .

Figure 4. Red and gray calcareous siltstones and fine grained sandstones of the red Sequatchie facies , Ringgold (scale in feet).

Figure 5. Red and gray mottled calcareous siltstone from the red Sequatchie facies, Ringgold.
Figure 6. Graded bedding and dessication breccias from the red Sequatchie facies, Ringgold. Note vertical cracks are joints, not dessication cracks. 79

Figurro 7 . Ca s Lof !llll de rete ks in fine grnin ed calcaTe u us sands Lone from Uw rPcl Seq l.l<lfchie facies, Hin ggol cl.
2:n Fi gure 8 . Laminated calcarPOUS siltstone~; from the gray s(~quul.chi -' [ac ic:; (l l<'d llll!TilH 'r
f{inggold.
80

The uppermost beds of the Red Mountain F ormation are repeated by a small fault between road cuts three and four. Beyond lie the Chattanooga Shale, Maury Shale, and Lavender Shale Member of the Fort Payne Formation, but they are poorly exposed.
The argillaceoU$ limestones of the Catheys Formation (top of Chickamauga Supergroup) are interpreted as shallow marine sediments. They are richly fossiliferous with brachiopods, bryozoans, bivalves, gastropods, orthoceratids and trilobites (Fig. 2). They are overlain abruptly, but gradationally, by unfossiliferous red beds of the Inman-Leipers Member (Figs. 3, 4 and 5). The combination of graded beds (Fig. 6), ripple marks, mud cracks (Fig. 7) and desiccation breccias indicates deposition in the supratidal zone (high-tidal-flat).
Gray shales, calcareous siltstones and limestones of the Shellmound Member represent lagoon, intertidal (low-tidal flat) and tidal channel environments, respectively. Notice the fining-upward cycles, poorly sorted calcarenites passing upward into laminated calcareous siltstones (Fig. 8), which record the migration of tidal channels across the tidal flats. Beds of ferruginous sandstone which occur in the lagoonal beds at the top of this interval contain small hematite-chamosite ooids. Brachiopods and bryozoans (sometimes in growth position in tidal channels) are the main faunal elements. The brachiopod Lepidocyclus? capax (Conrad), a Richmondian index fossil, occurs abundantly in the uppermost limestone bed.
The base of the Red Mountain Formation is placed immediately above the highest of these ferruginous beds. The basal Silurian beds are interpreted as barrier island sediments which record the beginning of the Silurian marine transgression. Trace fossils including Skolithos, Tigillites, Monocraterion, Diplocraterion, Trichophycus, Arenicolites and Chondrites are common in the washover sandstones of the littoral facies.
The overlying alternating sandstone and shale beds (Figs. 9, 10) are promolasse slope and platform sediments deposited by westward flowing turbidity currents. Check for graded bedding (Fig. 11), Bouma sequences (Fig. 6) and sole markings (poorly developed) in the turbidites. Also watch for sandstones with massive load casts, which mark the position of the
slope break near the top of the tmit. This is the horizon at which the turbidity currents are
believed to have been initiated. The main trace fossils in the turbidites are Trichophycus, Planolites, Dictyodora and Chondrites.
Above are medium to coarse grained, hematitic, crossbedded sandstones representing beach, tidal channel and tidal delta deposits of a regressive barrier island (Fig. 12). Torn up clasts of lagoonal shale are common in the tidal delta sands.
The lagoonal deposits which lay behind this barrier are obscured in the interval between the first and second cuts. However, they may be examined across the valley to the north along U.S. 41. Thin ironstone seams are exposed at this locality and were formerly marked in small strip mines.
Beyond the gap is a transgressive barrier sandstone followed by more platform and slope deposits which will not be visited on the trip.
Fossils occur fairly commonly in the Red Mountian Formation but they are usually poorly preserved. Brachiopods and crinoid columnals are most abundant but bivalves, gastropods, nautiloids, tentaculitids, trilobites and corals also occur.

2.3

19.6

3.5

23.1

0.2

23.3

0.8

24.1

5.7

29.8

0.9

30.7

4.6

35.3

0.8

36.1

0.8

36.9

0.6

37.5

3.7

41.2

Continue on I-75 (south) Intersection of I-75 and U.S. 41. Turn off interstate,
across bridge, and back on I-75 heading north.
Turn right onto Ga. 151. Turn right onto Ga. 2. Downtown Ringgold. Turn left on Ga. 151 and
proceed northwards.
Georgia-Tennessee boundary Stop sign. East Brainerd Road.
Stop sign. Railroad crossing. Junction with U. S. 11. Turn left. Junction with I-75. Turn right (north). Stop 2. Green Gap road cuts.
81

Figure 9. Thin bedded distal turbidites (bed number 35, Red Mountain Formation, Ringgold). Scale in feet.
Figure 10. Thin to medium bedded turbidites, more proximal than figure 9. (Bed number 37, Red Mountain Formation, Ringgold). Scale in feet.
82

83

Figure 12.

Prom lasse platform and barr ier sandstones. The top of the main road cut, Ri_nggo ld; a) Medium to thick bedded platform sandstones (h<'d nun1lwr 38); b) Cross bedded beach sandstone (bed number i39); c) Tidal channel and tidal cl Ita sandstonr~s (bed numb r 40 l.
84

STOP TWO.,.... GREEN GAP, WHITEOAK MOUNTAIN (Richard E. Bergenback and T. M. Chowns)
Green Gap, Whiteoak Mountain lies approximately sixteen miles to the north, along strike, from Ringgold Gap and road cuts on I-75 expose the same stratigraphic interval between the Catheys Formation and the Chattanooga Shale. The following section is modified from Milici and Wedow (in preparation).

Sequatchie Formation

Chattanooga Shale
Red Mountain Formation
{ Red and gray clacareous shales and siltstones with massive limestones near top. - Shellmound Member. Fine grained red calcareous sandstones- Inman-Leipers Member
Catheys Formation

612'
110' 121'
50' seen

The purpose of this stop is to examine the facies changes which have taken place in the

Sequatchie Formation. Three main differences may be recognized when this section is com-

pared with the Ringgold section.



1. The lnman-Leipers Memberis thicker.

2. Red supratidal beds extend upwards into the lower half of the Shellmound

Member replacing gray intertidal and lagoonal beds seen at Ringgold.



3. Massive Fernvale calcarenites and calcirudites, interpreted as barrier island

sediments, replace part of the upper lagoonal shale unit of the Ringgold

section.

5.3

46.5

19.2

65.7

6.7

72.4

0.2

72.6

0.1

72.7

1.1

73.8

End of First Day.

Continue on I-75 (north) Junction of U.S. 11 and U.S. 64 with I-75. Turn
off Interstate, go over bridge, and turn back on 1-75 heading south. Junction of I-75 and 1-24. Turn right (west) onto 1-24. Turn right at Lookout Mountain Exit. U.S. 11, 64, and 41. Stop sign. Go straight ahead. Stop light. Turn left. Albert Pick Motor Inn.
85

ROAD LOG -SECOND DAY

Between Points 0.0

Mileage

Cumulative 0.0

2.7.

2.7

1.5

4.2

2.9

7.1

1.3

8.4

Remarks .
Leave Albert Pick Motor Inn, Chattanooga, Tennessee on U .S. 41, driving north.
Lookout Creek
Junction with 1-24 we~t. Turn left
Georgia-Tennessee boundary.
Stop 3. Hooker road cuts.

STOP THREE -HOOKER ROAD CUTS (T. M. Chowns)

The 1oad cuts on 1-24 in the vicinity of Hooker, Georgia, were measured and -compiled

by Milici (Milici and Wedow, in Preparation) to give an almost complete section of. the Upper

Ordovician. The section is as follows:

'

Shellmound Formation
(92')
Lei.pers Limestone
Inman Formati on

Red Mountain Formation
Red and gray calcarenites and calcirudites (Femvale Facies) - exit ramp from I-24 west onto Ga. 299
Gray calcaxeous shales and siltstones with limestone { interbeds (Gray Sequatchie Facies)- road cuts
south-west of Ga. 299 exit
Gray, biotmbated, massive silty limestone - quarry on Ga. 299 immediately east of 1-24
Gray, laminated, calcareous siltstones and silty limestones (Gray Sequa'tcbie Facies with minor red beds) - at base of quarry. Section incomplete

38' 54' 38'
8' seen

86

A comparison between this section and the previous sections at the same stratigraphic interval {Green Grap and Ringgold Gap) illustrates the magnitude of t he facies changes within the Upper Ordovician and the diachronous nature of the red Sequatchie Facies. .A-part from a minor group of red beds in the immediate vicinity , supratidal sediments are absent.
The stop will be made specifically to examine the top of the Leipers Dimestone and the lagoonal shales at the base of the Shellmound. It is these lagoonal beds which contain the Hooker ironstone seams (Chowos, 1970). Notice the discoidal (flaxseed) shape of the chamosite ooids and their hematite pseudomorphs, and compare the distribution of chamosite (green) and hematite with the degree of current sorting.
Fossils which may be collected include branching and encrusting bryozoans, brachiopods, bivalves (including Modiolopsis in life position) and gastropods.

Mileage Between Points Cumulative

1.3

9.7

7.1

16.8

2.3

19.1

Continue on I-24 west.
Junction with I-59 south. Continue on 1-24 west (towards Nashville).
Junction with U. S. 64. Turn off interstate, over bridge and back on I-24 east.
Stop 4. Paris Hollow road cuts.

STOP FOUR- PARIS HOLLOW SECTION (William H. McLemore)
The Mississippian succession in northwest Georgia consists of two distinct lithosomes, a carbonate lithosome to the north and a terrigenous shale lithosome to the south and east. In general, the system thickens to the south and southeast as one passes from shallow water platform carbonates into deeper water promolasse clastics derived from active borderlands to the east, south and west. (Fig. 2)
The next three stops {4, 5, 6) have been chosen to give an overview of the main lithofacies and formations which comprise the carbonate lithesome, while stops 7 and 8 illustrate the transition to the shale lithesome.
87

(Stop 4) (Stop 5) (Stop 6)

The following stratigraphic summary is taken from McLemore (1971).

north

south

93-390' 120-475'
20- 70' 200-550'
125-225' 100-200'

Pennington Formation

Bangor Limestone

Hartselle Formation

Monteagle Limestone

Floyd Shale

Tuscumbia Limestone

Fort Payne Formation with Lavender Shale Member in south

180' 260' 180-450'
700-1000' (Stop 7 & 8)
200'

The Bangor Limestone at Stop 4 consists of dolomitic skel tal wackeston s and skeletal packst ones with beds of dark gray silty shale. The carbonate rocks appear t o h ave been deposited in a shallow marin environment with pr ograding tidaJ.flat-islan d complexes, locally capp d by calich soil zo nes (Bergen back et al., 1972, p. 1 7 ). Such aliches develop as a result of subaerial weat hering in semiarid climates, t hrough the evaporation of ground-water and precipitation of mineral sal ts at the top of the soil profil . The shale units probabl y represent
the feather edges of Pennington , shore-face shale facies further north in Tenn ssee (see Ferro , etal. 1972, p. 6).

4.6
15.9 0.4 0.6 1.2 0.4 1.7
0.6

23.7
39.6 40.0 40.6 41.8 42.2 43.9
44.5

Continue on I-24 east.
Junction of 1-24 with I-59. Head south on 1-59 (towards Birmingham)
Rising Fawn Exit. Turn left (east).
U. S. 11. Turn right.
Junction with Ga. 189. Turn left.
Old mine office of Southern Iron and Steel Co . Turn left from pav~ment on to dirt road; still Ga. 189.
Outcrop of Chattanooga Shale and Fort Payne Formation.
Stop 5. Johnson Crook Section. Park on dirt road heading off to right and walk uphill to beginning of exposures.

88

STOP FIVE- NEWSOM GAP ROAD, JOHNSON CROOK (William H. McLemore)
The strata which will be examined at this stop include the upper part of the Tuscumbia Limestone, the Monteagle Limestone and the Hartselle Formation up to the base of the Bangor Limestone.
The Tuscumbia Limest011 consists of cherty skeletal wackestones and packstones with cherty dolostones and calcareous mudstones. Like the Bangor limestones these beds appear to represent shallow marine or lagoonal deposits with intervals of intertidal and supratidal sediment. Calcite pseudomorphs after gypsum have been recognized in some of supratidal dolostones and crenulated algal mats also occur.
The Monteagle Limestone consists of skeletal, i.ntraclastic and oolitic packstones and grainstones with occasional beds of dolomitic, skeletal wackestone. Some beds may be crossbedded or show scour channels. Overall the formation contains less chert and dolostone, and appears to have been deposited in more open-water, higher energy environments than either the Bangor or Tuscumbia lim stones. The oolite shoals of the Bahama Platform immediately spring to mind as an analog for many of the limestones encountered in these beds.
The shallow marine platform carbonates of the Monteagle Limestone mark the culmination of the Mississippian transgression in Georgia and Tennessee.

1.3

45.8

2.0

47.8

0.8

48.6

1.2

49.8

3.0

52.8

1.6

54.4

3.7

58.1

2.7

60.8

0.6

61.4

2.2

63.6

Hartselle Formation. End of Stop Five.
Crossroads at top of mountain, go straight ahead. Junction with Ga. 143. Turn right.
Junction with Ga. 157. Go straight ahead. Road Quarry. The Monteagle-Tuscumbia contact is
exposed in this quan-y. Note the Large "cannonball" chert nodules. These are common at the top of the Tuscumbia. Junction with Ga. 193. Go straight ahead. Junction with Ga. 341. Turn right (south). Railroad crossing. Junction with Ga. 193. Turn left (east). Stop 6. Dug Gap, Pigeon Mountain.

89

STOP SIX -DUG GAP, PIGEON MOUNTAIN (T. M. Chowns)

The road and railroad cuts on the west side of Pigeon Mountain leading into Dug Gap

expose a fairly complete section between the Lebanon Limestone of the Chickamauga Super-

i group (see Stop 5 in Milici and Smith, 1969) and the Mississippian Tuscumbia Limestone. The complete sequence of strata is as follows:

Mississippian

Tuscumbia Limestone - cherty skeletal limestones

6' seen

and dolostones.

Fort Payne Formation - cherty dolomitic limestones.

115'

Devonian

Chattanooga Shale - black shale and mudstone

25'

Silurian

Red Mountain Formation -alternating sandstones, shales and limestones with ironstone seams

472'

Ordovician

Sequatchie Formation -red and gray calcareous shales

{

and siltstones Chickamauga Limestone

.

160'

Only the Chattanooga Shale and Fort Payne Formation will be examined in detail on this trip, but the Silurian sections in the vicinity of Estelle are well worth a visit. The iron ore workings at Estelle were formerly the most extensive in the state and this is one of the few places where the ironstones and associated strata may still be seen.
The black color and bituminous, pyritic nature of the Chattanooga lithosome, coupled with its sparse fauna, show that it was deposited in a restricted euxinic environment, while its widespread distribution over the southeastern part of the North American craton indicates a shallow landlocked sea.
The Chattanooga Shale, like other incompetent horizons in the Paleozoic succession in the Valley and Ridge Province, is frequently involved in low angle thrust faults (e.g. at Ringgold Gap, Taylor Ridge and Green Gap, Whiteoak Mountain). Evidence of bedding plane thrusting is particularly well displayed here in Dug Gap. Whereas the Red Mountain Formation and the upper part of the Chattanooga Shale and overlying formations are underformed, the lower part of the Chattanooga Shale is extensively crumpled and brecciated (Fig. 13). Note the abundant polished and slickensided shale fragments derived from the breccia zones.
This road cut also offers a rare opportunity to examine the Fort Payne Formation in its unweathered state. The base is marked by 21h feet of gray, silty, glauconitic shale representing the Maury Shale Member (Fig. 14), which may be examined at the waterfall. Above, the formation consists of light gray, cherty, dolomitic, bryozoan wackestones and mudstones with occasional interbeds of crinoid - bryozoan packstone. Small quartz geodes which occur in the more dolomitic beds contain relict anhydrite replaced by quartz and calcite (Chowns and Elkins, 1971; and in preparation). They provide a key to the depositional environment of the Fort Payne lithosome and similar cherty dolomitic limestones which are recurrent in the Mississippian of the Eastern Interior (Chowns, 1972). This facies finds a recent analog in the Sabkha measures of the arid tidal flats of the Persian Gulf, where the evaporation of saline marine groundwaters leads to the precipitation of anhydrite nodules within dolomitized carbonate sediments.
Silica for the formation of chert and replacement of the anhydrite nodules appears to have been derived from sponge spicules which occur abundantly in this facies.
The stages involved in the conversion of these rocks to the more familiar cherty saprolite may be examined at the top of the cut.
The base of the Tuscumbia Limestone, a bryozoan crinoid packstone with occasional ooids and endothyroid foraminifera, may be examined on the north side of the road at the top of the hill.

90

Figure 13. Contact between Red Mountain Formation (Srm) and Chattanooga Shale (De) at Dug Gap, Pigeon Mountain. Crosses indicate areas of crumpled strata. Survey rod is six feet long.

Figure 14.

Contacts between the Chattanooga Shale (De), Maury Shale (Mm) and Fort Payne Formation (Mfp) at Dug Gap, Pigeon Mountain. Note the buckling of the Chattanooga Shale beneath bedding thrust -f. Survey rod is six feet long.

91

6.0

69.6

12.6

82.2

4.5

86.7

5.1

91.8

1.0

92.8

Continue on Ga. 193. Junction with U. S. 27 in LaFayette. Turn right (south). Triangle Shopping Center in Trion, Ga. Downtown Summerville. Continue on U. S; 27. Base of Mississippian. Stop 7. Gore section.

STOP SEVEN -GORE SECTION (William H. McLemore)
South of Gore the Mississippian section begins to thicken and carbonates are replaced by clastics. These changes are particularly marked at the horizons of the Tuscumbia and Monteagle Limestones which pass into the Floyd Shale.
The rocks exposed in the drainage ditch at this stop are argillaceous limestones and calcareous shales equivalent to the Monteagle Limestone. Above are interbedded shales and sandstones of the upper tongue of the Floyd Shale (510') and beyond, about a mile to the south east, the Hartselle Formation (180') is exposed in a low linear ridge.

4.3

97.1

0.7

97.8

1.2

99.0

6.8

105.8

4.7

110.5

1.0

111.5

1.4

112.9

Continue on U. S. 27. St. Clair Grocery. Bear right. Storey Lumber Co. Turn right (south). Big Texas Valley Road. Turn right.
Fork in road. Bear right. Fork in road. Bear left. Dead End. Turn lef~.
An old road bears off to the right. Park here, disembark from the bus and walk down the road for several hundred feet. Stop 8, Judy Mountain section.

92

I.
STOP EIGHT -JUDY MOUNTAIN SECTION (William H. McLemore)
This stop is, or is very close to, the type locality of the Floyd Shale. The formation has an estimated thickness of 1487 feet and consists of brown to black, unfossiliferous, silty, calcareous and carbonaceous shales with siderite mudstone nodules. The Tuscumbia and Monteagle Limestones are gone.
The top of the succession in this area is formed by the Hartselle Formation which caps Judy Mountain to the southeast.
93

REFERENCES Bergen back, R. E., Horne, J. C., and lnden, R. F., 1972, Depositional environments of
Mississippian carbonate rocks at Monteagle, Tennessee in Ferm, J. C., Milici , R. C., and Eason, J. E., Carboniferous depositional environments in the Cumberland Plateau of southern Tennessee and northern Alabama: Tenn. Div. Geol. Report of Investigations, 33, p. 14-18. Chowns, T. M., 1970, A chamosite-hematite oolite from the Sequatchie Formation in northwest Georgia (abs.): Georgia Acad. Sci. Bull. 28, p. s19. ___ 1971, Stratigraphy of the Ordovician and Silurian section exposed in the Ringgold road cuts: a proposed geological monument (abs.): Georgia Acad., Science Bull. v. 29, p.129.' ___ 1972, Recurrent Sabkha facies in the Mississippian of the Eastern Interior, U.S.A. (abs.): Geol. Soc. Amer. Abs. with Programs, v. 4, p. 65. Chowns, T. M., and Elkins, J. E., 1971, Origin of geodes from the Fort Payne Formation, Woodbury, Tennessee (abs.): Geol. Soc. Amer. Abs. with Programs, v. 3, p. 303. ___ (in preparation), The origin of quartz geodes and cauliflower cherts through the silicification of anhydrite nodules. Ferm, J. C., Milici, R. C., and Eason, J. E., 1972, Carboniferous depositional environments in the Cumberland Plateau of southern Tennessee and northern Alabama: Tennessee Div. Geol. Report of Investigations 33, 32 p. McLemore, W. H., 1971, The geology and geochemistry of the Mississippian System in northwest Georgia and southeast Tennessee: unpublished Ph. D. Thesis, Univ. of Georgia. Milici, R. C., and Smith, J. W., 1969, A guide to the stratigraphy of the Chickamauga Supergroup in its type area: Georgia Geol. Surv. Guidebook. Milici, R. C., and Wedow, H., (in preparation), Upper Ordovician and Silurian stratigraphy in Sequatchie Valley and parts of the adjacent Valley and Ridge, Tennessee.
94

APPENDIX 95

SECTION OF ORDOVICIAN AND SILURIAN STRATA EXPOSE.Q IN ROAD
CUTS ON I-75 AT RINGGOLD GAP, GEORGIA (UNIVERSAL TRANSVERSE
MERCATOR GRID; ZONE 16FP; 674,000 E; 3,854,000 N)
Measured by T. M. Chowns and J. Hatten Howard III
Chattanooga Shale:
Exposed in fourth road cut.
Red Mountain Formation:
47 Interbedded SHALE and fine grained SANDSTONE. Shale greenish gray with some reddish partings. Sandstones very thin to medium bedded, laminated; greenish gray to gray; dolomitic. Crinoidallenses with Atrypa?, Dalmanella? and Calymene. Forms rusty weathering strata on dip slope of third road cut; repeated by fault in fourth cut beneath Chattanooga Shale.
46 Interbedded SHALE and fine grained SANDSTONE with intervals of SHALE. Shales medium to dark gray becoming greenish gray on weathering. Some partings of reddish shale in top 45 feet. Sandstones very thin to thick bedded, laminated and graded; medium to light gray; dolomitic and occasionally hematitic. Sole markings mainly tool marks and burrows; occasional crinoidallenses with Campophyllum, Poleumita, and straight nautiloids.
45 SHALE with intervals of interbedded fine grained SANDSTONE. Shales reddish gray. Sandstones reddish gray, very thin to medium bedded; laminated. Sole markings include flute marks, tool marks and burrows. Fauna of crinoids and Eocoelia. Exposed at base of third cut and at the very top of second cut; partly obscured.
44 SHALE with minor sandstones. Shales reddish gray. Sandstones fine grained reddish gray very thin to thin bedded, occur at four intervals. Fauna includes crinoids and Eocoelia. Forms upper half of second cut.
43 Fossiliferous SANDSTONE. Fine to medium grained, light gray, weathering in shades of yellowish orange. Thin to thick bedded. (Pentamerus, Eocoelia and other brachiopods).
42 Interbedded SHALE and fine grained SANDSTONE. Shale medium gray. Sandstone light gray, mainly very thin to thin bedded at base becoming medium bedded above. Lowest part of unit obscured at base of second cut.
41 SHALE with minor sandstones and thin hematite ironstones near the base. Shales mediurn gray, unfossiliferous. Sandstones fine grained, light gray, very thin to thin bedded. Interval largely obscured between first and second cuts but partially exposed to the north on Hwy. 41.
40 SANDSTONES with minor shale interbeds. Sandstones consist of interbeds of coarse grained, very thick bedded, dusky red hematitic sandstone; with fine to medium grained, thin to medium bedded, greenish gray sandstone. Hematitic sandstones are cross-bedded, gray sandstones plane-bedded with ripple marks, shale pebble conglomerate, and Arenicolites burrows. Interbeds of medium gray shale occur in association with the gray sandstones. Unfossiliferous except for trace fossils.
39 SANDSTONE; fine to medium grained, very thick bedded, massive, dusky red and hematitic; shows cross-bedding on weathering. Fossiliferous in places (Phacops, bryozoans, crinoids and brachiopods).
97

36.8
180.3 136.2 113.8
13.2 25.0 157.6
59.3 13.5

38 Interbedded SHALE and fine to medium grained SANDSTONE, increasing in importance towards top. Shales dark gray, more fissile than below. Sandstones very thin to thick bedded, laminated; light gray to reddish gray; sometimes fossiliferous and with shale pebbles. (Brachiopods, bryozoans, bivalves, gastropods, tentaculitids, crinoids.) Sole markings include tool marks, flutes, load casts and burrows (Planolites, Trichophycus, Chondrites, Monocraterion, Gyrochorte, "Fraena "). Base of unit marked by medium bedded sandstone with prominent load casts
37 Interbedded SHALE and fine grained SANDSTONE. Shales dark gray. Sandstones very thin to medium bedded, light gray, dolomitic, laminated, and graded. Sole marks include grooves, flutes, tool marks and burrows (Planolites, Trichophycus, Dictyodora, Chondrites) . Fossils rare (Dalmanella?)
36 IRONSTONE consisting of hematite replaced fossil fragments (crinoids, bryozoa, brachiopods); dusky red, sandy, dolomitic.
35 SHALE with intervals of interbedded SHALE and SANDSTONE. Shale dark gray. Sandstones subordinate, very thin to thin bedded, light gray, dolomitic, laminated, occasionally ripple marked. Sole marks include tool marks, flutes and burrows (Planolites, Trichophycus, Chondrites). Fossils include Leptaena, Dalmanella?, gastropods, tentaculitids and crinoids. Base of unit marked by thick bedded sandstone (2-3ft.).
34 SHALE with minor very thin sandstone interbeds. Shale dark gray, sandstones light gray.
33 BIOTURBATED sandy SHALE and shaly SANDSTONE with very thin to thin interbeds of laminated dolomitic sandstone. Light to medium gray. Burrows include Trichophycus and Diplocraterion. Fossiliferous in places.
32 SHALE with minor sandstone interbeds. Shales medium to dark gray, sandy. Sandstones very thin to medium bedded, medium to light gray, dolomitic . Grain size varies from fine to coarse with granules of phosphatized skeletal debris. Much of sediment is bioturbated with Trichophycus, Arenicolites, Skolithos, Tigillites and other trace fossils. Body fossils rare.

Total Red Mountain Formation

967.9

Sequatchie Formation (measured along second terrace)
Shellmound Member:
31 SHALE very dusky red to dark greenish gray with some thin lenses and interbeds of fine to medium grained sandstone. Contains phosphatic granules and other skeletal debris (crinoid columnals, brachiopods, and rolled bryozoan fragments). Indigenous fauna includes Modiolopsis in life position. Top of unit is marked by three thin dolomitic, hematitic sandstones.
30 SHALE dark gray with thin lenses of dolomitic sandstone . Pyritic in places.
29 BIOTURBATED sandy SHALE and hematitic, shaly SANDSTONE. Shales medium dark gray, pyritic; sandstone thick bedded medium to coarse grained, very dusky red with phosphatic granules and hematitic ooids.
28 SHALE; dark greenish gray, sandy.

98

80.6 46.3
0.1
67.9 1.9
19.6
16.2
14.1 15.4
3.5 2.1

27 BIOTURBATED sandy SHALE and shaly SANDSTONE; medium greenish

gray to medium dark gray, dolomitic. Sandstones thick bedded, pyritic and

very poorly sorted with granules of quartz and phosphate. Base marked by

phosphatized limestone pebbles.

11.3

26 BRACHIOPOD CALCARENITE and SHALE; calcarenite shaly, cobbly

weathering, light gray; shale medium gray, calcareous. Unit is very fossili-

ferous containing abundant Lepidocyclus? capax (Conrad), with

Raphinesquina, Hebertella and bryozoans.

3.4

25 SHALE; very dusky red to dark greenish gray.

2.4

24 BRYOZOAN CALCARENITE; medium light gray, dolomitic, sandy.

Fossiliferous with brachiopods, bryozoa and crinoids.

0.9

23 CALCAREOUS SILTSTONE, very fine grained SANDSTONE and SHALE;

interbedded and interlaminated, medium to medium light gray, dolomitic.

Contains dessication breccias and lenses of skeletal debris (L.? capax, other

brachiopods and bryozoa).

6.4

22 CALCAREOUS SANDSTONE, and SILTSTONE; interbedded and inter-

laminated, grayish red to medium light gray, dolomitic. Sandstones very

fine grained ripple marked. Generally unfossiliferous but with occasional

lenses of bryozoan debris. Base marked by convoluted load casts.

8.1

21 BRYOZOAN CALCARENITE; medium gray, dolomitic. Cross-bedded and

wedging into beds above and below. Skeletal debris mainly comminuted

bryozoa and brachiopods.

1.4

20 CALCAREOUS SILTSTONE, very fine grained SANDSTONE and SHALE;

interlaminated, medium to medium light gray, dolomitic. Ripple marked.

2.7

19 BRYOZOAN CALCARENITE; medium light gray, dolomitic.

0.3

18 CALCAREOUS SILTSTONE, very fine grained SANDSTONE and SHALE;

interlaminated, medium to medium light gray, dolomitic.

0.3

17 BRYOZOAN CALCARENITE; thick bedded, medium to medium light gray,

dolomitic. Contains bryozoan colonies in positions of life.

4.0

16 CALCAREOUS SILTSTONE, very fine grained SANDSTONE and SHALE;

interbedded and interlaminated, medium to medium light gray, dolomitic.

Bryozoa occurs in lenses. Base marked by two sandstone horizons with load

casts.

2.4

15 BRYOZOAN CALCARENITE; medium gray, vuggy and dolomitic. Skeletal

remains include bryozoa and brachiopods.

0.4

14 CALCAREOUS SILTSONTE, very fine grained SANDSTONE and SHALE;

interbedded and interlaminated, medium to medium light gray, dolomitic,

and fossiliferous. (Bryozoa, brachiopods, crinoid columnals.)

3.7

13 BRYOZOAN CALCARENITE; medium gray, dolomitic.

0.4

12 CALCAREOUS SANDSTONE; fine grained, medium gray, ripple marked

and cross-laminated, dolomitic.

1.5

11 BRYOZOAN CALCARENITE; medium gray, cross-laminated with calcareous

sandstone in upper part.

1.5

10 CALCAREOUS SHALE and SILTSTONE; medium light gray to greenish

gray, with lenses of bryozoan debris. On the third terrace this unit thickens

to 3.6' with a thick bed of contorted (slumped?) calcareous shale and

siltstone at the base.

0.3

99

9 BIOTURBATED CALCAREOUS SANDSTONE and SHALE; medium

light gray to dark greenish gray, dolomitic. Sandstone fine to medium

grained with bryozoan debris. Partially truncated by bed 10.

2.1

8 SHALE; dark greenish gray with very thin to thin beds of calcareous

sandstone and siltstone. Ripple marks. Bioturbated and with some

bryozoan debris.

5.7

7 SANDSTONE; coarse grained, well rounded, dolomitic with phosphatic

granules.

0.1

6 CALCAREOUS SILTSTONE and SHALE; medium gray to medium light

gray, dolomitic, sandy. Bioturbated and with Modiolopsis.

3.1

5 VARIAGATED CALCAREOUS SILTSTONES; in obscure beds. Greenish

gray to reddish gray. Unfossiliferous, but bioturbated.

6.0

4 CALCAREOUS SILTSTONE; medium light gray laminated and with

desiccated intraclasts of greenish gray shale and light gray calcareous

siltstone.

1.1

Total Shellmound Member

104.0'

Inman-Leipers Member:

3 SANDSTONE, SILTSTONE and SHALE; pale red to grayish red, inter-

laminated and interbedded. Bedding and lamination vary from distinct

to obscure depending on the selectiveness of the reddening process and

the development of local reduction zones. Sedimentary structures include

small scale ripple marks, cross-lamination, graded beds and laminations,

mud cracks and desiccation breccias, and load casts. Unfossiliferous

except at base. Burrows common.

79.9

Total Inman-Leipers Member

79.9'

Catheys Formation:

2 Interbedded SHALE, CALCAREOUS SILTSTONE and CALCARENITE;

medium light gray to grayish red. Thin bedded fossiliferous with bryozoan

lenses.

5.0

1 Interbedded SHALE, CALCAREOUS SILTSTONE, and CALCARENITE; medium dark to medium light gray, very thin to thin bedded fossiliferous (bryozoans, brachiopods, bivalves, gastropods, straight nautiloids, trilobites).

Maximum thickness measured at road level

188.0'

100

Statistics of Sandstone Distribution and Graded Bedding in the Red Mountain Formation at Ringgold Gap From data collected by T. M. Chowns, Marith J. Reheis and Jan D. Smith

Bed Number

5 ft. Interval

Percentage Sandstone

Percentage Sandstones Graded

Percentage Graded Beds Beginning (a)

Percentage Graded Beds Beginning (b)

Percentage Graded Beds Beginning (c)

ABC Index A+'hB

32

1

9.1

2

12.5

3

17.5

4

15.0

33

34

5 (1.9')

13.0

35

6

60.8

0

0

0

0

0

7

39.1

0

0

0

0

0

8

22.5

0

0

0

0

0

9

28.3

38

0

0

100

0

10

24.1

45

0

80

20

4Q

11

13.3

50

0

67

33

33

12

20.0

33

0

50

50

25

13

15.0

29

0

100

0

50

14

27.5

36

40

40

20

60

15

19.1

75

33

33

33

50

16

13.3

56

40

60

0

70

17

32.5

38

0

60

40

30

18

27.5

56

30

40

30

50

19

30.8

57

50

25

25

62

36

37

20

38.3

100

50

25

25

62

21

38.3

100

0

100

0

50

22

38.3

86

33

67

23

24.1

100

20

so

0

67

0

60

24

27.5

100

50

50

0

75

25

27.7

80

75

25

0

88

26

25.0

100

84

16

0

92

27

32.5

100

50

50

0

75

28

22.6

66

50

50

0

75

38

29

40.8

100

50

50

30

51.6

88

55

45

31

37.5

80

50

50

32

22.5

88

45

55

33

40.8

100

50

50

34

41.6

50

33

67

35

55.0

50

100

0

36

24.1

60

0

100

37

38.3

50

100

0

38

61.6

50

0

100

39

50.0

50

67

33

40

55.0

57

100

0

41

40.8

80

33

67

42

35.8

40

50

50

43

43.3

50

100

0

44

53.3

33

0

100

0

75

0

78

0

75

0

73

0

75

0

67

0

100

0

50

0

100

0

50

0

83

0

100

0

67

0

75

0

100

0

50

39

40

41

-

..

--

42

45

45

46

40.8

47

45.8

48

40.8

49

67.5

43

100

44

50

34.1

51

21.5

52

24.1

53

50.8

54

41.6

55

5.0

56

9.1

57

31.6

58

2.5

59

10.8

60

22.5

61

32.5

62

15.0

63

12.5

64

14.1

65

26.6

66

1.6

67

41.8

45

68

23.4

69

38.2

70

37.6

71

14.8

72

15.4

46

73

57.9

74

37.6

75

33.9

76

44.4

77

30.2

78

8.1

79

50.0

80

45.0

81

35.0

82

49.1

83

41.6

84

33.3

85

38.3

86

48.0

87

34.5

71

20

40

40

40

88

43.1

75

22

45

33

44

gg

56.1

100

0

44

56

22

90

-

82

22

33

45

38

91

-

88

29

50

21

54

92

40.1

92

19

73

8

56

93

56.7

77

20

50

30

45

94

37.6

83

20

60

20

50

95

28.4

100

0

67

33

33

96

29.0

50

33

67

0

50

97

33.3

78

29

71

0

65

98

19.7

83

20

60

20

50

99

17.9

83

0

80

20

40

100

-

90

44

45

11

66

47

101

102

45.0 30.0

101