Stratigraphy and economic geology of Cambrian and Ordovician rocks in Bartow and Polk counties, Georgia [1981]

STRATIGRAPHY AND ECONOMIC GEOLOGY OF CAMBRIAN AND ORDOVICIAN ROCKS IN BARTOW AND POLK COUNTIES, GEORGIA
compiled by T. M. Chowns

GUIDEBOOK 16-A

12th Annual Meeting and Field Trip

Reprinted 1981 by the Georgia Geologic Survey Branch of the Environmental Protection Division, Department of Natural Resources

Atlanta 1977

STRATIGRAPHY AND ECONOMIC GEOL.OGY OF CAMBRIAN AND ORDOVICIAN ROCKS
IN BARTOW AND POLK COUNTIES, GEORGIA
Compiled by T .M ChONns , Fl"'om contributions by C ,W. Cressler, T .J. Ct"'awfor-d,
S. Bearden and E. L. Lipps
Geot"'gia Geological Society Atlanta, Geot"'gia Octobel"', 1977

GEORGIA GEOLOGICAL SOCIETY OFFICERS 1976-77

President Secretary Treasurer Councilor Councilor

Timothy M. Chcwns Bruce O'Connor Eric V. Eslinger Doral S. Mills, Jr. Duncan G. Johnson

President President-Elect Secretary Treasurer Councilor Councilor

OFFICERS 1977-78 Thomas J Crawford Charles 0. Pollard, Jr. Richard P. Sanders James A Whitney Duncan G. Johnson M. Eugene Hartley

FIELD TRIP COMMITTEE Timothy M. Chowns, Chairman Charles W. Cressler Thomas J Crawford Stanley D. Bearden Heward R. Cramer C. Sumner Long

ACKNOWLEDGEMENTS The Georgia G&ologi.cal Society gratefully acknCMiledgas donations from the New Riverside Ocher Company, and Freeport Kaolin Company which have helped to defray the cost of' the smol<&r. The guidebook was typsd by Denise ShQfimake and was printed by West Georgia Collsgs.

1 INTRODUCTION The Valley and Ridge Province of Georgia is divided into r:wo distinct parts by the Rome Fault. To the northwest of the fault the outcrops are mainly of Ordovician to Pennsylvanian age with resistant sandstones in the Silurian and Pennsylvanian systems giving rise to spectacular li.near ridges, separated by valleys largely underlain by li.mestones of Middle Ordovician and Mississippian age. Southwest of the fault there is a distinct change; the section is dominated by Cambrian and Ordovician rocks; the Pennsylvanian and most of the Mississippian has been removed from the top of the section and the Silurian was either never deposited or
I
removed prior to Devonian times; the most distinctive ridge formers are gone. In addition where correlatives are present on opposite si9es of the fault they tend to belong to different facies, the contrast being strengthened by crustal shortening along the thrust fault.
When the Georgia Geological Society last visited the Valley and Ridge Province (see Chowns, 1972) attention was directed towards' the younger part of the stratigraphic section northwest of the Rome Fault. The lower part of the section southeast of the Rome Fault was poorly exposed and 1ittle known, it was claimed. The latter situation has now been remedied by Charles Cressler who has recently completed the remapping of this part of the Valley and Ridge, and this guidebook is mainly based on the results of his work (see Cressler 1970, 1974,and in press). However, a large number of new problems in stratigraphy, sedimentology and paleontology have surfaced and this field trip is an attempt to focus attention on these problems.
Although, lack of exposure remains a handicap i.n the southeastern

2 part of the Valley and Ridge, the Cartersville - Rockmart area is exceptional for its large number of working pits and abandoned quarries. Principle mineral commodities which have been mined include brown iron ore, manganese, ocher and umb~r pigments, barite, dolosta;e, limestone, lightweight aggregate and chert. Included in the field trip will be visits to the operations of the New Riverside Ocher Company, mining barite as well as iron pigments from residuum of the Shady Dolomite near Cartersville; Florida Rock Industries, which quarries Conasauga limestone for cement and aggregate near Kingston; and Georgia Lightweight Aggregate Company (Gali.te) producing lightweight aggregate from the Rockmart Slate at Rockmart.
All the stratigraphic units in the Cartersville - Rockmart area are overthrust by the Cartersville fault. Most cf the stops are within a few miles of the fault and must have lain just beneath the sole prior to the retreat of the Cartersville escarpment. It i.s therefore appropriate that we include a stop on the fault.
T .M. Chowns

, ,

Ro ute

oCf a

fi rt

e e

,d I
rsv

t i

r1.
11

~ D

on first f'.rea

day.

Hfp

Fort Payne Chert 100'+ seen

Or

Rockmart Slate 600'+

01 Od On
OE:k
c r

..r J

1

I

I

j_
I I 1
I I
L
I I J
J I
I I I
I I I
I
I I
1
I J
I
I I I

I

_}

I

I

0

Lenoir Lst. incl. Mosheim & Deaton Hembers

Newala Limestone 300'+

0-100'

Longview Limestone

Chepultepec Dolomite Copper Ridge Dolomite

Knox Group 2500-3500'

Maynardville Lst. ? 50-300'
Nolichucky Shale ? 200-1000'
Maryville Lst. ? 200-600'
Rogersville Shale ? 200-400 1
Honaker Dolomite ? 300-500'
Rome Formation 100-500 1 +

Conasauga Group

s

1

.:: .... ... .

ch .....-....-....-........-...

Shady Dolomite 300-500' Chilhowee Group 500'+ seen

Stratigraphic column for the Cartersville-Rockmart area

MISSISSIPPIA.l\1 ORDOVICIAN
CAHBRIAN
o'
10001

3

ROAD LOG

MILEA.GE

Inte l""!"'n ed tate

Cumulative

o.o

o.o

0.4

0.4

0.2

0.6

LO

1 .6

FIRST DAY
Remarks
Leave parking lot at Quality Inn Motel and head north on Dixie Avenue (access road parallel to US 41).
Intersection with East Main Street. Turn right across US 41 at red light and then right again on Momingside Drive (access road on other si.de of US 41). Turn left on road to county landfHl.
Park in Bartcw County landfill

STOP i BARTOW COUNTY LANDFILL The oldest stratigraphic unit i.n the Valley and Ridge Province of Georgia is the Chilhcwee Group (Weisner Quartzite) of Early Cambrian age, which with the exception of one small area i.n Murray County, i.s restricted to Bartcw County east of Cartersville. Although the local geology i.s complicated by thrust faulting whi.ch thrcws the Chilhowee over younger Shady dolostones, one of the best and most accessible exposures i.s in the Bartow County landfill (the old Parrott Springs barite mine). The Chi.lhcwee group consists mainly of shale interbedded with orthquartzite. \1\/hen fl""esh the shale i.s fair1y hard and brittle, sometimes weakly graphtic, wi.th a dark - gray color, but upon weathering i.t becomes very soft, light - gray to white i.n color. The orthquartzites are light to dark gray, buff to brcwn weathering, mostly fine grained but with some very coarse grained conglcrneratic beds. They may show crossbedding or Scolithos burrows. In natural exposures. the thicker beds form hard ledges and low cliffs, but i.n quarries and road cuts the orthoquartzite is generally close-jointed and breaks into small angular pieces. Near the top of the

4

unit, as at this locality, much of the orthoquartzite is friable, and easily

worked with earth - moving equipment. It is therefore used with the shale

as cover material in the landf'ill. These peculiarities of weathering are

characteristic of the Chi.lhOvVee group in Georgia and help to differentiate

it from older Ocoee rocks with which it is sometimes confused.

Because of structural complications the total thickness of the

Chilhowee group has never been determined, but judging from the width of

the outcrop belts it is probably several hundred feet thick, The age of

the unit has been established from the occurence of LONer Cambrian fossils

at some localities.

1 .o

2.6

Return to Morningside Drive and turn right.

0.2

2.8

Intersection with East Main Street; tum

right and then right again on dirt service

road into the barite pits of New River-

side Ocher Company,

STOP 2

BARITE PITS OF NEW RIVERSIDE OCHER CO.

The most important formation in the Cartersville area from an ec-

anomie point of view i.s the Lcwer Cambrian Shady Dolomite. All the pri.n-

ctple mineral deposits i.n this area including deposits of bal"'i.te, brown iron

ore, ocher, umber and manganese are associated with this unit. The form-

r-:.ti.on varies between about 300 to 500 feet thick, and consists of thinly to

massively bedded light-gray to dark-gray :Jolostone and dolomitic limestone,

with some thin beds and laminations of dark gray shale and phyllite i.n the

,_,pper part, r1early ider1tical to the overlying Rome Formation. The lower

Cambria'! age of the formati.or"1 is established pc>.leontologically from a Faur1a cf archaeocyathids, brachiopods, trilobites and gastropods. The dolostone

is highly siliceous and contains irregular veins and replacements of barite

throughout most, if not its entire thicf<ness. Upon weathering the barite

5

becomes concentrated in a thick red clay residuum and is recovered by

strip mining o

The section in the New Riverside Ocher Company's pit on the east

side of Cartersville is typical o 3 o Red alluvium and colluvium (overburdsn)

20 - 40 1

2. Red, buff, ysllc:w, brown residuum derived by weathering of the Shady Dolomite (6 12 percent barite)

30 - 60 1

1 o Pinnacles of cherty dolostone with archaeocyathids and algal stromatoli.tes.

20 1 seen

The ore is stripped by dragl ine, washed, ground and then bene-

fitiated by jigging, floatation and magnetic separation , prior to marketing

as chemical grade barite used in the manufacture of barium salts o Be-

tween 2 - 3 acres are stripped and reclaimed each year.

The New Riverside Ocher Company also continues to mine ocherous

clay which is used for coloring bricks and mortar, and as an extender for

synthetic iron pigments. The ocher is obtained from areas which were

formerly worked for brc:wn iron ore, and appears to form by the weathering

of beds of specular haematite, which occur within the basal 30 feet of the

Shady Dolomite o After mining, the ocherous clay i.s washed, clarified,

made i.nto a slurry, and dispersed before bei.ng dried, pulverized and bagged

for marketing

Return to Morningside Drive and turn right o

Oo5

3o3

Intersection with Moon Street; turn

left and cross US 41 at red light o

Oo4

3o7

Cross North Tennessee Street and

continue west on Moon Street o

OPEN PIT HINE

.,........

NEW RIVERSIDE OCHRE COMPANY Box 387
BASIC FLOW SHEET FOR CHEMICAL GRADE BARITE

WASHER PLANT

MAGNETIC SEPARATOR

.......
/

PLANT

---,. Concentrate

Log washer -JJ muds

Washer
W Sands

Fine Sands
~
1-
FLOTATION PLANT
t
Concentrate

78" double

screw akins f-7- Coarse

classifier

Sands

-
FLOTATION AND AGGLOMERATE TABLE
PLANT
1
Concentrate

MINERAL PROCESSING EQUIPMENT: Log washer, jigs, classifiers, rougher cells, cleaner cells, spiral classifiers, conditioners, hammer mills, double roll crusher, stedman mill, agglomerate tables, dry magnetic separators, disk filter, wet cyclones, rotary dryers.
MINING EQUIPMENT: 5 yard dragline, elevating scrapers, 35 ton trucks, dozers, front end loaders, etc.

G.G.S. , 1977

6

0.5

4.2

Junction with North Avenue; tum left.

0 .1

4.3

Turn right across railroad crossing and

then back north along Red Comb Drive.

0 .1

4.4

Road Forks; continue to the left on Red

Comb Drive.

0.3 0.2

4.7

Fork left on dirt road belew power lines.

4.9

Park behird city dog shelter and Follc:w

track to old borrc:w pits

STOP 3

ROME FORMATION

The town of Cartersville is mainly underlain by shales, siltstones,

and sandstones of the Rome Formation in a belt which extends northeast-

wards through White and Rydal. The shale is dominantly gray, often with
a distinctive silver sheen (referred to locally as silver shale or slate), but

weathers to shades of tan, pink, and purple. Tre sandstones and siltstones

are generally gray, purple, white or tan and occur in thin beds except east of Rydal wher'Q sandstone units up to thirty Feet thick crop out. This entire

belt i.s underlain by a shallow, Flat - lying thrust Fault whi.ch has displaced

the Rome Formation WQstwards over younger dolostones of the Conasauga

Group. Combined evidence from the outcrop pattern and from a gravity

survey indicates that the thrust sheet ranges i.n thickness From less than

100 f'eet up to about 400 feet. The total thickness of the Rome Formation

is diffi.cult to deterrni.ne because of poor exposure but it is probably several

hundred Feet.

The outcrops in the v'icini.ty of the dog shelter He close to the Fault,

which may be traced northeastwards from the occurence of si.li.cifi.ed Fault

breccia (jasperoi.d). The Rome sediments are tightly folded with a steep

axial plane cleavage striking 295

7

A second belt of Rome rocks makes up Johnson Mountain and adjacent

ridges about 4 miles northwest of Cartersville. Here cuts made for Inter-

state 75 reveal that the fresh rock may be very calcareous and vary in

color from purple to pale red, white, gray or green.

0.7

5.6

Return along Red Comb Drive to inter-

section with Montgomery Street and turn

right across tracks onto North Erwin

Street.

0.6

6.2

Intersection with Cassville Road, Ga 293;

turn right (north) .

4.9

11 .1

Intersection with Ga 293 spur; bear left

and continue on Ga 293 towards King-

ston.

2.3

13.4

Entrance to Kingston Quarry of Florida

Rock Industries; ll..lrn left, and park

alongside entrance road.

STOP 4

KINGSTON QUARRY

The Conasauga Group in Georgia consists of a complex association

of interbedded shales and carbonate rocks which is still largely unstudied.

In the Cartersville area the group is divided into five informal units as

follows.

5. Upper carbonate unit

50 1 - 300 1

Thinly to massively bedded dolostone, interbedded with clayey limestone. Contains abundant black chert beds and nodules at the top~which are quite distinct from the light gray cherts derived from the overlying Knox Group. Probably equivalent to the Maynardville Limestone of Tennessee

4. Upper shale unit

700 1 - 1000 1

Greenish gray, and sligrtly purplish shale interbedded with thin layers of limestone and dolostone. Probably equivalent to the Nolichucky Shale of Tennessee.

3 . Middle limestone unit

200 1 - 600 1

Massive blue-gray limestone with irregular layers of silty dolo-

8

stone . Probably equivalent to the Maryville Limestone of Tennessee.

2 Lc::wer shale unit

up to 400 1

Light- green, olive-green and silver gray shale with local limestone lenses. Probably equivalent to the Rogersville
Shale of Tennessee.

1 Lc::wer dolostone unit

500 1 -.!.

Thin - to massive - bedded, light - to medium - gray dolostone, commonly with distinctive reddened bedding and joint
surfaces. Locally oolitic and cherty. Weattlers to produce a siliceous residuum with many hard gray Fragments of jasperoid Possibly equivalent to the Honaker Dolomite of Tennessee

The Florida Rock Industries Quarry near Kingston exposes the middle

limestone unit (? Maryville Limestone).

This locality is of particular interest because it demonstrates the manner

in which sink holes develop when the water table is lowered during mining op-

erations in areas of karst topography. On account of its susceptibilty to

weathering the limestone occupies lc::wlying ground, and develops a very

irregular, pinnacled surface blanketed by a thick clay residuum. Lc::wering

of the water table leads to the doJimwashing of the residuum into openings in

the acqui.fer and the development of cavities at the base of the soil profile,

which are Hable to failure o Alternatively, where the limestone is cavernous

belON the watertable, the water plays a part in supporting the cavem structure~

so that is the watertable falls the structure may become unstable and Fan o

Return south on Ga 293 towards Cartersville.

2.3

15 o7

Intersection with Ga 293 spur; turn left,

0.4 0.4 5.6
0.4

16 .1 16.5 22 .1
22.5

9 Cross US 41 and tum left into rest area for LUNCH STOP.
Retum to Ga 293 and turn left.
Intersection with West Cherokee Street; foHcw Ga 293 to the left and then tum right immediately on Fite Street.
Junction wii:h West Avenue (Ga 61); turn right (west).

1 .1

23.6

Stop on crest of hHl, turn leFt and

park i.n shale excavations close to the road.

STOP 5

CONASAUGA SHALE

The shales at this locality lie in the lcwer shale unit of the Cona-

sauga Group below the horizon of the ? Maryville Limestone. They have

a distinctive silver - gray color, weathering to shades of tan, pink, and

orange. Occasional linguloid brachiopods are found.

At the west end the outcrop i.s cut by a northwesterly trending fault,

which i.s marked by the occurence of siliceous fault breccia and manganese

staining. The entire outcrop i.s capped by terrace gravels of the Etowah River

V/r.tch lies about two miles to the south.

0.9 0.5

24.5
25 .o

Return to Ga 61 and continue west to Ladds; turn hard right across the ranroad t rae ks
Entrance to Ladds Quarry; tum left, drive to west end of quarry and park.

STOP 6

LA DDS QUARRY

Ladds Quarry exposes about 300 fe.et of medium -to light-gray,

thick-to massive-{)edded siliceous dolostone in the basal part of the Knox

Group (Copper Ridge Dolomite). It was fol""""lerly worked for cer:-:ent ~. r.d flux for

the iron industry, and is one of the few major exposures in the state at thi.s

10

The west wall of the quarry intersects a prorninant fault which is a

splay From a major north - south trending Fault which runs the length of

Nancy Valley just east of this locality. In consequence of the faulting,

bedding is verti.cal throughout much of the quarry, and some brecciation

occurs.

Groundwater has exploited lines of weakness produced by jointing and

faulting and formed solution cavities, which may be Filled with collapse

breccia or f1owstone. At the top of the quarry solution pits are filled

with a red clay residuum which has yielded a large suite of Pleistocene

land vertebrates (Lipps and Ray, 1967). These include at least 48 species

of mammals, 25 percent being extinct forms (Ray, 1967), 23 species of

amphibians and reptiles (Holman, 1967), and 4 species of birds (Wetmore,

1967), as well as 25 species of mollusks especially land snai.ls (La Roque, 1967).

Further i.nformati.on on the herpetofauna is forthcoming 'in a PhD thesi.s

by Vince Wilson of Mi.chi.gan State.

Southwestwards from thi.s location the full thickness of the Knox,

totalling between 2,500 - 3, 500 feet is present, but the outcrop is generally

obscured by a thick residuum of cherty, si.lty clay ranging from 25-200 feet

thick.

0.5

25.5

Return to Ga 61, turn left across bridge

over Petti.t Creek and then right immed-

iately.

1 .3

26.8

T junction; turn right

0.8 0,4

27.6
28 .o

Intersection with Etowah Mounds Road; continue straight on. Car.:o,~sville Fault line escarpment ahead.
Cross bridge over Etowah River.

11

0.3

28.3

Stop at T junction and turn left.

0.3

28.6

Stop and park beside road. Follow path

up valley of Ward Creek to fi.rst tributary

on the west bank and walk upstream for

about 200 yards.

STOP 7 a

CARTERSVILLE FAULT

With the excQpti.on of stop 4 all the stops on this field trip l i.e wtthtn

a few miles of the Cartersville fault, whtch follows the foot of the prom-

inent escarpment south of Cartersville and Rockmart, and marks the bound -

ary between the Piedmont and Valley and Ridge provinces. In this area the

fault is a low angle thrust, which generally dips tot he southeast at angles

estimated between 8 - 15 degrees. Mapping along the boundary indicates

that all stratigraphic units in the fald trip area, from the Chilhowee Group

(Cambrian) to the Fort Payne Chert (Mississippian) pass beneath Piedmont

rocks (various units of the Talladega Group) at the fault. In detail it i.s

found that the fault frequently deviates from the line of the escarpment, swinging

out into the lower grrund to the north, and that in places the main thrust is

cornpl icated by imbricate slicing of Piedmont and Valley and Ridge rocks.

At this stop the combination of a low dip on the fault plane and downcutting

along one of the tributaries of Ward Creek has exposed a small window of Cona-

sauga carbonate rocks surrounded by schists and metagraywackes of the

Talladega Group. The Conasauga is represented by light - to medium-

gray, buff - weathering, siliceous dolostone, which is i.nterlayered with

chloritic and calcareous quartz-feldspar-muscovite schist. Light-and dark-

gray banding in the schist suggests segregation by shearing On the west side

of the window, in outcrops along the creek, the Conasauga is overthrust in

different places by quartzose, feldspathic, graphitic schist and conglomeratic

12

schists with associated thin quartzite beds, both. belonging to the Talladega

Group. All these rock units have been severely folded and intensely sheared

in places.

0.6

29.2

Continue east along road which changes

to dirt.

0.7

29.9

Crossroads; continue straight ahead. In

this vicinity the trace of the cartersville

fault lies about 1200' in front of the es-

carpment.

0.4

30.3

Cross ford.

0.9

31 .2

Park beside road and climb steep

bluff to the south.

STOP 7b

CARTERSVILLE FAULT

At this locality the Cartersville fault crops out on the north - facing

escarpment. The lower part of the slope is formed by the Shady Dolomite,

while the upper part consists of schists and metagrayvvackes of the Talla-

dega Group. The unit of tre Talladega exposed here consists of feldspar-

quartz -muscovite schist interlayered with muscovite - quartz - feldspar

metagraywacke; both chloritic and calcareous. The schist is fine to medium-

grained, very feldspathic and quartzose, wi.th abundant quartz pods; the

metagraywacke is very feldspathic. Boundaries between interlayered schist

and metagraywacke are gr~dational layering is poorly developed and the

abundance of quartz pods gives the rock a very irregular "rolling" foliation.

During weathering these rocks form cliffs with overhanging ledges, rock

shelters,. and rarely, caves as a result of their calcareous nature. They also

develop a brONnish ~d to dark Indian - red soi.l.

5.1

36,3

Continue on dirt road to first intersection

(0 .3 mi.les), tum around and retrace

13

route back to Etowah Mounds Road; turn right.

0,8

37 .1

Entrance to EtOJVah Indian Mounds; turn right and park.

STOP 8

ETOWAH INDIAN MOUNDS

The EtOJVah Indian Mounds comprise three ceremonial or temple

mounds with smatter domiciliary mounds clustel"'9d close to the Etcmah

River. The main concentration of mounds, occupied between 1000 AD

and 1500 AD, covers some forty acres, surrounded by a large di.tch which

runs into the ri.ver.

Apart From the mounds there is an excellent museum illustrating the

cultural and re ltgious life of the settlerre nt.

0.2

37.3

Exi.t from Mounds and continue on

Etowah Mounds Road

2.3

39.6

Intersection with Ga 61; stop at 1"'9d light

and tum hard ri.ght onto West Avenue.

0.6

40.2

Cross S Tennessee Street and continue on

Postelle Street.

0,2

40.4

Junction with Di.xie Avenue; turn ri.ght.

0.2

40.6

Return to Qual tty Inn.

- ,....--- -c:::'

_.),.---- ~

'

)

'

~ , .. . -.

I
~/~-.5,:)..

-- .

I .~

- -- ~\--~ - . . . - .(..

= _; ......___. :_t .J,. Ir"i:_:'

->..,

,

~

_,.I

-/

'-''

-~

:._

-

/ '
/

Route of field trip on second day, P.ockm:>.rt r.rea,

!
;,~\
. ...I.
d~
-f.., "' I
\..._._
!

0

1

tu

mllc.s

20 (( 1

Geologic :a~ of Rockmart /rP.a frcf'l Cressler, 1Cl70,

14

ROAD LOG

SECOND DAY

MILEAGE

I ntel"'mediata

Cumulative

o.o

o.o

0.2

0.2

0.8

1 .o

2 .1

3.1

1 .6

4.7

Remal"'ks
Leave pal"'king lot at Quality Inn and dl"'ive nol"'th on Dixie Avenue
Intel"'section with Postelle Stl"'eet; tul"'n left . Poste lle becomes West Avenue aftel"' one block.
Intel"'section with Ga 61, 113; stop at l"'ed light and take Ga 61 , 113 west
Ladds.
Junction of Ga 61 and 113; continue west on Ga 113

5.1

9.8

Entrance to Geol"'gi.a Powel"''s 80\Nen

electl"''ic generating plant on l"'ight.

3.3

13 .1

Entel"'ing Taylol"'sville; tum l"'ight.

0.1

13.2

Intel"'secti.on with Taylol"'sv'ille Road;

tul"'n left.

0.5

13.7

Taylol"'svi.lle CI"'OSSI"'oads; keep straight

on.

1 .5

15.2

Stop beside l"'oad and walk south into woods

to si.te of the old Deaton il"'on mines.

STOP 9

DEATON IRON MINES

At the end of the last centul"'y thi.s mine and other'S in the nei.gh-

bol"'hood wel"'e actively Wol"'ked fol"' bl"'own i.l"'on Ol"'e fl"'om outcl"'ops close to tre

contact between the Newala L i.mestone and Rockmal"'t Slate. The Ol"'e was

apparently del"'ived by the weathel"'ing of a localized occul"'ence of fei"'I"'Uginous limestone which is CUI"'I"'ently mapped as the Deaton Member' of the

Lenoir Limestone. Even though mi.ni.ng was di.sconti.nued mol"'e than eighty

year's ago the v.1orkings still provide an ex<.;ellent secti.cn of the upper part

of the Newala Limestone and the ovel"'lying Deaton beds.

15

The Newala Limestone consists of interbedded sandy limstone and

dolos~one in th'ick to massive beds generally ranging between one to six

feet in thickness. Both lithologies are laminated and bioturbated,

and occasional chert nodules occur. Contacts between limestone and dolo-

stone are sharp and probably channeled in places. Silicified opercula of

the gastropod Ceratopea are fairly common in the limestone and indicate

an Early Ordovician age (approximately equivalent to tre upper Kingsport

and lowEtr Mascot formations of east Tennessee).

Like the overlying Rockmart Slate the limestones of the Newala show

slaty cleavage, which in this case superfici.ally resembles cross-bedding when

seen on weathered outcrops. Resting unconformably above the Newala Lime-

stone, the Deaton Member i.s a dark-gray sandy, magnetite-t>earing limestone,

with beds of conglomerate containing pebbles of dolostone, siltstone and shale,

all apparently derived from underlying formations. When fresh it yields up

to about 30 percent iron but this increases to about 80 percent upon weathering.

At outcrop the Newala Limestone weathers i.nto spectacular pinnacles and the

overlying ferruginous Deaton residuum i.s let down i.nto the intervening pits.

It was apparently these pits which contained the richest ore so that the area

is nON a labyrinth of open cuts separated by walls of solid limestone.

The Deaton beds are relatively unfossiliferous, containing only poorly

preserved conodonts and shell fragments, possibly li.nguloid brachiopods. They

are dated mainly by stratigraphic position as Middle Ordovician in age.

Retum to Taylorsville Road and continue west to.vards Aragon.

4.2

19.4

Intersection with Oak Street; take left fork

and drive south .

0.6

20.0

Junction with Ga 101; turn left.

16

0 .1

20.1

Cross Euharlee Creek and tum 16ft immediately on Portland Road, Following railroad tracks.

1 .8

21 .9

Park beside road just west of Portland

and walk northeastwards along rai.lroad

tracks for about 0 .5 m i.les to old trestle,,

where path leads east i.nto Portland

Quarry.

STOP 10

PORTLAND QUARRY

In the Portland Quarry, only a mile and a half west of the Deaton

mines, the Deaton beds are absent and the Rockmart Slate lies unconformably

on the Lenoir Limestone whic:'"' in turn rests unconformably on the Newala

Lim$stone.

The Lenoir consists of two distinct lithologies; a medium -to dark-gray

sUty aphanitic limestone and a medium-to light-gray bird 's-eye limestone

(Mosheim?). Upon weathering they appear distinctly different The first

breaks down into thin slabs, the lat~r retains a massive bedding and develops

a thick chalky crust beneath a soH cover. Both lithologies are Fossiliferous,

the most common forms being gastropods including Maclurites In con-

junction with stratigraphic posi.tion these indicate a Middle Ordovician age.

Until the 1950's the Lenoir together with the upper part of the Newala

was extensively used for the manufacture of cement. However, more

stringent quality controls have eliminated the Newala as a source and the

Lenoir is generally too thin to be worked independently. All the quarries

in the vicinity of Aragon are now abal'")doned therefore, and the Marquette

Cement Plant is util i.zing Mississippian limestone From the Ledbetter quarry

in Rome.

1 .s

23.7

Retum to Ga 101 , t:.Jrn left and proceed
south towards Rockmart.

17

1 .3

25.0

Marquette Cement Plant on right.

0.4

25.4

Quarry in Middle Ordovician 1imestone

on left.

0.4

25.8

Rockmart , qity 1i.m its .

0.5

26.3

Junction with Ga 113; keep straight on

0.5

26.8

Junction wi.th US 278; turn right.

0.6

27.4

J'..lnction with South Marble Street; turn

leFt at red 1ight

0 .4

27 .8

Entrance to Galite (Georgia Lightweight Aggregate Co.) Plant; turn left and park next to office .

S T0 P 11

R 0 C K MART S LATE Q U A R R Y

The Rockmart Slate consists mainly of dark-gray mud rock with a

moderately to well developed slaty cleavage. In the past it was mined for

building stone and roofing slate, which may be seen in some of the local

buildings, but now it is mainly used for the manufacture of lightweight agg-

regate.

The slate contains graptolites (climacograptids and retiograptids) which

can be collected in favorable exposures where cleavage and bedding coincide.

These indicate a Middle Ordovician age (zones 10-11 of Berry, 1960). It is

therefore probably stratigraphically equivalent to the lower part of the Chick-

amauga Limestone further northwest in Georgia.

Lithologically the Rockmart resembles other Middle Ordovician black

graptolitic shales such as the Athens Shale of Tennessee and Alabama, al-

though it is not precisely the same age. It consists predominantly of clay

slate with laminations and interbeds of dolomi.tic? silt slate. Interl aminations

of these two types are particularly well seen in this quarry. The si.lt

laminae are commonly graded and show ripple cross-laminations, scour

18

marks, and slump sti"'Uctul"'es. Taken together the fauna, lithology, and

sedimentary sti"'Uctures suggest the deposition in a deep water basin pri-

mar'ily by suspension sedimentation. Some gravitational instability is

suggested by the presence of slump sti"'Uctul"'es.

0.4

28.2

Retum to US 27 8 and turn ri.ght

0.6

28.8

Junction with Ga 101, 113; turn left.

0.2

29.0

Intersection with College Straet; turn right.

0.7

29.7

Cross railroad and turn right following tracks.

l.6

31 .3

Stop beside road and examine outcrops

in north bank.

STOP 12

ROCKMART CONGLOMERATE

Although the Rockmart Slate is pl"'edomi.nantly mudrock, interbeds of

sandstone and sandy conglomerate, like those at thi.s stop, occur at in-

tervals, near the top of the section, especially i.n the eastern part of the

outcrop belt near Rockmart

The most common type of conglomerate consists of cobbles (up to

si.x i.nches) and pebbles of mi.cri.te limestone, dolostone, shale, sand-

stone, chert, and quartzite, generally in that order of abundance, set i.n a matrix

of feldspathic sandstone Because of the preponderance of carbonate clasts,

weatheri.ng produces a characteristic honeycomb appearance. Some of these

lithologies can be matched with underlyi.ng formations such c:s the Newala,

Lenoi.r, Knox, and Shady carbonates and the Rome and Chilhowee clastics.

In most exposures the clasts are flattened and elongated parallel to the

cleavage so that it i.s difficult to determine their origi.nal size and shape.

HONever, it is clear that soma lithologies, mainly the mi.cri.tic limestone

and shale behaved incompetently whi.le others were competent. This

19

probably indicates a difference in induration, which in turn suggests that

many of the clasts were derived from contemporaneous asediments and

underwent soft sediment deformation

The origin of these conglomerates is sti.ll uncerl:ai.n. They ap!JEiar to occur as isolated lenses (or perhaps sh~stri.ngs) in the more normal Rocl<n'larl:

mudrock lithology) and to have been derived from the southeast, judging by clast

size, thickness on the units, and frequency of occurence I f the Rockmart

Slate is a basi.nal deposit as suggested at the last stop, the most likely means

of emplacement might be by gravity sliding, perhaps in submarine channels.

Whatever the origin, the lithology and si.ze of the clasts indicates a source

area, probably with a nari"''N carbonate shelf, at no great distance to the

southeast.
1 .o

32.3

Continue east on highway and turn right on dirt road i.nto Marquette Si.li.ca Quarry.

STOP 13

SILICA QUARRY

The youngest rocks i.n Polk and Bartow Count~es are Mississippian,

which everywhere li.e di.sconformably on the older strata. In this quarry the basal

Fori: Payne Chert rests on the Rockmart Slate, so that the entire Silurian

and Devonian sections ar"S m i.ssi.ng The Fori: Payne Chert consists of recrystallized silty chert interbedded

with fine""9rained sandstone and siltstone suggestive of the Lavender Shale

Memter. It contains few fosstls, but elsewhere in the area cri.noi.ds, horn

corals, brachiopods, and bryzoans occur.

Further west, near Cedarl:ONn, where the Fori: Payne again rests

unconformably on the Rockmart, Butts (tn Butts and Gildersleeve, 1948,

p. 53) apparently thrught that outcrops of fossiliferous Fort Payne were pari: of the Rocl<n'larl: and consequently mistakenly ascribed a Missi.ss-

20

ippian age For the tatter. This conFusion persisted until 1970 when the area

was r9mapped by Cressler.

Retum to highway and turn right (south).

32.6

Road Forks; bear right.

0.4

33.0

Cartersville Fault exposed on ri.ght wi.th

graphitic schi.st of the Talladega Group

thr-Ust over Fori: Payne Chert

0.9

33.9

Junction wi.th US 278; tum left for

Atlanta and ri.ght for Rockmart,

Rome, and Cartersvi.He.

REFEqENCES
Berry, W .B .N ., 1960, Graptolite Faunas of the Maratnon region, West Texas; Texas Univ. Pub. 6005, 170 p.
Butts, C., Gildersleeve, B., 1948, Geology and mineral resour"ces of the Paleozoic area in nort:1west Georgia; Georgia Geol. Survey Bull. 54, 176 p.
Cressler, C .W., 1970, Geology and groundwater resources of Floyd and Polk Counties, Georgia; Georgia Geol. Survey Inf. Circ. 39, 95 p.
Cressler, C .W., 1974, Geology and groundwater resources of Gordon, Whitfield, and Murray Counties, Georgia; Georgia Geol. Survey lnf. Circ . 47, 56 p.
Cressler, C .W., (in press), Geology and groundwater resources of Bartow County, Georgia; Georgia Geol. Survey Inf. Circ.
Holman, J .A., 1967, A Pleistocene her~=eto fauna from Ladds, Georgia; Georgia A cad . Sci . v . 25 p . 154 - 166 .
La Rocque, A., 1967, Pleistocene Mollusca of the Ladds deposit, Bartow County, Georgia; Georgi.a Acad. Sci., v. 25 p. 167 - 1.87.
Lipps, E . 1-. and Ray, C .E., 1967, The Pleistocene fossiliferous deposits at Ladds, Bartow County, Georgia; Georgia Acad. Sci. v 25 p. 113 -119.
Ray, C.E., 1967, Pleistocene Mollusca of the Ladds, 8artow County, Georgia; Georgia Acad. Sci. v. 25, p. 120 - 150.
Wetmore, A., 1967, Pleistocene Aves from Ladds, Georgia; Georgia Acad. Sci. v. 25 p. 151 - 153.