Hydrogeology of Greene, Morgan, and Putnam counties

HYDROGEOLOGY OF GREENE, MORGAN, AND PUTNAM COUNTIES
Thomas W. Watson
DEPARTMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION
GEORGIA GEOLOGIC SURVEY
INFORMATION CIRCULAR 60

r

HYDROGEOLOGY OF GREENE, MORGAN, AND PUTNAM COUNTIES
Thomas W. Watson
GEORGIA DEPARTMENT OF NATURAL RESOURCES J. Leonard Ledbetter, Commissioner
ENVIRONMENTAL PROTECTION DIVISION Harold F. Reheis, Assistant Director GEORGIA GEOLOGIC SURVEY William H. Mclemore, State Geologist ATLANTA 1984
INFORMATION CIRCULAR 60

CONTENTS
Abstract .................... . ...................... . ..... ... . . .. ..... ....... .. . 1 Introduction .... .. .. ............... . . .. ............ ..... .. . .. . .. ... . . ........ . . 1
Goals .. . .. . ....... . ........ . . . ............... . .... ..... . .. .. .. .. . ...... . .. 1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Previous Investigations . . ... .. ..... . ..... .. .. .. ..... . .. . . .... .......... .... 2 Geography of the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Geology .. ..................... .. ....... .. .... . . . ... ....... .. .. . ............... 3 Mobilized Inner Piedmont Belt . . .. ....... .... . .... ... . ............ ....... 3 Charlotte Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Carolina Slate Belt ..... ... . ...... . . .. .............. . . ..... . ............... 3 Faulting . ................................................................ . 3 Saprolite .... .. .. .... .. . .. .. . .... .. ..... . . . .. .. ....... . .... . ............ . .. 4 Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . 5 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Ground-Water Availability in the Piedmont ......... ........... . ..... . ..... 5
Geologic Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Well Depth ........ . .................... . ....... . .. .... ..... .. .... . . 6 Optimum Well Location . ........ ... . ..... . ......................... . 7 Concerns of Ground-Water Users in the Piedmont . .. .. . ..... . ............ . 7 General ................................ . . . . .. . .. .. . .. .. .. .......... . 7 Low Initial Yield . .. . . .. .. .. . . .. . ..... . .. . .. . .. ....................... 7 Declining Well Yield .............. .. .. .. .... ...... ..... ............ . 7 Contamination of Well Water ....................................... . 8 Ground-Water Availability in Greene, Morgan, and Putnam Counties ..... . 8 Geologic Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Well Depth ... .... . .. .... . . .. . ..... ......... ....... .............. .. . 8 Ground-Water Favorability . .... ..... .. ......... . .......... ... ..... . . 9 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Conclusions . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Recommendations . .. . ..... . ..... .. .. ......................... .. . .... . .. .. .... 11 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Appendix ........ .............. ...... ....... .. . .. ..... .. .. .. .. . .. .......... . .. 13
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ILLUSTRATIONS
Figure 1. Map showing location of study area ......... .. .. .. ...... . .... .. ..... . . 2 Figure 2. Map showing geologic subdivisions of the Piedmont Physiographic
Province .. . ....................... .. . .... . .. . .. .. . ............ ........ 4 Figure 3. Schematic diagram of ground-water movement in a cry~talline
rock aquifer .... ............ ...... .. .. ... . .. . .. .. . . .. .. ... .. .......... 5 Figure 4. Map showing examples of the linear nature of some stream beds . . .. . . . 9
TABLES
Table 1. Summary of water-quality analysis . .. ....... . . .... . .... . ... . ..... . . . .. . 10 Table 2. Well data .................... ...... .. .. .. . .... . . .. .... .. ....... .. ... .. 13
PLATES (plates in pocket)
Plate 1. Geologic map of Greene, Morgan, and Putnam Counties Plate 2. Location of wells with data presented in Table 2 Plate 3. Map showing ground-water favorability
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HYDROGEOLOGY OF GREENE, MORGAN, AND PUTNAM COUNTIES
Thomas W. Watson

ABSTRACT
The metasedimentary and igneous rocks in Greene, Morgan, and Putnam Counties provide approximately 40 percent of the consumptive water-use in the. area. Data from the files of local water-well contractors indicate that ground-water yields are highly variable from one location to the next. Maximum yield is approximately 300 gallons per minute, whereas yields of 1 to 2 gallons per minute are common. Depths for drilled wells range from 63 feet to a maximum of 700 feet. Well yields showed no apparent correlation with topography or rock type. Of the 145 high-yielding (20 gallons per minute or more) wells inventoried, approximately 110 obtained water moving through fractures within 400 feet of the surface. A total of 35 wells were drilled deeper than 400 feet. Of these 35, six were essentially dry before intercepting deep water-bearing zones. The water-producing interval was undetermined in the remaining 29 wells.
Streams valleys in the study area show a rectangular drainage pattern, a possible indication of structural control. Drainage may indicate zones of enhanced ground-water yield through fractures and foliation planes.
Water quality in the study area is generally within drinking water limits established by the Georgia Environmental Protection Division. Concentrations of total dissolved solids average less than 150 milligrams per liter, and do not exceed 270 milligrams per liter anywhere in the study area.
INTRODUCTION
Greene, Morgan, and Putnam Counties are located in the Piedmont Physiographic Province of northcentral Georgia (fig. 1). The area is little more than a one-hour automobile drive from Atlanta, Macon, Augusta, or Athens. Census figures show that the population of the three-county area was 33,000 in 1980, a 17-percent increase over 1970. Because of the potential

for further growth and development in the area, the Georgia Geologic Survey initiated a reconnaissancelevel investigation of the geohydrology of Greene, Morgan, and Putnam Counties.
The study area is underlain by igneous (both plutonic and volcanic) and metamorphic rocks. Groundwater availability in these rocks is controlled primarily by the intensity of jointing and fracturing and thickness of the weathered zone overlying the bedrock. Most of the larger communities in the study area, those requiring more than about 100,000 gallons per day (gal/d) of water, rely entirely on streams as a source of water. These communities include Greensboro, Union Point and Eatonton. The City of Madison obtains approximately 75 percent of its water supply from streams and the remainder, approximately 217,000 gal!d from wells. Farms, rural residences, and smaller communities rely entirely on wells for water. Total water use in the threecounty area, excluding thermoelectric and hydroelectric use, is approximately 6 mgal/d. An estimated 41 percent of this total is ground water. Of the 1.14 billion gal!d used for thermoelectric power, and 1.33 billion gal!d for hydroelectric power, none is from ground-water sources (Pierce, and others, 1982).
Goals of this investigation were:
1. define the geology, ground-water availability, and water quality of Greene, Morgan, and Putnam Counties; and
2. make recommendations for future hydrogeologic investigations based on the findings of this report.
Objectives leading to these goals were:
1. present the available geologic data on a base map;
2. plot available well data on a base map and relate well characteristics and water availability to geologic structure; and
3. determine the quality of ground water from existing chemical analyses, and relate analytical results to geologic conditions.

Figure 1. Map showing location of study area.

PREVIOUS INVESTIGATIONS
Several investigators have mapped the geology in Greene, Morgan and Putnam Counties. Myers (1968) and Libby (1969) mapped in Greene County; and Lawton (1966) mapped the Hard Labor Creek area of Morgan County. Davis (1980) suggested the existence of a cataclastic zone in parts of Greene and Morgan Counties. Vincent (1984) mapped the Siloam granite and vicinity in Greene and Putnam Counties.
GEOGRAPHY OF THE STUDY AREA
The study area occupies approximately 1,100 sq mi of the Piedmont Physiographic Province of Georgia.

This area is characterized by a crystalline metamorphic and igneous bedrock overlain by weathered rock and soil. The topography of the area is probably the result of long-term erosion of a formerly smooth, broad plain. A large part of the area consists of broad ridges and long, smooth slopes. Streams have cut deep v-shaped valleys. Topographic-map data indicate that slopes range from 0 to more than 25 percent. Soils on uplands where the slope is less than 15 percent are generally deeper than soils on steeper slopes. Where the slope is 15 percent or more, erosion removes soil material almost as fast as it forms. Consequently, soil cover is thinnestwl-lere slope is steepest (Payne, 1965). Maximum topographic relief in the three-county area exceeds 350 ft, with altitudes ranging from over 700 ft near Madison in Morgan County to approximately 340 ft in the vicinity of Lake Sinclair in Putnam County.

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Climate in the study area is characterized by warm to hot summers and mild winters. Precipitation averages about 48 in. per year. Ordinarily more precipitation occurs in spring than either summer or winter, and fall is the driest season of the year. The average precipitation in any month is more than 2 in. and less than 51;2 in. Summer precipitation comes primarily from localized convective storms and is much less uniform in coverage than winter precipitation. The summer storms, though small in extent and of short duration, are often intense and can cause considerable runoff and erosion. Thunderstorms occur on an average of 50 or more days per year (Payne, 1965).
The economy of Greene, Morgan, and Putnam Counties is largely agricultural, with dairy production being the chief source of farm income. Light industry in the area includes the manufacture of aluminum cookware, garments, fertilizer, mobile homes and marine recreational products. Mineral production includes crushed granite, feldspar, dimension stone, sand and gravel.
GEOLOGY
The bedrock of the study area consists of igneous rocks and metamorphic rocks (plate 1) exhibiting multiple folding, fracturing, and lineation features. These rocks were divided into a series of northeast-southwesttrending belts by King (1955), and Overstreet and Bell (1965). They defined and delineated these belts on the basis of distinct lithologies, structures, and metamorphic grades. Within the study area, three of these belts, the Mobilized Inner Piedmont, Charlotte, and Carolina Slate belts, come together (fig. 2).
Mobilized Inner Piedmont Belt
The Mobilized Inner Piedmont belt consists of a broad zone of highly metamorphosed and migmatitic granite gneisses, biotite gneisses, and mica schists extending from Alabama to Virginia. It is bounded on the southeast and northwest by two northeast-trending shear zones with rock of lower metamorphic grade than that of the Inner Piedmont (Hatcher, 1972, 1978). The northwestern shear zone is the Brevard fault, and the southeastern zone is the Towaliga-Middleton-Lowndesville fault (Davis, 1980).1n Greene, Morgan, and Putnam Counties, foliations,and compositional layering resulting from metamorphism and deformation of Inner Piedmont lithologies exhibit steep dips toward the northwest and southeast.

Charlotte Belt
The Charlotte belt is an assemblage of metavolcanics and metasedimentary rocks extending from southern North Carolina to eastern Alabama (Hatcher, 1972). Lithologies include granite gneiss, metagabbro, metabasalt, quartzite, mica schist, and talc schist (Griffin, 1978). Metamorphic intensity is medium to high (amphibolite facies). Structurally, rocks in the Charlotte belt are interpreted to lie in an upright to slightly overturned anticlinorium cored by Precambrian basement rocks (Hatcher, 1972; Griffin, 1978).
Carolina Slate Belt
lhe Carolina Slate belt is a Late Precambrian assemblage of metavolcanic, metaplutonic, and metasedimentary rocks. It extends from southern Virginia into northeastern Georgia. In the study area, the Carolina Slate belt is bounded on the northwest, in part by the Towaliga-Middleton-Lowndesville fault, and in part by the Charlotte belt. To the south the boundary is the Charlotte belt. Dominant lithologies within the metamorphosed sequence include felsic pyroclastics, volcaniclastics, felsic to intermediate plutons, and metasediments. Structurally, rocks of the Slate belt are interpreted to lie in a northeast-southwest trending synclinorium. The nature of the boundary between the Charlotte belt and the Carolina Slate belt is controversial and presently unresolved. This contact is not exposed in the study area but is located near the junction of the Oconee and Apalachee Rivers.
Faulting
A major fault system extends through the study area (Davis, 1980). The Towaliga-Middleton-Lowndesville fault zone is proposed as an extension of the southern splay of the Towaliga fault to the southwest joining the Middleton-Lowndesville fau It to the northeast. The TowaligaMiddleton-Lowndesville fault is an integral part of the boundary between the Inner Piedmont belt and the Charlotte and Carolina Slate belts (Davis, 1980). Geophysical data provide the best evidence for the existence of the Towaliga-Middleton-Lowndesville fault zone. Aeromagnetic maps published by the U.S. Geological Survey show a sharp break in aeromagnetic signatures across the fault boundary (Zietz, 1977). According to Davis (1980), the Towaliga-Middleton-Lowndesville fault indicates an early Paleozoic period of ductile deformation followed by a period of movement prior to the Triassic. This period of brittle faulting may be especially significant in terms of increased permeability and

3

8~' 30'

0

5

10

15 Miles

_ L_.______.._~j _ _ _, _ __ _____j

Figure 2. Map showing geologic subdivisions of the Piedmont Physiographic Province.

ground-water availability. Although jointing and fracturing are evident in outcrops and are suggested by drainage patterns, no systematic measurement of orientation was conducted in the study area.
Saprolite
Exposed crystalline rocks exhibit extensive changes resulting from physical and chemical weathering. Unweathered rock is exposed at only a few locations in

the study area. What is most commonly seen in outcrop is saprolite and soil weathered from saprolite. Saprolite is rock weathered in place that retains some of the original structure of the rock. Thickness of the saprolite depends on the chemistry and degree of fracturing of the parent rocks, as well as drainage and climate. Well data demonstrate that saprolite thickness may vary significantly, even between two closely spaced drill holes. Thickness of the saprolite zone ranges from zero to more than 150ft.

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HYDROLOGY
Surface Water
Annual precipitation in Greene, Morgan, and Putnam Counties is approximately 48 in. per year (NOAA, Environmental Data and Information Service). Approximately 30 in. per year of the total annual precipitation is returned to the atmosphere by evapotranspiration (Peter W. Bush, U.S. Geological Survey, unpublished data). Subtracting evapotranspiration from total precipitation leaves 18 in. of water income. An estimate of surface runoff can be obtained by measuring the flow volume of the Oconee River upstream and downstream from the study area. Any addition to stream flow in this interval can be attributed to surface runoff. It is recognized that the boundaries of the study area do not correspond with the Oconee River watershed area, and that the flow of the Oconee River is regulated by dams; however, the results are within the limits of accuracy of this discussion. Surface runoff distributed evenly over the study area is equivalent to approximately 15 in. of precipitation per year (U.S. Geological Survey, 1981). Subtracting this amount from the water income leaves approximately 3

in. of the original 48 in. of annual precipation. Tliis remaining 3 in. is assumed to represent the contribution to the ground-water regime.
The study area is drained by a network of streams of the Oconee, Ogeechee, and Little River drainage basins. Regional drainage patterns of streams in the study area are dendritic. Inspection of detailed maps of the area, however, reveals a smaller-scale drainage pattern that is trellised or rectangular, suggesting geologic control of drainage patterns. As the streams eroded into the crystalline Piedmont rocks, drainage may have begun to follow joints and fractures in the rock, resulting in the rectangular drainage patterns and linear stream beds common to the area.
Ground-Water Availability In The Piedmont
Geologic Controls
Ground-water availability in crystalline rocks is controlled primarily by the intensity and degree of interconnection of jointing and fracturing of the rock (fig. 3). Distribution of joints and fractures is a function of

EXPLANATION
Waler Table
)
Water Movement

Q)

I I

I

I I

Joinls and Fractures

D

I III

1

I, 1 r

1 J

Saprolite/Soil

Figure 3. Schematic diagram of ground-water movement in a crystalline rock aquifer.
5

rock type, plus internal stress produced by tectonics, and stress relief from erosion, weathering, and metamorphism. Different types of rocks have different susceptibilities to jointing and fracturing. Some generalizations based on rock type can be used when evaluating aquifer potential in the Piedmont (Cressler and others, 1983):
1. Brittle rocks such as quartzite and rocks containing high percentages offeldspar and quartz are subject to fracturing and jointing, and the fractures are likely to be interconnected; these types of rock tend to provide good aquifer material.
2. Rocks such as gneiss and amphibolite tend to be variable in their susceptibility to fracturing and jointing, and are thus variable in aquifer capacity.
3. Rocks such as phyllite and schist tend to have tight, poorly connected joints and fractures; these rocks generally yield small quantities of water to wells.
4. Where rocks of contrasting character are in contact, different responses to stress and weathering can create zones of enhanced permeability.
Faults or cataclastic zones are features that can indicate fracturing, jointing and enhanced permeability of the rock. In the Piedmont, however, it is important to note the relative age of the last faulting event, and the type of faulting. Metamorphosis after faulting can "heal" fault fractures, thereby negating secondary permeability.
A second major influence on the availability of ground water in the Piedmont is the thickness and areal extent of the regolith, the layer of unconsolidated material, whether residual or transported, that overlies the more coherent bedrock. For purposes of this discussion, regolith includes soil, saprolite, and alluvium.
Because saprolite is often more permeable than the underlying coherent rocks, ground water tends to accumulate at the contact between saprolite and parent rock. Springs commonly form where the saprolitebedrock interface is at land surface, as on a hillside. Many dug and bored wells in the Piedmont terminate at the bottom of the saprolite zone or penetrate only slightly into the top of the underly.ing hard rocks.

In addition to supplying water to springs, dug wells, and bored wells, the saprolite serves as a surficial mantle covering large drainage areas, absorbing surface water which would otherwise be lost to overland runoff. Much of the water absorbed by saprolite is released slowly to fractures in the underlying bedrock. In areas where a substantial thickness of saprolite is found, the water table is generally above the bedrock-saprolite interface. Therefore, aquifer storage capacity is significantly enhanced by thick saprolite. It is also generally correct to conclude that wells are more productive and tend to have more stable year-round yields where there is a thick mantle of saturated saprolite as opposed to where unweathered rock is near the surface.
Well Depth
Geology is the main influence on regional groundwater availability. However, at a specific location, well construction may be a major factor influencing water availability. Well depth is a subject of discussion among well drillers, ground-water geologists, and individuals seeking a reliable ground-water supply. Generally it was thought that beyond a depth of approximately 400 ft, ground-water yield decreased with increasing depth, presumably because increasing lithostatic pressure inhibited fracture formation or tended to close fractures.
Studies in other areas of the Georgia Piedmont, however, indicate that drilling deeper than 400 ft is justified in some instances. Water already available to a well is seldom lost by drilling deeper than 400 ft. Therefore, there is nearly always a chance of getting more water by increasing the depth of a well. Investigations into the feasibility of gas storage in crystalline rocks near the City of Jonesboro (Stewart, 1962) indicate that appreciable flows of water can occur in dense crystalline rocks at depths as great as 500ft. The study described by Stewart deals with quartz-feldspar to hornblende-biotite gneiss similar to bedrock in much of the present study area. Horizontal permeabilities of 0.010 gpd/ft2 were observed at a depth of 490 ft in one test hole. Stewart gives examples of other wells near Jonesboro with depths greater than 500ft capable of yielding more than 20 gal/min.
In a study of ground-water availability in the metropolitan Atlanta area, Cressler and others (1983) noted numerous wells that derive 40 gal/min or more from fractures occurring at depths of 400 to 600ft. They

6

attribute the existence of deep fracture zones to the upward expansion of the rock column in response to erosional unloading. Because of the erosional mechanism of stress relief, topographic features indicating removal of large volumes of rock relative to specific areas may suggest areas where deep horizontal fracturing is likely to be found. Three distinct types of topographic settings which may indicate the presence of stress relief fracturing in the subsurface are cited (Cressler and others, 1983):
1. Points of land formed by streams converging at acute angles, or between subparallel tributaries entering a large stream.
2. Broad, relatively flat ridge areas, commonly on divide ridges, surrounded by stream heads.
3. Broad valleys formed by removal of large volumes of material relative to the land on either side.
Optimum Well Location
Optimum locations for higher-yielding wells in the Piedmont province are commonly in valleys where a fracture system or fault is present. The following reasons are given for drilling in valleys rather than hilltops or ridges (LeGrand, 1967):
1. Surface runoff is more rapid from hilltops and slopes resulting in less recharge than in lower, flatter areas.
2. Unconfined ground-water flow is from hill to valley; wells located in valleys can intercept a greater volume of natural ground-water flow.
3. The water table surface is generally a subdued image of the land surface (fig. 3); the water table is usually closer to the surface in lowland areas than on uplands.
4. The saprolite layer is generally thicker in valleys and lowland areas than on resistant hills and ridges; saprolite tends to enhance storage capacity of an aquifer, while retarding surface runoff.
5. Rocks underlying lowland areas often have a more effective system of openings to conduct ground water; commonly, highland areas exist because they are composed of rocks more resistant to erosion than lowlands; this resistance to erosion can often be attributed to the lack of

a well-developed system of joints and fractures; penetration of water into fractures accelerates chemical and physical weathering, resulting eventually in a valley or lowland area.
Concerns of Ground-Water Users In The Piedmont
General
Ground water in the Piedmont is avaluable resource that is largely undeveloped. Potential ground-water users often would rather install expensive surface-water treatment plants than develop a ground-water system. Concerns most commonly expressed regarding groundwater supplies include low initial well yield, declining well yield, and susceptibility of the well to contamination. The following comments may help clarify these concerns.
Low Initial Well Yield
Drilling a water well involves a certain amount of risk. However, the majority of wells drilled in the Piedmont are sited without regard for hydrogeologic principles. Random site selection tends to increase the number of dry or nearly dry wells drilled. By taking advantage of available hydrogeologic knowledge and using properly designed multiple well systems, adequate municipal and industrial supplies of ground water can be developed in most areas of the Piedmont.
Declining Well Yield
The sustained yield predictions of a well in a crystalline rock aquifer must be based on a carefully executed pumping test. Specific capacity, the yield of a well per unit of drawdown, decreases as the pumping level is lowered below the water-producing fractures. The well continues to produce water, but at a reduced rate. Therefore, accurate specific capacities of a well should be determined when the well is pumped at its maximum rate. A 24-hour step-drawdown test should be used to find maximum pumping rate. This is followed by a pump test of at least 72 hours duration to establish aquifer characteristics (Caswell, 1982). Pumping tests should be based on one or more of the various techniques for evaluation of unconfined aquifers (Bouwer, 1978). The transmissivity value used to estimate

7

long-term well capacity should be the lowest value obtained, thus providing a conservative estimate. When planning the construction of a high capacity well, it is important to note that pumping tests done in late summer through early fall provide more conservative values of transmissivity and storage than tests in late winter and early spring. The quantity of water stored in the aquifer reflects seasonal variations in precipitation.
Failure of a well is seldom a sudden occurrence. Most commonly, well failure is the cumulative result of one or more of the following (Cressler and others, 1983): an inadequate pumping test; pumping a well in excess of safe yield; a gradual decline of capacity due to improper maintenance and cleaning of the well and pump; the onset of a period of prolonged drought.
Contamination of Well Water
A concern of some ground-water users is that contaminants might travel for miles along water-bearing fractures in the rock, often in unknown directions. Direct entry of contaminants along fractures is not a likely problem, however, if a well has been properly located and constructed. Fracture zones yielding large quantities of water are usually associated with substantial thicknesses of an unconsolidated mantle of saprolite and alluvium. This unconsolidated mantle ordinarily provides adequate filtration of ground water.
Transport of contaminants along fractures in a crystalline rock aquifer can occur, especially within the area of influence of the well or upgradient of the well. Distances of contaminant transport are usually on the order of hundreds or thousands of feet, rather than miles as is sometimes suggested. A well normally obtains water from within an area of influence that can be defined by a pumping test and geologic analysis of the area.

mation presented to this point of this Information Circular is general and applies to all areas where ground water is controlled by fractures.
The best evidence of fracture systems in the study area is resultant from an analysis of stream valleys. Close examination of drainage patterns shows that many stream valleys exhibit a remarkable linearity. In addition, changes in stream direction often are angular. Such lineation and angularity of drainage are possible fracture zones in the bedrock. One ofthe most striking examples of geologic control of drainage is near the confluence of the Oconee and Apalachee Rivers (fig. 4), on the Buckhead lV2-minute quadrangle. Lineations also are evident on the Greensboro, Harmony, Liberty and Penfield 7V2-minute quadrangles. Linear stream valleys are favorable drilling locations, as wells in these areas probably would intercept ground water flowing toward the stream through fractures.
The Towaliga-Middleton-Lowndesville fault zone is apparently the result of largely ductile deformation (Davis, 1980). Field inspection, however, reveals secondary brittle textures, suggesting possible postorogenic movement. Such brittle rock fabric probably would indicate an area of enhanced permeability.
Regolith in Greene, Morgan, and Putnam Counties is extensive. Most natural outcrops of unweathered rock are limited to some stream beds. Exceptions to this statement are found in the vicinity of the Siloam granite where boulders of unweathered granite and areas of pavement outcrops are common. Thickness of the regolith is generally greatest in river bottoms and least on crests of hills and ridges. Local variations in thickness can be extreme. Logs of wells in apparently similar geologic settings separated laterally by 200 or 300ft can show differences in saprolite thickness of 100ft or more.
Well Depth

Ground Water Availability in Greene, Morgan, and Putnam Counties

The following conclusions are based on well data in the study area (table 2):

Geologic Controls

1. At depths less than 100ft, the deeper the well is drilled the greater the productivity.

The search for geologic environments favorable for

ground-water development was accomplished through

a successive elimination process. During this process the

size of the area under consideration was progressively

..

reduced and study of the remaining area was intensified. Preceding sections of this report define the geology of

the area and discuss the various geologic and well-

construction controls on ground-water availability. Infor-

2. Between depths of 100ft and 400ft, well yield with increasing depth is not well defined; most Piedmont wells are within this depth range.
3. Between depths of 400 to 500 ft, if a well is relatively dry, and if no lithologic changes or fractures have been encountered, deeper drilling may not be advisable.

8

83"22' 30"

83 " 15'

33"37'30!"!..-l------..,-.,......,..--------.-- - - < " - - - -- - - " - -- : -- - ; ----j-33"37'30"

\

/'

(~-- '- /

' /

, : , - -, J
I

.,r'
)
)I , I

33" 30'-l-------------L_------~-------r--33" 30 '

83"22' 30"

0

2 Miles

83 " 15 '

Figure 4. Map showing examples of the linear character of some stream beds.

4. It is often desirable to drill two wells of intermediate depth rather than continue a lowyielding well to extreme depth.
Of the wells inventoried for this report, only six were 100ft deep or less, median well depth was 280ft, and the maximum depth was 700 ft. Thirty-five of the wells inventoried were drilled to depths in excess of 400 ft. Of these 35 wells, at least six were essentially dry until penetrating water-bearing fractures near the bottom of the hole (William Martin, Virginia Supply and Well Co., oral commun., 1982). Nine of the 35 wells exceeding
depths of 400 ft were drilled in areas considered
optimum for drilling.

Ground-Water Favorability
By observing rock type, possible areas of extensive fracturing, saprolite thickness and well depth, Greene, Morgan, and Putnam Counties can be divided into three types of subarea based on relative favorability for water well drilling (plate 3). The favorability map does not imply the success or failure of a particular well. It merely takes into consideration the number of favorable criteria within a particular environment and attaches a weighted value. To make the best use of the favorability map, one would select several areas designated " Most favorable" and proceed with more detailed hydrogeologic investigation. Other examples of exploration

9

techniques might include magnetometer surveys to detect areas of anomalous weathering associated with increased secondary permeability, and resistivity surveys to detect buried fracture systems. The final step in the exploration program would be test drilling.
Water Quality
Chemical quality of ground water is a complex function reliant in part on solubility of the reservoir rock, pH and temperature of the infiltrating water, and residence time of the water in the aquifer. Although rocks and minerals are only slowly soluble in water, residence time of ground water is commonly measured in tens to thousands of years. As a result, ground-water quality commonly reflects the character of the soluble components of the aquifer.
Chemical analyses of water from 19 wells in Greene, Morgan, and Putnam Counties show the water to be within normal ranges for ground water in the Piedmont. Concentrations of dissolved solids are low to moderate. Two distinctive chemical classes of ground water are present. The first includes soft, slightly acidic water, with low dissolved mineral content. Usually this type of water comes from light-colored rock of granitic composition. The second includes a hard, slightly alkaline water, comparatively high in dissolved solids. Water of this second category comes from dark rock such as gabbro, hornblende gneiss, and amphibolite. Except for occasional instances of high iron (table 1), concentrations of inorganic constituents are within drinking water standards recommended by the Environmental Protection Division (1977). Individual wells having unusually high levels of particular dissolved inorganic constituents are usually the result of water coming in contact with mineralized zones.

CONCLUSIONS
The following conclusions can be drawn regarding ground-water availability and water quality in Greene, Morgan, and Putnam Counties:
1. Specific aquifers cannot be delineated, based on available data. Water availability is affected by topography, saprolite thick[less, well depth, and degree of fracturing, as well as rock type.
2. Rectangular drainage patterns are indicative of structural and lithologic control of drainage, and support the concept that permeability of the bedrock is higher in linear stream valleys.
3. Brittle rock fabric in the vicinity of the TowaligaMiddleton-lowndesville fault zone probably indicates enhanced permeability in the immediate area of the fault.
4. Well yields are highly variable from one location to the next. Maximum yield is approximately 300 gal/min while yields of 1 to 2 gal/min are common. The sustained yield of most wells is less than 100 gal/min. Sometimes a few tens of feet separate a producing well from an essentially dry well. Therefore, average well-yield figures would be of little use in planning localized water supplies.
5. Most well sites in the area have been randomly located without regard for hydrogeologic principles. Convenience and/or economics are the most common considerations when choosing a well location. The incidence of "dry" holes could be minimized by using appropriate siteselection criteria as shown on the ground-water favorability map (plate 3).

Dissolved pH

Maximum 270

8.7

Mean

142

6.8

Minimum 44

5.5

Number

of

Samples

18

17

Table 1.- SUMMARY OF WATER QUALITY ANALYSES Values in milligrams per liter except pH

Silica (Si02)
55 36 18

Iron

Calcium Magnesium Sodium Potassium Alkalinity Bicarbonate Sulfate Chloride Fluoride Nitrate

(Fe)

(Ca)

(Mg)

(Na)

(k)

(CaC03) (HC03) (S04)

(CI)

(FI)

(N03)

0.3

161

11

15

4.0

113

149

110

22

1.0

17

0.05

22

4.5

10.7

2.4

76

72

14

8

0.3

2.9

0

2

0.7

2.6

1.4

37

16

0.4

1.5

0.1

0.2

15

11

13

14

18

12

9

14

15

18

16

13

10

6. Water quality in the three-county area is generally within limits for drinking water as defined by the Georgia EPD (1977). Aquifers of granitic composition commonly yield soft, slightly acidic water, while aquifers containing quantities of ferromagnesian minerals yield harder, slightly alkaline water.
RECOMMENDATIONS
Ground water can be an important water source in Greene, Morgan, and Putnam Counties. Increasing population will intensify demand for water, and at the same time, increase the risk of ground-water contamination. Information necessary for making effective decisions in ground-water management is not widely available in the crystalline rock areas of Georgia. The following activities are considered fundamental to a continuing ground-water reconnaissance program:
1. Detailed geologic mapping is essential to a ground-water study. Geologic maps provide information about rock type, rock origin, structure, and the existence of faulting, fracturing, and joint patterns.
2. Collection of well data is crucial to making accurate statements regarding ground-water availability. Necessary data include depth of the well, length of the casing in the well, and yield. Well data should be accompanied by accurate well locations.
In addition to the basic tasks of a ground-water program in a crystalline-rock area, the following suggestions could be used to augment a ground-water evaluation program in the Piedmont and Blue Ridge:
3. Standard geophysical surveys would enhance a geologic mapping program. Gravity and magnetometer surveys are effective methods for locating and delineating geologic structure which might be pertinent to water availability. Seismic refraction surveying is a rapid, accurate method of determining thickness of regolith. Resistivity surveys can help locate saturated fracture zones in bedrock.
4. Thorough aquifer testing should be done prior to putting a new well in service. Conservative well yields should be used in evaluating groundwater availability at a site. Well drawdown and yield should be monitored periodically to avoid "sudden" well failure.

5. A chemical analysis of raw water should be made when a new well is put into service. Periodic monitoring of raw water-quality should be done by trained personnel using standard techniques to obtain consistent results. The water should be analyzed for major dissolved constituents as well as trace elements. Common organic contaminants should be included in routine analyses.
REFERENCES
Bouwer, H., 1978, Groundwater hydrology: McGrawHill, p. 106-113.
Callahan, J.T., and Blanchard, H.E., 1963, The quality of ground water and its problems in the crystalline rocks of Georgia: Georgia Mineral Newsletter, v. 16, nos. 3-4, p. 66-72.
Callahan, ].T., Newcomb, L.E., and Geurin, ].W., 1965, Water in Georgia: U.S. Geol. Survey, Water-Supply Paper 1762, 88 p.
Caswell, B., 1982, Municipal fractured-rock wells: Water Well Journal, v. 36, no. 9, p. 40-41.
Cressler, C.W., Blanchard, H.E., Jr., and Hester, W.G., 1979, Geohydrology of Bartow, Cherokee, and Forsyth Counties, Georgia: Georgia Geol. Survey, Info. Circ. 50,45 p.
Davis, G.]., 1980, The southwestern extension of the Middleton-Lowndesville cataclastic zone in the Greensboro, Georgia area, and its implications: M.S. thesis, Univ. Georgia, 151 p.
Georgia Environmental Protection Division, 1977, Rules for Safe Drinking Water, Chapter 391-3-5, p. 601-657.
Georgia Geologic Survey, 1976, Geologic map of Georgia, scale 1 :500,000.
Grantham, R.G., and Stokes, W.R., 1976, Ground-water quality data for Georgia: U.S. Geol. Survey, Openfile Report, 216 p.
Griffin, V.S., Jr., 1978, Detailed analysis of tectonic levels in the Appalachian Piedmont: Geologishe Rundschau, v. 67, p. 180-201.
Hatcher, R.D., Jr., 1972, Developmental model for the southern Appalachians: Geol. Soc. America Bull., v. 83, p. 2735-2760.
_ _ , 1978, Tectonics of the western Piedmont and Blue Ridge, southern Appalachians: Review and Speculations: Amer. Jour. Science, v. 278, p. 276-304.

11

Humphrey, R.C., 1969, Geology, petrology, and mineral resources of the crystalline rocks of Greene and Hancock Counties: M.S. thesis, Univ. Georgia, 100
p.
Joiner, T.j., Warman, J.C., Scarborough, W.L., and Moore, D.B., 1967, Geophysical prospecting for ground water in the Piedmont area, Alabama: Geol. Survey of Alabama, Circular 42, 48 p.
King, P.B., 1955, A geologic section across the southern Appalachians, in Russell, R.j., ed., Guides to Southeastern Geology; Boulder, Colorado, Geol. Soc. America, p. 332-373.
LaForge, L., Cooke, C.W., Arthur, K., and Campbell, M.R., 1925, Physical geography of Georgia: Georgia Geol. Survey, Bull. 42, 189 p.
Lawton, D.E., 1966, Geology of the Hard Labor Creek area in West-Central Morgan County, Georgia: M.S. thesis., Univ. Georgia, 51 p.
LeGrand, H. E., 1962, Perspective on problems in hydrogeology: Geol. Soc. America Bull., v. 73, p.1147-1152.
_ _ , 1967, Ground water of the Piedmont and Blue Ridge Provinces in the southeastern states: U.S. Geol. Survey, Circular 538, 11 p.
Libby, S.C., 19 71, The petrology of the igneous rocks of Putnam County, Georgia: M.S. thesis, Univ. Georgia, 99 p.
Libby, S.C., and Radcliffe, D. 1971, Geology, petrolo~y, and mineral resources of Putnam County, Georg1a: Georgia Geol. Survey, Open-file Report, 61 p.
McCallie, S.W., 1908, A preliminary report on the underground waters of Georgia: Geol. Survey of Georgia, Bull. 15, 371 p.
Medlin, J.H., 1964, Geology and petrography of the Bethesda Church area, Greene County, Georgia: M.S. thesis, Univ. Georgia, 100 p.
Myers, W.C., II, 1968, Geology of Pres!ey's Mill are.a, northwest Putnam County, Georg1a: M.S. thes1s, Univ. Georgia, 67 p.
Overstreet, W.C., and Bell, H., Ill, 1965, The crystalline rocks of South Carolina: U.S. Geol. Survey, Bull. 1183, 126 p.

Payne, H.H., 1965, Soil survey of Morgan County, Georgia:. Soil Conservation Service Report 6, 75 p.
Pierce, R.R., Barber, N.L., and Stiles, H.R., 1982, Water use in Georgia by county for 1980: Georgia Geol. Survey, Info. Circ. 59, 180 p.
Snipes, D.S., 1981, Ground-water quality and quantity in fracture zones in the Piedmont of northwestern South Carolina: Clemson Univ. Water Resources Research Institute, Tech. Report no. 93, 87 p.
Snow, D.T., 1977, Induced seismicity at Richard B. Russell Reservoir, in U.S. Army Corps of Engineers, 1977, Section E, 45 p.
Sonderegger, j.L., Pollard, L.D., and Cressler, C.W., 1978, Quality and availability of ground water in Georgia: Georgia Geol. Survey, Info. Circ. 48, 25 p.
.Staheli, A.C., 1976, Topographic expression of superimposed drainage on the Georgia Piedmont: Geol. Soc. America Bull., v. 87, p. 450-452.
Stewart, j.W., 1962, Relation of permeability and jointing in crystalline metamorphic rocks near Jonesboro, Ga.: U.S. Geol. Survey, Professional Paper 450-D, p. 168-170.
Summers, W.K., Specific capacities of wells in crystalline rocks: Ground Water, v. 10, no. 6, Nov.-Dec., 1972.
Thompson, M.T., Herrick, S.M., Brown, E., et al. 1956, The availability and use of water in Georgia: Georgia Geol. Survey, Bull. 65, 329 p.
U.S. Geological Survey, 1981, Water resources data, Georgia Water year 1981, 446 p.
Vincent, H.R., 1984, Geologic map of the Siloam Granite and vicinity: Georgia Geol. Survey, GeologicAtl as 1 (in press).
Wenner, D.B., Gillon, K.A., 1980, Review of potential host rocks for radioactive waste disposal in the Piedmont Province of Georgia: E.J. Du Pont de Nemours Co., 57 p.
Williams, H., 1978, Tectonic lithofacies map of the Appalachian orogen: Memorial University of Newfoundland, Map 1.
Zietz, 1., 1977, Aeromagnetic maps of part of northern Georgia: U.S. Geol. Survey, Open-file Report 77-190.

12

APPENDIX

Table 2- WELL DATA

ID Number
35 36 37 38 50 51 52 55 56 57 58 59 82 84 86 95 100 101 102 103 104 106 107 200 201 202 203 204 205 206 207 208 210 211 212
213
214 215

Latitude & Longitude

33 14 45 33 14 42 33 14 41 33 14 40 33 34 45 33 36 08 33 36 06 33 35 02 33 50 00 33 19 42 33 40 22 33 36 59 33 37 54 33 40 35 33 44 13 33 37 45 35 25 20 33 13 24 33 43 26 33 40 00 33 30 56 33 32 22 33 11 42 33 25 24 33 29 38 33 36 27 33 36 16 33 33 31 33 35 57 33 30 14 33 33 09 33 43 37 33 41 44 33 41 58 33 36 12 33 29 14 33 29 11 33 29 23

83 21 52 83 21 48 83 21 51 83 21 53 83 34 45 83 39 36 83 27 52 83 28 46 83 28 57 83 22 42 83 06 20 83 04 25 83 36 24 83 06 40 83 30 55 83 36 32 83 23 47 83 18 OS 83 18 18 83 10 36 83 03 24 83 18 36 83 24 58 83 14 28 83 16 01 83 18 24 83 17 10 83 17 10 83 17 20 83 16 38 83 17 20 83 17 48 83 19 47 83 18 45 83 18 00 83 11 15 83 11 04 83 09 06

Date Drilled
1973 1973 1974 1974 1968 1968 1978 1976 1980 1954 1980 1955 1967 1969 1963 1967 1952 1975
1980 1960
1969 1958 1981 1965 1962 1971 1974 1980 1973 1960 1980

Diameter (in)
10 10 10 10 6 6 6 6 6 8 6 8 6 8 6 6 6 6 6
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

Cased to (ft)
108 70 75 80 66 96 93 98 85 38 110 95 94 98 60 94 67 50 50 14 45 120 30 50 58 100 60 70 101 60 109 50 90 60 137 60 53 110

Total Depth
500 345 425 505 500 300 346 645 605 436 605 600 360 650 494 360 414 550 400 63 138 285 187 405 300 200 175 436 145 265 128 400 300 233 200 345 185 505

Capacity (gal/min)
6.3 55 108 87 47 42 203 76 63 316 50 20 30 36
30 75 28 20
22 40 25 50 200 25 60 30 20 20 40 30 60 20 40

13

Table 2- WELL DATA (Continued)

ID Number

Latitude & Longitude

Date Diameter Cased to

Drilled

(in)

(ft)

Total Depth

Capacity (gal/min)

216 33 26 52 83 11 37 1977

6

120

515

25

217 33 26 43 83 10 31 1981

6

140

265

25

218 33 26 25 83 11 02 1978

6

76

425

60

219 33 26 39 83 11 03 1978

6

140

265

25

220 33 25 10 83 10 21 1981

6

45

225

25

221 33 24 13 83 10 30 1980

6

26

225

50

222 33 24 17 83 10 so 1980

6

120

185

30

223 33 25 47 83 14 15 1980

6

46

385

28

224 33 36 52 83 09 54 1958

6

62

168

44

225 33 36 01 83 08 57 1981

6

8

125

25

226 33 36 08 83 08 30

6

29

500

25

227 33 35 31 83 08 43 1981

6

8

65

60

228 33 35 03 83 09 44 1971

6

14

100

22

229 33 34 41 83 11 10

10

700

100

230 33 34 53 83 11 28 1948

8

151

450

53

231 33 35 33 83 12 32 1979

6

100

250

30

232 33 35 17 83 12 59 1970

6

58

120

30

233 33 33 39 83 13 23 1977

6

80

141

30

234 33 32 47 83 14 04 1981

6

138

230

110

235 33 32 10 83 13 00 1971

6

101

260

30

236 33 30 55 83 13 35 1959

6

96

165

44

237 33 30 57 83 11 03

6

90

150

20

238 33 30 17 83 08 44 1978

6

23

440

50

239 33 30 04 83 08 14 1979

6

40

200

30

240 33 32 20 83 07 38 1970

6

50

150

40

241 33 32 25 83 07 38

6

58

125

60

242 33 32 27 83 09 56 1977

6

20

173

30

243 33 36 04 83 07 34 1970

6

30

80

20

244 33 33 51 83 08 34 1953

6

194

167

35

245 33 34 03 83 09 04 1963

6

144

315

30

246 33 34 16 83 09 17 1964

8

29

365

22

247 33 33 57 83 09 19 1958

6

33

105

30

248 33 39 58 83 10 25

6

168

275

20

249 33 41 25 83 13 51 1975

6

145

45

250 33 28 25 83 01 OS 1969

8

75

465

51

251 33 27 17 83 02 03 1977

6

18

203

40

252 33 29 02 83 02 15 1972

6

9

463

100

253 33 36 51 83 04 31 1948

8

22

254 33 30 53 83 03 17 1958

6

45

138

30

255 33 36 56 83 04 40 1943

8

221

600

40

256 33 36 41 83 03 53 1956

8

100

600

35

14

Table 2- WELL DATA (Continued)

ID Number

Latitude & Longitude

Date Diameter Cased to

Drilled

(in)

(ft)

Total Depth

Capacity (gal/min)

257 33 36 06 83 07 10 1974 258 33 33 24 83 00 49 259 33 33 23 83 00 37 260 33 34 19 83 06 38 261 33 33 17 83 06 13 1972 262 33 32 41 83 OS 12 1954 263 33 32 19 83 04 53 1956 264 33 30 55 83 OS 55 1975 265 33 31 04 83 03 27 1956 266 33 31 00 83 03 24 1958 267 33 30 05 83 02 29 1982 268 33 30 11 83 00 30 1972 269 33 30 53 83 00 02 1972 270 33 39 07 83 06 00 1956 271 33 37 32 83 OS 32 1955 272 33 37 38 83 03 01 1969 273 33 37 41 83 02 51 1968 274 33 38 39 83 00 56 1972 275 33 40 13 83 01 27 1982 300 33 34 56 83 39 50 1972 301 33 29 59 83 33 12 1980 302 33 37 24 83 37 03 303 33 33 37 83 33 04 1968 304 33 31 07 83 32 11 1980 305 33 31 16 83 31 54 1969 306 33 35 31 83 31 30 308 33 42 18 83 31 46 1981 309 33 41 58 83 32 55 1981 310 33 39 20 83 30 23 1979 311 33 40 34 83 31 50 1961 312 33 43 55 83 32 35 1961 313 33 49 00 83 30 21 1975 314 33 45 32 83 32 34 1972 315 33 28 17 83 25 21 1965 316 33 28 25 83 25 29 1972 317 33 28 44 83 25 26 318 33 27 53 83 24 56 1977 319 33 29 00 83 27 36 1955 320 33 29 53 83 27 51 1971 321 33 29 39 83 27 51 1974 322 33 35 48 83 27 38 1980

6

25

100

200

6

135

275

20

6

121

275

20

6

90

105

75

6

38

200

20

6

47

124

25

6

44

138

20

6

30

209

100

6

87

135

40

6

87

141

25

6

57

150

35

6

19

68

40

6

325

60

6

132

186

30

6

121

261

20

6

51

140

25

6

70

200

20

6

98

200

20

6

90

125

75

6

35

45

60

6

55

305

30

400

115

6

52

100

25

6

55

190

30

6

100

280

30

6

73

173

70

6

125

260

75

6

40

200

35

6

87

126

25

6

41

160

48

6

38

500

29

6

34

263

200

6

31

258

50

6

117

150

26

6

62

413

30

6

60

565

25

6

60

565

25

6

154

236

20

6

75

185

75

6

76

140

40

6

66

335

125

15

Table 2 - WELL DATA (Continued)

ID Number

Latitude & Longitude

Date Diameter Cased to

Drilled

(in)

(ft)

Total Depth

Capacity (gal/min)

323 33 35 52 83 27 37 1980 324 33 36 26 83 25 26 1979 325 33 36 22 83 23 12 1961 326 33 31 04 83 26 48 1969 327 33 30 20 83 23 21 1981 328 33 32 09 83 28 45 1972 329 33 33 29 83 28 48 1981 330 33 33 30 83 26 24 1981 331 33 41 30 83 27 10 1974 332 33 43 25 83 28 53 333 33 42 10 83 27 42 1974 334 33 40 59 83 25 45 1970 335 33 41 27 83 26 12 1979 336 33 41 37 83 26 23 1982 337 33 39 39 83 26 57 1981 338 33 40 57 83 26 30 1981 339 33 29 52 83 21 29 1979 340 33 32 27 83 17 48 1981 341 33 34 39 83 19 47 342 33 32 44 83 21 OS 1972 343 33 30 07 83 17 20 1974 344 33 32 44 83 17 52 1975 345 33 34 20 83 19 39 1981 346 33 32 31 83 22 06 347 33 31 18 83 22 20 1972

6

104

265

so

6

58

225

20

6

109

210

30

6

110

300

20

6

91

455

150

6

63

140

120

6

95

480

40

5

35

430

45

6

84

225

37

6

52

205

100

6

22

325

20

6

173

260

20

6

65

325

20

6

126

485

60

6

125

265

so

6

40

85

40

6

118

260

so

6

126

405

24

6

65

155

40

6

60

100

20

6

70

290

so

6

89

120

20

6

68

165

so

6

95

145

100

6

125

240

20

16

GEORGIA GEOLOGIC SURVEY

0

5

10

15 Miles

EXPLANATION

Lithologic Contact Fault - - Inferred Fault /VINV\JVv\. Shear Zone
Granite Gneiss Undifferentiated

Porphyritic Megacrystic Granite
Porphyritic - Sparsely Megacrystic Granite

Granite Gneiss I Amphibolite

Granite I Granite Gneiss

Granite Gneiss I Granite

Granite I Gneissic Biotite Granite

Biotite Gneiss I Feldspathic Biotite Gneiss

Hornblende Gneiss

Biotite Granite Gneiss I Feldspathit Biotite Gneiss 1 Amphibolite-Hornblende Gneiss
Biotite Gneiss Undifferentiated

Hornblende Gneiss I Amphibolite I Granite Gneiss
Amphibolite I Epidote Quartzite I Granite Gneiss

Biotite Gneiss 1

F~3 Amphibolite I Mica

Mica Schist I Amphibolite

Schist I Biotite Gneiss

~J Biotite Gneiss I Amphibolite

Amphibolite

Sillimanite Schist

~~ Gabbro

~ Sillimanite Schist I Gneiss I Amphibolite
i!J Granite Undifferentiated

Micaceous QuartzoFeldspathic Gneiss I Amphibolite
Biotite Muscovite Schist I Amphibolite

Geologic map of Greene, Morgan, and Putnam Counties.

INFORMATION CIRCULAR 60

Plate 1.

I

33o45' - - ( Bostwick

312





32 5

51

30 3



I

" """'

3330'

'

""" '

JATION

""" ' """

:>cation and

326
320 321 3 9 317.~16
318~15 .---;. ::::---
---

nber

/

.c57 ;
Eatonton

33 15'----'
I
I
I
I
I---~- - -
8330'

.,35.36
37 38

0

5

10

15 Mil

Plate

IRVEY

Location of wells with data presented in Table 2.

INFORMATION CIRCULAR

EORGIA GEOLOGIC SURVEY

8 30'

EXPLANATION

20c2ooJ

Data Point
First number indicates well yield Number in parentheses indicates well depth

D

Area of most favorable geologic criteria
Saprolite thickness - 20 to 150 feet Slope- 0 to 15% Probable jointing and fracturing of bedrock Receives drainage from adjacent areas
Area of moderately favorable geologic ct
Saprolite thickness - 10 to 60 feet Slope - 8 to 25% Possible jointing and fracturing of bedrock Drainage is through the area
Area of least favorable geologic criteric:
Saprolite thickness - 0 to 60 feet Slope - 15% or more Bedrock resistant to jointing and fracturing Drainage is away from area

0

5

10

15 Miles

Ground-water favor ability map.

INFORMATION CIRCULAR 60

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