Water-Resources Investigations Report 884176 

GEOLOGY OF AN AREA NEAR BRENTWOOD, 

WILLIAMSON COUNTY, TENNESSEE 

Prepared by the 

U.S. GEOLOGICAL SURVEY 

in cooperation with the 

TENNESSEE DEPARTMENT OF HEALTH AND ENVIRONMENT, 

DMSION OF SUPERFUND 
GEOLOGY OF AN AREA NEAR BRENTWOOD, 

WILLIAMSON COUNTY, ‘TENNESSEE ” 

By Dorothea Withington Hanchar 

U.S. GEOLOGICAL SURVEY .a 

Water-Resources Investigations Report 88-4176 

Pepared in cooperation with the 

TENNESSEE DEPARTMENT OF HEALTH AND ENVIRONMENT, 

DIVISION OF SUPERFUND 

Nashville, Tennessee 

1988 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

For additional information write to: Copies of this report can be purchased from 

District Chief 

U.S. Geological Survey 

A413 Federal Building 

Nashville, Tennessee 37203 

U.S. Geological Survey 

Books and Open-File Reports Section 

Federal Center, Building 810 

Box 25425 

Denver, Colorado 80225 
CONTENTS 

Abstract 1 

Introduction 1 

Geology 6 

Lithology 6 

Structure 14 

Summary 15 

References 24 

ILLUSTRATIONS 

Figure 1. Map showing location of study area and observation and domestic wells 2 

2. Map showing structural setting of study area 4 

3. Generalized geologic section along lines A-A! and B-B1 across the study area 5 

4. Map showing thickness of the Bigby-Cannon Limestone 8 

5. Gamma and neutron geophysical logs for well Wm:N-053A 10 

6-10. Maps showing: 

6. Thickness of the Hermitage Formation 12 

7. Thickness of the Carters Limestone 16 

8. Structure of the top of the Carters Limestone 18 

9. Structure of the top of the Lebanon Limestone 20 

10. Structure of the top of the T-3 bentonite bed of the Carters Limestone 22 

TABLES 

Table 1. Thickness of formations 7 

2. Depth to the top of formation or unit 11 

CONVERSION FACTORS 

For use of readers who prefer to use metric units, conversion factors for inchpound unit used in this report are listed below: ., 

Multiply inch-pound unit BY To obtain metric unit 

foot (ft) 0.3048 meter (m) 

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) 

mile (mi) 1.609 kilometer (km) 

Sea level: In this report “sea level” refers to the National Geodetic Vertical 

Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, 

formerly called “Sea Level Datum of 1929..” 

. . . 

ill 
GEOLOGY OF THE AREA AROUND 

A HAZARDOUS-WASTE DISPOSAL SITE 

IN WILLIAMSON COUNTY, TENNESSEE 

By Dorothea Withington Hanchar 

.i 

ABSTRACT 

‘The lithology and geologic structure of an 

area near Brentwood, Williamson County, Tennessee, were studied to define the potential 

aquifers and confining units of the ground-water 

flow system. Four formations were identified. 

They are, in descending order, the Bigby-Cannon 

Limestone, the Hermitage Formation, the 

Carters Limestone, and the Lebanon Limestone. 

The B&by-Cannon Limestone and the Carters 

Limestone are potential aquifers. The Hermitage Formation and the Lebanon Limestone 

are confining units. The Bigby-Cannon Limestone and the Hermitage Formation have been 

affected by recent erosion. Any variation of the 

Carters Limestone is controlled by pre-Carters 

erosion of the top of the Lebanon Limestone. 

The thickness of the Carters Limestone ranges 

from 65 to 79 feet. Structurally, the area reflects 

the regional northwest dip. A small scale anticline-syncline pair also is evident. This feature 

is not a result of erosion and also occurs in the 

T-3 bentonite bed in the Carters Limestone. 

INTRODUCTION 

An area near Brentwood,Williamson 

County, Tennessee (fig. l), was used to dispose 

of approximately 800 barrels of industrial waste 

in 1978. In June 1986, the U.S. Geological Survey, in cooperation with the Superfund Division 

of the Tennessee Department of Health and Environment, began a study to characterize the 

hydrogeology of the areas and the surrounding 

area. This characterization includes a thorough 

understanding of the geology to define the extent 

of the potential aquifers and confining units that 

comprise the ground-water flow system. This 

report describes the geology of the area and compares it to the regional geology. 

Regionally, the study area is located along 

the northwestern dipping flank of the Nashville 

Dome (fig. 2) (Wilson, 1948, p. 57). Previous 

work by Wilson and Miller (1963) has identified 

four formations of Ordovician age at or within 

300 feet of the land surface that underlie the site 

and are discussed in this report. From youngest 

to oldest these formations are: the BigbyCannon Limestone, and the Hermitage Formation of the Nashville Group, and the Carters 

Limestone and the Lebanon Limestone of the 

Stones River Group (fig. 3). These formations 

have been described in detail by Wilson (1949). 

Descriptions of the lithologies penetrated 

during the drilling program are presented by 

Withington (1988). 

A network of 34 observation wells was installed at 17 sites for this project (Withington, 
Location map 

11 r-ll,dXmWr’ 

Williamson 

County 

Study area 

EXPLANATION 

unlllln DISPOSAL SITE 

A-A’ LINE OF SECTION 

53A& OBSERVATION WELL AND NUMBER--FUiI Well 

identification includes the prefix Wm:N-##. 

‘33a DOMESTIC WELL AND NUMBER--Full well 

indentification includes the prefix Wm:N-##. 

Figure 1. --Location of study area.and 

observation and domestic wells. 

2 
86”d -17’22” 86’45’ 

35’58’ 

1 

-7 

; 

I 

ese from U.S. Geologlcel Survey 

24.000. I Frenklln. 1991 0 0.5 MILE 

I I I k I 

HH 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEE-i 

DATUM IS SEA LEVEL 

3 
, 

, 

, 

, 

1 

. 

P 

, 

; 

I 
t 

.I 

u A’ 

FEET m 0 

Obc 3 700- 

I 

- ! 

- \ 

I oc 

I 

500 01 

800- 

a 

cl- 64 2 

=G 

B’ 

0 

700- 

600 ’ 

0 2.000 FEET I I 

Vertical exaggeration X 5 

DATUM IS SEA LEVEL 

EXPLANATION 

GEOLOGIC UNITS 

Obc Bigb y-Cannon Limestone 

Oh Hermitage Formation f 

Nashville Group 

oc Carters Limestone 

ItOrdovician 

Stones River Group 

01 Lebanon Limestone 

Figure 3.--Generalized geologic section along 

lines A-A’ and B-B’ across the study area. 
1988). A shallow well and a deep well were 

drilled at each site. Major changes in lithologic 

type were identified on the basis of the lithology, 

texture, and color of the cuttings, which were collected every 5 feet during drilling of the wells. 

Upon completion of drilling, the deep wells were 

logged by using caliper, gamma, and neutron 

borehole-geophysical tools (Withington, 1988). 

Formation contacts were identified on the basis 

of interpretation of both lithologic and geophysical logs. 

Geophysical logs obtained from five 

domestic wells near the study area (fig. 1) were 

used to supplement lithologic data derived from 

drilling operations. The wells from which these 

logs were obtained ranged in depth from 148 to 

1,050 feet. The geophysical logs from these wells 

were used in conjunction with the lithologic and 

geophysical logs of the Geological Survey observation wells to construct structure contour and 

formation thickness maps. 

GEOLOGY 

Lithology 

The formations in the study area are, in 

descending order, the Bigby-Cannon Limestone, 

the Hermitage Formation, the Carters Lime- 

-stone, and the Lebanon Limestone. These units 

are overlain by 3 to 15 feet of soil and weathered 

rock. This material is generally brown to reddish-brown clay and silt. All drilling, once 

through the weathered rock, began in either the 

Bigby-Cannon Limestone or the Hermitage Formation. 

Regionally, the correlative Bigby and Cannon Limestones (referred to as the BigbyCannon Limestone in this report as defined by 

Wilson, 1947) consists of three major lithologic 

types: the Bigby facies, the dove-colored facies, 

and the Cannon facies (Wilson, 1949, p. 107). All 

three types occur in northern Williamson County (Wilson, 1948, p. 114). The Bigby facies is a 

coarse-granular limestone, composed of fossil 

fragments, and is blue-gray in color when fresh 

(Wilson, 1949, p. 115). The dove-colored facies 

interfingers with the Bigby and the Cannon 

facies and is a light-gray (“dove-colored”) 

lithographic limestone (Wilson, 1949, p. 122). 

The Cannon facies, which also interfingers 

with the Bigby facies, is a fine- to mediumgrained blue limestone with coarse-grained 

variations (Wilson, 1949, p. 126). In the study 

area, the Bigby and the Dove-colored facies were 

recognized. The formation is predominantly 

silt-free with solution openings, making this unit 

a potential aquifer where solution openings are 

present. The Bigby-Cannon Limestone is a 

coarse- to medium-grained, dark yellowishbrown limestone with interbeds of dove-colored 

lithographic limestone. Regionally, the thickness of this formation ranges from 50 to 100 feet. 

In the study area, this formation has been 

thinned by recent erosion, and the thickness 

ranges from0 to 41 feet (table 1; fig. 4). The maximum thickness does not represent a complete 

section. The contact between the Hermitage 

Formation and the Bigby-Cannon Limestone is 

transitional and is based on texture and color 

changes seen in the cuttings during drilling as 

well as changes seen in the geophysical logs. The 

Bigby-Cannon-Hermitage contact is seen in 

gamma logs by an increased number of gamma 

counts per second, which corresponds to an increased shale content in the Hermitage Formation (fig. 5). This contact was determined in 

neutron logs by an increase in counts per second, 

indicating decreased porosity with depth (fig. 5). 

The Hermitage Formation is partially eroded. 

Depth to the top of the Hermitage ranges from 

0 to 41 feet (table 2; fig. 3). 

The Hermitage Formation consists of four 

facies. These are (in de‘scending order): the 

Dalmenella Coquina limestone, the silty nodular 

limestone, the granular phosphatic limestone, 

and the laminated argillaceous limestone. Of 

6 
Table L-Thickness of formations 

[Values in feet] 

Well Bigby-Cannon 

No. Limestone 

Hermitage 

Formation 

Carters 

Limestone 

WM:N-041A 25 101 70 

WM:N-042A 25 72 68 

WM:N-043A 0 26 65 

WM:N-044A 0 26 66 

WM:N-045A 35 97 70 

WM:N-046A 0 57 71 

WM:N-047A 0 78 77 

WM:N-048A 32 80 71 

WM:N-050A 28 103 71 

WM:N-051A 16 79 77 

WM:N-052A 20 80 68 

WM:N-053A 30 74 79 

WM:N-054A 12 99 70 

WM:N-055A 0 102 72 

WM:N-056A 27 87 70 

WM:N-057A 41 83 71 

WM:N-058A 25 78 72 

WM:N-023 

WM:N-024 

WM:N-033 

WM:N-039 

WM:N-040 

U.S. Geological Survey Wells 

0 88 78 

0 39 78 

36 86 -_ 

22 102 72 

0 37 77 

Domestic Wells 

these four, only the laminated argillaceous and study area, the Hermitage Formation is a 

the Granular Phosphatic limestones are present 

in the study area. These are respectively a thinpredominantly fine-grained, dusky yellowishbedded, or laminated argillaceous bluish-gray 

brown, argillaceous limestone with shale partings and fossil fragments. This facies 

limestone, interbedded with thin shale partings; corresponds to the laminated argillaceous limeand a coarse-grained gray limestone composed 

entirely of ground-up fragments, pellets, or unstone. Variations include an overlying coarsercomminuted shell particles (Wilson, 1962, 

grained, salt-and-pepper, dark to duskyyellowish-brown limestone, possibly the 

p. 485-486). The high argillaceous contact granular phosphatic limestone. The Hermitage 

makes this formation a confining unit. In the Formation also is distinctly odoriferous, and 

7 
86O, 

35’58’ 

86’45’ 

se from U.S. Geological Survey 

24.000. Frenklin. 1981 

0 0.5 MILE 

I I i I 1 

HH 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 

8 
EXPLANATION 

ulmml DISPOSAL SITE 

x=iL _^ 

IzTl 

me : “3j& AREA OF HERMITAGE FORMATION OUTCROP 

-2o- LINE OF EQUAL THICKNESS OF THE BIGBYCANNON LIMESTONE--Interval 20 feet. Datum 

is sea level 

250 WELL LOCATION AND THICKNESS OF THE 

BIGBY-CANNON LIMESTONE. IN FEET 

Figure 4.--Thickness of the Bigby-Cannon Limestone. 
GAMMA COUNTS 

PER SECOND 

125 

225 

NEUTRON COUNTS 

PER SECOND 

200 300 400 500 600 

I I 1 

FORMATION 

Bigby-Cannon Limestone 

Hermitage Formation 

- -T-3 Bentonite- - 

bed 

Carters Limestone 

Lebanon Limestone 

Figure 5.--Gamma and neutron geophysical logs for well Wm:N-053A. 

10 
Table 2.--Depth to top of formation or unit 

[Values in feet below land surface] 

Well Hermitage 

No. Formation 

Carters 

Limestone 

T-3 

bentonite 

bed of 

Carters Limestone 

Lebanon 

Limestone 

WM:N-04iA 25 101 136 

WM:N-042A 25 97 105 

WM:N-043A 0 25 32 

WM:N-044A 0 26 32 

WM:N-045A 35 132 143 

WM:N-046A 0 57 65 

WM:N-047A 0 78 90 

WM:N-048A 32 112 123 

WM:N-050A 28 131 141 

WM:N-051A ( 16 95 105 

WM:N-052A 20 100 107 

WM:N-053A 30 104 113 

WM:N-054A 12 111 120 

WM:N-055A 0 102 110 

WM:N-056A 27 114 120 

WM:N-057A 41 124 132 

WM : N-058A 25 103 111 

WM:N-023 0 95 104 

WM:N-024 0 56 117 

WM:N-033 31 132 141 

WM:N-039 15 117 126 

WM:N-040 0 46 54 

U.S. Geological Survey Wells 

Domestic Wells 

196 

165 

90 

92 

mm 

128 

153 

-- 

mm 

172 

-- 

183 

mm 

174 

-- 

195 

me 

166 

189 

115 

possibly petroliferous, which was evident during 

drilling by a strong sulphur smell. This formation has been extensively eroded in the study 

area. Thicknesses of the Hermitage Formation 

range from 26 to 103 feet (table 1; fig. 6). 

The Hermitage Formation-Carters Limestone contact was also determined from a combination of lithologic and geophysical logs. During 

drilling, this contact was placed at the depth 

when the overflow changed from medium gray 

(Hermitage Formation) to pale yellowish-brown 

(Carters Limestone). The contact is sharp and 

easy to pick. Drill cuttings change from a 

medium- to fine-grained dusky yellowish-brown 

argillaceous limestone, the Hermitage, to a veryfine to cryptocrystalline, dark yellowish-brown 

limestone, characteristic of the upper member of 

11 
86“45’ 

Base from U.S. GeoloQical 

1:24.000. Franklin. 1991 015 M’LE 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 

12 
EXPLANATION 

m DISPOSAL SITE 

-8O- LINE OF EQUAL THICKNESS OF THE 

HERMITAGE FORMATION--Interval 

20 feet. Datum is sea level 

860 WELL LOCATION AND THICKNESS OF 

THE HERMITAGE FORMATION, 

IN FEET 

Figure 6.--Thickness of the Hermitage Formation. 
the Carters Limestone. This contact is also evident in the gamma logs as a decrease in counts 

per second (fig. 5). The depth to the contact between the Hermitage Formation and the Carters 

Limestone ranges from 26 to 132 feet below land 

surface (table 1). 

The Carters Limestone, the uppermost formation of the Stones River Group, consists of an 

upper and a lower member. These are separated 

by a bentonite bed named the T-3 bentonite bed. 

The upper member of the Carters Limestone observed during drilling is a dark yellowish-brown, 

cryptocrystalline limestone with characteristic 

conchoidal fracturing. This corresponds to the 

description given by Wilson (1949). The lower 

member consists of a dark yellowish-brown, crystalline, pelletal limestone. Both the upper and 

lower members of the Carters Limestone are 

aquifers where solution openings are present. 

The average thickness of the Carters Limestone 

regionally has been reported as 70 feet (Wilson, 

1949; p. 54). In the study area, the upper member of the Carters Limestone has an average 

thickness of 10 feet, while the lower member of 

the Carters Limestone has an average thickness 

of 60 feet. The total thickness of the Carters 

Limestone in the study area ranges from 65 to 79 

feet, and averages 72 feet (table 1; fig. 7). 

The T-3 bentonite bed, which separates 

these two members, is the thickest and most continuous of the regionally persistent bentonite 

beds within the Carters Limestone (Wilson, 

1949). The reported thickness of this bentonite 

ranges from 1 to 21 inches. In the study area, the 

thickness of the T-3 bentonite bed ranges from 

12 to 18 inches. The T-3 bentonite is readily 

recognized during drilling. Local drillers named 

this bed “pencil cave” because of the ease of drilling and because of the resemblance of the cuttings to carpenters’ lumber-marking pencils. 

The T-3 bentonite bed is also obvious in gamma 

logs, where it is indicated by a sudden increase in 

the number of counts per second (fig. 5). 

The contact between the Carters Limestone and the Lebanon Limestone is defined 

both by lithologic change and gamma logs. The 

Lebanon Limestone consists of interbedded argillaceous limestone and shale, which is evident 

during drilling by the different rates of drilling 

and the change in lithology. In the gamma logs, 

this interbedded nature is evidenced by the alternating high and low counts per second, which 

correspond to shale and limestone layers, respectively (fig. 5). The depth to the Carters Limestone-Lebanon Limestone contact in the study 

area ranges from 90 to 196 feet below land surface (table 2). As is the contact between the 

Bigby-Cannon Limestone and the Hermitage 

Formation, this contact is transitional. 

The Lebanon Limestone, also of the Stones 

River Group, is a thin-bedded, fossiliferous limestone with shale partings (Wilson, 1949). A maximum of 20 feet of this formation was penetrated 

in this study during the drilling phase. This 

upper part of the Lebanon Limestone consists of 

a fine-grained, dusky to dark yellowish-brown 

fossiliferous limestone with shale partings. Because of this shaley nature, the Lebanon Limestone is a confining unit. This formation is 

characterized by alternating slow and fast drilling rates. Lebanon Limestone was penetrated in 

only 8 out of 17 deep wells drilled (table 2). 

Reported average thickness of the Lebanon 

Limestone in northeast Williamson County is 

100 feet (Wilson, 1949). Thicknesses obtained 

from gamma logs of local domestic wells indicate 

an average thickness of 110 feet of Lebanon 

Limestone in the study area. 

Structure 

The study area is located on the 

northwestern flank of the Nashville Dome 

(fig. 2). Regional dips in this area are 15 feet per 

mile to the northwest (Piper, 1932; Wilson, 

1948). Secondary folds are common along this 

14 
northwest margin (Piper, 1932; Wilson, 1948), 

and large scale folds occur in southern Williamson County (Piper, 1932). 

Structure contour maps were constructed 

for the top of each formation penetrated. Contact depths derived from geophysical logs and 

lithologic descriptions were used together with 

surveyed elevations to calculate elevations of the 

tops of formations. 

The top of the Bigby-Cannon Limestone 

and the Hermitage Formation are controlled by 

erosion; thus, the elevations of the exposed top 

of these formations do not reflect local structure. 

At many well sites, the Bigby-Cannon Limestone 

is missing and the Hermitage Formation has 

been thinned as a result of erosion (figs. 4 and 6). 

The structure of the study area is apparent 

in the contour maps of the altitude of the tops of 

the Carters and Lebanon Limestones (figs. 8,9, 

and 10). From these maps, a regional northwest 

dip is evident, as well as an anticline-syncline 

pair. The axes of these folds trend northeast, 

which is consistent with the orientation of other 

folds in the area reported by Piper (1932) and 

Bassler (1932). 

SUMMARY 

As part of a study of the hydrogeology of an 

area near Brentwood, Williamson County, Tennessee, 34 wells were drilled at 17 sites in the surrounding area. The area is underlain by Ordovician limestones, of which four formations 

were identified. These are, from youngest to 

oldest, the Bigby-Cannon Limestone and the 

Hermitage Formation of the Nashville Group, 

and the Carters Limestone and the Lebanon 

Limestone of the Stones River Group. Of these 

formations, the Bigby-Cannon Limestone and 

the Carters Limestone have been identified as 

potential aquifers because of the occurrence of 

solution openings. The Lebanon Limestone and 

the Hermitage Formation are defined as confining units because of their argillaceous nature. 

Based upon data collected both during drilling 

operations and from borehole geophysical investigations, depths to contacts of the different formations were determined. From these depths, 

structure contour and thickness maps were constructed. The thickness maps show that the 

Bigby-Cannon Limestone and the Hermitage 

Formation have been affected by erosion. The 

slight variability of thickness of the Carters 

Limestone is due to erosion following deposition 

and is probably controlled by the erosion surface 

on the Lebanon Limestone. Because the Hermitage Formation has been affected by modern 

erosion, the upper surface of this formation does 

not reflect the structure of individual rock layers. 

Some structure is obvious in the contour maps of 

the top of the Carters Limestone, the altitude of 

the T-3 bentonite bed, and the altitude of the top 

of the Lebanon Limestone. These maps indicate 

a small anticline-syncline pair. Such small folds 

are consistentwith the regional structural setting 

identified in previous work. 

15 
86Or 

35’58’ 

86’45’ 

Base from U.S. Geoloaical SurVeY 

1:24.00 . 0. Franklin. 1581 

O-” M’LE 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 

16 
EXPLANATION 

mllml DISPOSAL SITE 

-7o- LINE OF EQUAL THICKNESS OF THE CARTERS 

LIMESTONE--Interval 10 feet. Datum is sea level 

O’* WELL LOCATION AND THICKNESS OF THE 

CARTERS LIMESTONE, IN FEET 

Figure 7.--Thickness of the Carters Limestone. 

17 
35057’ 3c 

86’47’22” 86’45’ 

B6 188 from U.S. Geological Survey 

1: 24.000. Frsnklln. 1991 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 

l.8 
EXPLANATION 

UlInInl DISPOSAL SITE 

-660- STRUCTURE CONTOUR--Shows altitude of the 

Carters Limestone. Hachures indicate depression. 

Contour interval 20 feet. Datum is sea level 

-- t - ANTICLINE--Showing trace of crestal plane. 

Dashed where approximately located 

-- 

t 

- SYNCLINE--Showing trace of trough plane. Dashed 

where approximately located 

6570 WELL LOCATION AND ALTITUDE OF THE 

CARTERS LIMESTONE 

Figure 8.--Structure of the top 

of the Carters Limestone. 

19 
35’58’ 

Base from U.S. Geologicel Survey 

1:24.000. Franklin. 1981 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 
EXPLANATION 

lImlnl DISPOSAL SITE 

-6OO- STRUCTURE CONTOUR--Shows altitude of the 

top of the Lebanon Limestone. Contour 

interval is 20 feet. Datum is sea level 

0585 WELL LOCATION AND ALTITUDE OF THE TOP 

OF THE LEBANON LIMESTONE 

Figure 9.--Structure of the top of the Lebanon Limestone. 

21 
35’58’ 

8S047’22” 8S045’ 

I 

-~ 

188 from U.S. Geologicel Survey 

24.000. Frenklln. 1981 o-6 MJLE 

0 0.5 KILOMETER 

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL 

22 
EXPLANATION 

uuuml DISPOSAL SITE 

- 7000 STRUCTURE CONTOUR--Shows the altitude 

of the top of the T-3 bentonite bed. 

Contour interval 20 feet. Hachures 

indicate depression. Datum is sea level 

0686 WELL LOCATION AND ALTITUDE OF THE 

T-3 BENTONITE BED 

Figure lO.--Structure of the top of the T-3 

bentonite bed of the Carters Limestone. 

23 
REFERENCES 

Bassler, R.S., 1932, The stratigraphy of the 

Central Basin of Tennessee: Tennessee 

Division of Geology Bulletin 38,268 p. 

Piper, A.M., 1932, Ground-water in northcentral Tennessee: US. Geological Survey 

Water-Supply Paper 640,238 p. 

Wilson, C.W., 1948, The geology of Nashville, 

Tennessee: Tennessee Division of Geology Bulletin 53, 172 p. 

----- 1949, Pre-Chattanooga stratigraphy in 

Central Tennessee: Tennessee Division of 

Geology Bulletin 53,172 p. 

----- 1962, Stratigraphy and geologic history of 

Middle Ordovician rocks of central Tennessee: Geological Society of America 

Bulletin, v. 73, p. 481-504. 

Wilson, C.W., and Miller, R.A., 1963, Geologic 

map of Franklin quadrangle, Tennessee: 

Tennessee Division of Geology, GM 63- 

NE, scale 1:24,000. 

yf4sL&&> Q#w, * I 

v . 1988, Construction, geologic, 

and water-&e1 data for observation wells 

near Brentwood, Williamson County, Tennessee: U.S. Geological Survey Open-File 

Report 87-248,33 p. 

24