The Lexington Limestone 

» (Middle Ordovician) 

of Central Kentucky

By DOUGLAS F. B. BLACK, EARLE R. CRESSMAN, and WILLIAM C. MACQUOWN, JR.

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1224-C

~*>

Prepared in cooperation with the 

Kentucky Geological Survey
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington D.C., 20402 - Price 15 cents (paper cover)
CONTENTS

Page

Abstract_________________________-_-___-_--.---___-__--___-________ Cl

Introduction _________._____._____-___-_--____--_.______--_-_________ 1

Development of nomenclature---._-_-_----------------_--------______ 2

Lexington Limestone.________________________________________________ 7

Curdsville Limestone Member___________________________________ 14

Logana Member_______________________________________________ 15

Grier Limestone Member.________________________________________ 17

Brannon Member______________________________________________ 20

Tanglewood Limestone Member..________________________ ______ 21

Devils Hollow Member_________________________________________ 23

Millersbur g Member _____________________________________________ 24

Nicholas Limestone Member_______________.______________________ 26

References cited.____________________________________________________ 28

ILLUSTRATIONS

Page 

FIGURES 1, 2. Map of central Kentucky showing:

1. Counties, location of lines of sections, location of newly 

designated type and reference sections, and limits of 

Brannon Member of Lexington Limestone __________ C3

2. Location of measured sections and 7)_-minute quadrangles ______--__-------__--------------_-_--___ 4

3. Comparison of nomenclature of this report with some past

usages.-_______________________________________________ 5

4. 5. Stratigraphic relations of Lexington Limestone:

4. West to east_____________________________________ 9

5. North to soutli____-_-_____-_-__-_-_--______-_-____ 10

in

CONTRIBUTIONS TO STRATIGRAPHY

THE LEXINGTON LIMESTONE (MIDDLE ORDOVICIAN) 

OF CENTRAL KENTUCKY

By DOUGLAS F. B. BLACK, EARLE E,. CRESSMAN, and 

WILLIAM C. MAcQuowN, JR.

ABSTRACT

The Lexington Limestone is revised to include the entire sequence of dominantly bioclastic generally fossiliferous limestone lying above lithographic 

limestone of the Tyrone Limestone and below interbedded tabular limestone and 

shale of the Clays Ferry Formation. The name Cynthiana Formation, formerly 

applied to the upper part of this sequence, is abandoned. The names Curdsville 

Limestone Member, Logana Member, Grier Limestone Member, Brannon Member, and Devils Hollow Member are retained for subdivisions of the Lexington 

Limestone. The Millersburg Member and the Nicholas Limestone Member, 

proposed by Foerste (1909, 1914) for subdivisions of the Cynthiana Formation, 

are adopted as members of the Lexington Limestone. The new name Tanglewood 

Limestone Member is introduced for the body of bioclastic calcarenite, commonly 

phosphatic, that makes up much of the upper part of the Lexington; the name 

Woodburn Limestone Member, which included only a part of the calcarenite 

unit, is abandoned. Two new names, Macedonia Bed and Cane Run Bed, are 

applied to units within the Grier Limestone Member.

INTRODUCTION

Rocks of Middle Ordovician age that crop out in central Kentucky 

have in the past been divided into five formations. These were, in 

ascending order, the Camp Nelson, Oregon, and Tyrone Limestones 

(the three of which compose the High Bridge Group), the Lexington 

Limestone, and the Cynthiana Formation. The Camp Nelson and 

Tyrone consist mostly of lithographic limestone, and the Oregon consists of dolomite; these three formations are lithologically distinctive 

and easily recognizable throughout their area of outcrop.

In contrast, stratigraphic relations within the body of bioclastic 

limestone that overlies the rocks of the High Bridge Group are complex. Various rock types recur throughout the sequence, and facies 

changes are common. Limestone formerly assigned to the Cynthiana

01
C2 CONTRIBUTIONS TO STRATIGRAPHY

Formation underlies and intertongues southward with interbedded 

shale and tabular limestone for which Weir and Greene (1965) have 

given the name Clays Ferry Formation.

The Lexington Limestone is herein redefined to include all the strata 

formerly assigned to both the Lexington Limestone and the Cynthiana 

Formation with the exception of those beds now included in the Clays 

Ferry Formation; the name Cynthiana is abandoned. The names 

Curdsville Limestone Member, Logana Member, Grier Limestone 

Member, Brannon Member, and Devils Hollow Member are retained 

for subdivisions of the Lexington. The terms Nicholas Limestone 

Member and Millersburg Member, proposed by earlier workers, are 

adopted. The name Tanglewood Limestone Member is used for the 

body of bioclastic calcarenite which is locally dominant in the upper 

part of the Lexington Limestone. The name Woodburn Limestone 

Member, which included only a part of this calcarenite, is here abandoned.

The revisions result from data gathered during the mapping of thirteen 7i/2-minute quadrangles. Approximately 35 stratigraphic sections have been measured and described from surface exposures and 

diamond-drill cores. In addition to the authors, the following members of the U.S. Geological Survey have participated in the mapping 

and measuring of sections: Ernest Dobrovomy, R. C. Greene, S. P. 

Kanizay, R. D. Miller, J. S. Pomeroy, and G. W. Weir. This report 

has been prepared in cooperation with the Kentucky Geological 

Survey.

The locations of stratigraphic sections mentioned in this report are 

shown on figures 1 and 2, and the locations of mapped quadrangles are 

shown on figure 2.

DEVELOPMENT OF NOMENCLATURE

The stratigraphic nomenclature as of 1943 of the Middle Ordovician 

rocks overlying the High Bridge Group is shown in the first column 

of figure 3. All names were derived from localities in central Kentucky except Hermitage, which was extended from Tennessee. All 

names but Sulphur Well (McFarlan, 1943, p. 20, 22) had been proposed by the year 1919. Most earlier workers had placed the Lexington-Cynthiana contact at the top of the Perryville Limestone, but, 

McFarlan (1943, p. 18) proposed that the Perry ville be excluded from

th.o Lexingtorx oncl given fon-national rank. TRe PerryVille W£IS

thought to rest unconf ormably on the Lexington Limestone,

McFarlan. and Wlxito (1948) demonstrated that the Perry ville of the

southern Blue Grass had been miscorrelated with younger beds of

similar lithology to the north for which they proposed the name 

Devils Hollow division of the Cynthiana Formation (McFarlan and
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FIGURE 1. Map of central Kentucky showing counties, location of lines of section

designated type and reference sections, and limits of Brannon Member of Lexi

Kentucky coordinate system, north zone.
CONTRIBUTIONS TO STRATIGRAPHY
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White, 1948, p. 1640). The resulting nomenclature is shown in the 

second column of figure 3. The contact between the Lexington Limestone and the Cynthiana Formation was placed at the top of the Devils 

Hollow or where the Devils Hollow is absent, at the top of the Woodburn. The name Logana was reintroduced for rocks earlier termed 

Hermitage.

Hamilton (1950, p. 18) noted that facies changes in the rocks above 

the Benson are common, perplexing, and difficult to map and remarked 

that the interval from the top of the Benson to the base of rocks of 

Eden age was relatively constant in thickness. He therefore redefined 

the name Cynthiana Formation to include all strata between the top 

of the Benson and the base of rocks of Eden age, and the Cynthiana 

thus included, from base upward, the Brannon Limestone Member, 

the Woodburn Limestone Member, and an unnamed upper member. 

Nosow and McFarlan (1960, p. 7) generally followed Hamilton's 

nomenclature (fig. 3, col. 3).

The Lexington was recently (Cressman, 1964) reduced to formational rank as the Lexington Limestone; the name Grier Limestone 

Member was introduced for rocks earlier included in the Jessamine 

and Benson Limestones, and the Logana and Curdsville were reduced 

to member rank.

In southern Fayette County and areas to the south, Weir and Greene 

(1965) applied the name Clays Ferry Formation to interbedded shale 

and tabular limestone that had been the Million Shale of Nickles 

(1905, p. 25) and the upper part of the Cynthiana Formation (fig. 

5, section 8). The lower part of the Clays Ferry intertongues northward with the upper part of the Lexington Limestone as defined in 

this paper. Tongues of the lower part of the Clays Ferry have been 

mapped as far north as the suburbs of Lexington, and reconnaissance 

indicates that similar tongues may locally extend much farther 

northward.

Where the Brannon Member is present, the contact between the 

Lexington Limestone and Cynthiana Formation as revised by Hamilton (1950, p. 18) is mappable with little difficulty. However, as has 

been known for years, the Brannon pinches out to the north near Lexington and Frankfort and to the southwest in Mercer and Anderson 

Counties (fig. 1); it is therefore absent throughout much of the area. 

According to McFarlan and White (1948, p. 1635-1636), the top of 

the Lexington as later redefined by Hamilton can be identified in areas 

where the Brannon Member is absent by a faunal assemblage that 

includes Stromatocerium pustulosum, Dinorthis ulrichi, Strophomena
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY 07

vicina, and CypJiotrypa frankfwtensis. However, Cypfiot^pa is not 

everywhere present; specimens of Dinorthis ulricM and Strophomena 

vicina can seldom be identified with confidence in the field; and the 

conspicuous zone of Stromatocerium pustulosum that occurs a few 

feet below the base of the Brannon in areas south of Lexington rises 

stratigraphically northward, crossing mapped contacts between lithologic units. Furthermore, in much of the area where the Brannon 

Member is present, the Brannon is both overlain and underlain by 

well-sorted crossbedded medium-grained bioclastic phosphatic calcarenite, and where the Brannon pinches out these two calcarenite 

bodies merge into a single lithologic unit. For these reasons, the contact between the Lexington and Cynthiana as defined by Hamilton is 

not usable for detailed geologic mapping throughout most of the area 

of exposed Middle Ordovician rocks.

There are several reasons for redefining the Lexington Limestone 

and abandoning the name Cynthiana rather than redefining both formations. First, similar rock types are found throughout the entire 

sequence. Second, a single formational term simplifies the problems 

of nomenclature presented by numerous local facies. Third, there is 

no lithologically defined contact sufficiently widespread to serve as 

a formation boundary.

LEXINGTON LIMESTONE

The name Lexington Limestone was first applied by Campbell 

(1898) to beds between the High Bridge Group below and the Flanagan 

Chert (subsequently abandoned) above. The lower part of Campbell's Flanagan Chert is the Brannon Member of the Lexington Limestone as defined in this paper. Campbell did not give a type section 

for the Lexington Limestone, but the type area was presumably in the 

Eichmond 30-minute quadrangle (lat. 37°30/ to 38°00', long. 84:°00' 

to84°30').

The Lexington Limestone is here revised to include the heterogeneous succession of bioclastic carbonate rocks, probably of Middle Ordovician age, bounded at the base by lithographic limestone of the 

Tyrone Limestone and overlain and in part laterally bounded by interbedded shale and tabular limestone which are included in the Clays 

Ferry Formation (Weir and Greene, 1965). Readouts along Interstate Highway 64 east of its crossing of the Kentucky River approximately 22/2 miles south-southeast of Frankfort are designated as a 

reference section.
C8 CONTRIBUTIONS TO STRATIGRAPHY

The Lexington Limestone is approximately 310 feet thick near 

Frankfort and Lexington. The upper part of. the formation intertongues southward with the lower part of the Clays Ferry Formation, 

and the Lexington thereby thins to about 230 feet in northwestern 

Madison County and 210 feet in northern Mercer County. The area 

of outcrop of the Lexington Limestone closely approximates that 

shown on previous geologic maps for the Lexington Limestone and 

Cynthiana Formation combined.

Stratigraphic relations of the Lexington Limestone are shown on 

figures 4 and 5.

At the reference section the Lexington Limestone is divided into 

the following members, listed from oldest to youngest: The Curdsville Limestone Member, the Logana Member, the Grier Limestone 

Member, the Branhon Member, the Tanglewood Limestone Member, 

the Devils Hollow Member, the Millersburg Member, and the Nicholas 

Limestone Member. Of these, the Curdsville, Tanglewood, and 

Nicholas Members are characterized by calcarenite consisting of subrounded bioclastic carbonate sand grains in large part well sorted 

and cemented with crystalline calcite and generally occurring in relatively planar surfaced beds. Crossbedding is common. The Logana 

and Brannon Members and the upper part of the Devils Hollow Member are composed mostly of very thin to thin, tabular beds of micrograined, silty argillaceous limestone interbedded with gray shale. 

Most of the Grier Limestone Member is fossiliferous bioclastic limestone, commonly with cryptograined and micrograined matrix, that 

occurs generally in lumpy-surfaced beds with thin undulatory shale 

partings but also as rounded nodules surrounded by shale partings. 

The Millersburg Member is similar to the Grier in bedding character 

and limestone type but is much more shaly; the limestone is very 

fossiliferous and commonly ocurs as nodules in a matrix of gray shale 

and in discontinuous beds with very irregular surfaces.

At. the reference section of the Lexington Limestone described 

below, the contact with the underlying Tyrone Limestone is exposed 

on the slope beneath the east bridge abutment about 80 feet 'below 

road level. The basal 50 feet of the Lexington is poorly exposed but

can be seen in nearby outcrops.
3 DO'-

200'-

LEXINGTON

 7-1 - 

Brannon Member

Logana Member

Curdsville Limestone 

Member

TYRONE

Shale and tabular

limestone 

(micrograined in part)

Irregular

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iferou

shale

LIMESTONE

Irregularly bedded to n

limestone (generally 

iferous)

(1) Sulphur Well Member of McFarlan (1943) (2) Unnamed bed, m

FIGURE 4. Stratigraphic relations of Lexington Limestone from central Ande
300S

2OO'-

100'-

0 J

N.

CLAYS

Tanglewood Limestone

LEXINGTON

Grier Limestone Member

Member

LIMESTO NE

s Cane Run Bed

EXPLANATION

Shale and tabular Irregularly bedded to nodular Calcarenite, generally 

limestone limestone (generally fossil- tabular; crossbed- 

(micrograined in part) iferous) and intercalated ded in part 

shale

(1) Unnamed bed, may be tongue of Clays Ferry Formation

(2) Unnamed bed, may be tongue of the Tanglewood Limestone Membe

FiotJBE 5. Stratigraphic relations of Lexington Limestone from southea

County, Ky.
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY Cl-1

Reference section of Lexington Limestone

[Measured in roadcuts along eastbound lane of Interstate Highway 64 on east side of Kentucky Kiver, Frankfort East quadrangle, Franklin County, Ky.; base of section at 

1,827,150 ft E., 241,350 ft N. (Kentucky coordinate system, north zone) ; Curdsville 

Limestone Member and Logana Member measured from cliff exposure immediately west 

of intersection of Hanley Lane and Glenns Creek Road, Frankfort East quadrangle, 

Woodfiord County, Ky.; base of section at 1,831,250 ft E., 236,950 ft N.]

Thickness 

Clays Ferry Formation ('basal part only) : (feet)

35. Limestone (30 to 50 percent) and shale interbedded; very 

thin bedded medium-light-gray micrograined argillaceous 

limestone; very thin bedded medium-light-gray fine-grained 

limestone; thinjbedded crinoidal, brachiopodal limestone; 

fossiliferous micrograined argillaceous limestone; mediumgray (weathers grayish orange) shale; 'brachiopods, gastropods, trilobite fragments, and crinoid columnals abundant 

in fossiliferous limestone :____ 25. 0 

Lexington Limestone:

Nicholas Limestone Member:

34. Limestone (70 percent) and shale interbedded. Limestone is 

thin bedded, grayish orange, coarse grained, bioclastic, phosphatic; contains abundant comminuted shell debris ___ 4.0

33. Limestone, mostly thick bedded ('but thin bedded near top), 

grayish-orange, coarse-grained, bioclastic, phosphatic; contains abundant comminuted shell debris___________ 8.0

32. Limestone, very thin to thin-bedded, partly crossbedded, lightgray, medium- to coarse-grained, bioclastic, phosphatic; 

contains some shale partings _ _____ _ _ 8. 5 

Millersburg Member:

31. Limestone (70 to 75 percent) and shale interbedded. Limestone is very thin to thin bedded, in part irregularly bedded, 

medium light gray, fossiliferous, fine- to very coarse grained, 

MooLastic; some limestone occurs as nodules in shale 

matrix. Shale is medium dark gray. Brachiopod valves 

and bryozoan fragments are common_____________ 23. 0 

Devils Hollow Member:

30. Limestone, partly argillaceous, thin-bedded, medium-gray to 

olive-gray, cryptograined; contains abundant ostracodes 

and some irregular, discontinuous laminae of comminuted 

shell debris _________________________ 8. 0

29. Limestone (25 percent) and shale interbedded. Limestone 

is very thin bedded, light gray, fossiliferous, micrograined 

to fine-grained. Shale is medium gray, calcareous. Limestone beds grade laterally and vertically into shale_____ 3.4

28. Limestone, coquinoid, thin-bedded, medium-light-gray, brachiopodal; some layers composed largely of bryozoan fragments _______________________________ 3.5 

Tanglewood Limestone Member:

27. Limestone, argillaceous, medium-dark-gray to light-gray; consists mostly of bryozoan fragments in an argillaceous 

matrix; grades into unit above___________.,____ 2.5
C12 CONTRIBUTIONS TO STRATIGRAPHY

Reference section of Lexington Limestone Continued

Lexington Limestone Continued . , Thickness Tanglewood Limestone Member Continued (feet)

26. Limestone, very thin to thin-bedded, partly crossbedded, 

medium-light-gray, coarse-grained, bioclastic, phosphatic; 

contains scattered bryozoan fragments_ _ 8. 0

25. Limestone, nodularly bedded, dark- to medium-gray, finegrained, bioclastic; interbedded with thin- and evenly bedded 

medium-gray medium-grained bioclastic phosphatic limestone; nodularly bedded limestone dominant; shale partings between many beds. _____ ~_____ 13.0

24. Limestone, thin-bedded, partly crossbedded, light-gray to lightolive-gray, coarse-grained, bioclastic, partly phosphatic; 

phospa'tic shale and siltstone partings %5 ito % in. thick 

(between many beds___ ______ _________ 8.5

Brannon Member:

23. Limestone, argillaceous, light-gray to medium-light-gray, 

micrograined; thin bed of medium-dark-gray to mediumgray shale at top; lower two-thirds of unit contains thick 

convoluted beds _______________________ 3. 0

22. Limestone, partly crossbedded; lower 5 ft is thin bedded, 

coarse grained, bioclastic, slightly phosphatic; upper 4.5 ft. 

very thin bedded and less phosphatic; dark-gray shale seam 

3 ft above base; unit is a tongue of the Tanglewood Limestone Member___________________________ 9.5

21. Limestone, argillaceous, medium-light-gray to light-gray, 

micrograined; subconchoidal fracture; contains some shale 

beds as much as 0.4 ft thick in upper half; convolute bedding, especially in lower 3 ft___________________ 5. 3 

Grier Limestone Member:

20. Limestone, upper 7.0 ft is medium-dark-gray, medium- to 

coarse-grained, bioclastic, slightly phosphatic; stromatoporoids 1 ft and 4 ft above base; lower 5.2 ft rubbly 

appearing, medium-gray to medium-dark-gray, medium 

grained as nodules separated by undulant shale partings__ 12.2

19. Limestone, partly crossbedded, coarse-grained, bioclastic, phosphatic ; abundant bryozoan fragments 1 ft below top___ 3.2

18. Limestone (85 to 90 percent) and shale interbedded. Limestone is fine to medium grained, bioclastic, argillaceous; 

interbedded with shale in lower and upper thirds; nodularly 

bedded, cryptograined, and argillaceous in middle third and 

convolutely bedded in lower third____________ 4.3

17. Limestone, medium-gray, medium-grained, bioclastic; as nodules in cryptograined argillaceous limestone matrix; 

course-ribbed brachiopods abundant; contains some interbeds 0.5 ft thick of medium-dark-gray coarse-grained limeStone composed of comminuted shell debris _ 11.0

16. Limestone, inaccessible, but is similar in appearance to nodular limestone described as unit 17__ 16.5

15. Limestone; very thin bedded, light-olive-gray, bioclastic,

slightly phosphatic; weathered surfaces are rough_____ 5.0
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C13

Reference section of Lexington Limestone Continued

Lexington Limestone Continued . . Thickness Grier Limestone Member Continued (feet)

14. Limestone, thin-bedded, brachiopodal, coarse-grained; limestone interbedded with nodular argillaceous limestone in 

beds about 2 ft thick; nodular limestone consists of mediumgrained medium-dark-gray limestone nodules in a medium 

gray micrograined argillaceous limestone matrix______ 22. 0 

Macedonia Bed:

13. Limestone (75 percent) and shale interbedded. Limestone is 

very thin to thin bedded, medium light gray, micrograined, 

argillaceous. Shale is very thin to thin bedded, fissile, 

medium dark gray to olive gray. Some limestone beds pinch 

and swell____________________________ _ 5. 5

12. Limestone, thin-bedded, light-gray, medium-grained, brachiopodal, slightly phosphatic; brachiopod valves are small and 

thin shelled_____________________________ 3.0 

11. Limestone (90 percent) and shale interbedded. Limestone is 

very thin to thin bedded, medium light gray, micrograined, 

and argillaceous. Shale is very thin bedded, fissile, medium 

dark gray to dark gray. Shale is more abundant in lower 

half; limestone beds contain blebs and irregular layers of 

very coarse grained limestone consisting of comminuted 

shell debris _____ 4.5

(Base of Macedonia Bed.)

10. Limestone, thin bedded, medium-gray, brachiopodal, coarse 

to very coarse grained, bioclastic, slightly phosphatic; contains some very thin interbeds of irregularly bedded micrograined limestone; some shale interbeds 0.1 to 0.2 ft thick 

in upper 2 ft; grades from unit below.____________ 12. 0 

9. Limestone, thin-bedded, yellowish-gray, brachiopodal, coarse, 

grained, bioclastic; slightly phosphatic limestone interbedded 

with very thin and irregularly bedded medium-gray micrograined argillaceous limestone and brachiopodal coarse- and 

very coarse grained bioclastic limestone containing blebs and 

stringers of aphanitic argillaceous limestone; some shale 

partings in basal 10 ft; basal 5 to 10 ft is mostly thin-bedded 

brachiopodal limestone, whereas rest of unit is mostly 

irregularly bedded to nodular.__________________ 48. 0 

Logana Member:

8. Limestone (70 percent) and shale interbedded; similar to

unit 5_____ __________________________ 5.2 

7. Covered ___ ___________________________ 1.2 

6. Limestone, thin-bedded, light-brownish-gray to brownish-gray; 

brachiopod coquina with abundant sparry calcite cement; 

wavy striated appearance on weathered joint surfaces 

results from orientation of brachiopod valves subparallel to 

bedding; contains several shale interbeds as much as 0.1 ft 

thick; 2.0-ft zone, 3.6 ft above base, contains micrograined 

argillaceous limestone with thin-shelled brachiopod valves 

exposed on bedding surfaces, interbedded with shale and 

brachiopod coquina; brachiopods are small, thin shelled, and 

fine ribbed ___________________________ 6.8
G14 CONTRIBUTIONS TO STRATIGRAPHY

Reference section of Lexington Limestone Continued

Lexington Limestone Continued _,. .

_ Thickness Logana Member Continued . (feet)

5. Limestone (70 percent) and shale interbedded. Limestone is 

very thin to thin bedded, light olive gray, and micrograined. 

Shale is brownish gray to medium gray, fissile, and calcareous. Small flat-shelled brachiopods on bedding surfaces. 5. 3

4. Covered ________________________________ 13.0 

Curdsville Limestone Member:

3. Limestone, thin-bedded, pale-yellowish-brown to light-brownish-gray, brachiopodal, coarse-grained, bioclastic; brachiopod 

valves are thin shelled and oriented subparallel to bedding_ 7. 3

2. Covered __________________________________ 2. 7

1. Limestone, thin-bedded, resistant, yellowish-gray, fine- to

medium-grained, bioclastic__________________ 10.1

Total thickness of Lexington Limestone _______________ 307 

Tyrone Limestone; lithographic limestone, 10 ft exposed.

CURDSVILLE LIMESTONE MEMBER

The Curdsville Limestone Member was named by Miller (1905, 

p. 18) the Curdsville Bed of the Lexington Limestone. The type 

locality is Curdsville in Mercer County. The unit was described as 

consisting of 30 feet of crystalline fossiliferous limestone, cherty in the 

lower half. Although Miller's description was brief and no measured 

section was given, the Curdsville generally contrasts with the units 

above and below, and little difficulty has been encountered in identifying it. The only obvious variation in past usage has been in the 

rank assigned to the Curdsville.

The Curdsville Limestone Member is dominantly well-sorted bioclastic calcarenite, crossbedded in part and phosphatic in part. It 

contains a few thin beds of micrograined limestone and shale and 

some very fine grained nodularly bedded limestone. Convolute bedding occurs in some of the finer grained beds. Silicified fossils, mostly 

brachiopods, are abundant in some beds. Nodular chert is abundant 

in the lower part of the member in southern Jessamine and Woodf ord 

Counties. Bentonitic shale occurs locally within the Curdsville; at 

Clays Ferry in the southwestern part of the Ford quadrangle three 

thin bentonite beds are present in the lower 10 feet of the member.

The contact between the bioclastic calcarenite of the Curdsville 

Limestone Member and lithographic limestone of the underlying 

Tyrone Limestone is sharp. Locally, the Curdsville rests on a bentonite bed that is included in the Tyrone Limestone. Where we have 

observed the contact the two units appear to be conformable, but Miller 

(1925, p. 131 and 132) presented evidence of an unconformity.
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C15

In most of its area of outcrop the Curdsville is overlain conformably 

by interbedded micrograined limestone and shale of the Logana Member of the Lexington Limestone, but in southern Fayette County it is 

directly overlain by thin and irregularly bedded to nodular fossiliferous limestone of the Grier Limestone Member. Where the Grier 

rests directly on the Curdsville, the contact is gradational.

The Curdsville is about 20 to 30 feet thick throughout most of 

Franklin, Woodford, and Jessamine Counties. It is exposed on both 

sides of the Kentucky Kiver and for some distance up the tributaries. 

The following section is representative of the member.

Section of Curdsville Limestone Member of Lexington Limestone

[Measured in small quarry on west side of Shryocks Ferry Road, 1 mile S. 10° W. of 

Milner, Tyrone quadrangle. Woodford County, Ky.; base of section at 1,838,500 ft E., 

189,650 ft N. (Kentucky coordinate system, north zone) ]

Lexington Limestone : ,. . 0 Thickness Curdsville Limestone Member: (feet)

1. Limestone, thin-bedded, pale-yellowish-brown to pale-orange, 

slightly phosphatic(?), medium-grained, bioclastic. Overlain by tabular micrograined limestone float from Logana 

Member of Lexington Limestone. _ 11. 0

6. Shale ________________________________ .3

5. Limestone, crosslaminated, very pale orange, slightly phosphatic(?), fine- to medium-grained, bioclastic_______ .8

4. Limestone and shale interbedded. Limestone is very thin to 

thin bedded, light gray, micrograined, argillaceous. Shale 

is yellowish gray________________._______ 2. 7

3. Limestone, thick-bedded, pale-yellowish-brown, fine-grained, 

slightly phosphatic(?), bioclastic; about 10 percent of unit 

is chert occurring as irregular nodules 0.1 to 1.2 ft in 

diameter ______ _ _ _ ___________ 2.9

2. Limestone, very thin bedded, pale-yellowish-brown, micrograined, argillaceous_______________________ . 8

1. Limestone, thin-bedded, very pale orange, fine- to mediumgrained, slightly phosphatic, bioclastic; abundant broken 

shells in some beds; chert layer 0.2 ft thick, 2 ft below top 

.of unit________________________________ 8.6

Thickness of Curdsville Limestone Member_______________ 27 

Tyrone Limestone.

LOGANA MEMBER

The Logana Member of the Lexington Limestone was named by 

Miller (1905, p. 19) for Logana Station (now abandoned) in southern 

Jessamine County. He described it at its type locality as consisting 

of 10 feet of argillaceous limestone containing abundant molluscan 

fossils. According to Miller, the Logana persists through Jessamine, 

Woodford, and Franklin Counties, but shale was said to predominate
C16 CONTRIBUTIONS TO STRATIGRAPHY

over limestone in Franklin County. Miller (1913, p. 321) subsequently abandoned the name Logana and replaced it with Hermitage, a term extended from Tennessee. Miller (1925, p. 133) described 

the Hermitage in Woodford County as 35 to 40 feet of thin-bedded 

fine-grained argillaceous or siliceous limestone and intercalated shale, 

containing beds of closely packed Dalmanella bassleri (identified by 

R. B. Neuman as Onniella bassleri in Cressman, 1964) in the upper 

part. The upper contact was placed at the top of the highest bed containing abundant 0. bassleri. Huffman (1945, p. 169) reintroduced 

the name Logana in central Kentucky, apparently for the same unit 

Miller called Hermitage.

The upper contact was defined by Miller on the basis of faunal 

rather than lithologic characteristics and cannot be used in geologic 

mapping. Limestone bearing abundant dalmanellid brachiopods 

occurs throughout much of the Logana and the loAver part of the overlying Grier Limestone Member. We therefore place the upper contact of the Logana at the top of the uppermost unit of interbedded 

micrograined limestone and shale. Near Nicholasville in Jessamine 

County, both the upper and lower boundaries of the Logana are 

gradational.

At Miller's type section near Logana Station the rocks typical of 

the Logana Member, as identified by Miller in Woodford County, 

grade eastward into irregularly bedded fossiliferous limestone. These 

fossiliferous limestone beds are indistinguishable lithologically from 

the overlying Grier Limestone Member; however, in western Jessamine County and in Woodford, Anderson, and Franklin Counties, 

the gross unit termed Logana, and subsequently Hermitage by Miller, 

is distinct from the overlying Grier Limestone Member. We therefore designate the section described below as a reference section.

Reference Section oj Log ana Member oj Lexington Limestone

[Measured in roadcut along entrance to Kentucky Utilities Plant, east side of Blackburn 

Memorial Bridge, U.S. Highway 62, Tyrone quadrangle, Woodford County, Ky.; base of 

section at 1,828,840 ft E,, 198,350 ft N. (Kentucky coordinate system, north zone)]

Lexington Limestone: m,. , Thickness Grier Limestone Member (basal part only) : . (feet)

12. Limestone, brachiopodal, very fine to coarse-grained, in irregular to lenticular beds 0.05 to 0.2 ft thick separated by 

irregular shale partings_____________________ 2. 5 

Logana Member:

11. Limestone (50 percent) and shale interbedded; similar to 

unit 2, but limestone beds are wavy and less than 0.2 ft 

thick. Some beds contain brachiopod values_______ 0.9

10. Limestone, light-brownish-gray, slightly phosphatic, mediumgrained, bioclastic, grades from brachiopodal micrograined 

limestone at base.________________________ 0. 8
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C17 

Reference Section of Logana Member of Lexington Limestone Continued

Lexington Limestone Continued Thickness 

Logana Member Continued (feet)

9. Limestone (60 percent) and shale interbedded; similar to unit 

2, but limestone beds are generally 0.3 to 0.4 ft thick and do 

not contain pelecypods .. 3. 2

8. Limestone, brachiopodal; similar to unit 3; wavy beds 0.1 ft 

thick 'apparent on weathered joint surfaces but are not separated by partings; conspicuous partings parallel to bedding spaced 0.2 to 1.5 ft apart___ 4.1

7. Limestone, light-brownish-gray, coarse-grained, bioclastic,

brachiopodal; in single even bed 0.6

6. Limestone, medium-gray to light-brownish-gray, medium- to 

coarse-grained, bioclastic, brachiopodal; in lenses and nodules separated by irregular shale partings 1.4

5. Limestone, brachiopodal, similar to unit 3____________ 1.7

4. Limestone (50 percent) and shale interbedded; similar to unit 

2 but contains a few lenses and beds of brachiopodal 

limestone -___________________________ 3.1

3. Limestone, brachiopodal, light-brownish-gray, in wavy to 

irregular beds 0.1 to 0.6 ft thick; a coquina of brachiopod 

sheila oriented subparallel to bedding with a matrix of 

coarse bryozoan and brachiopod fragments and cemented 

by sparry calcite ._ ____________________ 2.0

2. Limestone (50 percent) and shale interbedded. Limestone is 

argillaceous or silty, brownish gray to olive brown, micrograined, in tabular beds generally 0.2 to 0.3 ft thick; petroliferous odor. Shale is brownish gray, fissile, in beds 

0.05 ft thick. Pelecypods common in some limestone 

beds _______________________________ 13.0

Total thickness of Logana Member___________________ 31

Ourdsville Limestone Member (uppermost part only) :

1. Limestone, in tabular to slightly wavy beds 0.3 to 0.9 ft thick; 

light brownish gray, phosphatic in part, fine grained, bioclastic; silified brachiopod valves abundant; uppermost 

most 0.2 ft contains micrograined calcite matrix_____ 2.0

As redefined, the Logana Member is 22 to about 30 feet thick 

throughout most of Jessamine, Woodford, and Franklin Counties. 

In easternmost Jessamine County it grades eastward into the basal 

part of the Grier Limestone Member and is absent in southernmost 

Fayette County.

GRIER LIMESTONE MEMBER

The Grier Limestone Member, named by Cressman (1964), includes 

about 135 feet of irregularly surfaced thin-bedded fossiliferous limestone overlying the Logana Member and underlying the Brannon Mem-
CIS CONTRIBUTIONS TO STRATIGRAPHY

her. The name was derived from Grier Creek in west-central Woodford County. A description of the type section follows:

Type section .of Grier Limestone Member of Lexington Limestone

[Measured in roadcut along Shryocks Ferry Road 1 mile S. 10° W. of Milner, Tyrone 

.quadrangle, Woodford County, Ky.; base of section at 1,838,500 ft B., 189,650 ft N. 

(Kentucky coordinate system, north zone). Measured by Jacob staff and corrected for 

dip as determined from structure contours on the geologic map]

Lexington Limestone: m,. ,

& . ^ Thickness Grier Limestone Member : (feet)

22. Limestone, irregularly bedded, very fine grained; covered interval above contains micrograined limestone float from 

Brannon Member of Lexington Limestone. Described from 

exposures in gully on west side of road- _ _ _ 1. 0

21. Limestone, in beds 0.04 to 0.4 ft thick; light gray, slightly 

phosphatic, medium grained, bioclastic, crossbedded in 

upper 3 ft; stromatoporoids 0.5 ft below top __ _ 11. 0

20. Limestone, nodular, light-gray to light-brownish-gray; irregular nodules of very fine grained bioclastic limestone in a 

micrograined argillaceous limestone matrix; contains 

abundant silicified brachiopods; bedding obscure, but irregular partings are spaced 0.2 to 0.5 ft apart 9. 0

19. Limestone, in beds 0.1 to 0.3 ft thick; medium gray to very 

pale orange, phosphatic, medium grained, bioclastic, crosslaminated in upper part _ 8. 0

18. Limestone, nodular, mottled light-gray and grayish-orange; irregular nodules of very fine grained bioclastic limestone in 

a micrograined argillaceous limestone matrix; contains 

abundant silicified brachiopods and some branching bryozoans; some interbeds of light-brownish-gray aphanitic 

limestone containing gastropods in lower third of unit; bedding obscure, but irregular partings are spaced 0.2 to 2 ft 

apart _______________________________ 16.0

17. Limestone, light-gray to pale-yellowish-brown, slightly phos^ 

phatic, medium- to coarse-grained, bioclastic, in beds averaging 0.5 ft in thickness; contains brachiopods and trilobite 

fragments; interbedded with micrograined argillaceous

limestone and very thin bedded very fine grained nodular

limestone containing abundant brachiopods 18. 0 

16. Macedonia Bed: consists of limestone that is argillaceous,

ligbt-olive-gray, and micrograined; in beds 0.1 to 0.3 ft

thick; about one-fourth of unit is interbedded shale. 7.0

15. Limestone, thin- to tnicK-beaaea, liglit-brownisli-sTay, pHosphatic, medium-grained, bioclastic; contains some brachiopods __________________________________ 5.0

14. Limestone, very thin and irregularly bedded, light-brownishgray, slightly phosphatic, micrograined to fine-grained ; contains some interbeds of medium- to coarse-grained limestone _______________________ 8.0

13. Limestone, thin- to very thin bedded, grayish-pink to very 

pale orange, slightly phosphatic, medium- to coarse-grained, 

bioclastic; contains abundant brachiopods__________ 5.0
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C19 

Type section of Grier Limestone Member of Lexington Limestone Continued

Lexington Limestone Continued Thickness 

Grier Limestone Member Continued (feet) 

12. Limestone, similar to unit 14 17. 0 

11. Limestone, light-gray to yellowish-gray, slightly phosphatic, 

medium- to coarse-grained, bioclastic, in beds 0.5 to 0.7 ft 

thick; interbedded with very thin and irregularly bedded 

to lenticular or nodular limestone and light-olive-gray to 

medium-gray micrograined to fine-grained limestone; commonly contains abundant brachiopods and some subconical 

bryozoans; micrograined argillaceous limestone in irregular to lenticular beds commonly contains gastropod shells; 

medium- to coarse-grained limestone makes up one-lthird of 

unit _________________________________ 30. 0

Total thickness of Grier Limestone Member 135 

Logana Member; argillaceous micrograined limestone and shale.

At the type locality the Grier Limestone Member is underlain by 

interbedded micrograined limestone and shale of the Logana Member, but in southeastern Jessamine and southern Fayette Counties the 

Grier rests directly on the Curdsville Limestone Member.

In eastern Woodford and western Fayette Counties, micrograined 

limestone and shale of the Brannon Member rest directly on thinand irregularly bedded to nodular f ossilif erous limestone of the Grier; 

however, in southern Fayette, Jessamine, and much of western Woodford Counties the two members are separated by a unit of crossbedded 

phosphatic calcarenite, locally as much as 30 feet thick, that is a 

tongue of the Tanglewood Limestone Member (fig. 4, section 3; fig. 

5, section Y). Where the Brannon Member terminates in northern 

Fayette, Scott, and Franklin Counties, this tongue merges with the 

main body of the Tanglewood.

The Grier Limestone Member is present throughout the area of 

figure 1.

Macedonia Bed. A distinctive unit of interbedded tabular argillaceous micrograined limestone and shale as much as 15 feet thick 

and 60 to 65 feet above the base of the Grier Limestone Member has 

been noted in Franklin, Woodford, and western Fayette and Jessamine Counties. We herein name this unit the Macedonia Bed and 

designate the type section to be in the readouts on the south side of 

the east-bound lane along Interstate Highway 64 on the east side of 

the Kentucky River (units 11 through 13 in the reference section of 

the Lexington Limestone). It is represented by bed 16 in the type 

section description of the Grier Limestone Member and figure 4, 

section 2. The name is derived from Macedonia Church in northwestern Woodford County 2 miles south of the type section. The 

Macedonia Bed grades eastward into irregularly bedded fossiliferous
C20 CONTRIBUTIONS TO STRATIGRAPHY

limestone that cannot be distinguished from the rest of the Grier in 

eastern Jessamine and southern Fayette Counties.

Cane Run Bed. In much of the area in which the Brannon Member is present, a bed of argillaceous micrograined limestone as much as 

5 feet thick and similar in character to the Brannon occurs at or near 

the top of the Grier Limestone Member. The base of the bed ranges 

from 15 to 25 feet below the base of the Brannon Member. The bed 

extends past the northern pinch-out edge of the Brannon into northern Fayette and southern Scott and Bourbon Counties (fig. 4, section 4; fig. 5, sections 5 and 6). This bed is herein named the Cane 

Run Bed for Cane Run in north-central Fayette County. A description of the type section follows:

Upper part of Grier Limestone Member of the Lexington Limestone

[Measured in Pemberton Quarry on east side ofi U.S. Highway 25, 0.9 mile north of Linlee 

School, Lexington West quadrangle, Fayette County, Ky.; quarry at 1,922,550 ft B., 

224,600 ft N, (Kentucky coordinate system, north zone) ]

Lexington Limestone:

Tanglewood Limestone Member (medium-grained bioclastic phosphatic

limestone). Thickness 

Grier Limestone Member: (feet)

3. Cane Bun Bed: consists of limestone that is medium to light 

gray, argillaceous, micrograined, and contorted and convoluted ; shaly partings in upper 1 ft; breaks into angular 

fragments with subconchoidal fracture___ ____ 4.2

2. Limestone (85 percent) and shale interbedded; fossiliferous 

granular bioclastic limestone interbedded with micrograined 

limestone and shale; in even beds 0.2 to 0.7 ft thick,____ 5.6

1. Limestone, medium- to dark gray, fossiliferous, coarsegrained, bioclastic, in even to irregular beds 0.3 to 0.5 ft 

thick interbedded with very fine grained limestone in nodular 

beds 1 to 2 in. thick________________________ 8.1

In many exposures the Cane Run Bed contains abundant irregular 

chert nodules, and in areas of poor exposure its position can commonly be located by the abundance of chert in the float.

The Cane Run Bed is present in southern Scott and Bourbon 

Counties and most of Fayette County. A similar bed in about the 

same stratigraphic position in south-central Woodford County and 

eastern Mercer County may be continuous with the Cane Run of the 

type area.

BRANNON MEMBER

The name Brannon Limestone Member is here shortened to Brannon Member of the Lexington Limestone. The unit generally includes

abundant shale.

The name Brannon was introduced and its type locality described 

by Miller (1913, p. 324). He stated,
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C21

We propose for this siliceous bed (it really is only siliceous though its appearance suggests an argillaceous limestone) the name "Brannon" from Brannon 

Station on the Q. & G. R.R., a little south of the southern boundary of the [Georgetown, Ky., 15-minute] quadrangle. The first two railroad cuts south of the 

station expose this formation, the first one the upper, or "bouldery" phase, the 

second one about a mile from the station, both this upper portion and also the 

lower even bedded layers which are more argillaceous looking.

Brannon Station is several miles south-southwest of Lexington in the 

Nicholasville quadrangle near the northern edge of Jessamine 

County.

The Brannon Member consists of a succession of intercalated 

tabular (locally convoluted) micrograined limestone and shale beds. 

Limestone is generally dominant, though in some areas the shale content approaches 50 percent. Individual micrograined limestone beds 

are generally less than 6 inches thick where the bedding is planar, 

but convoluted beds are generally thicker. Locally, large slumped 

blocks of clastic limestone of the Tanglewood Limestone Member 

are included within the convoluted micrograined limestone and shale.

The contacts with the coarser grained calcarenites of the overlying 

and underlying units are sharp where well exposed. A discontinuous 

bed of bentonite just above the base of the Brannon Member is present 

at Versailles City Park in the Versailles quadrangle, at three widely 

separate locations in the Coletown quadrangle, and at one location in 

the Lexington West quadrangle. These local occurrences of bentonite at about the same stratigraphic horizon suggest that the lower 

contact is isochronal.

In the area mapped to date (1964), the Brannon Member reaches 

a maximum thickness of slightly more than 30 feet. It pinches out 

northeastward and southwestward (figs. 1, 4, and 5).

Near its northern edge the Brannon Member is locally divided into 

two tongues separated by a tongue of calcarenite of the Tanglewood 

Limestone Member. This relation is apparent in the reference section 

of the Lexington Limestone, in phosphate excavations near Wallace, 

Versailles quadrangle, and in readouts along the bypass north of 

Lexington.

TANGLEWOOD LIMESTONE MEMBER

The name Tanglewood Limestone Member is here given to the extensive irregularly shaped body of bioclastic calcarenite which in the 

Central Blue Grass Eegion of Kentucky makes up much of the upper 

half of the Lexington Limestone. The name Tanglewood is taken 

from a suburban area south of Frankfort, Ky.

The following section, selected as the type section for this member, 

was measured from roadcuts along Interstate Highway 64 west of its 

crossing of the Kentucky River near the Frankfort-Lawrenceburg 

interchange.
C22 CONTRIBUTIONS TO STRATIGRAPHY

Type section of Tanglewood, Limestone Member of Lexington Limestone 

[Measured in readouts along Interstate Highway 64 on west side of Kentucky River, 

Frankfort West quadrangle, Franklin County, Ky., in December, 1962 ; base of section 

at 1,816,000 ft E., 240,200 ft N.; top of section at 1,813,900 ft B., 2,40,300 ft N. .(Kentucky coordinate system, north zone) ]

_ Thickness Clays Ferry Formation: (feet)

17. Limestone (50 percent) and shale (50 percent) interbedded; 

very thin bedded medium-dark-gray micrograined argillaceous limestone; thin-bedded medium-dark-gray crinoidal 

limestone that locally contains abundant brachiopod 

valves; micrograined limestone containing abundant gastropods; medium-gray fissile shale_________ 19 

Lexington Limestone:

Tanglewood Limestone Member (upper part) :

16. Limestone, thin-bedded, grayish-pink, phosphatic, coarse and 

very coarse grained, bioclastic; some beds contain abundant 

bryozoan fragments________________________ 9. 0

15. Limestone, very thin bedded, partly crossbedded, light-gray to

pinkish-gray, phosphatic, medium-grained, bioclastic____ 6. 3

14. Limestone, very thin to thin-bedded, party crossbedded, lightgray to pinkish-gray, phosphatic, medium- to coarsegrained, bioclastic; dark-reddish-brown phosphatic siltstone 

or shale laminae between many beds; uppermost 2 ft 

contain abundant bryozoan fragments____________ 7. 5

13. Limestone, thin- to thick-bedded, light-gray, slightly phosphatic, coarse to very coarse grained, bioclastic; some 

strata are largely composed of pebble-sized bryozoan fragments which are abundant throughout unit; basal 1.5 ft is 

crinoidal and crossbedded____________.______ 6.0

12. Limestone, thin-bedded, medium-gray to medium-dark-gray, 

coarse- to fine-grained bioclastic; in middle of unit, nodular 

limestone with intercalated shale laminae__________ 3. 0 

Devils Hollow Member:

11. Limestone, thin-bedded, laminated, light-gray, lithographic; 

contains blebs and tubules of sparry calcite; bed not present 

where unit 12 was measured. Section offset; correlation 

made on top of unit 10_____________________ 1.0

10. Limestone coquina, yellowish-gray; alternating thin and 

thick beds composed largely of gastropod and brachiopod 

shells and bryozoan fragments___________ 9.0 

Tanglewood Limestone Member (lower part) :

9. Limestone (75 percent) and shale (25 percent) intea-bedded. 

Limestone is thin bedded, medium dark gray, medium 

grained, bioclastic. Shale is dark gray, fissile. Abundant 

bryozoan fragments in several of the limestone beds__ 4. 6 

8. Limestone, thin- to thick-bedded, partly crossbedded, mediumlight-gray to medium-dark-gray, phosphatic, medium- to 

coarse-grained, bioclastic; contains some nodular limestone 

interbeds in zones 1 to 3 ft thick; shale partings common in 

upper part; bryozoan fragments abundant in upper 15 ft__ 25. 0

Total thickness of Tanglewood Limestone Member (upper ana lower

parts) _ _ 61 

Brannon Member; micrograined limestone.
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C23

In the type section, the Tanglewood Limestone Member is divided 

into two parts 'by the Devils Hollow Member of the Lexington Limestone, but several miles to the south where the Devils Hollow Member 

is absent the Tanglewood extends uninterrupted from the Brannon 

Member to the Clays Ferry Formation.

The Tanglewood Limestone Member is characterized by calcarenite, 

much of which is phosphatic, composed predominantly of subrounded 

skeletal fragments, ranging from fine to coarse sand and generally 

cemented by sparry calcite. Its bedding character is somewhat 

variable, though bedding surfaces are commonly smooth and crossbedding is common.

Throughout much of its area of outcrop this member is underlain 

by the micrograined limestone and shale of the Brannon Member. 

Where the Brannon is absent, bioclastic calcarenite of the Tanglewood 

rests directly on thin- and irregularly-bedded fossiliferous limestone 

of the Grier Limestone Member. Locally, the Cane Eun Bed of the 

Grier Limestone Member immediately underlies the Tanglewood. 

The Tanglewood Limestone Member in large areas east of its type 

locality underlies and intertongues with nodular fossiliferous limestone and shale of the Millersburg Member (figs. 4 and 5). Where the 

Millersburg Member is absent, the Tanglewood calcarenite directly 

underlies the planar-bedded limestone and shale of the Clays Ferry 

Formation. The Tanglewood Limestone Member is locally divided 

into two parts by the Devils Hollow Member. The part of the Tanglewood between the Devils Hollow and Brannon Members in the past 

has been called the Woodburn Limestone Member (Miller, 1913, 

p. 326 and 327). Vertical extension of the name Woodburn to include 

all of the rock here included in the Tanglewood Limestone Member 

is inadvisable as major redefinition would be required.

DEVILS HpLLOW MEMBER

The Devils Hollow was named and the type locality established by 

McFarlan-and "White (1948, p. 1640) who stated, "An excellent development of these beds having a thickness of 25 feet is found along 

the Devils Hollow road a few miles west of Frankfort, and the name 

Devils Hollow division of the upper Lexington limestone is proposed 

for them." The name was subsequently adopted by the U.S. Geological Survey (Cressman, 1964) as the Devils Hollow Member of the 

Cynthiana Formation. It is amended herein to the Devils Hollow 

Member of the Lexington Limestone.

The Devils Hollow Member is divisible into two parts at the type 

locality. The lower 15 feet was described by McFarlan and White 

(1948, p. 1637) as "porous coarsely crystalline light gray massive
C24 CONTRIBUTIONS TO STRATIGRAPHY

limestone containing in its typical development a crowded mass of 

gastropod shells, chiefly Belleroption troosti, Owydiscus su~ba(MtuS) 

and Lophospira medialis. Silicification in weathering gives rise to a 

conspicuous fossiliferous chert horizon." Unit 10 on page C22 represents this rock type. At its type section the upper 10 feet of this 

member was described as "compact limestone suggesting Tyrone. 

Characteristic fossils are Isocliilina jonesi, Leperditia (several 

species), and OrthorJiynchula linneyi. Locally it is softer and more 

argillaceous." This rock-type is represented by unit 11 on page C22 

and units 29 and 30 on page Cll. The simple twofold division described from the type locality does not everywhere apply. In Woodford County south of Versailles the Devils Hollow Member is composed entirely of coquinoid limestone similar to that described for 

the lower 15 feet at the type section. North of Versailles this coquina 

is overlain by cryptograined limestone and dull, earthy ostracode-bearing micrograined limestone^ the member thereby presenting the twofold aspect described by McFarlan. In the northwestern part of the 

Coletown quadrangle and the northeastern part of .the Nicholasville 

quadrangle, the Devils Hollow Member is dominantly micrograined 

to cryptograined limestone containing some ostracodes; locally, it contains abundant coarse-ribbed brachiopods rarely seen elsewhere in this 

rock type. In the northeastern part of the Nicholasville quadrangle 

and in parts of the Tyrone and Frankfort East quadrangles, the micrograined and coquinoid lithologies locally intertongue. In the Clintonville quadrangle the Devils Hollow is discontinuous; locally, it occurs 

as thin beds in the transition zone between the Tanglewood and Millersburg Members. The lateral extent of the Devils Hollow Member 

has been shown by McFarlan and White (1948, fig. 4, p. 1633).

MILLERSBURG MEMBER

The name Millersburg Member of the Lexington Limestone is here 

adopted for the nodular, irregularly bedded fossiliferous limestone and 

shale unit of that formation. Rocks to be included in this member

have in the past been variously named Greendale and Millersburg.

The name Greendale is abandoned; according to McFarlan (1943,

p. 20), it has been used with little precision, and less than 5 feet of

the unit is exposed at the type locality.

The name Millersburg was proposed by Foerste (1914, p. 112):

"For the richly fossiliferous, argillaceous, irregularly bedded limestones, frequently weathering into the irregular fragments called rubble and containing 

OrthorhyncJiula linneyi, Hebertella, parlcsensis, Platystrophia colbiensis, Rafinesquina Winchester'ensis, Cyclonema varicosum, Constellaria emadata, Homotrypella norwoodi, Heterotrypa parvulipora, and numerous other species, the term 

Millersburg limestone is proposed."
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C25

The name was derived from the town of Millersburg in northeastern 

Bourbon County.

Rocks of the Millersburg Member are readily distinguished from 

those of the overlying and underlying units by their irregular to nodular bedding, general profusion of fossils, and relative abundance of 

shale. On weathering, the Millersburg produces a thick yellowish 

soil which near bedrock generally contains fossiliferous limestone 

rubble.

The Millersburg Member varies considerably in thickness (figs. 4 

and 5). It intertongues with and is vertically bounded !by calcarenite 

of the Tanglewood and Nicholas Limestone Members and, in some 

areas, by micrograined limestone and shale of the Clays Ferry Formation. In northeastern Fayette, western Bourbon, and southeastern 

Scott Counties, the Millersburg Member contains a microgained limestone and shale unit (fig. 5, sections 5 and 6) which, as mapping proceeds, may prove to be laterally connected to the main body of the 

Clays Ferry Formation. The Millersburg Member is locally more than 

60 feet thick in the Clintonville quadrangle.

Though we have not yet mapped near the type area of this member, reconnaissance indicates lateral continunity between the Millersburg of the type locality and similar rocks near Lexington. The following stratigraphic section, measured from roadside exposures along 

the Athens-Boonesboro road just west of the Interstate Highway 75 

overpass, is a reference section.

Reference section of Millersburg Member of Lexington Limestone

[Measured in roadcut on Athens-Boonesboro road 0.4 mile northwest of interchange with 

Interstate Highway 75, Coletown quadrangle, Fayette County, Ky.; base of section in 

creek bottom at 1,958,650 ft E., 178,050 ft N. (Kentucky coordinate system, north 

zone)]

Lexington Limestone: HT-II v, TIT v. Thickness Millersburg Member: (feet)

13. Limestone (50 percent) and shale; nodules of medium-gray 

fine- to medium-grained bioclastic limestone in mecliumdark-gray shale matrix; very fossiliferous; covered above, 

but probably less than 5 ft to base of Nicholas Limestone 

Member of Lexington Limestone_________________ 7. 0

12. Limestone and shale; similar to unit 13 but contains stromatoporoids at base and top____________________ 2.0

11. Limestone and shale; similar to unit 13 but contains thin

greenish-gray claystone bed at base-______________ 7.0

10. Limestone and shale; similar to unit 13 but contains some thin 

interbeds of bioclastic limestone throughout and stromatoporoids in light-gray mudstone bed at base_________ 7. 6 

9. Limestone, medium-grained, bioclastic, in resistant beds with 

irregular surfaces; fossiliferous nodular limestone near 

middle of unit___________________________ 2. 0
C26 CONTRIBUTIONS TO STRATIGRAPHY

Reference section of Millersburg Member of Lexington Limestone Continued

Lexington Limestone Continued

Millersburg Member Continued (feet)

8. Limestone (50 percent) and shale; similar to unit 13 but less

fossiliferous ______________ _ ____:_____ 6. 8

7. Limestone, medium-dark-gray, very fine to fine-grained bioclastic; in very thin tabular beds, crossbedded in part; 

contains some interbeds of medium-dark-gray shale_____ 2. 9

6. Limestone (60 percent) and shale; similar to unit 13 but less 

fossiliferous; contains some thin, even beds of very fine 

grained dark-gray limestone; locally convoluted 3 ft above 

base of unit_ _____________________ 4. 7

5. Limestone, medium-grained, bioclastic; contains abundant 

brachiopod fragments; minor bluish-gray shale as interbeds 

near base; unit forms resistant ledge ______._____ 2. 4

4. Limestone, medium-grained, bioclastic; sparry calcite cement; 

in planar surfaced to slightly wavy beds averaging 3 in. 

thick _______________________________ 3.6

3. Limestone (80 percent) and shale. Limestone is nodular, 

medium-gray, bioclastic, and somewhat fossiliferous. Shale 

occurs as undulatory laminae 7.0

2. Covered __________________________ 4.0

Total exposed Millersburg Member____________ ____ ___ 57

Tanglewood Limestone Member:

1. Limestone, medium- to coarse-grained, bioclastic, in irregular, 

crenulated, and gently wavy beds; contains some fossiliferous interbeds; poorly exposed. Underlain by Brannon 

Member ______________________________ 35. 0

NICHOLAS LIMESTONE MEMBER

The Nicholas Limestone Member, formerly a member of the Cynthiana Formation, is here applied to the extensive unit of calcarenite 

which throughout much of the area overlies the Millersburg Member

and forms the top of the Lexington Limestone. Where the Millersburg is absent, the calcarenite rocks of the Tanglewood Limestone

Member locally merge with and cannot be differentiated from those

of the Nicholas Limestone Member (fig. 4). TVhere the two members merge, the Tanglewood Limestone Member is extended upward

and its lateral boundary with the Nicholas is established arbitrarily.

The term Nicholas bed was first applied by Foerste (1909, p. 294)

to "the upper part of the Cynthiana Formation, consisting of rather

coarse-grained, limestone with relatively few fossils. This part is

typically exposed between Pleasant Valley and Millersburg." The

Nicholas Limestone Member is composed in large part Ol -taoular

beds of coarse-grained and poorly fossiliferous calcarenite. Crossbedding is common. The Nicholas weathers to a fertile reddish-
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C27

brown soil. In fresh exposures both upper and lower contacts are 

well defined by change in bedding character, limestone type, and a 

marked increase in the abundance of shale. .The following stratigraphic section from this type area was measured from steep exposures 

on the southwest side of the Licking Eiver near the Parks Ferry Road.

Reference section of Nicholas Limestone Member of Lexington Limestone

[Measured In two parts; lower 48.5 ft from roadcut In Kentucky State Highway 32 at 

south end of bridge across Licking River, 1.5 miles southwest of Pleasant Valley, Moorefield quadrangle, Nicholas County, Ky.; remainder of section from steep exposures between railroad tracks and Parks Ferry Road % mile to the west; base of section at 

2,087,050 ft E., 312,650 ft N.; top of section at 2,085,550 ft E., 313,950 ft N. (Kentucky coordinate system, north zone) ]

Thickness (feet) 

Clays Ferrry Formation (basal part only; from exposure west of Parks

Ferry Road) :

14. Limestone (50-60 percent) and shale. Limestone is mostly 

micrograined but some is coarsely clastic; in very thin, 

tabular beds; crinoid fragments and delicate brachiopods 

abundant; partly covered. Not measured. 

Lexington Limestone:

Nicholas Limestone Member:

13. Limestone, coarse-grained, bioclastic; sparry calcite cement; 

commonly iron stained; in thin to very thin, planar to 

wavy surfaced beds that become thinner and more irregular 

toward base; weathered surface rough to hackly; poorly 

 fossiliferous; limestone with included crinoid stem plates 

approximately 3 ft below poorly exposed upper contact; 

unit forms resistant ledge____________________ 20.0

12. Limestone (80 percent) and shale. Limestone is fossiliferous, 

mostly fine grained, bioclastic; occurs as elongate nodules 

and in very thin crenulated to irregular beds. Shale is 

medium gray; occurs as matrix of limestone nodules and 

as thin undulatory partings. Micrograined limy mudstone 

bed 1 ft thick about 1.5 ft above base of unit; stromatoporoids throughout; unit is poorly resistant, forms recess 

in cliff exposure_________________________ 6.8

11. Limestone, fine-grained, 'bioclastic, in very thin irregularly 

surfaced beds with thin interbeds of very coarse grained 

'bioclastic calcarenite as below _ __________ 4.7

10. Limestone, coarse to very coarse grained, bioclastic; sparry

calcite cement; in thin, wavy-surfaced beds________ 2.6 

9. Limestone, medium-grained, bioclastic; sparry calcite cement;

in very thin tabular beds; crossbedded in part_______ 2.8 

8. Limestone, bioclastic, as below but in thick convoluted beds;

very thin clay bed at base of unit_______________ 3.0 

7. Limestone, medium-grained; well-sorted, bioclastic; in very 

thin tabular beds, partly crossbedded; basal contact clearly 

defined, forms resistant overhanging ledge__________ 4.0

Total Nicholas Limestone Member_,____________:____ 44
C28 CONTRIBUTIONS TO STRATIGRAPHY

Reference section of Nicholas Limestone Member of Lexington Limestone Con.

Lexington Limestone Continued m.. 7

 -n u nr ^ Thickness Millersburg Member: (feet)

6. Limestone and shale. Limestone is fine to medium grained, 

bioclastic, mixed with blebs of micrograined limestone, very 

fossiliferous; as nodules and in very thin lumpy beds. 

Shale is medium to medium dark gray; occurs as matrix 

of nodular limestone; varies in amount approaching 50 percent in upper part of unit; yields nodular rubble on weathering _______ _ __ __ __ 17. 5

5. Limestone and minor shale; in very irregular to crenulated

beds; forms resistant ledge___ ___ _ __ 4.0

4. Limestone (70 percent) and shale. Limestone is fine to medium grained, bioclastic, fossiliferous in very thin crenulated beds with intercalated zones of nodular limestone and 

shale. Shale is medium to medium dark gray and occurs 

as matrix of limestone nodules and as undulatory interbeds ________________________________ 7.0

3. Limestone and shale. Limestone is nodular to crenulated, 

bioclastic, fossiliferous as above; thin zone of micrograined 

limestone and flat-bedded shale at top of unit________ 5.0

2. Limestone (70 percent) and shale. Limestone is micrograined, 

in very thin tabular smooth-surfaced beds. Shale is medium gray and approximately 30 percent of unit. Discontinuous stratum of crossbedded medium-grained bioclastic 

calcarenite, 1 ft thick, at top of unit____________ 8. 0

1. Limestone (80 percent) and shale. Limestone is bryozoan 

bearing, medium to coarse grained, bioclastic, in irregular 

to crenulated beds as much as 8 in. thick. Shale is medium gray to medium dark gray; as undulatory interbeds; 

yields nodular rubble on weathering. Covered below____ 7. 0

REFERENCES CITED

Campbell, M. R., 1898, Description of the Richmond quadrangle, [Kentucky] :

U.S. Geol. Survey Geol. Atlas, Folio 46. 

Cressman, E. R., 1964, Geology of the Tyrone quadrangle, Kentucky: U,S. Geol.

Survey Geol. Quad. Map GQ-303. 

Foerste, A. F., 1909, Preliminary notes on Cincinnatian and Lexington fossils:

Denison Univ. Sci. Lab. Bull., v. 14, p. 289-324.

 1912, Strophomena and other fossils from Cincinnatian and Mohawkian 

horizons, chiefly in Ohio, Indiana, and Kentucky: Denison Univ. Sci. Lab. 

Bull. 16, p. 17-172.

 1914, The Rogers Gap fauna of central Kentucky: Cincinnati Soc. Nat.

History Jour., v. 21, p. 109-156. 

Hamilton, D. K., 1950, Areas and principles of ground-water occurrence in the

inner Bluegrass region, Kentucky: Kentucky Geol. Survey, ser. 9, Bull. 5,

68 p. 

Huffman, G. G., 1945, Middle Ordovician limestone from Lee County, Virginia,

to central Kentucky: Jour. Geology, v. 53, p. 145-174. 

McFarlan, A. C., 1943, Geology of Kentucky: Lexington, Ky., Univ. Kentucky,

531 p.
THE LEXINGTON LIMESTONE OF CENTRAL KENTUCKY C29

McFarlan, A. C., and White, W. H., 1948, Trenton and pre-Trenton of Kentucky:

Am. Assoc. Petroleum Geologists Bull., v. 32, p. 1627-1646. 

Miller, A. M., 1905, The lead and zinc-bearing rocks of central Kentucky, with

notes on the mineral veins: Kentucky Geol. Survey Bull. 2,35 p.

 1913, Geology of the Georgetown quadrangle: Kentucky Geol. survey, 4th 

ser., pt. 1, p. 317-351.

 1925, Geology of Woodford County: Kentucky Geol. Survey, ser. 6, v.

21, p. 119-144. 

Nickles, J. M., 1905, The Upper Ordovician rocks of Kentucky and their Bryozoa :

Kentucky Geol. Survey, Bull. 5, 64 p. 

Nosow, Edmund, and McFarlan, A. C., 1960, Geology of the central Bluegrass

area: Lexington, Ky., Kentucky Geol. Survey, Univ. Kentucky, 56 p.; Geol.

Soc. America, Southeastern Sec., Guidebook, Field trip 1960, no. 1. 

Weir, G. W., and Greene, R. C., 1965, Clays Ferry Formation (Ordovician), new

map unit in south-central Kentucky; U.S. Geol. Survey Bull. 1224-B.

o