Strodes Creek Member 

(Upper Ordovician)-- 

A New Map Unit in the 

Lexington Limestone of 

North-Central Kentucky

By DOUGLAS F. B. BLACK and NORMAN P. CUPPELS

CONTRIBUTIONS TO STRATIGRAPHY 

GEOLOGICAL SURVEY BULLETIN 1372-C

Prepared in cooperation with the 

Kentucky Geological Survey

Description of a body of distinctive 

micrograined limestone in the upper 

part of the Lexington Limestone
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 72-600315

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973

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

Washington, D. C. 20402 

Stock Number 2401-00290
CONTENTS

Abstract ______________________. 

Introduction ____________________.

Geologic setting _________________.

General description of Strodes Creek Member 

Fossil collections _________________. 

Type section ______________________.

Reference section ______________________.

References cited ___________________.

Page

Cl

1

5

6

8

11

13

16

ILLUSTRATIONS

Page

FIGURE 1. Index map of report area, north-central Kentucky, showing 7%-minute quadrangles ___________ ___ C2

2. Isometric diagram showing relation of the Strodes Creek 

Member to other members of the Lexington Limestone 

and to the Clays Ferry Formation ______ 3

3. Strodes Creek section and explanation for graphic sections --___-_______________________ ___ _ 4

4. Photograph of bedding characteristics of Strodes Creek

Member ____________________.________ ___ _ 7

5. Columnar sections for Winchester composite section ___ 14

6. Photograph showing relation between graphic representation and roadcut at locality B, Winchester composite section __________________________________ 15

7. Photograph showing relation between graphic representation and roadcut at locality C, Winchester composite section __ _________________ _____ 15

in

CONTRIBUTIONS TO STRATIGRAPHY

STRODES CREEK MEMBER (UPPER ORDOVICIAN)-

A NEW MAP UNIT IN THE LEXINGTON 

LIMESTONE OF NORTH-CENTRAL KENTUCKY

By DOUGLAS F. B. BLACK and NORMAN P. CUPPELS

ABSTRACT

The Strodes Creek Member, a body of distinctive micrograined limestone 

in beds of bouldery aspect, was defined in the course of mapping the complex relations among members of the upper Lexington Limestone and the 

Clays Ferry Formation in the northeast part of the inner Bluegrass region 

of Kentucky. It consists chiefly of brownish-gray dense lime mudstone, characteristically containing abundant stromatoporoids and sparse but conspicuous ostracodes. The member is a lens, or possibly a tongue, in the easterly 

thickening upper part of the Lexington Limestone and is lithologically similar 

to parts of the Perryville Limestone Member and Devils Hollow Member of 

the Lexington of the western Bluegrass. The western edge of the new member trends north-northwest between Winchester and Cynthiana. Fossils identified from these rocks indicate an early Edenian age.

INTRODUCTION

Recent geologic mapping in north-central Kentucky, done as 

part of the current U.S. Geological Survey-Kentucky Geological 

Survey cooperative program, has resulted in the recognition of a 

previously undetected mappable rock-stratigraphic unit in the 

upper part of the Lexington Limestone. This new unit is here 

named the Strodes Creek Member of the Lexington for Strodes 

Creek in the Austerlitz quadrangle, Kentucky.

The Strodes Creek is chiefly brownish-gray dense lime mudstone, characteristically containing abundant reddish-brown and 

light-pinkish-gray stromatoporoids and sparse but conspicuous 

ostracodes. The member is a lens, or possibly a tongue, within 

the Millersburg Member of the Lexington. Its western edge 

trends north-northwest between Winchester and Cynthiana, Ky., 

and has been traced for 28 miles in this area (fig. 1). Near Winchester, the Strodes Creek is no more than 10 feet thick (fig. 2, 

loc. 6) but it is as much as 30 feet thick in the eastern outskirts

Cl
C2 CONTRIBUTIONS TO STRATIGRAPHY

84°30'

BRECKENRIDGE

>MILLERSBURG 

2

MiileFsDurg 

section

\ 

\ 

\

SHAW-N 

MAN

EXPLANATION

Known occurrence of Strode s

Creek Member

Western limit shown by

dunked line

USGS Diamond-drill hole

Outcrop or location of 

measured section

X A-C

Fossil collections

Numbered localities are

keyed to fiutire 2

LEXINGTON EAST CLINTONVILLE

Winchester 

compo: 

sectic

38° 15'

5 MILES

FIGURE 1. Index map of report area, north-central Kentucky, showing TVzminute quadrangles.

of Cynthiana. The eastern extent of the member has not been 

determined.

Two units of similar lithology lower in the Lexington Limestone 

to the west and southwest are: (1) part of the Devils Hollow 

Member, a lens in the middle Lexington of the FrankfortVersailles area, Kentucky (Black and others, 1965); and (2) 

still lower stratigraphically, the Faulconer Bed of the Perryville 

Limestone Member near Danville, Ky. (Cressman, 1972).
STRODES CREEK MEMBER OF LEXINGTON LIMESTONE, KY.

EXPLANATION 

LITHOLOGY

Nodular limestone

STRATIGRAPHY 

Ocf, CLAYS FERRY FORMATION

LEXINGTON LIMESTONE 

Olt. Tanglewood Limestone Member 

Olm. Millersburg Member 

Olsc, Strodes Creek Member 

Olb. Brannon Member 

Olg, Grier Limestone Member

Olb

FIGURE 2. Isometric diagram showing relation of the Strodes Creek Member to other members of the Lexington Limestone and to the Clays Ferry 

Formation. Line of section shown in figure 1.
C4 CONTRIBUTIONS TO STRATIGRAPHY

The Strodes Creek section (figs. 1 and 3), measured from roadcuts along U.S. Route 227 south of the Strodes Creek crossing in

70-

50-

40-

30-

10-

Miilersburg 

Member

Strodes Creek 

Member

Millersburg 

Member

Tongue of 1 

/ Clays Ferry I 

_ Form_atj cm___j 

Miilersburg 

_J\/[embe_r__

Tongue of I

Clays Ferry ^

Formation i o

Millersburg 

Member

Alhmychin 

zone

3 Tanglewood

Limestone 

Member

Grier

Limestone 

Member

EXPLANATION

Lime mudstone

Circles represent algal limestone

Nodular fossiliferous

limestone and shale

Resistant coqumoid limestone

Calcarenite and calcirudite

Tabular, partly micrograined

limestone and shale

Covered interval

^s^ 

Stromatoporoid

<=3 

AUonycMa

Letters adjacent to section 

identify fossil collections 

discussed in text

FIGURE 3. Strodes Creek section and explanation for this figure and figures 

5-7. Location of section shown in figure 1.
STRODES CREEK MEMBER OF LEXINGTON LIMESTONE, KY. C5

the north-central part of the Austerlitz quadrangle, is the type 

section; exposures at localities A, B, and C (figs. 1 and 5) constitute the Winchester composite reference section.

GEOLOGIC SETTING

The Lexington Limestone (Black and others, 1965) is a body 

of fairly coarse bioclastic generally fossiliferous limestone overlying cryptograined (micritic) limestone and finely crystalline 

dolomite of the High Bridge Group. Tabular micrograined (calcisiltitic) to coquinoid limestone and interbedded shale of the 

Clays Ferry Formation (Weir and Greene, 1965) overlie and 

interfinger with the upper part of the Lexington.

In the report area, beds of the upper Lexington dip gently eastward and are capped on some of the higher hills by the Clays 

Ferry. The lowest rocks exposed (fig. 2) are nodular fossiliferous 

beds of the Grier Limestone Member. Above the Grier is an intertonguing sequence of micrograined limestone and shale of the 

Brannon Member of the Lexington and the Clays Ferry Formation, calcarenite and calcirudite of the Tanglewood Limestone 

Member of the Lexington, and nodular fossiliferous limestone 

and shale of the Millersburg Member of the Lexington. Micrograined limestone and shale of the Brannon Member, a lens 

within the Lexington, occurs only in the southern part of the area. 

Tongues of similar lithology, traceable into the Clays Ferry 

Formation, occur higher in the section and extend into the Lexington from the north and south.

Calcarenite and calcirudite of the Tanglewood Limestone 

Member, which constitutes most of the upper Lexington near 

Frankfort, Ky., are present in the report area as three tongues, 

two of which pinch out, as shown in figure 2. Nodular fossiliferous 

limestone and shale of the Millersburg Member are thickest in 

the southern part of the area and intertongue with other units 

of the upper Lexington and with the Clays Ferry.

Within this intertonguing sequence of repetitive lithologic types, 

several widely persistent fossil marker zones are useful for 

stratigraphic correlation (figs. 2, 3, and 5). The highest zone is 

in the Clays Ferry Formation within a few feet of the top of 

the Lexington and consists of abundant plectambonitid brachiopods commonly identified as Sowerbyella rugosa. Stromatoporoids 

in the Strodes Creek Member are part of a zone that extends 

southwestward, far beyond the limits of the Strodes Creek, into 

the Millersburg Member. Internal molds of the large pelecypod 

Allonychia flanaganensis are locally abundant in a zone in the 

lower 10 feet of the Millersburg Member.
C6 CONTRIBUTIONS TO STRATIGRAPHY

GENERAL DESCRIPTION OF STRODES CREEK MEMBER

The Strodes Creek Member is well exposed in many roadcuts 

along U.S. Route 227 and Interstate Highway 64 between the 

type locality and locality B of the Winchester reference section 

(fig. 1). The member is readily recognized by its bouldery aspect 

(fig. 4) attributable to a combination of pinch-and-swell bedding, 

ball-and-pillow structure, and bulbous stromatoporoids. Some 

stromatoporoids are large (as much as 2 ft across), light pinkish 

gray, and sugary textured, but most are smaller, reddish brown, 

vitreous, and commonly fractured.

The rock is chiefly limestone with minor amounts of gray to 

reddish-brown fissile shaly argillaceous calcisiltite as partings and 

in places as beds. The dominant limestone type is moderategrayish-brown to gray dense nonfissile rock having the textural 

characteristics of a mudstone. It is composed mostly of clay- and 

silt-sized calcite particles and commonly contains disseminated 

rounded medium- to coarse-sand-sized fossil fragments. The rock 

is difficult to break; fractured surfaces are smooth and subconchoidal.

The lime mudstone commonly occurs as a disturbed matrix 

through which irregular fragments and deformed masses of 

brown vitreous stromatoporoidal material are distributed. It also 

contains sparsely disseminated but conspicuous smooth ostracodes 

generally less than 2 mm (millimeters) across. Cephalopods, 

corals, gastropods, algal lumps, and brachiopods also occur in 

the member but are not everywhere present.

In some places, notably west of locality 2 of figures 1 and 2, 

the member includes bedding sets as much as 4 feet thick of 

grayish-brown very fine grained even-bedded calcarenite that 

weathers to smooth surfaces. This very fine grained calcarenite 

may become coarser to the west and grade into the middle 

tongue of the Tanglewood Limestone Member at locality 1 of 

figure 2, or the Tanglewood and Strodes Creek may be separated 

by nodular limestone of the Millersburg Member as shown.

The Strodes Creek float is generally distinctive but sparse. It 

consists largely of smooth rounded boulders, stromatoporoids, 

and coral heads which weather out on slopes where soil is thin. 

Contacts are rarely seen, but in roadcuts where the unit is best 

exposed, the contact with the underlying Millersburg Member 

is sharp, whereas the upper contact is gradational through an 

interval of several feet in which beds of nodular fossiliferous 

limestone, characteristic of the Millersburg, are intercalated with 

beds of the Strodes Creek. A lens of limestone conglomerate 0 to 

42 inches thick, composed chiefly of algal lumps 0.1 to 0.4 foot
STRODES CREEK MEMBER OF LEXINGTON LIMESTONE, KY. Q7

across, is the basal stratum of the member at locality B of the 

Winchester reference section. Anomalously abundant bryozoans 

in a zone of shaly limestone several feet thick directly underlie 

the Strodes Creek at several places in the Hedges, Sideview, and 

Millersburg quadrangles.

air v

-^

'"i^ifc^tr^i

i*P<~S£ WM »^^fe.^1fei|

fff'-as^aS^^^m^L'^ r I. ^i>*^.^- ^^* "!i<,^M; V

""^^l^^^^^-^l

FIGURE 4. Bedding characteristics of the Strodes Creek Member. 

Roadcut at Paris-Winchester exit from westbound lane of Interstate Highway 64, locality A, Winchester composite section. Location of section shown in figure 1. Abney-level staff is 5 feet long.
C8 CONTRIBUTIONS TO STRATIGRAPHY

FOSSIL COLLECTIONS

Fossil collections made at localities shown on the index map 

and columnar sections (figs. 1, 3, and 5) are described below. 

Fossil identifications were by R. B. Neuman, brachiopods; O. L. 

Karklins, bryozoans; J. W. Huddle, conodonts; W. A. Oliver, Jr., 

corals, stromatoporoids, and stromatolites; E. L. Yochelson, gastropods; J. M. Berdan, ostracodes; John Pojeta, Jr., pelecypods; 

and R. J. Ross, Jr., trilobites.

Species of brachiopod genera shown are currently under review, 

according to R. B. Neuman (written commun., 1972). Species 

names generally applicable to these genera are: Hebertella parkensis Foerste, Orthorhynchula linneyi (James), Platystrophia 

colbiensis Foerste, Rafinesquina Winchester ensis Foerste, and 

Zygospira modesta (Hall).

O. L. Karklins reports that, in general, the bryozoan faunule 

is similar to that in the upper part of the Lexington Limestone 

and the Clays Ferry Formation. (See also Cressman and Karklins (1970).) Several specimens found in these collections show 

close relationship to forms and species present in the lower part 

of the Edenian strata near Cincinnati, Ohio, and probably in 

strata of Edenian Age at Tanner's Creek, Ind.

The general aspect of the ostracodal assemblage also suggests 

that these rocks are very early Edenian in age, according to 

J. M. Berdan.

John Pojeta (written commun., 1972) reported that the 

coarsely ribbed ambonychiid species Ambonychia byrnesi (Ulrich) 

is known only from rocks which are currently regarded as Late 

Ordovician in age. This species was previously identified in collections from the Point Pleasant Formation near Falmouth, Ky., 

and from the Clays Ferry Formation near Kirksville, Ky. Allonychia flanaganensis Foerste consistently has been identified 

in collections from the Millersburg Member of the Lexington 

Limestone from Frankfort, Ky., eastward.

Fossil-collecting localities shown on illustrations by capital 

letters are keyed to U.S. Geological Survey fossil-collection numbers below. Stratigraphic units from which fossil collections 

were made are designated by letter symbols in parentheses as 

follows: Ocf, Clays Ferry Formation; Olm, Millersburg Member 

of Lexington Limestone; Olsc, Strodes Creek Member of Lexington Limestone; Olt, Tanglewood Limestone Member of Lexington 

Limestone.

A 7310-CO (Olsc) :

Bryozoans: Constellaria tcres Ulrich and Bassler, trepostome(?) indet. 

Pelecypods: Ambonychia spp. indet., Modiolopsis aff. M. simulatrix 

Ulrich.
STROBES CREEK MEMBER OF LEXINGTON LIMESTONE, KY. £9

A 7310-CO Continued:

Stromatolite indet. 

B 7311-CO (Olsc) :

Gastropods: Bellerophontaceans, probably Bucania and Tropidodiscus,

Loxoplocus (Lophospira) sp., Murchisonia sp. 

C 7312-CO (Olsc) :

Coral: Favistina sp.

Ostracodes: Ceratopsis sp. indet., Ctenobolbina sp. aff. C. ciliata 

(Emmons), Ci/stomatochilina sp. aff. C. tiara (Henningsmoen), 

Ectoprimitial sp., "Bollia" sp. aff. "B." persulcata (Ulrich), Milleratiat sp., Leperditella sp., leperditellid indet., Pseudoaparchites sp., 

Pseudobythocyprist sp., Shenandoia sp., "Bythocypris" sp. aff. "B." 

cylindrica (Hall). 

A-C 7313-CO (Olsc) :

Brachiopods: Hebertella sp., Platystrophia sp. 

D 7314-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Escharopora sp.

form b.

Pelecypod: Modiomorphid genus and sp. indet. 

Fingerlike organic structure, probably an algal stromatolite. 

Trilobite: Gravicalymene cf. G. hagani Ross. 

E 7315-CO (Olsc) :

Fingerlike organic structure, probably an algal stromatolite. 

F 7316-CO (Olsc) :

Conodonts: Rhipidognathiis symmetrica descreta Bergstrom and Sweet,

cordylodian element of unknown species. 

G 7317-CO (Olsc) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp. 

Gastropods: Cyclonema varicostatum (Hall), steinkerns indet. possibly Loxoplocus (Lophospira). 

H 7318-CO (Olsc) :

Ostracodes: Ceratopsis sp. indet., Ctenobolbina sp. aff. C. ciliata (Emmons), Cystomatochilina sp. aff. C. tiara (Henningsmoen), Leperditella sp., Pseudoaparchites sp., Pseudobythocyprisl sp., Shenandoia 

sp. Krausella"! sp., smooth ostracodes indet. 

Stromatoporoid: Labechia sp. 

I 7319-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp. 

Bryozoans: Ceramoporella sp., Constellaria teres Ulrich and Bassler, 

Peronopora sp. form c, Heterotrypa sp. form g, Ceramoporella distincta 

Ulrich.

Gastropods: Cyclonema varicostatum (Hall), steinkern indet. doubtfully Cyclonema.

Pelecypods: Allonychia flanaganensis Foerste, Ambonychia byrnesi 

(Ulrich), Ambonychia cf. A. ulrichi (Pojeta), modiomorphid genus 

and sp. indet. 

Sponge: Hindia"! sp. 

J 7320-CO (Olm) :

Brachiopod: Hebertella sp.

Bryozoans: Constellaria teres Ulrich and Bassler, Peronopora sp. form

c, Dekayiat sp., Hallopora sp. form d. 

Gastropod: Cyclonema sp. indet.
CIO CONTRIBUTIONS TO STRATIGRAPHY

J 7320-CO Continued

Sponge: Hindia! sp. 

K 7321-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.

Bryozoans: Constellaria teres Ulrich and Bassler, Heterotrypa sp. form

g. 

L 7322-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.,

Zygospira sp. 

Bryozoans: Ceramoporella sp., Constellaria teres Ulrich and Bassler,

Peronopora sp. form c, Atactoporella! sp., Homotrypella! sp. 

Pelecypod: Modiomorphid genus and sp. indet. 

M 7323-CO (Olsc) :

Fossils unreported. 

N 7324-CO (Olsc) :

Brachiopods: Hebertella sp., Platystrophia sp., Zygospira sp. 

Coral: Favistina sp.

Gastropod: Cyclonema varicostatum (Hall). 

0 7325-CO (Olsc):

Brachiopod: Hebertella sp. 

Gastropod: Cyclonema sp. indet.

Ostracodes: Ceratopsis sp. indet., Ctenobolbina sp. aff. C. ciliata 

(Emmons), Cystomatochilina sp. aff. C. tiara (Henningsmoen), 

"Bollia" sp. aff. "B." persulcata (Ulrich), Milleratial sp., Leperditella sp., leperditellid indet., Pseudobythocypris"! sp., Shenandoia sp., 

"Bythocypris" sp. aff. "5." cylindrica (Hall), smooth ostracodes indet. 

Pelecypod: Ambonychiid genus and sp. indet. 

P 7326-CO (Olsc):

Fossils unreported. 

Q 7327-CO (Olsc):

Brachiopods: Hebertella sp., Platystrophia sp.

Gastropods: Cyclonema sp. indet., gastropod indet., possibly Liospira. 

Stromatoporoid: Labechia sp. 

Trilobite: Calymenid indet. 

R 7328-CO (Olsc) :

Brachiopods: Hebertella sp., Platystrophia sp. 

Coral: Favistina sp.

Gastropods: Cyclonema sp. indet., steinkern possibly Cyclonema. 

Fingerlike organic structure, probably an algal stromatolite. 

Stromatoporoid: Labechia sp. 

S 7330-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.,

Zygospira sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Homotrypa sp. form

g(?), Ceramoporella sp., Dekayiat sp. 

Gastropod: Cyclonema cf. C. varicostatum (Hall). 

T 7331-CO (Olsc) :

Brachiopods: Hebertella sp., Orthorhynchula sp., Zygospira sp. 

Bryozoans: Constellaria cf. C. emaciata Ulrich and Bassler, Hallopora

sp. form d, "eridotrypid"(?), trepostome(?) indet. 

Stromatoporoid: Labechia sp. 

U 7332-CO (Olm):

Brachiopods: Hebertella sp., Platystrophia sp.
STROBES CREEK MEMBER OF LEXIXGTON LIMESTONE, KY. Cll

U 7332-CO Continued

Fingerlike organic structure, probably an algal stromatolite. 

V 7333-CO (Ocf) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.,

Zygospira sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Escharopora sp. form

b, Homotrypa sp. form g(?). 

W 7334-CO (Olm) :

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.,

Zygospira sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Eridotrypa sp. form

c-1.

Coral: Favistina sp.

Gastropod: Steinkern possibly Cyclonema. 

Pelecypod: Ambonychia sp. indet. 

X 7335-CO (Ocf):

Brachiopods: Hebertella sp., Platystrophia sp., Rafinesquina sp.,

Zygospira sp. 

Gastropods: Sphaenosphera sp., Loxoplocus (Lophospira) sp., indet.,

Hormotoma cf. H. subangulata Ulrich in Ulrich and Scofield. 

Pelecypods: Ambonychia sp. indet., Lyrodesma subplamtm Ulrich,

Modiolopsis(t) sp. indet., Whiteavesia sp. 

Trilobite: Isotelus sp. 

Y 7336-CO (Olm) :

Brachiopods: Platystrophia. sp., Rafinesquina sp., Zygospira sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Peronopora sp. form

c.

Gastropods: Steinkerns possibly Cyclonema and another indet. 

Pelecypod: Allonychia ftanaganensis Foerste. 

Z 7337-CO (Olt) :

Brachiopods: Platystrophia sp., Rafinesquina sp., Zygospira sp. 

Bryozoans: Constellaria teres Ulrich and Bassler, Peronopora sp. form

c, Heterotrypa sp. form g.

TYPE SECTION

[Measured from a series of roadcuts beginning at hillcrest at Kentucky coordinates 2,021,200 

ft E., 215,450 ft N., north zone, in the north-central part of the Austerlitz quadrangle, 

Clark County, Ky., and extending northward along U.S. Route 227 to its crossing of 

Strodes Creek. (See fig. 3 and loc. 4, fig. 1.) ]

Lexington Limestone: Thickness

(feet)

Millersburg Member (incomplete) :

13. Limestone and minor shale; nodules of gray to brown fineto medium-grained bioclastic limestone with dark-gray 

shale as partings and as thin irregular beds; fossiliferous, brachiopods dominant (USGS loc. 7330-CO); 

ledge-forming brachiopodal calcirudite at base _____ 3.5

Strodes Creek Member:

12. Limestone and shale: Limestone is moderate-grayishbrown to gray dense lime mudstone chiefly composed of 

silt- and clay-sized calcite particles with scattered 

medium to coarse fossil fragments in undulatory pinchand-swell smooth-surfaced beds 0.2 to 0.5 ft thick, the 

bottoms of which commonly have lobate structure, con-
C12 CONTRIBUTIONS TO STRATIGRAPHY

Lexington Limestone Continued

Strodes Creek Member Continued 'tStT" 

vex downward, resembling load casts; some beds have 

ball-and-pillow structure; beds and partings of gray 

to reddish-brown argillaceous fissile calcisiltite correspondingly show pinch-and-swell structure, fissility paralleling swells in overlying beds of lime mudstone; contains abundant stromatoporoids, either whole or as irregular fragments churned and rolled into enclosing 

matrix; brown vitreous stromatoporoids predominate, 

but a larger light-pinkish-gray variety also occurs; 

unornamented ostracodes are thinly but conspicuously 

scattered through the lime mudstone (USGS loc. 

7331-CO) ____________________________- 7.2 

Millersburg Member:

11. Limestone, gray, fine- to medium-grained, fossiliferous,

unevenly bedded, ledge-forming _____ __ _______ 4.0

10. Limestone and shale: Limestone (60 percent), gray to 

brown, fine-grained, nodular; contains an abundant 

and varied fauna (USGS loc. 7332-CO). Shale, darkgray, fissile, poorly exposed _____________________ 9.0

Tongue of Clays Ferry Formation:

9. Limestone and shale: Limestone (55 percent), dominantly 

micrograined, light-brown, partly fossiliferous (USGS 

loc. 7333-CO) ; in tabular beds 0.1 to 0.3 ft thick; yields 

smooth tablets where weathered. Shale, dark-gray, 

fissile, poorly exposed; weathers light yellowish brown 2.0 

Millersburg Member:

8. Limestone (50 percent) and shale; nodules of mediumgray fine- to medium-grained bioclastic limestone in 

matrix of dark-gray shale; fossiliferous (USGS loc. 

7334-CO); weathers to limonite-stained nodular rubble __________________________________ 4.5 

Tongue of Clays Ferry Formation:

7. Limestone and shale: Limestone (50 percent), light gray 

to light-brown, micrograined, partly fossiliferous 

(USGS loc. 7335-CO); in tabular beds 0.2 to 0.3 ft 

thick. Shale, brownish-gray; weathers light yellowish 

brown; fissile; partly exposed as beds 0.1 to 0.3 ft thick. 

Smooth-surfaced light-gray weathered tablets of limestone conspicuous in float ___________________ 9.5

6. Covered ________________________________ 17.0 

Millersburg Member:

5. Limestone (60 percent) and shale: Similar to unit 8 but 

coarser nodular texture; contains abundant internal 

molds of large pelecypod Allonychia flanagenensis 

(USGS loc. 7336-CO) _____________________ 12.0 

Tanglewood Limestone Member:

4. Limestone (calcarenite), gray to light-grayish-brown, 

fine- to medium-grained, bioclastic, slightly phosphatic, 

sparry-calcite-cemented; in even beds 0.05 to 0.3 ft 

thick, crossbedded in lower part; some beds contain
STROBES CREEK MEMBER OF LEXINGTON LIMESTONE, KY.

Lexington Limestone Continued

Tanglewood Limestone Member Continued T>(feet) eSS 

large brachiopod and bryozoan fragments (USGS loc. 

7337-CO) _____________________________ 11.0 

3. Covered ______________________________ 10.0 

2. Limestone (calcarenite and calcirudite), light-brownishgray to grayish-brown, medium- to very coarse grained, 

bioclastic; phosphatic in part; sparry-calcite-cemented; 

crossbedded in upper part with foreset beds as much as 

0.5 ft thick and thinly and evenly bedded in lower part 4.0 

Grier Limestone Member (incomplete) :

1. Limestone and minor shale; light-gray to light-brownishgray nodular to irregularly bedded fine-grained bioclastic limestone and very thin beds of gray shale__-_ 2.0

Total section __________________ 95.7 

REFERENCE SECTION

The Winchester composite reference section (fig. 5) consists 

of three separate sections measured at localities A, B, and C 

(fig. 1). Sections are shown graphically in figure 5, and graphic 

sections at B and C are compared with photographs of the outcrops in figures 6 and 7.

Locality A. A section (figs. 4 and 5) was measured from 

roadcuts in the northeast quadrant of the interchange of Interstate Highway 64 and U.S. Route 227 in the south-central part 

of the Austerlitz quadrangle, Kentucky. The section is not continuous; the lower part was measured from the roadcut along 

the Paris exit from westbound Interstate Highway 64; the upper 

part was measured from south-dipping beds in the roadcut along 

the Winchester entrance to westbound Interstate Highway 64.

Locality B. The Strodes Creek Member and its contacts with 

the enclosing Millersburg Member are well exposed in roadcuts 

along Maple Street, U.S. Route 227, in the northern outskirts of 

Winchester, Ky. The Millersburg above the Strodes Creek includes several resistant ledge-forming beds which are well exposed 

in this section. The section (figs. 5 and 6) was measured from 

the roadcut along northbound lane north and south of the Louisville and Nashville Railroad overpass. U.S. Geological Survey 

fossil collections from these rocks are identified by letter symbols 

in figure 5 as follows: D, 7314-CO; E, 7315-CO; F, 7316-CO; 

G, 7317-CO; H, 7318^CO; I, 7319-CO; J, 7320-CO; K, 7321-CO; 

L, 7322-CO.

Locality C. Strata of the Millersburg Member below the 

Strodes Creek Member are well exposed in the steep roadcut along 

the westbound lane of Interstate Highway 64 at the eastern overpass of the Louisville and Nashville Railroad in the south-central
C14 CONTRIBUTIONS TO STRATIGRAPHY

FEET

100

90-

rht/clltj zone 

CLAYS FERRY FORMATION

LEXINGTON LIMESTONE

Millersburg 

? Member

,Strodes Creek 

i Member

Millersburg 

Member

Interval 

projected

by 

altimetry

Tanglewood Limestone Member

FIGURE 5. Winchester composite section. Locations of sections shown in 

figure 1. See figure 3 for explanation.

part of the Austerlitz quadrangle (fig. 7). The Strodes Creek 

is quite thin at this locality, which is very near its western limit.
STROBES CREEK MEMBER OF LEXINGTON LIMESTONE, KY. C15

FIGURE 6. Roadcut and its graphic representation at Maple Street, locality 

B of Winchester composite section. Location of section shown in figure 1.

FIGURE 7. Roadcut and its graphic representation at Louisville and Nashville Roadroad-Interstate Highway 64 overpass, locality C of Winchester 

composite section. Location of section shown in figure 1.
C16 CONTRIBUTIONS TO STRATIGRAPHY

REFERENCES CITED

Black, D. F. B., Cressman, E. R., and MacQuown, W. C., Jr., 1965, The 

Lexington Limestone (Middle Ordovician) of central Kentucky: U.S. 

Geol. Survey Bull. 1224-C, 29 p.

Cressman, E. R., 1972, Geologic map of the Danville quadrangle, Mercer and 

Boyle Counties, Kentucky: U.S. Geol. Survey Geol. Quad. Map GQ-985.

Cressman, E. R., and Karklins, O. L., 1970, Field trip No. 2, Lithology and 

fauna of the Lexington Limestone (Ordovician) of central Kentucky, 

in Guidebook for field trips Geol. Soc. America, Southeastern Sec., 

18th Ann. Mtg., Lexington, Ky., 1970: Lexington, Ky., Kentucky Geol. 

Survey, p. 17-28.

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

A new map unit in south-central Kentucky: U.S. Geol. Survey Bull. 

1224-B, 18 p.