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Revised Stratigraphy and Correlations of the 

Niagaran Provincial Series (Medina, Clinton, 

and Lockport Groups) in the Type Area of 

Western New York 

By Carlton E. Brett, Dorothy H. Tepper, William M. Goodman, Steven T. LoDuca, and 

Bea-Yeh Eckert 

U.S. GEOLOGICAL SURVEY BULLETIN 2086 

Prepared in cooperation with the U.S. Environmental Protection Agency 

and the Department of Earth and Environmental Sciences of the 

University of Rochester 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1995 
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY 

GORDON P. EATON, Director 

For sale by U.S. Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government. 

Published in the Eastern Region, Reston, Va. 

Library of Congress Cataloging in Publication Data 

Revised stratigraphy and correlations of the Niagaran Provincial Series (Medina, Clinton, 

and Lockport Groups) in the type area of western New York I by Carlton E. Brett ... [et 

al.]. 

p. em- (U.S. Geological Survey bulletin ; 2086) 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3:2086 

1. Geology, Stratigraphic-Nomenclature-New York (State)-Niagara County Region. I. 

Brett, Carlton E. (Carlton Elliot) II. Series. 

QE75.B89 no. 2086 

[QE645] 

557.3 s---dc20 

[551.7'009747] 95-10156 

CIP 
CONTENTS 

Abstract ......................................................................................................................... . 

Introduction . . . . . . . . .. ... . .. . . . . . . . . . . ... ....... .......... ... . . . . . . ............................... ... . . . . . . . . .. . . . . . . . . . . . ...... 2 

Purpose and Scope . . . . . .. . . . . . . ........ ... .. . . . .......... ............................... .......... .. .. . . . . . . . . . . . . .. 2 

Previous Work......................................................................................................... 4 

Acknowledgments ................................................................................................... 7 

Revised Stratigraphy and Correlations . . . . ........ .. ... . . . . . . . . . . . . ..... .. .. . ...... .. . . . . . . . . . . .. .. .... .. . . . . . . . . 8 

Medina Group ......................................................................................................... 10 

Whirlpool Sandstone ....................................................................................... 13 

Power Glen Shale ............................................................................................ 17 

Devils Hole Sandstone .................................................................................... 18 

Grimsby Formation ......................................................................................... 19 

Artpark Phosphate Bed ........................................................................... 20 

Thorold Sandstone .......................................................................................... 21 

Cambria Shale ................................................................................................. 22 

Kodak Sandstone ............................................................................................ 23 

Clinton Group ......................................................................................................... 24 

Neahga Shale .................................................................................................. 27 

Densmore Creek Phosphate Bed ............................................................. 29 

Reynales Limestone ........................................................................................ 31 

Hickory Comers Member ....................................................................... 33 

Budd Road Phosphate Bed .............................................................. 33 

Merritton Limestone ....................................................................................... 34 

Williamson Shale ............................................................................................ 35 

Second Creek Phosphate Bed ................................................................. 36 

Rockway Dolomite ......................................................................................... 37 

Salmon Creek Phosphate Bed ................................................................. 39 

Irondequoit Limestone .................................................................................... 39 

Rochester Shale ............................................................................................... 40 

Lewiston Member ................................................................................... 41 

Unit A .............................................................................................. 41 

Unit B .............................................................................................. 41 

Unit C .............................................................................................. 42 

Unit D .............................................................................................. 42 

Unit E .............................................................................................. 42 

Burleigh Hill Member ............................................................................. 43 

DeCew Dolomite ............................................................................................ 44 

Lockport Group ....................................................................................................... 45 

Gasport Dolomite ............................................................................................ 49 

Gothic Hill Member ................................................................................ 50 

Pekin Member ......................................................................................... 51 

Goat Island Dolomite ...................................................................................... 52 

Niagara Falls Member ............................................................................. 53 

Unit A .............................................................................................. 53 

Unit B .............................................................................................. 54 

Ancaster Member .................................................................................... 54 

Vinemount Member ................................................................................ 56 

Eramosa Dolomite .......................................................................................... 57 

III 
IV 

1-3. 

4-9. 

10. 

11. 

12-15. 

16. 

17. 

18, 19. 

20-22. 

CONTENTS 

Unit A ..................................................................................................... 51 

Unit B ...................................................................................................... 58 

Unit C ...................................................................................................... 58 

Unit D ........................................................... , ......................................... 58 

Unit E ...................................................................................................... 58 

Unit F .............................................. , ....................................................... 58 

Guelph Dolomite ............................................................................................. 58 

Unit A .................................................................................................... ,59 

Unit 8 ...................................................................................................... 59 

Unit C ...................................................................................................... 60 

Summary and Conclusions ............................................................................................. 60 

References Cited ............................................................................................................. 61 

FIGURES 

Maps showing locations of: 

1. Study area and significant geographic features referred to in text............................................................... 3 

2. Pertinent features in the vicinity of the Niagara River Gotge .. .............. ..................... .......... ...... .. .......... .... . 4 

3. U.S. Geological Survey wells from which cores were obtained.................................................................. 5 

Charts showing: 

4. Revised stratigraphic nomenclature for the Niagaran Provincial Series in the Niagara region ................... 6 

5. Niagaran Provincial Series nomenclature for the Niagara region of western New York accepted by 

the U.S. Geological Survey prior to the publication of this report............................................................... 7 

6. Nomenclature accepted by the Ontario Geological Survey for the equivalent of the Niagaran 

Provincial Series in the Niagara Peninsula of Ontario .. . . ...... ... .. .. . . . . . . .......... .. . .. ..... ... .. ... . ..................... ........ 7 

7. Historical summary of Medina Group nomenclature in the Niagara region ................................................ 11 

8. Stratigraphic nomenclature from Rickard (1975) and revised nomenclature for the Medina Group in the 

Niagara region .............................................................................................................................................. 12 

9. Stratigraphic correlations for the Medina Group and lower part of the Clinton Group in parts of 

Ontario and New York .................................................................................................................................. 13 

Diagrammatic geologic section showing stratigraphic relations in the Medina Group, with regional 

correlations between Hamilton, Ont., and the Genesee River Gorge at Rochester, N.Y. ..................................... 14 

Descriptive stratigraphic column for the Medina Group at the Niagara River Gorge near Lewiston, N.Y. ......... 15 

Charts showing: 

12. Natural-gamma logs and stratigraphic correlations from U.S. Geological Survey Queenston cores .......... 16 

13. Historical summary of Clinton Group nomenclature in the Niagara region ................................................ 25 

14. Stratigraphic nomenclature from Rickard (1975) and revised nomenclature for the Clinton Group in the 

Niagara region .............................................................................................................................................. 26 

15. Stratigraphic correlations for the upper part of the Clinton Group and the Lockport Group in parts of 

Ontario and New York .................................................................................................................................. 27 

Generalized geologic section showing stratigraphic relations in the lower part of the Clinton Group in 

western New York ................................................................................................................................................ 28 

Diagrammatic geologic section showing stratigraphic relations in the upper part of the Clinton Group, 

with regional correlations between Clappison's Comers, Ont., and Rochester, N.Y ............................................ 29 

Descriptive stratigraphic columns for: 

18. The upper part of the Medina Group and the lower and basal upper parts of the Clinton Group at 

(A) Merritton, Ont., and (B) Lockport, N.Y .................................................................................................. 30 

19. The upper part of the Clinton Group at Niagara River Gorge near Lewiston, N.Y. ..................................... 31 

Charts showing: 

20. Natural-gamma logs and stratigraphic correlations from U.S. Geological Survey Neahga cores ............... 32 

21. Historical summary of Lockport Group nomenclature in the Niagara region .............................................. 45 

22. Stratigraphic nomenclature from Rickard (1975) and revised nomenclature for the Lockport Group 

in the Niagara region .................................................................................................................................... 46 
CONTENTS 

23. Diagrammatic geologic section showing stratigraphic relations in the Lockport Group, with regional 

correlations between Clappison's Comers, Ont., and Penfield, N.Y .................................................................... .47 

24. Descriptive stratigraphic column for the Lockport Group in Niagara County .................................................... .48 

CONVERSION FACTORS AND VERTICAL DATUM 

Multiply By To obtain 

inch (in.) 25.4 millimeter 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum 

of 1929 (NGVD of 1929)-a geodetic datum derived from a general adjustment of the 

first-order level nets of both the United States and Canada, formerly called Sea Level 

Datum of 1929. 

v 

Revised Stratigraphy and Correlations of the Niagaran Provincial 

Series (Medina, Clinton, and Lockport Groups) in the Type Area of 

Western New York 

By Carlton E. Brett1

, Dorothy H. Tepper2, William M. Goodman3, Steven T. LoDuca4, 

and Bea-Yeh Eckert5 

ABSTRACT 

Recent stratigraphic analysis of the Niagaran Provincial Series (Medina, Clinton, and Lockport Groups) in the 

classic Niagara region of western New York has helped 

refine correlations that allow a uniform stratigraphic 

nomenclature to be applied throughout the region and into 

southwestern Ontario, Canada. A revision of Niagaran Provincial Series stratigraphic nomenclature is presented that 

builds on and partly revises the stratigraphic column of 

Rickard (1975), the most recent correlation of rocks of Silurian age for western New York published by the New York 

State Geological Survey. Six newly recognized units are 

established, and 13 are revised-that is, the rank or stratigraphic contacts of previously established units are 

changed. Six units have been extended geographically into 

the Niagara region from adjacent areas where they have 

been previously recognized. The revised nomenclature is 

intended to apply primarily to Niagara County, N.Y., but is 

generally applicable within the region between Hamilton, 

Ont., and Rochester, N.Y. 

Development of the revised nomenclature has been 

facilitated by the availability of nine cores drilled in the 

Niagara Falls area that permit detailed correlations within 

the Niagaran Provincial Series. These drill cores were 

obtained as part of a 1987-91 study of the hydrogeology of 

the Niagara region by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency. 

1 Work done under Contract No. 186148 for U.S. Geological Survey. 

Current address: Dept. of Earth and Environmental Sciences, Hutchison 

Hall, University of Rochester, Rochester, NY 14627. 2U.S. Geological Survey, 903 Hanshaw Rd., Ithaca, NY 14850. 

3Current address: The Sear-Brown Group, 85 Metro Park, Rochester, 

NY 14623. 

4Current address: Dept. of Geography and Geology, Eastern Michigan University, Ypsilanti, MI 48197. 

5Current address: 405-693 Woolwich St., Guelph, Ontario NlH 3Y8. 

As established herein, the Medina Group consists of 

the following seven formations: the Whirlpool Sandstone, 

the Power Glen Shale, the Devils Hole Sandstone, the 

Grimsby Formation, the Thorold Sandstone, the Cambria 

Shale, and the Kodak Sandstone. New formations proposed 

herein include the Devils Hole Sandstone and the Cambria 

Shale. In addition, a distinctive, laterally traceable phosphate-pebble bed at the base of the Grimsby Formation is 

herein formally proposed as the Artpark Phosphate Bed. 

Stratigraphic contacts of the Power Glen Shale and the 

Grimsby Formation have been revised. The Thorold Sandstone and the Kodak Sandstone are herein placed in the 

Medina Group rather than in the Clinton Group. 

As established herein, the Clinton Group is divided 

into the following eight formations: the Neahga Shale, the 

Reynales Limestone, the Merritton Limestone, the Williamson Shale, the Rockway Dolomite, the Irondequoit Limestone, the Rochester Shale, and the DeCew Dolomite. The 

Merritton Limestone, the Second Creek Phosphate Bed (at 

the base of the Williamson Shale), the Williamson Shale, 

and the Salmon Creek Phosphate Bed (at the base of the 

Rockway Dolomite) have been extended into the Niagara 

Falls area from adjacent areas in which they have been previously recognized. Stratigraphic contacts of the Irondequoit Limestone have been revised. The Rockway Dolomite 

is raised herein to formation rank. 

As established herein, the Lockport Group consists of 

the following four formations: the Gasport Dolomite, the 

Goat Island Dolomite, the Eramosa Dolomite, and the 

Guelph Dolomite. The Gasport Dolomite consists of two 

newly proposed members: a lower dolomitic grainstone 

designated the Gothic Hill Member, and an upper, argillaceous, locally biohermal, dolomitic wackestone unit termed 

the Pekin Member. The Goat Island Dolomite contains three 

newly proposed members: a lower biohermal and grainstone unit designated the Niagara Falls Member; a middle, 

cherty dolomitic wackestone termed the Ancaster Member 

(also revised and geographically extended); and an upper, 
2 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

argillaceous dolomitic wackestone and shale unit designated the Vinemount Member (also revised and geographically extended). The Eramosa and Guelph Dolomites are 

not formally divided into members, although several informal units are recognized within each formation and are discussed herein. Stratigraphic contacts of the Gasport 

Dolomite, Goat Island Dolomite, Eramosa Dolomite, and 

Guelph Dolomite have been revised. 

INTRODUCTION 

The Niagaran Provincial Series (Medina, Clinton, and 

Lockport Groups) of western New York, which has been 

established as the type area for eastern North America, consists of about 400 ft of dolomite, limestone, shale, and sandstone. These richly fossiliferous rocks were deposited in 

shallow epeiric seas during the Silurian (439-408 Ma, on 

the basis of dates from Harland and others, 1982). The Niagaran Provincial Series correlates with the Llandoverian, 

Wenlockian, and Ludlovian Series of the Welsh Borderland, 

the European reference section. The Niagaran Series record 

diverse environments ranging from nonmarine sandstones 

to deep-water shales and reefal carbonates. This sequence, 

which was deposited along the northern rim of the Appalachian foreland basin, preserves the record of sediments in 

an evolving foreland basin (Cheel, 1991). The lateral equivalents of these units crop out along the Niagara Escarpment, 

which trends east-west from the Rochester, N.Y., area to 

Hamilton, Ont., Canada. The escarpment continues northwestward across the Bruce Peninsula of Ontario; the Niagaran belt then wraps around the Michigan Basin and extends 

into Michigan, Wisconsin, Illinois, Indiana, and Ohio. 

Although the Niagaran Provincial Series of New York 

and Ontario has been the focus of several comprehensive 

stratigraphic analyses, lack of a uniform nomenclature 

across the international boundary has made precise physical 

stratigraphic correlation difficult. Resolution of questions 

related to nomenclature and correlation is timely because 

recently developed allostratigraphic and geodynamic models require high-resolution data bases. The stratigraphic 

refinements discussed herein are based on detailed study of 

cores from nine test holes drilled as part of a study during 

1987-91 of the hydrogeology of the Niagara region by the 

U.S. Geological Survey (USGS) in cooperation with the 

U.S. Environmental Protection Agency (USEPA). Newly 

recognized units that are traceable in these cores can also be 

identified in outcrops in New York and Ontario. Physical 

traceability of rock units indicates that a uniform stratigraphic nomenclature can be established across the Niagara 

region, which includes the international boundary. In addition to the inclusion of new units, this revision also resolves 

conflicts in current stratigraphic nomenclature that arose 

from miscorrelation of key stratigraphic units. Part of this 

miscorrelation results from a lack of exposure of some 

stratigraphic intervals in areas immediately adjacent to the 

Niagara River Gorge. 

The revisions discussed herein comply with the 

requirements of the North American Stratigraphic Code 

(NASC) of the North American Commission on Stratigraphic Nomenclature (1983). This study was done in cooperation with the USEPA and the Department of Earth and 

Environmental Sciences of the University of Rochester. 

Partial funding was provided by grants from the Petroleum 

Research Fund of the American Chemical Society (grant 

21987-AC8), the Geological Society of America, the New 

York State Geological Survey, and the Paleontological 

Society. 

PURPOSE AND SCOPE 

This report presents a revision of Niagaran Provincial 

Series stratigraphic nomenclature for the type area of westem New York (figs. 1-3). The stratigraphic nomenclature is 

modified and refined, particularly where the improved 

stratigraphic data base has provided answers to previously 

unresolved questions. Changes include proposal of newly 

recognized units and revision of established units. This 

study is a preliminary step in revision of the entire Silurian 

column for New York. To promote use of uniform nomenclature in the Niagara region, where several geologic and 

hydrogeologic studies are being conducted, the revisions for 

this area are presented in this report rather than delay publication until statewide revisions are completed. 

Changes presented in this report include formal establishment of newly recognized units and revision of previously established units~ the revised stratigraphic nomenclature is presented in figure 4. All of the new units and 

some of the revis:.~·,:;:-:.s ;'resented herein were inf0nnally presented in the folk· .. ving guidebook and journal articles by 

the authors of this report: Brett and others (1990a,b; 1991 ); 

Goodman and B~ert (1994); LoDuca and Brett (1991, 

1994); and Teppe~ J.nd others ( 1990). Duke ( 1991) also used 

some of the un~ts mformally. 

This study builds on and partly revises the stratigraphic 

column of Rickard (1975), the most recent correlation of 

rocks of Silurian age for western New York published by 

the New York State Geological Survey (NYSGS). Niagaran 

Provincial Series nomenclature for the Niagara region of 

western New York accepted by the USGS prior to the publication of this report is shown in figure 5. The nomenclature 

is discussed in detail under the individual unit descriptions. 

This study included a detailed literature search and 

analysis of outcrops and of USGS cores (locations shown in 

fig. 3). Cores were examined in detail from nine deep test 

holes drilled as part of the previously mentioned cooperative USGS/USEPA study of the hydrogeology of the Niagara region. Four of the cores extend into the Ordovician 

Queenston Shale; the remaining five end in the Neahga 
INTRODUCTION 3 

ONTARIO 

ERIE ~, 

42°30' 

Base modified from Duke, 1991 10 20 30 MILES 

I 

L _ I 

I r - _l - - - - ,_ - - -

/L--~ I I / ___ ,_...J 

- _ JNEW YORK', 

[ ) 

1 LIVINGSTON 

r ' 

I 

ONTARIO 

,------~ 

\ 

YATES 

r------'----, 

EXPlANATION 

10 20 30 KILOMETERS 

Approximate location and width of 

Clarendon-Linden Fault zone 

(Modified from Isachsen and McKendree, 

1977.) 

80° Niagara Escarpment 

2 Number refers to name of municipal area • or geographic feature listed below CANADA 

1. Albion 17. Sodus 

2. Brockport 18. Walworth 

3. Cambria 19. Wheatfield 

NEW YORK 4. Gasport 20. Williamson 

5. Gates 21. An caster 

6. Genesee River Gorge 22. Balls Falls 

7. Hickory Corners 23. Grimsby 

8. Lockport 24. Guelph 

9. Medina 25. Hamilton 

10. Middleport 26. Merritton 

11. Niagara Falls, N. Y. 27. Rockway PENNSYLVANIA 50 100 MILES 

50 100 KILOMETERS 

12. Niagara River Gorge 28. St. Catharines 

13. Oak Orchard Creek 29. Stoney Creek Base from U.S. Geological Survey, 1970, 1 :7,500,000 

LOCATION MAP 14. Pekin 30. Thorold 

15. Penfield 31. Vinemount 

16. Royalton 

Figure 1. Location of study area and significant geographic features referred to in text. 

Shale (Silurian Clinton Group). These cores have provided 

a continuous, unweathered record to supplement the observations made at outcrops. 

The revised nomenclature (fig. 4) applies primarily to 

Niagara County, N.Y., but is generally applicable to the 

region between Hamilton, Ont., and Rochester, N.Y. A 

summary of nomenclature accepted by the Ontario Geological Survey (Johnson and others, 1992) for the equivalent of 

the Niagaran Provincial Series in the Niagara Peninsula of 

Ontario is shown in figure 6. North of Hamilton, in the 

Bruce Peninsula region of Ontario, Niagaran Provincial 

Series stratigraphic nomenclature is consistent with that of 
4 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

ONTARIO 

NEW YORK 

~ 

• 

EXPLANATION 

City of Niagara Falls 

New York Power Authority 

pump/ storage reservoir 

- - - International boundary 

Localities 

1. Artpark 

2. Robert Moses Powerplant 

3. Forebay Canal 

4. South haul road 

5. Sir Adam Beck Powerplant 

6. Devils Hole State Park 

7. Whirlpool 

8. Old sewage-treatment plant 

9. Schoellkopf Powerplant site 

0 2 3 MILES 

0 2 3 KILOMETERS 

Figure 2. Location of pertinent features in the vicinity of the Niagara River Gorge. Location of area is shown in figure 3. (Modified from 

Tepper and others, 1990, fig. 1.) 

genetically related Michigan Basin strata of Manitoulin 

Island and northeastern Michigan. East of Rochester, some 

correlative strata, particularly the Lockport Group, undergo 

rapid, lateral facies changes that require a stratigraphic 

nomenclature that emphasizes facies similarities with sections of the Clinton Group type area of east-central New 

York. 

PREVIOUS WORK 

The correlation chart of Rickard (1975) is the culmination of about 150 years of research on the Silurian rocks of 

New York. James Hall (1838, 1839, 1840, 1843) is generally credited with defining key stratigraphic units in western 

New York, although the pioneering efforts of Hall's mentor, 

Amos Eaton (1824; 1830a,b; 1832), must be recognized as 

the starting point in the historical development of Medina, 

Clinton, and Lockport stratigraphic nomenclature. Hall 

( 1839) proposed a new system of naming rocks on the basis 

of the geographic name of the type locality; the Rochester 

Shale and Lockport Limestone were among the first formally named stratigraphic units in North America. 

Vanuxem (1842) introduced the New York System, in 

which the Medina Sandstone, Clinton Group, and Niagara 

Group made up the Ontario Division. Hall (1843) and 

Emmons (1846) refined Eaton's earlier observations. 

The contributions of the pioneering workers in New 

York were followed by comprehensive refinements published near the turn of the century by Clarke and Schuchert 

(1899, 1900), Hartnagel (1907, 1912), Kindle and Taylor 

(1913), Schuchert (1914), and Chadwick (1918). The 

stratigraphy of the Clinton Group was investigated in 'detail 

by Sanford (1935, 1936) and Gillette (1947). Subsequent 

work on the Silurian stratigraphy of New York includes 

Fisher's (1953a,b) work on the Clinton Group and the 

Medina Group ( 1954, 1966) and his correlation chart of the 

Silurian rocks of New York (1960), Kilgour's (1963) work 

on the Clinton Group, Zenger's (1965) work on the 
INTRODUCTION 5 

79° 

43°07'30" 

•I WHEATFIELD - 3 I 

78°45' 

City of 

Lockport 

Area shown in fig. 2 

r43° 

I 

•I WHEATFIELD - 1 I 

NIAGARA COUNTY 

.-./· ........... I .I PENDLETON - 1 I 

r . --. • EXPLANATION 

) ~ Incorporated area 

COUNTY 

2 MILES 

I 

• New York Power Authority 

pump/ storage reservoir 

I NIAGARA - 1 I 

e Identifier and location of 

USGS wells from which cores were obtained 

- - - International boundary 

2 KILOMETERS 

Figure 3. Location of U.S. Geological Survey wells from which cores were obtained. Location of area is shown in figure 1. 

(Modified from Tepper and others, 1990, fig. 1.) 

Lockport Formation, and Rickard's (1975) correlation chart 

for the entire Silurian section of New York. Martini (1971), 

Duke (1987a,b), and Duke and Fawcett (1987) provide discussions of the sedimentology and stratigraphy of the 

Medina Formation. The paleontology and environments of 

deposition of the Niagaran Provincial Series are discussed 

in Brett (1981a,b). Brett and others (1990a,b; 1991) and 

Goodman and Brett ( 1994) discuss in detail the sequence 

stratigraphy of the Niagaran Provincial Series and identify 

six unconformity-bound sequences and several smaller 

scale disconformity-bound stratal packages that can be correlated into Pennsylvania, Maryland, Ohio, Michigan, and 

the Bruce Peninsula of Ontario. 

Study of the Silurian rocks of Ontario has an equally 

long history, beginning with the pioneering work of Murray 

(1845). Early comprehensive stratigraphic treatises were 

developed by Logan (1863), Bell (1867, 1870), Parks 

· (1913), and Williams (1914a, 1919). More recent syntheses 

of regional stratigraphy include Bolton's (1957) comprehensive stratigraphy and paleontology of the Niagara 

Escarpment and subsequent studies by Sanford ( 1969), 

Hewitt (1972), Martini (1971, 1974), Telford (1978), and 

the Ontario Geological Survey (1991). 

Many workers have contributed significantly to the 

interpretation of particular stratigraphic units within the 

Niagaran Provincial Series. These authors are cited in the 

appropriate sections. Lukasik's (1988) work on the lithostratigraphy of Silurian rocks in Ohio, Kentucky, and West 

Virginia was useful in determining regional correlations. 

References helpful in tracing nomenclatural history include 

Wilmarth (1938), Keroher and others (1966), Keroher 

( 1970), Berry and Boucot ( 1970), and Luttrell and others 

(1981, 1991). 
6 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

(f) 

IUJ 

b:O: z OUJ _J 

~ <( z(f) <( INFORMAL w zz 0 0... w FORMAL UNITS Q...(/) a:(} Z(f) ::::> I- 0~ UJ- >!:!:! 0 UNITS (f) 1--a: a:: a: (/)UJ Oa: a: >- ::JW <(:2 U:UJ (f) W(l) UJ<( D... (f) (9 FORMATION MEMBER BED 

z z +--::5 <( <( 1-o (9 z ::J ::::i 

g >- <( <( VERNON SHALE A a: 0 (/) 

z Cl...a: <( w GUELPH DOLOMITE A,B,C 

> 0... - - - - - - - - - - - - - - - - - - - - ~-- - 0 0... ..... ERAMOSA DOLOMITE A,B,C,D,E,F _J ::::> ct - - - - - - I 

0 0 ::J V/NEMOUNT* 

~ GOAT ISLAND -- _J 

DOLOMITE --- ANCASTER * 

0 

-- NIAGARA FALLS A,B 

..... - - - - - - GASPORT - PEKIN z DOLOMITE -- GOTH/CHILL <( 

0 

~ --_DE~EY:i, --QQLQ.MI~ ----_ . ------------ 1- - -- 0 13u'RLEiGHHILL - - - - - - - - ~- - - _J ROCHESTER z - ~---- - - - - - - - - ~- - - z w SHALE -- ~E'CL]SI9N_ ~,s...c,IJ...E_ ~ ~ - - - - --- - - - - - - - - - ~ z ~ IRONDEQUOIT LS. <( 

a: a: ROCKWA y DOLOMiTE - - S8l MQ!:::,J CK EtiQS - BED - :::::> - <( ~ -wiLLIA'MsoN sHALE- !"'" - - - - - SECOND CK. PHOS. BED 1- - - - __J (9 ..... MEBBIIIO~ I IMESI"o~E - - - - (f) ~ u 

a: 

w 

z --REYNALES --LIMESTONE --- ~ HICKORY ---CORNERS --------- 1- - -- ~ NEAHGA SHALE - - - BUDD ROAD PHO~ B5,L) I 

0 z _.J - J>E~M~R~K~H~. ~D 1- -- ----- ~ ----- ---I <( 

ffi KODAK SANDSTONE 

> CAMBRIA SHALE 

0 -- - - - ~ - - - - - - - - - - - - ~- - - 0 

~ _TH.QRQ.LD_§A~D~O~E z ~- - - - - - - - - - - - -- - - <( GRIMSBY FORMATION ~BieABK. eH.DS. BE.O _J 

~ _J -- - - - - - 1- - - - - - - - - - - - - D.E'l.LLS. HOLE 

5./At:J..D.S.TDt:J..E 

-- - - - - - 1- - - - - - - - - - - - - - - - - POWER GLEN SHALE 

WHIRLPOOL SANDSTONE 

z ------- ~ z z ------------. --- ~ <( 0 OUEENSTON SHALE <( i= 0 :::i a: z 

> _.J w <( 0 0... z 

0 (9 z ~ 

0 I 0... I 

a: (f) ::::> 0 0 

0 <( z a: 0 

EXPLANATION 

DIASTEM- Minor discontinuities, 

including distinct bedding planes and 

sharp sedimentary contacts, with no 

evidence of erosional or biostratigraphic 

gaps 

- • • MINOR UNCONFORMITYDisconformities that show evidence of 

minor erosion and (or) biostratigraphic 

gaps on the order of a subzone 

• • MAJOR UNCONFORMITYRegionally angular erosional surfaces 

that may completely bevel one or more 

underlying stratigraphic units 

LTALLC/ZED At:J..D llNDERl /NED = NEW UNIT, PROPOSED HEREIN 

(FORMAL UNIT) 

ITALICIZED ONLY= REVISED HEREIN: CONTACTS 

OR RANK CHANGED 

VERTICAL AND UNDERLINED= EXTENDED GEOGRAPHICALLY 

VERTICAL= CHANGE IN GROUP ASSIGNMENT 

VERTICAL = NOT REVISED OR OTHERWISE 

* 

CHANGED 

IN ADDITION TO REVISION 

HEREIN, THESE UNITS ARE 

EXTENDED GEOGRAPHICALLY, 

AND ARE PROPOSED HEREIN AS 

MEMBERS OF THE GOAT ISLAND 

DOLOMITE 

LS. = Limestone 

PHOS. = Phosphate 

CK. =Creek 

Figure 4. Revised stratigraphic nomenclature for the Niagaran Provincial Series in the Niagara region. 
INTRODUCTION 7 

(f) 

IW ti:O: 

ow --' 

:2: z(f) <( 

~~ 0 a.. w Z(f) ::::) 

I- w- ;;w 0 (/) t-Il: 

>- (J)W oa: a: <(:2 a:w (/) W<( a. (f) (!) FORMATION MEMBER 

a: z w <( <( 

a.. <.9 z ::J ::::; a.. >- <( ::::) <( (/) VERNON SHALE A (.) ,_ _______ -------

OAK ORCHARD :j:: 

ERAMOSA:j:: 

LOCKPORT 

DOLOMITE GOAT ISLAND :j:: 

GASPORT LIMESTONE 

DECEW 

f.- ------- ------ - - z ROCHESTER SHALE:::: BURLEIGH HILL :j:: 

z <( w <( LEWISTON :j:: 

a: _J a: 0 <( IRONDEQUOIT LIMESTONE :::> 0 (!) z _j 0 ~ ~ Ci5 I- WILLIAMSON SHALE z z :J REYNALES 

-- ROCKWAY DOLOMITE :j:: () 

LIMESTONE 

-- HICKORY CORNERS :j:: 

NEAHGA SHALE :j:: 

- ----- -- -------- THOROLD SANDSTONE 

-- z GRIMSBY SANDSTONE :j:: a: 0 w iii 

$: _J POWER GLEN SHALE :j:: 

0 <( 

_J WHIRLPOOL SANDSTONE 

z <( 

z -------------- <( "' t= 0 QUEENSTON SHALE 

0 a: z w <( 0 > a.. z :2: 0 z 0 a.. 0 I ::::) () a: z 0 a: 0 

EXPLANATION 

:j:: Formation and member names that are not formally accepted by the U.S. 

Geological Survey (USGS) but are mentioned in some form (for example, they 

may be shown as formations rather than members as above) in the USGS 

lexicons of geologic names (Wilmarth, 1938; Keroher and others, 1966; Keroher, 

1970; Luttrell and others, 1981; and Luttrell and others, 1991) 

* Name formally accepted by USGS for usage in areas other than New York 

Ordovician - Silurian boundary 

Group boundary 

Figure 5. Niagaran Provincial Series nomenclature for the 

Niagara region of western New York accepted by the U.S. 

Geological Survey prior to the publication of this report. 

ACKNOWLEDGMENTS 

The authors express gratitude and appreciation to the 

many individuals who aided this research, especially Robert 

Blair of Golder Associates (Mississauga, Ont.), and 

Michael Johnson and Derek Armstrong of the Ontario Geological Sur;vey, for their assistance with stratigraphic 

nomenclature and correlation of units in Ontario with our 

revised units. Special thanks are extended to Ed Landing of 

the New York State Geological Survey for his thorough 

technical review of the manuscript and many helpful suggestions. Others who assisted with fieldwork, shared their 

knowledge of the subsurface, and participated in discussions include Gordon C. Baird (State University of New 

~ (j) w w 1-

(j) ii 

>- w (j) (j) 

a: 

w 

0. 

0. 

::::l 

w 

_J 

0 

0 

z ~ 

~ 

a: 

::J 

.....J 

U5 

--

a: 

w 

3: 

0 

_J 

z 

<( a: 0 w > 0. 

0 0. 

0 ::::l 

a: 

0 

0. 

::::l 

0 

a: 

(9 FORMATION MEMBER 

SALINA A 

GUELPH 

- -~ --- ----- ---- --

--

z 

0 

1-

z 

::::i 

0 

f-. -

1-

0 

<( 

a: 

<( 

1-

<( 

0 

ERAMOSA 

LOCKPORT GOAT ISLAND 

GASPORT 

---- ---- ---- -- DECEW 

ROCHESTER 

IRONDEQUOIT 

REYNALES 

NEAHGA 

THOROLD 

--- - --- - ------

>- OJ 

(/) 

:2: 

a: 

(!) 

CABOT HEAD '----

MANITOULIN I 

WHIRLPOOL 

--------· ------· 

OUEENSTON 

EXPLANATION 

Ordovician - Silurian boundary 

Group boundary 

Figure 6. Nomenclature accepted by the Ontario Geological 

Survey for the equivalent of the Niagaran Provincial Series in the 

Niagara Peninsula of Ontario. (Modified from Johnson and others, 

1992, figs. 20.15, 20.19, 20.24.) (Published with permission from 

the Ontario Geological Survey.) 

York College at Fredonia), Terry Carter (Ministry of 

Natural Resources of Ontario), Samuel J. Ciurca (private 

geologist), Donald J. Crowley (Pecten International Company), Mark Domagala (New York State Department of 
8 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Environmental Conservation), James D. Eckert (Guelph 

University), Donald Hoskins (Pennsylvania State Geological Survey), Gerard V. Middleton (McMaster University), 

Mark A. Pearce (United States Gypsum), Lawrence V. 

Rickard (New York State Geological Survey), Arthur Van 

Tyne (Van Tyne Consulting), and Donald H. Zenger 

(Pamona State College). 

REVISED STRATIGRAPHY AND 

CORRELATIONS 

During development of Silurian nomenclature in New 

York, Niagara and Niagaran have been used at the formation, group, and series levels. For example, Niagara Limestone was first introduced by Vanuxem (1839); it is now 

recognized as the Lockport Dolomite by the USGS. Niagara 

Group was first introduced by Hall (1842) and included the 

Rochester Shale and Lockport Limestone; Hall ( 1867) later 

included the Guelph Limestone in the Niagara Group. 

Clarke and Schuchert (1899) modified Niagara Group to 

include the Clinton beds, Rochester Shale, Lockport Limestone, and the Guelph Dolomite. Prior to this report, the 

USGS did not assign the Lockport Dolomite (formation), 

with its five members, to a group but used Clinton Group 

for the interval above the Thorold Sandstone up to and 

including the Rochester Shale. Rickard ( 197 5) also included 

the Thorold Sandstone and the DeCew Dolomite in the 

Clinton Group. Prior to this report, the USGS used Albion 

Group for the stratigraphic interval that includes the Whirlpool Sandstone, Power Glen Shale, Grimsby Sandstone, 

and Thorold Sandstone. This interval, except for the 

Thorold Sandstone, is shown as the Medina Group on Rickard's (1975) correlation chart. Chamberlain and Salisbury 

(1906) grouped the New York Silurian formations into the 

Oswegan Series, Niagaran Series, and Cayugan Series. 

Fisher (1960) divided the Silurian into two series, the Niagaran and the Cayugan. This usage was accepted by the 

USGS and by Rickard (1975). The Medina, Clinton, and 

Lockport Groups were included in the Niagaran Series by 

Rickard (1975) and that usage is followed herein. 

Berry and Boucot ( 1970) emphasize that the only diagnostic fauna within the New York Silurian is that of the Niagaran Series, which is the only Silurian subdivision that can 

be demonstrably recognized outside the type area. Because 

the term Niagaran has become essentially synonymous with 

Silurian in the western part of North America, Berry and 

Boucot ( 1970) suggest that the Series nomenclature of the 

British Silurian be used for the Silurian of North America. 

They recommend restriction of the New York Silurian terminology to that area in which the units can be traced on a 

lithologic and stratigraphic basis. With specific regard to the 

term Niagaran, they state (p. 15, 16): 

The continued usage of the term "Niagaran" for all of North 

America has led to its corruption, until now it has become, for all 

practical purposes, synonymous with "shelly Silurian." It is recommended that the term "Niagaran" be used only as a provincial series 

term in areas adjacent to western New York where its usage can be 

justified on a lithologic and stratigraphic basis.*** It is recommended that North Americans discontinue the futile efforts to use the 

New York section as a standard for purposes of correlation. (Paraphrased from Berry and Boucot ( 1970) and published with permission of the authors.) 

The authors agree with Berry and Boucot (1970) and 

herein restrict the use of Niagaran Provincial Series to the 

recommended geographical area. British Series names 

(Llandoverian, Wenlockian, and Ludlovian) are used 

throughout the text, however, to assist the reader in correlation of the New York Silurian units with strata elsewhere. 

Additional information on correlation and ages of selected 

units is presented in Rickard (1975). 

Usage in New York of the term Middle Silurian was 

abandoned by Rickard (1975), who then divided the Silurian into Lower and Upper Silurian for consistency with 

European usage. The term Middle Silurian is not used 

herein for consistency with Rickard (1975) and with international convention. Rickard (1975) placed the Lower and 

Upper Silurian boundary between the Llandoverian and the 

Wenlockian Series. Harland and others (1982) have placed 

this boundary between the Wenlockian and the Ludlovian 

Series; this placement is used herein. 

The revised stratigraphic nomenclature is presented in 

figure 4. Stratigraphic units are identified in figure 4 and in 

the text as belonging to one of the following five categories: 

(1) new unit, proposed herein; (2) revised herein (stratigraphic contacts or rank of unit changed); (3) geographic 

extension of unit previously recognized outside Niagara 

County; (4) change in group assignment; and (5) not revised 

herein (no change to unit as defined by previous workers). 

As required in the NASC (North American Commission on 

Stratigraphic Nomenclature, 1983, p. 859), lithic terms have 

been added to each of the previously established names of 

the four marker beds in the Clinton Group. A summary of 

revisions or other modifications is provided, as appropriate, 

at the end of the discussion for each unit. 

Many stratigraphic units in figure 4 are shown as separated by diastems or by minor or major unconformities. 

Diastems are minor discontinuities, including distinct bedding planes and sharp sedimentary contacts with no evidence of erosion or biostratigraphic gaps. Minor and major 

unconformities shown in figure 4, in contrast, represent 

gaps estimated to encompass tens of thousands to millions 

of years. Minor unconformities are disconformities that 

show evidence of minor erosion and (or) biostratigraphic 

gaps on the scale of a subzone. These surfaces do not substantially truncate regional stratigraphic units but they are 

sharp and indicate ( 1) local removal of up to a few feet of 

underlying beds, (2) minor channeling, and (3) clasts 

eroded from adjacent beds. Major unconformities, which 

include most stratigraphic sequence boundaries (as defined 
REVISED STRATIGRAPHY AND CORRELATIONS 9 

by Brett and others, 1990a), are regionally angular erosion 

surfaces that can completely bevel one or more underlying 

stratigraphic units. Typically, hiatuses spanning one or more 

biostratigraphic zones are evident in areas where the unconformity is most pronounced. 

The relation between Rickard's (1975) chronostratigraphic units and the revised units for the Medina, Clinton, 

and Lockport Groups is shown in figures 8, 14, and 22. 

Although all of the group names remain the same as in 

Rickard (1975), the contacts of the Medina, Clinton, and 

Lockport Groups are· revised. Changes at the formation 

level include (1) use of Canadian stratigraphic nomenclature (for example, Guelph Dolomite) to establish uniformity 

across the international border; (2) geographical extension 

of two formations (Merritton Limestone and Williamson 

Shale) that had been previously recognized beyond Niagara 

County but have now been recognized as actually extending 

into Niagara County; (3) proposal of two new formations 

(Devils Hole Sandstone and Cambria Shale); and ( 4) the 

rank or stratigraphic contacts of eight formations have been 

revised. In addition to these changes at the formation level, 

several new members are proposed and two are revised and 

extended geographically. Some new informal units are 

included in the revised column. Of particular importance to 

regional stratigraphic correlations are four distinctive, laterally traceable, phosphate-pebble horizons that are herein 

given formal bed-level status. Phosphate-pebble beds are 

particularly useful for stratigraphic correlation because they 

formed over large areas of the sea floor during periods of 

extremely slow deposition or nondeposition. Phosphate precipitates on the sea floor as nodules, crusts, or infilling of 

shells, and these precipitates are often reworked by 

storm-related depositional processes that produce widespread marker beds. 

The following principles have been consistently 

applied in the revisions herein: ( 1) definition of stratigraphic units is based on the type sections or localities; (2) 

when possible, names in long-standing use are retained with 

appropriate revisions or redefinitions instead of being 

replaced with new stratigraphic names; (3) when names for 

stratigraphic intervals are duplicated, the more recently proposed name is abandoned in favor of the earlier proposed 

term; and ( 4) a stratigraphic name for an interval is applied 

uniformly over the entire region over which that interval, as 

defined by general lithology and bounding contacts, can be 

recognized; that is, the same name is used despite (a) local 

facies changes and (b) crossing of geopolitical boundaries 

such as the U.S.-Canadian border. Strict application of 

these principles has led to some changes in usage of names. 

To resolve conflicts in the present stratigraphic nomenclature that have been caused by miscorrelation of units 

between New York and Ontario, particularly in the Lockport Group, the contacts between units with Canadian type 

sections or localities have been shifted considerably for 

consistency with Canadian usage. Thus, for example, the 

name Eramosa Dolomite is applied herein to a different 

interval of the Lockport Group than that recognized in earlier reports (for example, Zenger, 1965; Rickard, 1975). 

This shift is warranted because recent work demonstrates 

that the Eramosa interval, as defined along the Eramosa 

River area in Guelph, Ont., has previously been miscorrelated in the Niagara region with a lower, argillaceous interval herein termed the Vinemount Member (also informally 

defined in Ontario as the Vinemount Shale) of the Goat 

Island Dolomite. In tum, the name Eramosa replaces the 

term "Oak Orchard," which must be abandoned because 

strata of the interval in question are not exposed at the type 

locality on Oak Orchard Creek in Medina, N.Y. Likewise, 

modifications in the previously applied definitions of the 

Grimsby Formation and Thorold Sandstone result in 

improved characterization of the units as exposed at their 

respective type sections. 

The NASC specifies that proposed stratigraphic units 

be identified as either allostratigraphic or lithostratigraphic 

units. In many ways, traditional Silurian units of formationor member-level qualify as allostratigraphic units although 

they might have been originally defined as lithostratigraphic units. For example, the Neahga Shale is defined as a 

gray to green shale overlying the Thorold Sandstone and 

underlying the Reynales Limestone (Sanford, 1935). The 

original definition of the Neahga Shale is based on both its 

lithologic character and stratigraphic position; however, the 

nature of its disconformable contacts also qualifies it as an 

allostratigraphic unit. The internal characteristics of the formation change slightly, but not significantly. Consequently, 

the Neahga is a legitimately mappable lithologic unit with 

bounding discontinuities marked by mappable phosphatepebble beds. 

Supporting the allostratigraphic nature of stratigraphic 

units within the Niagaran Provincial Series is the elimination of the concept of laterally extensive, diachronous, 

transgressive, sheet sandstones. The Thorold-Kodak sandstone sheet, traditionally considered to be a laterally continuous, diachronous unit, actually represents two discrete, 

closely isochronous sandstone bodies at different stratigraphic levels (Duke and others, 1987). The revised units 

that result from recently improved correlations are lithostratigraphic in the sense that they remain mappable lithologic units, but they also have allostratigraphic significance 

because of their high degree of isochroneity; generally 

sharp, disconformable boundaries; and their relation to allocyclic sedimentary patterns. A major consequence of the 

revisions presented herein has been the elimination of lithostratigraphic units with grossly diachronous boundaries. 

The following discussion of stratigraphic revisions 

begins at the base of the Silurian column with the Medina 

Group and proceeds upward through the Clinton Group and 

the Lockport Group. Names for all of the new units proposed herein have been formally reserved through the Geologic Names Committee of the USGS. All revisions have 
10 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

been made in accordance with the NASC. Because the 

NASC does not allow use of the "submember" category, 

units that would be of this rank are treated as informal units 

and have been given alphanumeric designations. Informal 

units are discussed under the appropriate "member" 

categories. 

The use of quotes for stratigraphic nomenclature in this 

report is restricted to units that have been misidentified or 

abandoned. If stratigraphic nomenclature for a unit has 

changed over time, the term for the unit is shown, with capitalization, as given in whatever reference is cited rather 

than according to the most recent nomenclature. For example, Second Creek Bed was formally named by Linn and 

Brett (1988) and in all references to their work, the bed is 

termed Second Creek Bed rather than Second Creek Phosphate Bed, as it has been renamed herein. 

As has been previously discussed, this study builds on 

and partly revises the stratigraphic column of Rickard 

(1975), the most recent correlation of rocks of Silurian age 

for western New York to be published by the NYSGS. Units 

that are established in the nomenclature of the NYSGS but 

that have not been previously accepted by the USGS or are 

not proposed herein are footnoted where first mentioned in 

the text. Nomenclature different than that accepted by 

USGS in Pennsylvania is also footnoted where first used in 

the text. Several stratigraphic names that have been used 

informally in Ontario but were not previously used in New 

York have been proposed as formal names in this reportfirst usage of these terms in the text is also footnoted. There 

are no footnotes concerning any other usage of Canadian 

terms because neither the USGS nor the NYSGS has jurisdiction over usage of these terms. 

A discussion of "first usage of nomenclature" is provided for each unit that is not revised or otherwise changed 

herein, or has been geographically extended herein, or has 

had a group assignment changed herein. For units that are 

revised herein, a section on "brief history of nomenclature" 

is included. A "background" discussion of nomenclature is 

provided for those units that are newly proposed herein. 

MEDINA GROUP 

(revised herein) 

As revised herein, the Medina Group consists of 80-

115 ft of white, green, and red, barren to moderately fossiliferous- sandstone, siltstone, and shale. Carbonates are conspicuously absent east of Hamilton, Ont., and the amount of 

carbonate cement is minimal (Fisher, 1966). The Medina 

Group is the principal reservoir for natural gas in western 

New York. The type locality for the Medina Group is along 

Oak Orchard Creek in the Village of Medina, Orleans 

County, N.Y. Excellent reference sections crop out at the 

Genesee and Niagara River Gorges and at DeCew Falls, 

Ont. 

The history of nomenclature of what is now termed the 

Medina Group, beginning with Conrad ( 1837) and ending 

with Bolton (1953), is presented in Fisher (1954); Bolton 

(1957, table 2) presents a detailed summary of this nomenclature for 1910-53. A historical summary of nomenclature 

of the Medina Group in the Niagara region is shown in figure 7. Early investigators of the Medina include Conrad 

(1837); Vanuxem (1840, first usage of Medina; 1842); Hall 

(1840, 1843); Gilbert (1899); Luther (1899); Fairchild 

(1901); Grabau (1901, 1905, 1908, 1909, 1913); Kindle and 

Taylor (1913); Kindle (1914); Schuchert (1914); Chadwick 

(1918, 1935); Williams (1919); Goldring (1931); and 

Swartz and others (1942). More recent workers include 

Fisher (1954, 1960); Bolton (1957); Martini (1971, 1974); 

Rickard (1975); Duke (1987a,b; 1991); Duke and Fawcett 

(1987); and Duke, Fawcett, and Brusse (1991). 

To date, no consensus has been reached regarding the 

stratigraphic rank of the Medina sequence. The term 

Medina Group is used by the NYSGS; prior to this report, 

the same strata were designated Albion Group by the 

USGS, and termed the Cataract Group in Ontario by Bolton 

(1957). The Medina was referred to as a formation as early 

as Vanuxem (1840) and Hall (1840), both of whom used 

Medina Sandstone to refer to the interval including the 

Queenston Shale to the base of the Thorold Sandstone. The 

Medina has been referred to as a formation as late as Duke 

(1987a), who included the following members in the Niagara River Gorge area: Whirlpool, Cabot Head, Grimsby, 

Thorold, and Neahga. Conversely, it was given group rank 

by Fisher ( 1954) (fig. 7) and is considered a group by the 

NYSGS (Rickard, 1975) (figs. 7, 8). The Medina is herein 

considered a group (figs. 7, 8) because at least two scales of 

units are traceable within the traditional, formally recognized subdivisions of the Medina (for example, Grimsby 

Formation). 

As defined herein, the base of the Medina Group is 

placed at the contact between the Whirlpool Sandstone and 

the Ordovician Queenston Shale; this contact is known as 

the Cherokee discontinuity (named by Dennison and Head, 

1975), which separates the Ordovician from the Silurian 

Systems. It is a nearly planar surface that slopes gently 

northwestward, and it is described by Middleton (1987) and 

Brett and others (1990b). The disconformity is of unknown 

duration in the Niagara region (Rutka and others,1991). At 

this unconformity across western and central New York, 

Lower Silurian formations assigned to the Medina Group 

progressively onlap the eroded Queenston surface eastward. 

Between Hamilton, Ont., and Medina, N.Y. (fig. 1), the 

Whirlpool Sandstone forms the base of the Medina Group, 

and the lower contact of the Medina Group is placed 

between the Queenston Shale and the overlying Whirlpool 

Sandstone. East of Medina, the basal units (Whirlpool 

Sandstone and Power Glen Shale) become condensed and 

their remnants have been mapped as basal units of the 

Grimsby Formation. At Rochester, N.Y., the basal units 
REVISED STRATIGRAPHY AND CORRELATIONS 11 

AUTHOR OR SOURCE 

KINDLE AND TAYLOR SWARTZ AND OTHERS FISHER (1954) SOL TON (1957) RICKARD (1975) THIS REPORT (1913) (1942) 

~::c. .fLiNTON FORMA 'ION 5~-L NEAHGA SHALE z NEAHGA SHALE NEAHGA SHALE NEAHGA SHALE Za.. ~ NEAHGA SHALE '"'-:::J <(a.. O::J 1-0 (§o I 

~~~ z::J Za.. Zo... 

<(a: oo o::J ~a: CAMBRIA SHALE o::J -CJ z THOPOLD l)CJ 1-a: 1-o 1-o dc:l ~a: THOROLD z THOROLD ZCJ 0 SANDSTONE THOROLD ~a: THOROLD @J- dCJ THOROLD f= SANDSTONE SANDSTONE dCJ SANDSTONE SANDSTONE <( (MEMBER) SANDSTONE 2 

a: 

0 

~ 

(f) 

(f) 

~ z a: Q <( OJ 

a.. _j 

a.. a: <( 

a.. ::J l.l..1 

~ Gi=liMSBY ::J GRIMSBY 0 GRIMSBY a.. GRIMSBY a.. GRIMSBY £- 0 a: SANDSTONE ::J SANDSTONE ::J FORMATION 6 SAf\JDS~CNE SANDSTONE CJ 0 0 2 a: 0: (') a: a: 1- a.. c::: CJ CJ z () 

::J z <( <( <( <( 

0 c z a: z z 0: 0 <( 

c: 1- 0 0 <.9 w CABOT HEAD SHALE <( LlJ LlJ 

< < 2 () 2 2 ~ MANITOULIN DOL. DEVILS HOLE SS. - c 

w ! CABOT rlE.Ai:: SHALE ! 2 

POWER GLEN 

POWER GLEN SHALE POWER GLEN 

MANITQL.:L;f\J FISH CREEK SHALE SHALE 

SHALE SHALE 

WHIRLPOOL SS. WHiqLPOOL WHIRLPOOL WHIRLPOOL WHIRLPOOL WHIRLPOOL 

(MEMBER) SANDSTONE SANDSTONE SANDSTONE SANDSTONE SANDSTONE 

EXPLANATION 

SS. = Sandstone 

DOL. = Dolomite 

Figure 7. Historical summary of Medina Group nomenclature in the Niagara region. 

pinch out, and the lower boundary of the Medina Group is 

placed at the contact between the Queenston Shale and the 

equivalent of the Devils Hole Sandstone that has been 

assigned previously to the Grimsby Formation. 

The stratigraphic placement of the Medina-Clinton 

Group contact has been controversial (fig. 7). On the basis 

of evidence of erosion at the Grimsby-Thorold contact in 

the Niagara River Gorge, several previous workers (for 

example, Bolton [1957] and Rickard [1975]) have suggested that the Thorold Sandstone and younger strata be 

included in the Clinton Group. Other stratigraphers (for 

example, Swartz and others [19421), however, have placed 

the Medina Group contact at the top of the Thorold Sandstone in the Niagara area. Duke (1987a) used the relative 

predominance of siliciclastic beds over carbonate beds as a 

criterion and proposed that the Medina Group contact be 

placed at the contact between the Neahga Shale and the 

overlying Reynales Limestone. 

The Thorold Sandstone, Cambria Shale. and Kodak 

Sandstone are herein considered part of the Medina Group, 

and the upper contact of the Medina Group is herein revised 

to be at the unconformable contact between the Kodak 

Sandstone and the Densmore Creek Phosphate Bed of the 

overlying Neahga Shale (fig. 8). The Medina Group contact 

is informally placed at this contact by Brett and others 

(1991), Duke (1991), and LoDuca and Brett (1994). These 

authors recognize that the Thorold and Kodak are distinct 

sandstone intervals separated by the Cambria Shale, and 

that the Thorold interval can be traced below the Cambria 

Shale between Niagara County and the Rochester, N.Y., 

area. The Thorold-Cambria-Kodak succession appears to be 

relatively conformable. 

These three units are progressively truncated along the 

low-angle regional unconformity that is marked by the 

Densmore Creek Phosphate Bed. Although the presence of 

phosphate pebbles at the Kodak Sandstone-Maplewood 

Shale6 contact was noted as early as Hall (1843), the traceability of this phosphate bed was not fully appreciated until 

recently. Fisher (1953b) recognized the potential for tracing 

phosphate beds in the Clinton Group, but the stratigraphic 

complexity of the uppermost part of the Medina Group led 

to miscorrelation of phosphate horizons. The availability of 

the USGS cores has facilitated accurate correlations of 

phosphate horizons above the Kodak Sandstone and within 

higher units that are herein assigned to the lower part of the 

Clinton Group. Because the contact is an unconformity, 

6Usage ofthe New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 
12 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

NOMENCLATURE FROM 

RICKARD (1975) 

REVISED NOMENCLATURE 

z 

oa.. 

1-=> 

zo 

::Ja: 

(.)(9 

a.. 

::::> 

0 

a: 

(9 

<( 

z 

0 

w 

~ 

I I

-

NOT RECOGNIZED OR 

WAS PREVIOUSLY 

TERMED "GRIMSBY" 

OR "THOROLD" _ _ _ 

THOROLD SANDSTONE -

GRIMSBY SANDSTONE -

POWER GLEN SHALE -

WHIRLPOOL SANDSTONE-[ 

-== --B--= -== - 11 -== -== - ~~~--~~~ 

.·: · .. -.>~··: :<:: :: . . . ,• .. . . . :·. ·. ·::'.: .· .. :::·:_ :_ .. . 

.. ·· · .. ·:. · . . : .. :.:: .· 

}!ij \~w:t:/ 

KODAK SANDSTONE 

CAMBRIA SHALE a 

THOROLD SANDSTONE a 

-- GRIMSBY FORMATION 

-- DEVILS HOLE SANDSTONE 

~~~ -- POWERGLENSHALE 

===~-=== 

-== -== -== -== -== -== -== - · .. :. :: ~ ·.: ... ·. :_:· : : . ::: · .. ·. ··. ': .· :. : 

}Y{I~···;i: -- WHIRLPOOL SANDSTONE 

EXPLANATION 

Average unit thickness, in feet, based on data from four U.S. 

Geological Survey cores, two Canadian cores, and several 

outcrops 

D Sandstone 

~ Shale 

a Because of their red color and apparent miscorrelation, strata in the eastern 

part of Niagara County that are shown as Thorold Sandstone and Cambria 

Shale in the revised nomenclature column (right side of diagram) were 

considered by Fisher (1953b) to belong to the Grimsby Formation 

a.. 

::::> 

0 

a: 

(9 

<( 

z 

0 

w 

~ 

Figure 8. Stratigraphic nomenclature from Rickard (1975) and revised nomenclature for the 

Medina Group in the Niagara region. Formation contacts and lithologic shading of units are based 

on the revised nomenclature. 

different formations are juxtaposed along it. From Niagara 

County westward to St. Catharines, Ont., the Thorold Sandstone directly underlies the basal Clinton unconformity that 

is marked by the Densmore Creek Phosphate Bed. Eastward 

from Niagara County, the Cambria Shale and the Kodak 

Sandstone form the section between the Thorold and the 

basal Clinton unconformity. 

detail in Martini (1971), Duke (1991), and Duke and others 

( 1991 ). According to Brett and Calkin ( 1987), the sequence 

from the Whirlpool Sandstone through the Grimsby Formation records an Early Silurian marine transgression over the 

eroded Queenston deposits, followed by regression resulting from active progradation of the Medina fringe delta. 

Conflicts in the current lithostratigraphic divisions of 

the Medina Group are discussed by Duke (1987a) and Duke 

and others (1991), who note that previously established 

The Medina Group sediments were deposited in deltaic 

and shallow marine environments, which are described in 
REVISED STRATIGRAPHY AND CORRELATIONS 13 

(/) w w (.!) ~ww Ot--w a: < t--Cz zzz w I- (f)QQ coo 

BRUCE 

PENINSULA, 

ONTARIO 

SOUTHERN ONTARIO 

AND WESTERN 

NEW YORK 

WEST-CENTRAL 

NEW YORK 

CENTRAL 

NEW YORK 

EXPLANATION 

(/) (/) OUN UCN [}J UNCONFORMITY 

M. 

z typus 

< i: 

u 

> ..J 

w 

1- 't: 

,g 

Q) 

~ " z 

< 

a: 

w z ?- > < 0 z 0 0 z a: < w ..J < ..J -?-

z 

< z 

< 0 

0 -? :::> P. 

:I: symplex a: ? 

WINGFIELD SHALE - - - -?-?-? 

DYER BAY 

LIMESTONE 

WILLOWVALE SHALE FM. =FORMATION 

MBR. = MEMBER 

DOL = DOLOMITE 

SH. =SHALE 

LS. = LIMESTONE 

55. = SANDSTONE 

F.I.O. = FURNACE IRON ORE 

1.0. = IRON ORE 

CONGL. = CONGLOMERATE 

EQUIV. =EQUIVALENT 

(lower) = terms in parentheses are informal nomenclature 

M. typus = Mastigobolbina typus 

B. rudis = Bonnemaia rudis 

M. lata = Mastigobolbina lata 

z. emaci = Zygobolba emaciata 

P. amorphognathoides = Pterospathodus 

amorphognathoides 

P. celloni = Pterospathodus cel/oni 

I. discreta = lcriodella discreta 

I. deflecta = lcriodella deflecta 

P. symplex = Pterospathodus symplex 

Figure 9. Stratigraphic correlations for the Medina Group and lower part of the Clinton Group in parts of Ontario and New York. 

(Modified from Brett and others, 1991, fig. 5.) 

formations have been defined on the basis of regional color 

variation. These authors emphasize that these regional patterns of color variation do not necessarily match lithologic 

correlations and attribute the color variation in the Medina 

to patterns of secondary diagenetic reduction of strata that 

were oxidized when deposited. 

As defined herein, the Medina Group consists of the 

following seven formations (fig. 8), in ascending order: the 

Whirlpool Sandstone, the Power Glen Shale, the Devils 

Hole Sandstone, the Grimsby Formation, the Thorold Sandstone, the Cambria Shale, and the Kodak Sandstone. New 

formations proposed herein (fig. 4) include the Devils Hole 

Sandstone and the Cambria Shale. In addition, a distinctive, 

laterally traceable phosphate-pebble bed at the base of the 

Grimsby Formation is herein formally proposed as the Artpark Phosphate Bed (fig. 4). Stratigraphic contacts of the 

Power Glen Shale and the Grimsby Formation are revised 

(fig. 4). The stratigraphic units of the Medina Group are 

described in the following sections. 

A comparison of stratigraphic nomenclature from 

Rickard (1975) with revised nomenclature for the Medina 

Group is shown in figure 8. Stratigraphic correlations for 

the Medina Group are shown in figure 9, and a geologic 

section showing stratigraphic relations in the Medina Group 

with regional correlations between Hamilton, Ont., and 

Rochester, N.Y., is shown in figure 10. A descriptive stratigraphic column for the Medina Group at the Niagara River 

Gorge near Lewiston, N.Y., is presented in figure 11, and 

natural-gamma logs and stratigraphic correlations for units 

within the Medina Group are shown in figure 12. 

Summary of Revisions: Rickard (1975) included only 

the Whirlpool Sandstone, Power Glen Shale, and the 

Grimsby Sandstone in the Medina Group. The contact 

between the Medina and Clinton Groups has been shifted 

formally herein from the contact between the Grimsby Formation and the Thorold Sandstone to the major unconformity between the Kodak Sandstone and the Densmore 

Creek Phosphate Bed, at the base of the Neahga Shale. New 

formations proposed herein include the Devils Hole Sandstone and the Cambria Shale. The Artpark Phosphate Bed is 

introduced at the base of the Grimsby Formation. Stratigraphic contacts of the Power Glen Shale and the Grimsby 

Formation have been revised. The Thorold Sandstone and 

the Kodak Sandstone are herein included in the Medina 

Group rather than in the Clinton Group. 

WHIRLPOOL SANDSTONE 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: First used by Grabau 

( 1909) for the white quartzose sandstone, which is 25 ft 

thick at its exposure in the Whirlpool in Niagara River 

Gorge (fig. 2). It was defined as the basal bed of the Upper 

Medina (later named Albion Sandstone); overlain by red, 

green, and gray sandstones and shale; and underlain by the 

Queenston Shale of the Richmond Group. 

Type Locality: Exposures along the Canadian side of 

the Whirlpool and extending downstream to Lewiston, Niagara River Gorge (Niagara Falls quadrangle) (Grabau, 

1909). 
14 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

WEST 

MANITOULIN 

DOLOMITE 

c 

~ 

·a 

ttl 

:r:: 

1 

..$ 

iO 

LJ. 

..$ 

iO 

a:l 

2 

t: ttl 

~ 0 ttl 0.. Ol ...::( 

u ttl 0 z ...J 

3 4 

' 20 

20 40 KILOMETERS 

LOCATION MAP 

EAST 

Ql ttl c Ql Ql c 0 Ill Ol 

.:a Ql ~ 

.:s c 0 Ql 

~ < ~\!j 

5 6 7 

NOT TO SCALE 

EXPLANATION 

t <'i 1 SANDSTONE 

E=-~ =_ =_ ~ SHALE 

Figure 10. Diagrammatic stratigraphic relations in the Medina Group, with regional correlations between Hamilton, Ont., and the 

Genesee River Gorge at Rochester, N.Y. Length of vertical line at each locality indicates units observed in the field or in drill cores. 

(Modified from Brett and others, 1991, fig. 7.) 

Reference Sections: DeCew Falls, Ont.; Route 403 

roadcut, Hamilton, Ont.; Lockport, N.Y., at railroad overpass on Niagara Street. 

Thickness: In the Niagara River Gorge, the thickness of 

the Whirlpool Sandstone ranges from 18 to 28 ft (Bolton, 

1957). In the USGS cores, the thickness ranges from 20.5 to 

23.6 ft. 

Lithologic Description: In the Niagara region (fig. 11), 

the Whirlpool Sandstone is a light-gray to white, mediumto coarse-grained (0.004-0.028 in., according to Middleton, 

1987), trough cross-bedded, quartzose sandstone with thin, 

dark-gray to greenish-gray shale clasts and interbeds. It has 

been classified by Rutka and others ( 1991) as a subarkose to 

quartz arenite. The contacts of shale interbeds and between 

laminae in trough cross sets are commonly microstylolitic. 

The Whirlpool Sandstone contains floral microfossils (Gray 

and Boucot, 1971). According to Middleton and others 

( 1987), a transgressive surface separates the nonmarine, 

braided fluvial environments of the lower part of the Whirlpool from the marine nearshore, wave-affected environment 

of the upper part of the Whirlpool. This bounding transgressive surface is sharp and is defined by the presence of either 

a shale clast lag deposit, the first appearance of symmetrical 

ripples, or more regularly interbedded shale (Rutka and others, 1991). Middleton and others (1987) and Rutka and others ( 1991) describe the paleontology, environments of 

deposition, and regional correlations of the Whirlpool and 

discuss facies within the lower and upper units of the Whirlpool. The lower part of the Whirlpool is characterized by 

medium- to fine-grained sandstone with large-scale, northwestward dipping trough cross bedding (Brett and others, 

1990a) and by large-scale tabular and festoon cross bedding 

and channels up to 300 ft across (Brett and Calkin, 1987). 

The lower unit typically comprises two-thirds of the total 
REVISED STRATIGRAPHY AND CORRELATIONS 

THOROLD 

SANDSTONE 

z 

0 

f= 

<( 

:2: 

a: 

0 

LL. 

>- Ill 

(/) 

:2: 

a: 

(!) 

ARTPARK 

PHOSPHATE BED 

·.:<·::···· .· 

r-:: ''' ' ', ', ',] 

:~:: ~ ~' :, _-_ ,~,j 

f--.----c. 

~------=-

f---'--' ~ 

:'~-----~if ~~~ 

Massive, argillaceous, pelletal sandstone, 

commonly exhibits soft-sediment deformation 

Interbedded red to green sandstone, 

siltstone, and shale 

~ ~ ~ ~ _;--1 Thin lag of black phosphate pebbles 

:c:::: :=~ in shale or sandstone matrix ----= 

DEVILS HOLE =~-,:~::',::~:-::::-:_-~: SANDSTONE 

Quartzose sandstone with some laminations, 

some interbedded shale; sets of storm beds 

are common throughout 

z 

w 

.....Jw 

(!).....J 

C:<( 

WI 3:(/) 

0 

a.. 

...................... 

-:-:--,-,',',',~ 

', ', ', ', -_, :- :' ::- F= 

t- -

Sparsely fossiliferous shale with some 

cross-stratified to bioturbated sandstone 

interbeds 

Thin lag of black phosphate pebbles 

in shale or sandstone matrix 

Medium- to coarse-grained, trough crossbedded, quartzose sandstone with thin shale 

intraclasts and beds 

L2J 

~ 

~ 

~ 

Jill 

~ 

' 

' 

~ 

~ 

EXPLANATION 

TROUGH CROSS-BEDDED 

SANDSTONE 

HUMMOCKY CROSS-BEDDED 

SANDSTONE 

BIOTURBATED 

SANDSTONE 

SHALE 

PLANAR LAMINATED 

SANDSTONE 

SMALL SCALE, TABULAR, 

CROSS-BEDDED, FINEGRAINED SANDSTONE 

SHALE INTRACLASTS 

~ SANDSTONE INTERBEDS 

15 

Figure 11. Descriptive stratigraphic column for the Medina Group at the Niagara River Gorge near Lewiston, N.Y. The uppermost 

Medina units, the Cambria Shale and the Kodak Sandstone, are missing as a result of erosion beneath the basal Clinton unconformity. 

(Modified from Brett and others, 1991, fig. 6.) 
a_ 

::> 

0 

a: 

CJ 

1-

a:: 

0 

a.:-

~ 

0 

0 

.....J 

a.. 

::> 

0 

a: 

CJ 

z 

~ z 

::::i 

0 

a.. 

::> 

0 

a: 

CJ 

<( 

z 

0 

w 

~ 

TOP OF ROCK 

ERAMOSA DOLOMITE 

VINEMOUNT MEMBER 

GOAT ISLAND DOLOMITE 

NIAGARA FALLS+ANCASTER MEMBERS 

WHIRLPOOL SANDSTONE 

QUEENSTON SHALE 

Niagara-1 

400 ...___,___.--'----'-----l----L----L--L--L_j 

0 50 100 

Grand lsland-2 FEET 0 .--.r--r---.----r----r--r-~~~~ 

FEET Wheatfield-1 

50 100 

450 50 1 00 400 0 0 550 ...____,___.___..______,__....___.___..._-'--_.___, 

50 100 0 

GAMMA, IN COUNTS PER SECOND 

Figure 12. Natural-gamma logs and stratigraphic correlations from U.S. Geological Survey Queenston cores (locations shown in fig. 3). Depths shown are depths below 

land surface, in feet. The common datum on the logs is the contact between the Queenston Shale and the Whirlpool Sandstone. 

..... 

0'\ 

g; 

< 

l.ll 

-ti1 

ti 

l.ll 

>-3 

::0 

>-

~ 

0 

::0 

>- '1::) 

::r:: 

--< 

>- z 

ti 

n 

0 

::0 

::0 

ti1 

t""' 

>-

~ 

0 

z 

l.ll 

0 

"Tl 

>-3 

::r:: 

ti1 

~ 

>- 0 

>- ::0 

>- z 

'1::) 

::0 

0 

< -

z 

n 

> t""' 

l.ll 

ti1 

::0 

-ti1 

l.ll 
REVISED STRATIGRAPHY AND CORRELATIONS 17 

formation thickness in outcrop, rarely contains shale interbeds, and is coarser grained and more massively bedded 

than the upper unit (Rutka and others, 1991 ). The upper unit 

is characterized by hummocky cross stratification, oscillation ripples, sparse fossils, and greater abundance of shale 

interbeds than the lower part of the Whirlpool (Brett and 

others, 1990a). Seyler (1982) suggests a nearshore, probably beach or shoreface, environment for this upper unit. 

Camerate crinoids (Ptychocrinus) in the Niagara River 

Gorge at Lewiston and pelecypods at Balls Falls (fig.1) 

have been observed in the upper part of the Whirlpool (J.D. 

Eckert, University of Guelph, oral commun., 1992). Ostracodes, linguloid brachiopods, and trilobites have been 

found in the upper 3-6 ft of the Whirlpool. The Whirlpool 

fauna is probably the oldest known North American assemblage of Silurian fossils (Kilgour and Liberty, 1981 ). 

Contacts: The Whirlpool Sandstone unconformably 

overlies the Upper Ordovician Queenston Shale. The basal 

contact of the Whirlpool Sandstone is sharp and planar 

nearly everywhere and contains abundant green shale rip-up 

clasts and impressions of desiccation cracks from the top of 

the Queenston (Brett and Calkin, 1987). The typically green 

color of the contact with the Queenston Shale indicates 

reducing processes. In the Niagara region, a thin bed containing fossil grains and phosphatic nodules is locally 

present at the contact between the Whirlpool Sandstone and 

the overlying Power Glen Shale (Brett and others, 1991 ). In 

other areas, the contact of the Whirlpool with the overlying 

Power Glen Shale is gradational over a few feet of interbedded sandstones and shales. In the Hamilton region, the 

upper beds of the Whirlpool grade laterally into carbonates 

of the Manitoulin Dolomite. 

Regional Correlations: Regional stratigraphic correlations and relations for the Whirlpool Sandstone are shown 

in figures 9 and 10, respectively. The Whirlpool Sandstone 

is mappable as far west as Hamilton, Ont., where it begins 

to undergo facies changes. North of Hamilton, it grades into 

carbonate facies of the Manitoulin Dolomite. To the east, 

near Medina, N.Y., the overlying Power Glen Shale pinches 

out, and the Whirlpool is overlain by the Devils Hole Sandstone; however, the Whirlpool has not previously been formally recognized as a separate unit there and has instead 

been mapped as a lowermost unit of the Grimsby Formation. In cores from the Albion area, in Orleans County, N.Y., 

a carbonate- and pyrite-enriched zone in the cross-bedded 

sandstone sequence appears to mark the boundary between 

the Whirlpool and Devils Hole Sandstones. The sandstones 

equivalent to the Whirlpool could thus be distinguished 

from the sandstones equivalent to the Devils Hole in eastern 

Orleans County; however, between Albion and Rochester, 

the Whirlpool Sandstone apparently pinches out (figs. 9, 

10). The Clarendon-Linden Fault is between Albion and 

Rochester and could play a role in the pinchout of the 

Whirlpool Sandstone, but the precise relation between the 

fault and the Whirlpool Sandstone remains to be defined. 

Age: Because the Whirlpool Sandstone does not contain any diagnostic macrofossils, its age cannot be established through biostratigraphic zonation. Floral microfossils 

could enable precise dating if a Silurian acritarch zonation 

can be established. Physical stratigraphic tracing of the 

Whirlpool Sandstone into fossiliferous carbonates of the 

Manitoulin Dolomite indicates an early Llandoverian age. 

Summary of Revisions or Changes: Not revised or otherwise changed herein. 

POWER GLEN SHALE 

(revised herein) 

Brief History of Nomenclature: Bolton (1953) proposed the name Power Glen Formation for the 48 ft of 

shales with interbedded sandstones and limestones between 

the Whirlpool Sandstone and the Grimsby Formation at 

DeCew Falls, Ont. The Power Glen was considered by Bolton (1957) (fig. 7) to be correlative to the Manitoulin Dolomite and, at least, to the lower part of the Cabot Head 

Formation. This interval was assigned by Fisher ( 1954) to 

the Fish Creek Shale, Manitoulin Dolomite, and Cabot 

Head Shale. Fisher ( 1966) states that this tripartite division 

is not traceable beyond the Niagara River Gorge and suggests use of Bolton's name Power Glen for the non-red 

argillaceous facies of the Medina Group. The name Power 

Glen is used on Rickard's (1975) correlation chart; the 

interval he identified as Power Glen has been divided herein 

into the Power Glen Shale, the Devils Hole Sandstone, and 

the basal beds of the Grimsby Formation (fig. 8). The formal revisions to the Power Glen Shale made herein have 

been informally introduced by Brett and others (1990a,b; 

1991). 

Type Section: DeCew Falls, Ont. (Fonthill, 30M/3c, 

Canadian National Topographic Survey (NTS)) (Bolton, 

1953). 

Reference Sections: Niagara River Gorge; railroad cut 

on Niagara Street, Lockport, N.Y.; cut in Niagara Escarpment at Ontario Hydro (DeCew Falls) generating station 

(Power Glen) just west of St. Catharines, Ont. 

Thickness: Where well exposed in outcrop, the thickness of the Power Glen Shale ranges from 20.0 to 27.5 ft. In 

the USGS cores, it ranges from 11.3 to 25.3 ft, with a mean 

thickness of 16.8 ft. 

Lithologic Description: In the Niagara region (fig. 11), 

the Power Glen Shale is a marine shale that is sparsely fossiliferous, dark-gray to green-gray with light-gray to bluegray, hummocky cross-stratified to bioturbated, quartzose 

sandstone interbeds. The sandstone interbeds are commonly 

prominent in the upper third of the formation. The Power 

Glen can also contain interbeds of dolomite, calcareous siltstone, and sandy limestone (Kilgour and Liberty, 1981). 

Contacts: As stated in the section on the WhirlpoolSandstone, the contact of the Power Glen Shale with the 
18 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

underlying Whirlpool Sandstone is typically gradational 

over 1-3ft of interbedded hummocky sandstone and shale. 

At some localities, however, a thin phosphatic horizon is 

present at the boundary between sandstone-dominated and 

shale-dominated intervals. The upper contact is placed at 

the relatively sharp contact between the gray shale of the 

Power Glen and the overlying white to pink Devils Hole 

Sandstone. This contact can be transitional, however, where 

the uppermost interval of the Power Glen locally contains 

abundant sandstone interbeds. 

Regional Correlations: Regional stratigraphic correlations and relations for the Power Glen Shale are shown in 

figures 9 and 10, respectively. East of Lockport, N.Y., the 

Power Glen thins rapidly and pinches out between Medina 

and Albion, in Orleans County. In a drill core from Middleport, in eastern Niagara County, the Power Glen interval 

consists of about 6 ft of maroon to gray shale with thin 

sandstone interbeds. West of DeCew Falls, Ont., the Power 

Glen grades laterally into the lower part of the Cabot Head 

Formation. 

Age: Bolton ( 1957) emphasized the similarities 

between the fauna of the Power Glen Shale and that of the 

Manitoulin Dolomite of the Bruce Peninsula region. This 

fauna, dominated by the bryozoan Helopora fragilis, is 

characteristic of the lower part of the Llandoverian Series 

(Rhuddanian). 

Summary of Revisions: The interval considered as 

Power Glen by Rickard (1975) has been divided herein into 

the Power Glen Shale, the Devils Hole Sandstone, and the 

basal beds of the Grimsby Formation. The lower contact of 

the Power Glen is not revised herein. The upper contact is 

herein revised to be with the Devils Hole Sandstone, a new 

unit proposed herein, rather than with the Grimsby Formation. In the Niagara area, the Devils Hole Sandstone and 

about 3-6 ft of overlying green shale that are herein 

assigned to the Grimsby were formerly included within the 

Power Glen. Where the lateral equivalents of the Devils 

Hole and the overlying shales are red, as at Lockport, they 

were formerly included in the Grimsby Formation. 

DEVILS HOLE SANDSTONE 

(new unit, proposed herein) 

Background: The Devils Hole Sandstone is formally 

proposed herein as a new formation. From Lockport eastward, this interval had previously been recognized as part of 

the Grimsby Sandstone (Brett and others, 1990b ). West of 

Lockport, where the Devils Hole is white, it had been 

included in the Power Glen Formation (Bolton, 1957). 

Rickard (1975) considered the Devils Hole interval as part 

of the Power Glen Shale (fig. 7). Brett and others (1990a,b; 

1991) referred to this unit as an unnamed sandstone and 

correlated it with the middle unit of the Cabot Head Shale in 

Ontario (Brett and others, 1990b ). Duke (1991) informally 

named this unit the Devil 's Hole Sandstone and correlated it 

with the Ball's Falls Formation, a thin interval of dolomitic 

shale and dolostone that is treated herein as a facies of the 

Devils Hole. 

Duke (1987a) and Duke and others (1991) demonstrated that the color range from pinkish to pale gray in 

sandstones of the Medina Group was probably the result of 

late diagenetic alteration. Where the sandstones are overlain 

by reddish, oxidized shale and sandstone, they are red or 

pink, but where they are overlain by gray marine shale, they 

are pale gray or white. Duke (1987a) noted that the sandstones are otherwise lithologically similar and that if the 

stratigraphy had been defined .without regard to color, these 

sandstones would most likely have been considered the 

same unit, as they are herein. 

This observation applies to the Devils Hole Sandstone 

as well as to the Power Glen Shale, the Thorold Sandstone, 

and the Grimsby Formation. The Devils Hole is clearly distinct from the Grimsby Formation although both are reddish 

in some areas. The Devils Hole is sharply separated from 

the Grimsby by a thin, condensed interval rich in phosphatic 

or hematitic clasts in nearly all sections (except the Niagara 

Falls-I core, in which the Devils Hole is absent). The Devils Hole could be included as a member of the Power Glen 

Shale, but in most outcrops, it is sharply set off from the 

Power Glen by a sharp to slightly erosional basal contact. In 

addition, the Devils Hole can be recognized in sections in 

western Niagara County and Orleans County where the typical gray shale facies of the Power Glen Shale is lacking. 

Type Section: Roadcut along the east side of Niagara 

River Gorge on the south haul road to the Robert Moses 

Powerplant, 0.4 mi north of Devils Hole State Park; town of 

Lewiston, Niagara County, N.Y. (Lewiston quadrangle). 

Reference Sections: North end of Niagara River Gorge 

at Artpark; outcrop at DeCew Falls hydroelectric plant in 

St. Catharines, Ont.; roadcut at W. Jackson Street beneath 

Somerset Railroad viaduct, city of Lockport, Niagara 

County, N.Y. 

Thickness: The Devils Hole Sandstone is 14.9 ft thick 

in the Grand Island-2 core; 13.5 ft thick in the Niagara 

Falls-1 core; 13.1 ft thick in the Niagara-I core, and is missing in the Wheatfield-! core. This absence is anomalous 

because the sandstone appears in all outcrops and is consistent in thickness (13-15 ft) in cores and outcrops. The Devils Hole was probably deposited in the Wheatfield-! area 

but could have been removed in a local erosional channel 

formed prior to deposition of the Artpark Phosphate Bed. 

Lithologic Description: At its type section, the Devils 

Hole Sandstone is a well-sorted, white to very pale pink, 

slightly dolomitic, medium- to fine-grained quartz arenite 

with some horizontal to hummocky cross lamination and 

minor interbeds of greenish-gray shale. It is similar in facies 

to the upper unit of the Whirlpool Sandstone (Brett and others, 1991). At the north end of Niagara River Gorge (fig. 11) 

and in outcrops near St. Catharines, Ont., the upper half of 

the formation consists of pale yellowish-gray, sandy 
REVISED STRATIGRAPHY AND CORRELATIONS 19 

dolostone or dolomitic sandstone with scattered small phosphatic nodules and fossil steinkerns; this facies, which was 

erroneously referred to as "Manitoulin Dolomite" by Fisher 

(1954), grades into the informally named Ball's Falls Formation of Duke (1991 ), which is at the top rather than the 

base of the Power Glen Shale. In eastern Niagara County 

(for example, in the Lockport area), the Devils Hole is represented by massive, mottled pink and pale gray sandstone 

with partings and rip-up clasts of red shale. It is barren to 

sparsely fossiliferous in most sections, although it can contain nautiloids and Planolites burrows. In the northern part 

of Niagara River Gorge, it contains abundant Helopora bryozoans and phosphatic steinkerns of small gastropods and 

bellerophontids. Shell fragments of lingulid brachiopods are 

present in outcrops in the Lockport, N.Y., area. 

Balls Falls facies: The Ball's Falls Formation that was · 

informally named in Duke (1991) is herein considered an 

informal facies, pending further detailed study. The Balls 

Falls facies consists of thin beds of dolomitic sandstone, 

fine-grained dolomite, and interbedded gray to red shale. 

Locally, the sandstone beds are hematitic and stand out as 

deep-red beds in otherwise greenish-gray Power Glen Shale 

and basal Grimsby (Cabot Head) Formation. The hematized 

beds are typically quite fossiliferous. The dominant faunal 

element is the branching bryozoan Helopora. 

Condensed eastern sandstone facies: The apparent 

eastern equivalents of the Devils Hole Sandstone in the 

Rochester area consist of laminated, porous, calcareous, 

oolitic, and arkosic sandstone. At the Genesee River Gorge, 

the condensed unit immediately overlies the Cherokee discontinuity and provides an excellent stratigraphic marker 

bed. Fossils are rare in this unit, although isolated crinoid 

ossicles have been observed in thin sections. 

Contacts: In the Niagara region, the Devils Hole Sandstone has a sharp contact with the underlying dark-gray 

shales of the Power Glen. In Orleans County, the pink, massive Devils Hole Sandstone directly overlies the Whirlpool 

Sandstone, and the cryptic contact is marked by a pyritic, 

calcareous interval in the quartz arenites. In the Rochester 

area, the basal contact of the equivalent of the Devils Hole 

coincides with the basal Silurian Cherokee discontinuity. 

The Devils Hole is locally shaly in its uppermost 1-2 ft. At 

the north end of Niagara River Gorge, it is thin and is overlain by the Artpark Phosphate Bed of the Grimsby Formation. To the south, in drill cores from Niagara Falls, the 

Devils Hole is overlain by or is amalgamated with a thin 

phosphatic or hematitic bed (Brett and others, 1991). 

Throughout the Orleans-Monroe County area, the upper 

contact is gradational with the basal argillaceous facies of 

the Grimsby Formation. 

Regional Correlations: Regional stratigraphic correlations and relations for the Devils Hole Sandstone are shown 

in figures 9 and 10, respectively. From St. Catharines westward to Hamilton, Ont., the typical dolomitic sandstones of 

the Devils Hole are thin and discontinuous, and phosphatic 

or hematitic sandy dolomites are persistent. Duke ( 1991) 

referred to this facies as the Ball's Falls Formation (informal usage). The typical Devils Hole sandstone and dolomitic facies interfinger in the northern Niagara River Gorge 

area. East of Niagara County, the Devils Hole appears to 

grade into massive, pink, mottled sandstones that have been 

quarried for building stones at Hulberton and Albion. 

Age: Early Llandoverian (Rhuddanian). 

Summary of Revisions or Changes: The Devils Hole 

Sandstone is proposed herein as a new formation. From 

Lockport eastward, this interval had previously been recognized as part of the Grimsby Sandstone (Brett and others, 

1990b ). West of Lockport, where the sandstone is white, it 

had been included in the Power Glen Formation (Bolton, 

1957). Rickard (1975) considered the Devils Hole interval 

as part of the Power Glen Shale. The basal contact is with 

the Power Glen Shale; the upper contact is with the Artpark 

Phosphate Bed of the Grimsby Formation. 

GRIMSBY FORMATION 

(revised herein) 

Brief History of Nomenclature: The name Grimsby 

Formation was first proposed by Williams (1914a,b). He 

stated that it consists of 6 ft of gray shale underlain by 

thickly bedded, mottled red and green sandstone that is 12ft 

thick at the type section but is 50 ft thick in the Niagara 

River Gorge. He defined it as overlain by the Thorold Sandstone and underlain by the Cabot Head Shale. Gillette 

(1940) and Fisher (1954) (fig. 7) used the name Grimsby to 

refer to the entire Lower Silurian sequence of red shales and 

sandstones below the Clinton Group. Fisher (1954) placed 

the Grimsby Formation at the top of the Medina Group and 

suggested that the Grimsby-Thorold contact should be considered the boundary between the Medina and Clinton 

Groups. Fisher's (1954) correlation chart shows the lower 

contact of the Grimsby to be with the Cabot Head Shale and 

its upper contact to be with the Thorold Sandstone in the 

Niagara River Gorg.e, but shows the Grimsby in Lockport as 

unconformably overlain by the Neahga Shale and underlain 

by the Fish Creek Shale. Liberty and Bolton (1956) use the 

term Grimsby Formation in Ontario to include the interval 

above the Power Glen or Cabot Head Shale and below the 

Thorold Sandstone. The Grimsby is also shown between the 

Power Glen and the Thorold on Rickard's (1975) correlation chart (figs. 7, 8). The Grimsby as defined herein 

includes all of the Grimsby as defined by Rickard (1975) 

and the upper part of the section that he recognized as the 

Power Glen (fig. 8). The formal revisions to the Grimsby 

made herein have been informally introduced by Brett and 

others (1990a,b; 1991). 

The authors prefer the use of Grimsby Formation to 

Grimsby Sandstone because this unit is heterolithic (fig. 

10). For example, at the type section, the Grimsby is a mixture of sandstone and shale. Shale facies are more promi-
20 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

nent in the Niagara River Gorge and in Ontario sections 

than in western NewYork. 

Type Section: Exposures along east side of gorge at 

Forty Mile Creek at Grimsby, Ont. (Grimsby, 30M/4h, 

Canadian NTS) (Williams, 1919). 

Reference Sections: Niagara River Gorge; Somerset 

Railroad cut at Lockport, N.Y.; gorge of Oak Orchard Creek 

at Medina, N.Y.; gorge of Sandy Creek at Albion, N.y.; 

Genesee River Gorge in Rochester, N.Y. 

Thickness: In the Niagara region, the thickness of the 

Grimsby Formation, as revised herein, ranges from 56 to 72 

ft in outcrop. In the USGS cores, however, it ranges from 

49.3 to 55.7 ft, with a mean thickness of 51.8 ft. The 

Grimsby is considerably thinner (29.5 ft) at the Genesee 

River Gorge and ranges from 53.5 to 57ft in the Hamilton, 

Ont., area. 

Lithologic Description: The Grimsby Formation consists of an interbedded sequence of red and green sandstones, siltstones, and shales (fig. 11 ). It comprises an 

overall shallowing upward sequence that represents progradation of shallow, marine tidal flat sands over marine muds 

(Martini, 1971; Duke and Fawcett, 1987). The Grimsby 

sequence tends to be most argillaceous at its base. Its contact with the underlying Devils Hole Sandstone is marked 

by the Artpark Phosphate Bed (discussed in next section). 

The matrix of the Artpark Phosphate Bed and the basal 5-

10 ft of the Grimsby typically consist of intensely burrowed 

greenish-gray to maroon shale. Fossils common in this 

basal argillaceous zone include pelecypods, cephalopods, 

ostracodes, bryozoans, linguloid brachiopods, and occasional rhynchonellid brachiopods. 

The remainder of the Grimsby succession consists of 

red and white mottled, fine- to medium-grained sandstone 

and conglomerate interbedded with shale; the ratio of sandstone to shale increases upward to the contact with the 

Thorold Sandstone. Shale interbeds are typically dusky 

maroon. Coarsening- and thickening-upward successions 

on the scale of 3-4 ft in the Grimsby at Niagara River Gorge 

have been mapped by Duke and Fawcett (1987). Such 

cycles can be capped by thin phosphatic lag deposits or can 

be partly or completely cut out by localized sandstone-filled 

channels. 

Sandstone beds, which are pinkish-red and commonly 

contain light-green reduction spots, are also characterized 

by Liesegang banding. Sandstone interbeds contain diverse 

primary sedimentary structures. Beds near the base of the 

Grimsby sequence are thinner than elsewhere and display 

hummocky cross stratification. Higher in the section, planar 

and low-angle trough cross stratification become increasingly common. Basal shale-clast conglomerates, interference and oscillation ripple marks, gutter casts, load casts, 

and ball and pillow structures are abundant in the upper 

sandstone beds. Locally, the upper beds of the Grimsby are 

also bioturbated. Common trace fossils include Arthrophycus, Daedalus, and Skolithos. 

Contacts: The sharp basal contact of the Grimsby Formation is with the Devils Hole Sandstone. As stated previously, the Artpark Phosphate Bed commonly overlies this 

contact. The lower contact of the Grimsby was previously 

drawn at a color change between greenish-gray shales 

assigned to the Power Glen and red shales assigned to the 

Grimsby. Duke (1987a) and Duke and others (1991) demonstrated, however, that this color-based contact (also 

applied to the Power Glen Shale, Devil 's Hole Sandstone, 

and Thorold Sandstone) is not an appropriate horizon at 

which to place the contact because it reflects secondary 

diagenetic reduction of strata rather than a true lithologic 

boundary between traceable units. In the Niagara region, 

the upper contact with the Thorold Sandstone is a sharp but 

conformable surface, and the basal bed of the Thorold 

Sandstone locally contains clasts of underlying Grimsby 

units. Farther to the west, near the Grimsby type section, the 

Thorold Sandstone and other overlying units are absent and 

the upper contact of the Grimsby is with the Merritton 

Limestone. 

Regional Correlations: Regional stratigraphic correlations and relations for the Grimsby Formation are shown in 

figures 9 and 10, respectively. As defined herein, the 

Grimsby Formation is a laterally extensive unit that can be 

traced at least from Rochester, N.Y., to Hamilton, Ont. In 

the Rochester area, it is considerably sandier than at the 

type section. West of the type section, the Grimsby becomes 

fine grained, particularly in its lower part. As the unit is 

traced westward, a green coloration becomes increasingly 

dominant. Green shale replaces red shale and sandstone 

from the base of the unit upward. 

Age: Although none of the taxa in the fossiliferous 

Grimsby are diagnostic biostratigraphic markers, Bolton 

(1957) emphasized the similarities with the early Llandoverian fauna of the Brassfield Limestone of the midcontinent. The Grimsby is herein considered to be early 

Llandoverian (latest Rhuddanian to earliest Aeronian). 

Summary of Revisions: The Grimsby Formation as 

defined herein includes all of the Grimsby and the upper 

part of the Power Glen as recognized by Rickard (1975). 

The basal contact of the Grimsby is herein revised to be the 

lower contact of the Artpark Phosphate Bed with the underlying Devils Hole Sandstone or, if the Devils Hole is missing, with the underlying Power Glen Shale. As such, 

greenish shales overlying the Artpark Phosphate Bed in 

some sections that were formerly assigned to the Power 

Glen are herein included within the Grimsby. The upper 

contact of the Grimsby is not revised herein. 

ARTPARK PHOSPHATE BED 

(new unit, proposed herein) 

Background: The Artpark Phosphate Bed is formally 

proposed herein as a new bed at the base of the Grimsby 

Formation. The term was first used informally by Brett and 
REVISED STRATIGRAPHY AND CORRELATIONS 21 

others (1990a,b; 1991) for the thin, phosphatic and (or) 

hematitic, sandy dolostone that overlies the Devils Hole 

Sandstone. 

Type Section: Small bluff at north end of Niagara River 

Gorge, 0.25 mi south of Artpark State Park, Lewiston, N.Y. 

(Lewiston quadrangle). 

Reference Sections: Somerset Railroad viaduct cut at 

West Jackson Street, Lockport, N.Y.; Balls Falls on Twenty 

Mile Creek at Jordan, Ont. 

Thickness: The Artpark Phosphate Bed is 4.9 ft thick at 

the type section, but its thickness ranges from 0.1 ft to 6 ft. 

Lithologic Description: At its type section (fig. 11 ), the 

Artpark Phosphate Bed is a phosphatic sandy dolomite. 

Observations of the four USGS Queenston cores indicate 

substantial facies variation within the Artpark Phosphate 

Bed. Phosphate pebbles in the USGS Niagara- I and Niagara Falls-1 cores are disseminated through several feet of a 

light gray to white, fine-grained, dolomitic sandstone or 

sandy dolomite overlying the Devils Hole Sandstone. In 

contrast, in the USGS Grand Island-2 and Wheatfield-! 

cores, the Artpark Phosphate Bed is a thin lag deposit of 

black pebbles in a gray or red shale matrix, completely 

devoid of sand. In spite of its local variations, the Artpark 

Phosphate Bed can be traced between the various cores and 

outcrops in the Niagara region. 

Contacts: Both the upper and lower contacts of the 

Artpark Phosphate Bed are sharp and well defined at most 

localities; near Artpark, however, the contact with the 

underlying Devils Hole Sandstone is more diffuse due to 

bioturbation and mixing processes. 

Regional Correlations: Regional stratigraphic correlations and relations for the Artpark Phosphate Bed are 

shown in figures 9 and 10, respectively. In the Niagara 

region, the Artpark Phosphate Bed lies slightly below the 

color change that was used by previous authors to define 

the Power Glen Shale-Grimsby Formation contact. This 

color change is diachronous; its position relative to the Artpark Phosphate Bed east of Niagara Falls differs from that 

to the west. 

To the east, near Medina, N.Y., the Power Glen Shale 

is missing as a result of truncation beneath the Devils Hole 

Sandstone. In Orleans County, the position of the Artpark 

Phosphate Bed is marked by the base of a shale intraclast 

zone in channel sandstones that have been mapped as 

Grimsby Formation. 

Westward from the Niagara region, the red coloration 

of facies of the Grimsby occurs at progressively higher 

stratigraphic intervals. The presence of the Artpark Phosphate Bed within the Cabot Head Formation of the Hamilton area illustrates that the Cabot Head Formation as 

defined by Bolton (1957) is correlative, in part, to both the 

Power Glen Shale and the lower part of the Grimsby Formation at Niagara. In the Jordan to Hamilton, Ont., area, the 

Artpark Phosphate Bed becomes hematitic and contains 

abundant trepostome bryozoa. 

Age: Although the Artpark Phosphate Bed is locally 

fossiliferous, none of its taxa have biostratigraphic significance. Like other units in the Medina Group, its fauna is 

similar to the early Llandoverian fauna of the Brassfield 

Limestone. The age of the Artpark Phosphate Bed, therefore, is probably late Rhuddanian to early Aeronian. 

Summary of Revisions or Changes: The laterally extensive Artpark Phosphate Bed is formally proposed herein as 

a new unit at the base of the Grimsby Formation. 

THOROLD SANDSTONE 

(group assignment changed herein) 

First Usage of Nomenclature: Originally called 

Thorold Quartzite by Grabau (1913), on the basis of an 

exposure on the Welland Canal at Thorold, Ont. Grabau 

(1913) stated that the Thorold Quartzite was underlain by 

the Medina red sandstones and overlain by the Sodus Shale, 

which he included in the Medina Group. The formation is a 

quartzite at the type locality (Williams, 1919), but in New 

York and in most places in Ontario, it is a sandstone 

(Gillette, 1947). 

Type Section: Exposure on the Welland Canal at 

Thorold, Ont. (St. Catharines, 30M/3g, Canadian NTS) 

(Grabau, 1913). 

Reference Sections: Jolly Cut, Hamilton, Ont.; Niagara 

River Gorge; railroad cut at Lockport, N.Y.; Genesee River 

Gorge in Rochester, N.Y. 

Thickness: The thickness of the Thorold Sandstone 

ranges from about 4.5 to 10 ft in outcrop. In the USGS 

cores, the thickness ranges from 6.9 to 9.5 ft. 

Lithologic Description: As defined herein, the Thorold 

Sandstone consists of two laterally correlative facies. To the 

east, between Rochester and Lockport, N.Y., it is a mottled 

pink to red, cross-bedded, channel sandstone with abundant 

Daedalus trace fossils. In the Niagara region (fig. 11) and 

westward, the Thorold is a light-gray to white, massive, 

argillaceous, pelletal sandstone that commonly exhibits 

soft-sediment deformation. It is typically interbedded with 

thin, green, silty shales. The shale content gradually 

increases toward the top of the unit. Although the Thorold is 

largely nonfossiliferous in the study area, a few fragments 

of linguloid brachiopods were reported from the Hamilton 

area by Bolton ( 1957). 

Contacts: The lower contact of the Thorold Sandstone 

with the Grimsby Formation is sharp but nearly conformable. This basal contact has been variably interpreted 

as either conformable (Duke, 1991) or unconformable 

(Gillette, 194 7), and these interpretations have served as a 

basis for previous inclusion of the Thorold within either the 

Medina or Clinton Group. As interpreted in this report, the 

Thorold Sandstone is related to the Medina Group in terms 

of its depositional history; evidence for this interpretation is 

presented below. 

Various stratigraphic units overlie the Thorold Sandstone as a result of the low-angle, regional unconformity 
22 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

immediately above it. Between Rochester and Niagara 

Falls, N.Y., the Thorold is sharply but conformably overlain 

by the Cambria Shale (see next section) of the Medina 

Group. Between Niagara Falls and Hamilton, Ont., the 

Thorold ty.e_ically is unconformably overlain by the phosphatic to calcareous Densmore Creek Phosphate Bed of the 

Neahga Shale (see discussion below) of the Clinton Group. 

At outcrops in the Hamilton area, the Thorold Sandstone 

has apparently been truncated beneath this erosional surface. Upper beds of greenish shale and sandstone previously 

assigned to the Thorold have been reassigned to the upper 

beds of the Grimsby (Duke, 1987a). The light coloration of 

these beds is due to secondary reduction (Duke, 1987a). 

Where the Thorold is overlain by the Neahga Shale, the 

sandstone typically is white; where overlain by the reddish 

Cambria Shale, the sandstone tends to be pink or red. 

Regional Correlations: Regional stratigraphic correlations and relations for the Thorold Sandstone are shown in 

figures 9 and 10, respectively. Lateral equivalency of the 

Thorold and Kodak Sandstones has been assumed since the 

work of Eaton (1824) and Hall (1843), although Kilgour 

( 1963) expressed some doubt as to their correlation. Recent 

mapping of the Densmore Creek Phosphate Bed and 

detailed correlation of intraformational Grimsby units by 

Fawcett and others (1988) indicates that the Kodak Sandstone of the Rochester area occupies a higher stratigraphic 

position than the Thorold Sandstone of the Niagara region, 

and that these units do not form a continuous sandstone 

sheet. The Thorold and Kodak Sandstones are separated by 

a fossiliferous, red, interbedded shale, siltstone, and thin 

bedded sandstone unit herein named the Cambria Shale. 

Age: On the basis of the presumed correlation with the 

Kodak Sandstone, Rickard (1975) placed the Thorold Sandstone in the lower Llandoverian (Aeronian B3). Revised 

correlations indicate that the Thorold Sandstone is slightly 

older but probably still Aeronian. 

Summary of Changes: The Thorold Sandstone as 

shown on Rickard's (1975) correlation chart has been 

herein divided into the Thorold Sandstone and a new unit 

(proposed herein), the Cambria Shale. The Thorold Sandstone is herein placed in the Medina Group rather than in 

the Clinton Group. 

CAMBRIA SHALE 

(new unit, proposed herein) 

Background: Rickard (1975) considered the strata 

herein assigned to the newly proposed Cambria Shale as the 

upper part of the Thorold Sandstone (figs. 7, 8). The interval that is assigned to the Cambria Shale was first referred 

to as an unnamed shale by Brett and others (1990a,b) and 

(informally) referred to as the Cambria Shale by Brett and 

others ( 1991 ). Because the strata are red, the Cambria Shale 

had previously been considered in places to be part of the 

Grimsby Sandstone by Fisher (1953a,b). Similarly, in areas 

where the Thorold Sandstone is pink, it was also considered 

part of the Grimsby. Correlation of the Thorold into the 

Rochester area demonstrates that the shales of the Cambria 

are separated from the true Grimsby by the intervening 

Daedalus-bearing Thorold Sandstone. 

The position of the Cambria Shale between the underlying Thorold Sandstone and the overlying Kodak Sandstone justifies designation of these red shales as a distinct 

formation. The Cambria could be designated as a member 

of either the overlying Kodak or the underlying Thorold but 

it is separated by relatively sharp contacts from both units. 

In addition, because the Cambria is missing at the type section of the Thorold in Ontario, it cannot be appropriately 

included as a member of the Thorold Sandstone. 

Type Section: Outcrop beneath and immediately north 

of the overpass of Lower Mountain Road over Lockport 

Junction Road (Routes 93 and 270) in the village of Hickory Comers, town of Cambria, Niagara County, N.Y. (Cambria quadrangle). The upper contact of the Cambria Shale is 

unconformable with the Neahga Shale at this outcrop. 

Reference Sections: Railroad overpass on Niagara St. 

in Lockport, N.Y.; Genesee River Gorge in Rochester, N.Y. 

Thickness: The thickness of the Cambria Shale ranges 

from a featheredge in the north end of the Niagara River 

Gorge to as much as 13.5 ft at the southernmost and easternmost parts of the Genesee River Gorge. It ranges in 

thickness from 5.1 to 8.9 ft in the Grand Island-2 and 

Wheatfield- I cores, respectively, the southernmost of the 

four USGS cores that penetrated the entire Medina section. 

The Cambria is not present in the other two USGS cores 

(Niagara-! and Niagara Falls-1 ). 

Lithologic Description: The Cambria Shale is a red to 

reddish-green, sparsely fossiliferous, interbedded sequence 

of shale, siltstone, and fine-grained sandstone. It is divisible 

into lower and upper shales separated by a middle sandstone interval. This internal stratigraphy is most apparent at 

the Genesee River Gorge in Rochester. The upper and lower 

shales contain abundant leperditiid ostracodes on bedding 

planes. The medial sandstone consists of a mottled red and 

green, bioturbated, argillaceous sandstone, with thin shale 

interbeds. Daedalus trace fossils dominate the fabric of the 

sandstone. Rusophycus also is found on the bottoms of 

sandstone beds in the Genesee River Gorge sections. 

This tripartite stratigraphy is less apparent at sections 

in Orleans and Niagara Counties than in the Genesee River 

Gorge. Thin siltstone and sandstone interbeds occur virtually throughout the interval. In western sections, caliche 

horizons and desiccation cracks are common, as are ostracodes and bivalves. 

Contacts: The Cambria Shale has a sharp contact with 

the underlying Thorold Sandstone. The stratigraphic position of its upper contact varies as a result of the low-angle, 

regional unconformity at the top of the Medina Group. 

Between Rochester and Lockport, N.Y., the Cambria 

Shale is sharply but conformably overlain by the Kodak 
REVISED STRATIGRAPHY AND CORRELATIONS 23 

Sandstone. West of Lockport, N.Y., the Kodak Sandstone is 

absent, and the Cambria is in sharp, unconformable contact 

with the overlying Densmore Creek Phosphate Bed 

(LoDuca and Brett, 1994) of the Neahga Shale (Clinton 

Group). The Cambria becomes dark green near its upper 

contact with the Neahga, apparently because of diagenetic 

reduction of iron. In Ontario, the Cambria Shale is erosionally truncated beneath the unconformity that marks the 

boundary between the Medina and Clinton Groups. 

Regional Correlations: Regional stratigraphic correlations and relations for the Cambria Shale are shown in figures 9 and 10, respectively. The Cambria Shale extends 

from Niagara Falls to at least as far east as Webster, in Monroe County, N.Y. It is fossiliferous throughout its extent and 

generally coarsens eastward. 

Age: The Cambria Shale is of early Llandoverian age, 

on the basis of the Aeronian (B3) age of the overlying 

Kodak Sandstone. 

Summary of Revisions or Changes: The Cambria Shale 

is a new formation, proposed herein. Rickard (1975) considered strata assigned herein to the Cambria Shale as the 

upper part of the Thorold Sandstone in western sections and 

as part of the Grimsby Sandstone at Rochester. Fisher 

(1953b) considered the strata assigned herein to the Cambria Shale in places to be part of the Grimsby Formation. 

The Cambria Shale displays a sharp basal contact with the 

Thorold Sandstone. The stratigraphic position of the upper 

contact of the Cambria varies as a result of the low-angle, 

regional unconformity at the top of the Medina Group. 

KODAK SANDSTONE 

(group assignment changed herein) 

First Usage of Nomenclature: First used by Chadwick 

(1935) as Kodak Sandstone to replace what was formerly 

called Thorold Sandstone, but was determined by Chadwick 

to be younger than the true Thorold of Niagara River Gorge, 

and equivalent to units of the Clinton Group in age. 

Type Section: In lower Genesee River Gorge from the 

lower falls to Kodak Park, Seth Green Drive (Rochester 

West quadrangle) (Chadwick, 1935). 

Reference Section: Oak Orchard Creek, Village of 

Medina, Orleans County, N.Y. 

Thickness: The reported thickness of the Kodak Sandstone varies widely because its lower contact with the Cambria Shale is locally difficult to establish based on criteria 

other than color. At Rochester, the Kodak is 5 ft thick; at 

Albion, it is as much as 11 ft thick in cores; and at Lockport, 

it is only a few inches thick. 

Lithologic Description: The Kodak Sandstone is a 

medium-gray to white, argillaceous, quartzose sandstone. In 

places, it contains abundant Daedalus trace fossils. Where 

primary bedding structures are preserved, a rhythmic alternation of sandy and shaly interbeds is apparent. 

Contacts: As stated above, the basal contact of the 

Kodak Sandstone with the underlying Cambria Shale has 

locally been masked by intense bioturbation. Both units 

contain abundant trace-fossil assemblages. In areas where 

bioturbation has not obliterated primary sedimentary fabric, 

however, the contact typically appears to be sharp because 

of diagenetic color change. In cores, structures resembling 

iron stromatolites are common and suggest a minor disconformity at the base of the Kodak. A major unconformity is 

present at the contact of the Kodak Sandstone with the overlying Densmore Creek Phosphate Bed of the Neahga Shale. 

Regional Correlations: Regional stratigraphic correlations and relations for the Kodak Sandstone are shown in 

figures 9 and 10, respectively. The Kodak Sandstone is preserved between Webster and L0ckport, N.Y. Between the 

cities .of Niagara Falls and Hamilton, Ont., no stratigraphic 

equivalents to the Kodak Sandstone are known; instead, 

the time interval spanning deposition of the Cambria and 

Kodak is represented by the unconformity between the 

Thorold Sandstone and the Neahga Shale. 

The phosphate-pebble horizon at the base of the 

Neahga-Maplewood Shale sequence has been designated 

the Densmore Creek Phosphate Bed (LoDuca and Brett, 

1994 ). In the Rochester area, the Densmore Creek Phosphate Bed is at the boundary between the Kodak Sandstone 

and the Maplewood Shale. As the phosphate bed is traced 

toward the Niagara region, however, the uppermost part of 

the Medina Group units becomes progressively beveled. 

The Kodak Sandstone underlies the Densmore Creek Phosphate Bed as far west as Lockport, but just west of Lockport, the Densmore Creek Phosphate Bed separates the 

Cambria Shale from the Neahga Shale, and no Kodak Sandstone is present. In the Niagara River Gorge, the Densmore 

Creek Phosphate Bed is at the contact between the Thorold 

Sandstone and the Neahga Shale, and both the Cambria 

Shale and the Kodak Sandstone are missing. 

As discussed previously, phosphate-pebble beds can be 

useful in locating stratigraphic breaks. In the preceding discussion, the Medina-Clinton Group contact is placed at the 

low-angle, regional unconformity overlain by the Densmore 

Creek Phosphate Bed. The Maplewood and Neahga Shales 

mark a basal Clinton transgression over an eroded surface at 

the top of the Medina Group. The presence of the Densmore 

Creek Phosphate Bed above the Kodak Sandstone at Rochester conclusively places the Kodak within the Medina 

Group. Gillette (1947) reported poorly preserved specimens 

of Zygobolba prolixa and Zygobolba curta in the Thorold in 

Oswego County, in beds that would now be considered 

Kodak (J.M. Berdan, U.S. Geological Survey, written commun., 1992). This is important because it could provide a 

younger age for the top of the Medina Group than previously suspected. 

Age: On the basis of ostracodes, the Kodak Sandstone 

is of early Llandoverian age (probably Aeronian [B3]) 

(Gillette, 1947; Berry and Boucot, 1970). 
24 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Summary of Changes: The Kodak is herein separated 

from the Thorold by the Cambria Shale, in contrast to Rickard's correlation chart (1975), where the Thorold and 

Kodak are shown as coextensive units. In addition, the 

Kodak Sandstone is herein placed in the Medina Group 

rather than in the Clinton Group. 

CLINTON GROUP 

(revised herein) 

In the Niagara region, the Clinton Group consists of 

about 100-110 ft of thin- to medium-bedded shale, limestone, and dolomite. It includes the Rochester Shale, one of 

the oldest formally designated stratigraphic units in North 

America (Hall, 1839). The type area of the Clinton Group is 

near the town of Clinton in central New York. The name 

Clinton Group was first proposed by Vanuxem ( 1839) and 

was established by Vanuxem (1842) as the Clinton Group of 

the Ontario Division of the New York System. Vanuxem's 

Clinton Group included what is now called the Thorold 

Sandstone up to the base of the Rochester Shale. James Hall 

(1843) accepted Vanuxem's Clinton Group and described 

the lithology and paleontology of this interval (Hall, 1852). 

Since that time, many workers, including Hartnagel (1907), 

Newland and Hartnagel (1908), Kindle and Taylor (1913), 

Schuchert (1914), Chadwick (1918), Grabau (1921), Ulrich 

and Bassler (1923), Sanford (1933, 1935, 1936), Gillette 

(1947), Fisher (1953b, 1960), Bolton (1957), Kilgour 

(1963, 1966), Zenger (1971), Lin and Brett (1988), LoDuca 

(1988), Brett and others (1990a,b; 1991), and LoDuca and 

Brett (1994) have revised and refined the internal stratigraphy. Gillette (1947), Bolton (1957), and Kilgour (1963) provide detailed reviews of Clinton nomenclature. A historical 

summary of nomenclature for the Clinton Group of the Niagara region is presented in figure 13. 

As defined herein, the base of the Clinton Group is 

placed at the base of the Neahga Shale, at an unconformity 

marked by the Densmore Creek Phosphate Bed (LoDuca 

and Brett, 1994 ). Traditionally, the lower contact of the 

Clinton Group had been placed at the base of the Thorold 

Sandstone (fig. 13). The Thorold Sandstone, however, and 

units that overlie it locally, including the Cambria Shale and 

Kodak Sandstone (described previously), lie beneath a 

regional angular unconformity overlain by the Densmore 

Creek Phosphate Bed at the base of the N eahga Shale. The 

Medina units are progressively truncated westward. The 

unconformity at the base of the Neahga provides a conclusive physical basis for definition of the Medina-Clinton 

Group contact. The interval below the Neahga Shale is 

therefore removed from the Clinton Group and assigned to 

the underlying Medina Group. A complete discussion is 

given in LoDuca and Brett (1994 ). The upper contact of the 

Clinton Group is placed at the sharp, erosional, regionally 

unconformable contact between the DeCew Dolomite and 

the overlying Gasport Dolomite of the Lockport Group. In 

the past, the DeCew has been included either as the uppermost unit of the Clinton Group (Bolton, 1957) or as the lowermost unit of the Lockport Group (Gillette, 1947; Zenger, 

1965). Because the DeCew appears nearly conformable and 

gradational with the upper part of the Rochester Shale at 

most localities and is truncated by an unconformity at the 

base of the Gasport in western New York and Ontario, it is 

herein placed in the Clinton Group (fig. 13). 

Within the Niagara region, the Clinton Group includes 

the following eight formations, in ascending order: the 

Neahga Shale; the Reynales Limestone (Hickory Comers 

Member); the Merritton Limestone; the Williamson Shale; 

the Rockway Dolomite; the Irondequoit Limestone; the 

Rochester Shale, including the Lewiston and Burleigh Hill 

Members; and the DeCew Dolomite. The Merritton Limestone, the Second Creek Phosphate Bed, the Williamson 

Shale, and the Salmon Creek Phosphate Bed are herein 

extended into the Niagara Falls area for the first time (fig. 

4 ). Stratigraphic contacts of the Irondequoit Limestone have 

been revised (fig. 4). The Rockway Dolomite is raised 

herein to formation rank (fig. 4). A comparison of stratigraphic nomenclature from Rickard (1975) with revised 

nomenclature for the Clinton Group is shown in figure 14. 

Although Gillette (1947) designated Lower, Middle, 

and Upper portions of the Clinton Group on the basis of discontinuities in ostracode biostratigraphy, his subdivisions 

will not be used herein; however, informal reference will be 

made to the lower, middle, and upper parts of the Clinton. 

In the Niagara region, the lower part of the Clinton Group 

includes the Neahga Shale and the Reynales Limestone 

(Hickory Comers Member) (fig. 9). The upper part of the 

Clinton Group within this region includes the Merritton 

Limestone, Williamson Shale, Rockway Dolomite, Irondequoit Limestone, Rochester Shale, and the DeCew Dolomite (figs. 9, 15). A major regional angular unconformity at 

the base of the Merritton Limestone in Ontario and the Williamson Shale in New York (fig. 9) separates the lower and 

upper parts of the Clinton Group. In the Niagara region, the 

unconformity separating the lower and upper parts of the 

Clinton has truncated the entire middle part as well as the 

upper beds of the lower part of the Clinton. Strata in the 

lower part of the Clinton Group are quite thin as a result of 

erosional truncation, which continues westward into 

Ontario to the extent that no strata from this interval are preserved between St. Catharines and Hamilton, Ont. 

In west-central New York, additional units are present 

between the Reynales Limestone and the overlying equivalent of the Williamson, the Willowvale Shale (fig. 9). These 

units, which iaclude the lower and upper parts of the Sodus 

Shale and the Wolcott Limestone, are progressively truncated westward beneath a major unconformity at the base of 

the Williamson Shale. In the Niagara region, this unconformity is marked in cores and field exposures by a phosphatepebble horizon named the Second Creek Phosphate Bed 
REVISED STRATIGRAPHY AND CORRELATIONS 

AUTHOR OR SOURCE 

GRABAU (1921) GILLETTE (1947) KILGOUR (1963) 

---

0.. 

::J 

0 

a: 

(!) 

z 

0 

1-

z 

::::i 

() 

ROCHESTER 

SHALE 

IRONDEQUOIT 

LIMESTONE 

0.. 

r----------~::J 

0 

a: 

(!) 

SODUS 

SHALE 

THOROLD SS. 

z 

0 

1-

z 

::::i 

() 

ROCHESTER 

SHALE 

IRONDEQUOIT 

LIMESTONE 

0.. 1----------f ::J 

REYNALES 

LIMESTONE 

NEAHGA 

SHALE 

THOROLD SS. 

0 

a: 

(!) 

z 

0 

1-

z 

::::i 

() 

ROCHESTER 

SHALE 

1-

-w Oz 

::Jo 

01-

w(/) 

ow 

Z::2: 0- a:......l 

UNNAMED 

MEMBER 

ROCKWAY 

DOLOMITE 

MEMBER 

0.. 

1---+------......f::J 0 

a: 

(!) 

(J)W 

wz 

......10 

<(1-

Z(f) >-W 

W::2: 

a:-......1 

HICKORY 

CORNERS 

LIMESTONE 

MEMBER 

NEAHGA 

SHALE 

THOROLD SS. 

z 

0 

1-

z 

::::i 

() 

EXPLANATION 

~ = Unit not recognized by author 

in equivalent stratigraphic position 

SS. = Sandstone 

LS. = Limestone 

SH. = Shale 

Figure 13. Historical summary of Clinton Group nomenclature in the Niagara region. 

THIS REPORT 

a: 

w 

1-w 

(/).....J 

W<( 

:c:c 

()(/') 

0 

a: 

DECEW 

DOLOMITE 

BURLEIGH 

HILL 

MEMBER 

LEWISTON 

MEMBER 

IRONDEQUOIT 

LIMESTONE 

SALMON 

CREEK 

PHOSPHATE 

BED 

\ 

WILLIAMSON SH. 

SECOND CREEK 

PHOSPHATE BED\ 

MERRITTON LS. 

(J)W 

wz 

......10 

<(1-

Z(f) >-W 

W::2: 

O:::J 

<Cw 

(!).....I 

:C<( <C:c 

~(/') 

HICKORY 

CORNERS 

MEMBER 

BUDD ROAD 

PHOSPHATE 

BED\ 

DENSMORE 

CREEK 

PHOSPHATE 

BED\ 

25 

(Lin and Brett, 1988). In the Clinton type area near Utica, 

N.Y., lower units of the Clinton are either absent as a result 

of depositional pinchout (Reynales and lower part of the 

Sodus) or have changed facies (upper part of the Sodus and 

Wolcott) into a thin conglomerate and sandstone unit known 

as the Oneida Conglomerate (fig. 9). In addition, a green 
26 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

c.. 

~ 

0 

a: 

(.9 

z 

~ z 

::J 

(.) 

NOMENCLATURE FROM 

RICKARD (1975) 

DECEW DOLOMITE --

ROCHESTER SHALE --

9 

REVISED NOMENCLATURE 

DECEW DOLOMITE 

BURLEIGH HILL MEMBER 

\ 

ROCHESTER SHALE 

/ 

LEWISTON MEMBER 

~~qr:f1~5:h=0~:::Q --- IRONDEQUOIT LIMESTONE 

IRONDEQUOIT LIMESTONE 

ROCKWAY DOLOMITE 

MEMBER 8 ROCKWAY DOLOMITE 

----- WILLIAMSON SHALE (0.6 feet) (UNIT NOT RECOGNIZED 

IN WESTERN N.Y.) -------'=- l:r:Q=s=~~~:Ea 

REYNALES LIMESTONE -- t::"Q~~5i:d~~~~~~ 

- MERRITTON LIMESTONE (0.5 feet) 

REYNALES LIMESTONE 

NOT RECOGNIZED OR 

WAS PREVIOUSLY 

TERMED GRIMSBY 

THOROLD SANDSTONE 

~~~~_S_t~~~~ 

EXPLANATION 

NEAHGA SHALE 

-- KODAK SANDSTONE 

-- CAMBRIA SHALE a 

-- THOROLD SANDSTONE a 

[1:gJ Average unit thickness, in feet, based on data from nine 

U.S. Geological Survey cores, two Canadian cores, and 

several outcrops 

[] Sandstone ~ Dolomite 

~ Shale ~ Limestone 

a Because of their red color and apparent miscorrelation, strata in the 

eastern part of Niagara County that are shown as Thorold Sandstone 

and Cambria Shale in the revised nomenclature column (right side of 

diagram) were considered by Fisher (1953b) to belong to the Grimsby 

Formation 

c.. 

~ 

0 

a: 

(.9 

z 

0 

fz 

::J 

() 

c.. 

~ 

0 

a: 

(.9 

<( 

z 

0 

L.U 

~ 

Figure 14. Stratigraphic nomenclature from Rickard (1975) and revised nomenclature for the 

Clinton Group in the Niagara region. Formation contacts and lithologic shading of units are based on 

the revised nomenclature. 
REVISED STRATIGRAPHY AND CORRELATIONS 27 

ww 01-w cz zzz oo ooo CJN CJCN 

BRUCE 

PENINSULA, 

ONTARIO 

SOUTHERN ONTARIO 

AND WESTERN 

NEW YORK 

WEST-CENTRAL 

NEW YORK 

CENTRAL 

NEW YORK 

ci 

::::> 

...J GUELPH 

DOLOMITE 

GUELPH 

DOLOMITE 

r-r----- GUE"~L-:::PH:-.----1 VERNON 

EXPLANATION 

D UNCONFORMITY 

DOL. = DOLOMITE 

SH. :SHALE 

DOLOMITE SHALE 1--.--------lll. 1--------lll. 1---=::...::.=:..:.:.;:.;;..;.;::...._-+---t---

z 1- ?-

<( -? 

> 0 

...J 

c 

;::) 

...J 

Eramosa ::1 ERAMOSA ::1 ERAMOSA 

Dolomite 0 DOLOMITE 0 DOLOMITE a.. LS. = LIMESTONE 

SS. = SANDSTONE z 

< 

t;; ~ ~ ~ ::1 :S (!) c (!) 1--------t 0 

w 1-

~ 

0 

..J 

0 

c 

a: 

0 

0 

~ ~z ~ ~ 

~ l)l ~ ~ I!! Vinemount ~ (!) w ..J 

<( 

::t: 

(/) 

LUD. = Ludfordian 

TEL. = Telychian 

~ ~ ll. ll. !!l:s ~ ~ 0 u ::1 Z Wiarton 5 ~ ~ Ancaster 5 PENFIELD ~ <( 

0 

c 

z 

0 

z 

0 

(.) 

(/) 

M. typus = Mastigobolbina typus 

P. amorph = Pterospathodus 

~ t--- ~ Q Dolomite 0 o c Niagara Falls O FORMATION ll. 

.s: ~ (!) ~ -.~ !i:~ I -.~ ~ 

z 

0 

;;;! 

amorphognathoides 

K. patula = Kockelella patula 

~ :§ w ::i 0 :E / Pekin U 

IU ~!!! -1 ~ g;g g P. siluricus = Polygnathoides siluricus 

S. ranuliformis = Spathodus ranuliformis 

z 

<( 

:;2 

(.) ~ 

g c 

z ~ w z 3: iij 

J: 

Ill 

.5; .._- ~ 1L < 0 Gothic Hill 

~ ~-~ ~ iil oc 

~ O (I) W ~ I DECEW DDL 

~ - a:l ::i 'w": .-/ 

~ ~ ch·c: E ~ <l_<C~Il.~/_ ::t: Burleigh Hill a.. ::1~ ::1 

~ .!!1 0 w 1:-v.----,.----10 :a E ffi ~ ffi ll ""-·~ Colpoy Bay ~ Dolomite Z u Lewiston Z :i ~ 0 0 ~ r----- !z~~ !z 

!ri ::i IRONDEQUOIT LS. -1 t- ?'.....L...?-t--.t:-='"" -i u u ~ e- Lions Head Dol. ROCKWAY DOL. 

TEL. ::! ~ ~ ~ !!WILLIAMSON SH.t"- Fossil Hill Dol. 

DECEW DOL. 

w 

~ r:::;:_ates CJi ::t: ll. (/) 

~ Burleig_h Hill S a: 

~ ffi ~ ~ Lewiston Z a: (.) 0 w 0 ~ ::t: 

DECEW DOL. 

i: 

.5 

iii 

0 

~ 

_!!!a; 

::c: 

> 0 c:- as"' -o"'O 

.... c: oas 

~(/) 

a: z 1--.L..----L...---1 IRONDEQUOIT LS. ~ KIRKLAND LIMESTONE 

ROCKWAY DOL. 

WILLIAMSON SHALE 

DAWES FORMATION 

WILLOWVALE SHALE 

Figure 15. Stratigraphic correlations for the upper part of the Clinton Group and the Lockport Group in parts of Ontario and New York. 

Formation names are shown in uppercase and member names are shown in upper- and lowercase. (Modified from Brett and others, 1991, 

fig. 9.) 

shale and sandstone unit up to 100 ft thick, the Sauquoit 

Formation7, is present between the Oneida and the overlying Willowvale Shale8 of the upper part of the Clinton (lateral equivalent of the Williamson Shale [Eckert and Brett, 

1989]) (fig. 9). The Sauquoit is absent in western New York 

as a result of erosional beveling. 

Correlation charts for the lower and upper parts of the 

Clinton Group are shown in figures 9 and 15, respectively. 

Geologic sections showing stratigraphic relations with 

regional correlations for the lower part of the Clinton Group 

in western New York are shown in figure 16 and for the 

upper part of the Clinton Group in figure 17. Descriptive 

stratigraphic columns for the lower part of the Clinton 

Group are presented in figure 18 and for the upper part of 

the Clinton Group in figure 19. Natural-gamma logs and 

stratigraphic correlations for units within the Clinton Group 

are presented in figures 12 and 20. 

Summary of Revisions: The Densmore Creek Phosphate Bed of the Neahga Shale is designated herein as the 

basal unit of the Clinton Group. The contact between the 

DeCew Dolomite and the Gothic Hill Member of the 

Gasport Dolomite is designated herein as the upper contact 

of the Clinton Group. The Merritton Limestone, the Williamson Shale and its Second Creek Phosphate.Bed, and the 

7Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 8Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

Salmon Creek Phosphate Bed of the Rockway Dolomite 

have been extended into the Niagara Falls area from areas 

where they were previously recognized. Stratigraphic contacts for the Irondequoit Limestone have been revised. The 

Rockway Dolomite is raised herein to formation rank. 

NEAHGASHALE 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: Sanford (1933) proposed the name Neahga Shale for the green shale of the 

lower part of the Clinton Group in the Niagara River Gorge 

(Neahga is the Native American name for the Niagara 

River). In 1935, he referred to the same interval as the 

Neahga Formation, and stated that it is underlain by the 

Thorold Sandstone and overlain by the Reynales Limestone. Sanford (1935) correlated the Neahga with the 

Maplewood Shale, stating that they occupy the same stratigraphic position and are of about the same age. 

Type Locality: Niagara River Gorge section south of 

Artpark, Lewiston, N.Y. (Lewiston quadrangle) (Sanford, 

1935, p. 170-174). 

Reference Sections: Along railroad track north of the 

junction of the tracks and Niagara Road immediately west 

of Lockport, N.Y.; roadcut along Budd Road 1.3 mi west of 

Hickory Corners, N.Y.; cliff in the east wall of Niagara 

River Gorge about 0.3 mi north of Robert Moses Powerplant and 1.4 mi south of Artpark, in Lewiston, N.Y.; railroad cut along Weiland Canal, St. Catharines, Ont. 
28 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

2 

Lockport 

railroad cut 

EXPLANATION 

3 

Albion 

drill 

core 

Q) 

c 

0 

(j) 

Q) 

!\ 

Cll 

a: 

4 

Rochester 

Gorge 

A' 

5 

Webster 

drill 

core 

g UMESTONE 

• SHALE 

PENTAMERID 

BRACHIOPODS 

SOFT -SEDIMENT 

DEFORMATION 

NODULAR BEDDING 

CHERT 

HEMATITE 

PHOSPHATIC 

PEBBLES 

B R = Budd Road Phosphate Bed 

DC = Densmore Creek Phosphate Bed 

S = Seneca Park Bed 

MULTI-GENERATIONAL 

PHOSPHATIC 10 20 MILES 

PEBBLES 

10 20 KILOMETERS 

WB = Webster Bed 

Figure 16. Generalized stratigraphic relations in the lower part of the Clinton Group in western New York. Top of columns represents 

top of bedrock in all sections except at Rochester Gorge. Datum is the base of the Reynales Limestone. (Modified from LoDuca and Brett, 

1994, figs. 1, 10.) 

Thickness: In the Niagara region, the Neahga Shale 

ranges in thickness from 2 to 6 ft. It is 6 ft thick at the type 

section, less than 2 ft thick at Lockport, N.Y., and 2.5 ft 

thick at St. Catharines, Ont. 

Lithologic Description: The Neahga Shale is green to 

gray, slightly silty, slightly calcareous, soft, and highly fissile (fig. 18). The basal bed of the Neahga is the Densmore 

Creek Phosphate Bed, which overlies the regional unconformity between the Medina and Clinton Groups. In the 

Niagara region, this bed consists of phosphate nodules, pebbles, and cobbles incorporated into a dolomitic sandstone 

matrix. Macrofossils within the Neahga are scarce and consist primarily of linguloid brachiopods. A complete faunal 

list is given in Fisher (1953a,b). Acritarch assemblages in 

the Neahga Shale have been studied by Fisher (1953a) and 

Cramer and Diez de Cramer (1970) and by Gray and 

Boucot (1971, 1972). 

Contacts: The basal bed of the Neahga Shale is the 

Densmore Creek Phosphate Bed, which overlies the 

regional unconformity between the Medina and Clinton 

Groups. This unconformity truncates successively older 

units westward. The upper contact is sharp and unconformably overlain by the Budd Road Phosphate Bed of the Hickory Comers Member of the Reynales Limestone. 

Regional Correlations: The Neahga has been traced 

westward to St. Catharines, Ont., and eastward to the Rochester, N.Y., area, where it is referred to as the Maplewood 

Shale (figs. 9, 16). Beyond Rochester, the unit pinches out 

rapidly and is absent east of Webster, N.Y. (LoDuca and 

Brett, 1994). 

Age: Gillette (1947) reported Zygobolba excavata it 

the Neahga Shale. According to LoDuca and Brett (1994), 

the age of the Neahga is late Aeronian (Llandoverian B2 to 

C1). 
REVISED STRATIGRAPHY AND CORRELATIONS 29 

WEST !IJ 

"" EAST Q) 

E 

0 Q) u El !IJ 0 -c " "" ~ ~ ~ ·a «l c c. .! Ol «l .!9 ~ 0 z < ~ 1 2 3 4 

MERRI~ONc:-~~~~~~~~~~~~~~~~~~~~~~~ 

LIMESTONE 

NOT TO SCALE --------

ROCHESTER SHALE 

80° 79° 78° 

EXPlANATION 

CONTORTED DOLOMITE 

~~~ SILTY SHALE ~ UMESTONE WITH BIOHERMS 

~ THIN BEDDED CALCISILTITES E2'153 DOLOMITE 

~AND CALCARENITES ~ 

LOCATION MAP 

Figure 17. Diagrammatic stratigraphic relations in the upper part of the Clinton Group, with regional correlations between Clappison's 

Comers, Ont., and Rochester, N.Y. Reference datum is the contact between the Lewiston and Burleigh Hill Members of the Rochester 

Shale. 

Summary of Revisions or Changes: Not revised or 

otherwise changed herein. 

DENSMORE CREEK PHOSPHATE BED 

(not revised or otherwise changed herein other than 

minor modification of unit name) 

First Usage of Nomenclature: The Densmore Creek 

Phosphate Bed of the Neahga Shale is first mentioned informally in Brett and others (1990a,b; 1991) where it is 

described as a thin, multigenerational phosphatic lag 

deposit that overlies a minor erosional surface that separates 

the Medina from the Clinton Group. The unit is formally 

named the Densmore Creek Bed in LoDuca and Brett 

( 1994) but is herein termed the Densmore Creek Phosphate 

Bed. 

Type Section: Exposure on Densmore Creek about 0.1 

mi east of Densmore Road bridge in the town of Irondequoit, Monroe County, N.Y. (Rochester East quadrangle) 

(LoDuca and Brett, 1994). 

Reference Sections: Genesee River Gorge section in 

Rochester, N.Y.; railroad cut north of the intersection of 

Niagara Road and railroad tracks west of Lockport, N.Y.; 

roadcut along Budd Road, 1.3 mi west of Hickory Corners, 

N.Y.; Niagara River Gorge section south of Artpark, 

Lewiston, N.Y.; Merritton railroad cut at Thorold, Ont. 

Thickness: The Densmore Creek Phosphate Bed ranges 

in thickness from less than 1 in. to over 6 in. In the Niagara 

region, it is typically 2-4 in. thick. 

Lithologic Description: The Densmore Creek Phosphate Bed is composed of phosphate pebbles and cobbles, 

some more than 4 in. in diameter, in a dolomitic shale 

matrix (fig. 188). In exposures near Hickory Corners and 

Lockport, the upper part of the bed is crowded with Hyattidina congesta brachiopods. Bryozoans and phosphatecoated gastropods are also locally abundant (Fisher, 1953b; 

LoDuca and Brett, 1994). A detailed discussion of the 

Densmore Creek Bed is provided by LoDuca and Brett 

( 1994 ), who describe this unit as a phosphatic, calcareous 

sandstone that is ubiquitous at the base of the Neahga Shale. 

Contacts: The Densmore Creek Phosphate Bed 

directly overlies and marks a regional unconformity that 

truncates successively older units to the west and is designated herein as the lowest unit of the Clinton Group. 
a_ 

~ 

0 

a: 

C) 

z 

0 

1-

z 

:::::::i 

() 

a_ 

~ 

0 

a: 

C) 

<( 

z 

0 

w 

:::a: 

A 

NEAHGA 

SHALE 

- Thick-bedded gray dolomite 

..L.-,~---'--r-~ - Argillaceous beds with abundant 

Costistricklandia brachiopods 

Medium-bedded, buff-weathering, 

gray dolomite 

Greenish-gray clay shale; phosphatic 

limestone nodules at base -

UNNAMED I: : : : : : j Sandy limestone or calcareous 

LIMESTONE I I I I 1- sandstone, pinkish gray, with 

abundant fossils, irregular bedding 

20 feet 

w 

z OQ 

-lfQ(J) 

ceo 

oz 

I<( 

I- (f) 

} S'/',{/{j,\m _ ~~~ ~~~~;;:eathering, white 

t--• •_ ~ ~ --; ~- Green, sandy shale 

-·-·-· 

a_ 

:::::> 

0 

a: 

CJ 

z 

0 

1-

z 

::J 

() 

a.. 

:::::> 

0 

a: 

CJ 

<( 

z 

0 

w 

~ 

>-W 

<(I-

$~ 

~0 ()_j 

00 

a::o 

1 , £ 0 ~, 1 -Whitish-buff dolomicrite 

_Transitional argillaceous dolomite; phosphatic pebbles at 

base (Salmon Creek Phosphate Bed) 

WILLIAMSON SHALE le i" a{- Gray-green shale with phosphatic pebbles at base 

Cl)w 

wZ 

_Jo 

<(1- z(/) 

>-w 

w~ 

a::::J 

\'--.._ D I .. o om1cnte bed (sharp contact) 

>-CJ)a: 

a:a:w 

o~m ::::S::::a:~ 

oow 

:Co~ 

NEAHGA SHALE -KODAKSANDSTONE~l~.---~ .... ~ .. F ...... ~,~--~ 

B 

w 

_J 

<( 

I 

(/) 

<( 

ii 

aJ 

~ 

<( 

() 

THOROLD 

SANDSTONE 

(EQUIVALENT) 

- Thin- to medium-bedded crinoidal biosparite 

~-I 1 1- I·,- Shaly, cherty limestone 

_ Phosphatic limestone (Budd - 1 - I - 1 - ,' Road Phosphate Bed) 

<( 

ii:w 

C!l_j 

::::2;<( 

<(I 

0(/) 

- Gray-green shale 

, .. ~."!"-:-""! 1- Phosphatic shale (Densmore 

Creek Phosphate Bed) 

Is feet 

Figure 18. Descriptive stratigraphic column for the upper part of the Medina Group and the lower and basal upper parts of the Clinton Group at (A) the railroad cut section in Merritton, Ont., 

and (B) the Somerset Railroad cut in Lockport, N.Y. (Modified from Brett and others, 1991, fig. 11.) 

(j.) 

0 

~ ;:S 

en 

t'I1 

0 

en 

~ 

~ ~ ....:: 

~ n 

t'I1 

~ 

~ ::j 

en 

~ 

0 

'Tj 

~ z 

> 0 

~ ~ 0 

;:S 

z 

n 

> t""' 

en 

~ 

til 

en 
REVISED STRATIGRAPHY AND CORRELATIONS 31 

a: 

w 

m 

:::E 

w 

t-

~~~~ (j) 

~ ~:;:::::;:~ ....IF;:;;:;~ 

>-W 

<X: I-

~~ 

~0 

O....J 

00 

ceo 

Thin- and medium- to massive-bedded 

argillaceous to sandy dolomite, locally 

contains shale interbeds, has highly contorted 

soft-sediment deformation features 

Highly calcareous to dolomitic mudstone, 

contains many thin interbeds of 

laminated calcisiltites 

Calcareous mudstone with interbedded 

fossiliferous lenses and beds; fossiliferous 

wackestones and packstones are particularly 

abundant at the base and top 

Reefs 

Dolomitic, stylolitic, crinoid- and brachiopodrich packstone to grainstone, with thin tongues of 

green shale 

Thin- to medium-bedded, dolomitic wackestones 

separated by medium-gray, very thin dolomitic 

shales 

Figure 19. Descriptive stratigraphic column for the upper part of 

the Clinton Group at Niagara River Gorge near Lewiston, N.Y. 

(Modified from Brett and others, 1991, fig. 13.) 

Regional Correlations: The Densmore Creek Phosphate Bed has been traced west to St. Catharines, Ont., and 

east to beyond Rochester, N.Y., where it becomes hematitic 

and forms the basal part of the Webster Bed9 (fig. 16). The 

Webster Bed is formally named in LoDuca and Brett 

(1994). 

Age: The age of the Densmore Creek Phosphate Bed is 

estimated to be Llandoverian (B2 to C1) (LoDuca and Brett, 

1994). 

Summary of Revisions or Changes: Not revised or otherwise changed herein other than minor modification of the 

name Densmore Creek Bed as formally named in LoDuca 

and Brett ( 1994) to Densmore Creek Phosphate Bed. 

REYNALES LIMESTONE 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: This unit was originally 

named the Pentamerus Limestone by Hall (1843) because 

9 Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

exposures in Rochester contain an abundance of the brachiopod Pentamerus oblongus. Chadwick (1918) introduced 

the term Reynales Limestone Member (of the Clinton Formation) for the same fossiliferous limestone exposed 

beneath the Sodus Shale at Rochester, Lockport, and Niagara. He stated that the Reynales is overlain by the Sodus 

Shale and is, therefore, older than the Wolcott Limestone, 

with which the Reynales had been previously correlated by 

Hartnagel (1907). 

Type Locality: Reynales Basin, 8 mi east of Lockport, 

Niagara County, N.Y. (Gasport quadrangle) (Chadwick, 

1918). Gillette (1947) designated an exposure on Johnson 

Creek (Jeddo Creek) in Middleport, N.Y., as the type 

locality. 

Reference Sections: Along tracks south of the intersection of railroad tracks and Niagara Road west of Lockport, 

N.Y.; Niagara River Gorge section south of Artpark, 

Lewiston, N.Y.; along haul road to the Sir Adam Beck Powerplant on the Canadian side of the Niagara River Gorge. 

Thickness: The Reynales Limestone ranges in thickness from 0 to 12ft in the Niagara region. 

Lithologic Description: In the Niagara region, the Reynales Limestone is represented only by the Hickory Corners 

Member, which consists of a fossiliferous gray to pink limestone with shale partings (fig. 18B). A detailed description 

is given in the following section. Paxton (1985) provided a 

detailed description and interpretation of the petrology of 

the Reynales. 

Contacts: The Reynales Limestone is underlain unconformably by the Neahga Shale. The upper contact of the 

Reynales is also unconformable and is marked by the contact with the Merritton Limestone or with the base of the 

Second Creek Phosphate Bed of the Williamson Shale. 

Regional Correlations: The type facies of the Reynales 

in Niagara County is somewhat different from the facies 

characteristic of the Reynales in the Genesee River Gorge 

region and elsewhere east of Monroe County. At the Genesee River Gorge in Rochester, the Reynales is about 20 ft 

thick and is divided into two members (Brewer Dock and 

Wallington Members), which are discussed in detail in 

LoDuca and Brett (1994). Regional stratigraphic correlations and relations for the Reynales Limestone are shown in 

figures 9 and 16, respectively. The Reynales Limestone 

extends eastward to the Martville, N.Y., area, where it 

becomes shaly and is referred to as the Bear Creek Shale10 

(Gillette, 1947). West of the Niagara region, the Reynales is 

truncated abruptly and is not present in Ontario west of the 

Niagara River Gorge section, although clasts of limestone 

and chert within the Merritton Limestone at Thorold could 

represent eroded fragments. The name "Reynales" is 

applied, although incorrectly, in Canada to refer collectively 

lOU sage ofthe New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 
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DECEW DOLOMITE 

I BURLEIGH HILL MEMBER 

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REYNALES LIMESTONE 

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GAMMA, IN COUNTS PER SECOND 

Figure 20. Natural-gamma logs and stratigraphic correlations from U.S. Geological Survey Neahga cores (locations shown in fig. 3). Depths shown are depths below land 

surface, in feet. The common datum on the logs is the contact between the Rockway Dolomite and the Irondequoit Limestone. 

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REVISED STRATIGRAPHY AND CORRELATIONS 33 

to two discrete units that are markedly younger than the 

Reynales of western New York-the Merritton Limestone 

and the Rockway Member of the Irondequoit Limestone. 

The age of the Merritton is Llandoverian C5; the age of the 

Rockway is Llandoverian C6 to early Wenlockian. At the 

type locality, however, the Reynales is Llandoveria~ C2. In 

addition, strata referred to as Reynales in Canada are above 

the Second Creek Phosphate Bed, whereas Reynales strata 

at the type locality in western New York clearly are below 

this phosphate bed. Thus, both physical and biostratigraphic 

criteria indicate that the term Reynales should no longer be 

applied to any strata in Canada other than those exposed in 

the Canadian face of the Niagara River Gorge. 

Age: The debate on the age of the Reynales is summarized in LoDuca and Brett (1994 ), who indicate that the 

lowest beds of the Reynales could be of Llandoverian C2 

age and that the remainder of the Reynales Limestone is 

probably also C2. Based on ostracodes and conodonts, Maxwell and Over (1994) suggest that the entire Reynales is of 

C1-2 (Aeronian) age. 

Summary of Revisions or Changes: Not revised or 

otherwise changed herein. 

HICKORY CORNERS MEMBER 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: The Hickory Comers 

Limestone Member of the Reynales Limestone was introduced by Kilgour (1963) (fig. 13), who stated that the unit 

overlies the Neahga Shale and underlies the Rockway Dolomite Member of the Irondequoit Limestone, which was also 

introduced by Kilgour (1963) (fig. 13). 

Type Locality: Roadcut along Budd Road, 0.1 mi north 

of intersection of Budd Road and Lower Mountain Road, 

1.3 mi west of village of Hickory Comers, town of Cambria, Niagara County, N.Y. (Cambria quadrangle) (Kilgour, 

1963). The Hickory Comers Member is 9ft thick at the type 

locality (Kilgour, 1963). 

Reference Sections: Along tracks south of the intersection of railroad tracks and Niagara Road immediately west 

of Lockport, N.Y.; Niagara River Gorge section south of 

Artpark, Lewiston, N.Y.; along haul road to the Sir Adam 

Beck Powerplant on the Canadian side of the Niagara River 

Gorge. 

Thickness: The Hickory Comers Member of the Reynales Limestone ranges in thickness from 0 to 12 ft in the 

Niagara region. At Middleport, N.Y., it is about 8ft thick; in 

the Niagara River Gorge, it thins (as a result of erosional 

truncation) to about 5 ft thick. The Hickory Comers has not 

been observed in Ontario west of the Niagara River Gorge. 

Lithologic Description: The Hickory Comers Member 

is a thin- to medium-bedded, gray to pink, nodular, locally 

fossiliferous, dolomitic limestone with thin shale partings 

(fig. 18B), and chert is common near the top. A widely 

traceable phosphate horizon, the Budd Road Phosphate 

Bed, fonns the base of this unit (see next section). 

Characteristic fossils within the Hickory Comers Member 

include the brachiopods Hyattidina and Eocoelia, crinoid 

columnals, and abundant trepostome bryozoa. Detailed 

lithologic descriptions are found in Kilgour (1963, 1966), 

Brett and Calkin (1987), and LoDuca and Brett (1994). 

Contacts: The Hickory Comers Member of the Reynales Limestone unconformably overlies the Neahga Shale; 

the surface of this unconformity is overlain by the Budd 

Road Phosphate Bed (discussed in the following section). 

The upper contact of the Hickory Comers is also unconformable and is overlain by the Merritton Limestone or, 

where the Merritton is absent, by the Second Creek Phosphate Bed of the Williamson Shale. 

Regional Correlations: Regional stratigraphic correlations and relations for the Reynales (Hickory Comers Member) are shown in figures 9 and 16, respectively. In the 

Rochester, N.Y., area, the Hickory Comers Member correlates with the Brewer Dock Member11 of the Reynales 

Limestone. The Hickory Comers probably also correlates 

with the basal part of the overlying Wallington Member12, 

although this relation is difficult to ascertain because the 

intervening hematite bed that is the primary basis for subdivision of the Reynales in the Rochester area is not present in 

the Niagara region. These correlations are discussed in 

more detail in LoDuca and Brett (1994). The equivalent of 

the hematite bed of the Rochester Gorge could be represented at Lockport by an 8-in. grainstone bed that lies about 

4 ft above the base of the Hickory Comers Member. The 2 ft 

of Hickory Comers strata exposed above the grainstone bed 

in Lockport are more massive than the underlying beds and 

contain abundant chert; this interval most likely represents 

the equivalent of the lower part of the Wallington Member 

of the Rochester area (LoDuca and Brett, 1994). This ambiguity in correlation with the Rochester section led Kilgour 

( 1963) to designate strata of the Reynales Limestone 

exposed in the Niagara region as a separate member. West 

of the Niagara region, the Hickory Comers Member is truncated abruptly and has not been observed in Ontario beyond 

the Niagara River Gorge section. 

Age: The age of the Hickory Comers Member is Aeronian. LoDuca and Brett (1994) provide a complete discussion of the age of this unit. 

Summary of Revisions or Changes: Not revised or 

otherwise changed herein. 

BUDD ROAD PHOSPHATE BED 

(not revised or otherwise changed herein other than minor 

modification of unit name) 

First Usage of Nomenclature: The Budd Road Bed of 

the Reynales Limestone is first mentioned informally in 

11 Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

12usage of the New York State Geological Survey; nomenclat;,.ure not 

formally accepted by the U.S. Geological Survey. 
34 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Brett and others (1990b, 1991), where it is described as a 

thin, phosphate-rich limestone bed. The unit is formally 

named the Budd Road Bed in LaDuca and Brett (1994) but 

is herein termed the Budd Road Phosphate Bed. 

Type Section: Exposure on Budd Road, 0.1 mi north of 

intersection of Budd Road and Lower Mountain Road, 1.3 

mi west of village of Hickory Comers, town of Cambria, 

Niagara County, N.Y. (Cambria quadrangle) (LaDuca and 

Brett, 1994). 

Reference Sections: Along railroad tracks north of the 

junction between tracks and Niagara Road on the west side 

of Lockport, N.Y.; Niagara River Gorge south of Artpark in 

Lewiston, N.Y. 

Thickness: The Budd Road Phosphate Bed is a thin but 

persistent unit that ranges in thickness from 1 to 4 in. 

Lithologic Description: The Budd Road Phosphate 

, Bed overlies a minor unconformity at the base of the Hickory Comers Member of the Reynales Limestone and consists of phosphate pebbles (l/8-1/4 in. in diameter) in a silty 

limystone matrix (fig. 18B). Phosphate pebbles within the 

Budd Road Phosphate Bed are typically smaller than those 

in the Densmore Creek Phosphate Bed of the Neahga Shale. 

A more complete discussion of this unit is provided in LaDuca and Brett (1994). 

Contacts: The base of the Budd Road Phosphate Bed 

marks a minor unconformity between the Neahga or Maplewood Shale and the overlying Reynales Limestone. 

Regional Correlations: Regional stratigraphic relations 

for the Budd Road Phosphate Bed are shown in figure 16. 

The Budd Road Phosphate Bed extends from Cambria 

westward to the Niagara River Gorge and eastward to the 

Rochester area, beyond which it becomes hematitic and 

forms the lower part of the Fumaceville Memberl3 of the 

Reynales (LaDuca, 1988; LaDuca and Brett, 1994). 

Age: Middle Llandoverian; Aeronian (C1 or C2): 

Distamodas kentuckiensis Zone (Kleffner, 1991). 

Summary of Revisions or Changes: Not revised or otherwise changed herein, other than minor modification of the 

name Budd Road Bed as formally named in LaDuca and 

Brett (1994) to Budd Road Phosphate Bed. 

MERRITTON LIMESTONE 

(geographic extension herein) 

First Usage of Nomenclature: Kilgour (1963) first 

introduced this unit as the Merritton Limestone Member of 

the Reynales Limestone and traced it across the Niagara 

Peninsula from Thorold westward to Georgetown, Ont. He 

noted a considerable unconformity at the base of the Merritton but pointed out that the disconformity at the top of the 

Merritton is not as marked as that at the base (Kilgour, 

13Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

1963). In Ontario, the Merritton has commonly been considered as part of the Reynales. It is shown as a formationrank unit, however, on Rickard's (1975) correlation chart, 

although it is not extended from Ontario into western New 

York. Brett and others (1991) state that the Merritton is 

clearly distinct from the Reynales and consider it a separate 

formation. 

Type Section: Cut along Canadian National Railroad, 

immediately west of Lock 5 on the Welland Canal near the 

village of Merritton, Ont. (St. Catharines, 30M/3g, Canadian NTS) (Kilgour, 1963). 

Reference Sections: Fifteen Mile Creek, Rockway, 

Ont.; roadcut on Victoria Avenue near Vineland and south 

of Jordan, Ont.; roadcut along Highway 20 in the town of 

Stoney Creek, Ont.; roadcut along south side of Highway 

403 along Niagara Escarpment northeast of Mohawk Road 

exit, town of Ancaster, Ont. 

Thickness: In outcrop, the thickness of the Merritton 

averages about 2.5 ft and is greatest in the Niagara Peninsula at Fifteen Mile Creek (Rockway, Ont.), where it 

reaches 3.5 ft. A greenish, argillaceous dolomite about 0.5 ft 

thick in the Niagara Falls-1 core and the Grand lsland-2 

core might represent the eastern feather-edge of the 

Merritton. 

Lithologic Description: At the type section (fig. 18A), 

and particularly near Hamilton, Ont., the Merritton contains 

three beds of subequal thickness (0.8-1.0 ft) that consist of 

light greenish-gray, buff-weathering dolomitic to argillaceous limestone with thin shale partings. A black, phosphate-stained hardground typically separates the lower and 

middle beds. The limestone contains abundant bright-green 

glauconite and pyrite, particularly in the basal 6-in. bed, 

which also contains sand-and gravel-sized phosphate nodules and chert pebbles. The lower two carbonate beds in the 

Merritton Limestone are fine-grained wackestone; the 

upper bed is typically coarser than the lower beds and contains an abundance of the brachiopod Pentameroides subrectus and crinoidal debris. Other brachiopods, including 

Coolinia, Atrypa, Dalejina, and Leptaena, and corals, such 

as F avosites and Enterolasma, are found at the Merritton 

type section. The lower beds are extensively bioturbated; 

glauconite can be concentrated in large Planolites burrows. 

Contacts: The basal contact of the Merritton is sharp 

and coincides with the major regional, angular unconformity that separates the lower and upper parts of the Clinton 

Group. The unconformity is overlain by a thin calcareous 

bed containing granules of phosphate and glauconite and 

small chert clasts. At the Merritton type section, the upper 

contact of the Merritton is also a sharp erosion surface that 

truncates Pentameroides brachiopods that are in their 

original life positions. The upper contact of the Merritton is 

also coated with black phosphatic material, and the overlying brownish- to greenish-gray shale of the Williamson and 

(or) Rockway Dolomite contains phosphatic pebbles. 
REVISED STRATIGRAPHY AND CORRELATIONS 35 

Regional Correlations: Kilgour (1963) originally 

defined the Merritton as a member of the Reynales Limestone but noted the sharp basal contact and chert pebbles 

within the Merritton that were derived from erosion of the 

Hickory Comers Member of the Reynales. The presence of 

this erosional unconformity indicates that the Merritton is 

distinct from the Reynales. This is discussed in the preceding section and in LoDuca and Brett (1994). Regional correlation indicates that the erosion surface that underlies the 

Merritton is coextensive with the major unconformity that 

underlies the Second Creek Phosphate Bed of the Williamson Shale farther east (Lin and Brett, 1988). In the Hamilton, Ont., area, the Sauquoit Shale, Wolcott Furnace Iron 

Ore, 14 Wolcott Limestone, Sodus Shale, and the Reynales 

Limestone have been removed by erosion at this unconformity (Lin and Brett, 1988; Brett and others, 1990a,b). 

Indeed, this regional pattern of progressive downcutting 

continues westward; Kilgour ( 1963) recognized that the 

erosion surface beneath the Merritton Limestone truncates 

the Neahga Shale and, ultimately, the Thorold Sandstone 

westward in Ontario. The Merritton Limestone, therefore, 

should not be considered a member of the Reynales Limestone because it overlies the regionally angular unconformity that truncates the Reynales. Instead, the Merritton is 

associated with the stratigraphic succession that overlies 

this major unconformity and is similar in age to the lower 

parts of the Williamson Shale and Willowvale Shale and the 

underlying Westmoreland Iron Ore 15 in the type area of the 

Clinton of central New York. 

These stratigraphic correlations are supported by both 

brachiopod and conodont biostratigraphic data. The Merritton contains abundant Pentameroides subrectus, a brachiopod known only from late Telychian (Llandoverian C5), 

whereas the Reynales at the type section contains Pentamerus oblongus, known from strata as old as Aeronian 

(Llandoverian C1 or C2) (Johnston and Colville, 1982). 

New conodont evidence also suggests a probable late Telychian (late Llandoverian C5) age for the Merritton; this suggests correlation with the Westmoreland Iron Ore, which 

lies immediately below the Williamson Shale in east-central 

New York (Mark Kleffner, Ohio State University, oral commun., 1990). The Merritton is disconformably overlain by a 

thin, greenish- to brownish-gray phosphatic shale that 

yields a distinctive acritarch assemblage typical of the 

Williamson Shale to the east, which is discussed in the following section. 

14Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

15 Usage ofthe New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

For the reasons outlined above, the Merritton Limestone has been removed from the Reynales Limestone and 

has been assigned to a formation rank (Brett and others, 

1991). An alternative interpretation would be to make the 

Merritton a member of the Williamson Shale, but this is not 

favored because a slight disconformity is present between 

the Merritton and the overlying, thin, shale tongue equivalent to the Williamson. The phosphatic zone at the contact 

between these units probably correlates with the Second 

Creek Phosphate Bed. 

West of the type section, the Merritton Limestone can 

be traced with certainty to the Hamilton area, where it is 

completely dolomitized .. Kilgour (1963) reported that the 

Merritton is absent at Limehouse, Ont.; however, reexamination of this locality indicates that the typical, tripartite 

carbonate sequence of the Merritton is present, although 

difficult to distinguish from the overlying Rockway Dolomite. Northwest of this area, near Orangeville, the Merritton 

appears to grade into coral-bearing carbonates mapped by 

Bolton (1957) as the Fossil Hill Formation. The Fossil Hill 

also overlies a regionally angular unconformity on the 

Bruce Peninsula (Brett and others, 1990a) and is approximately of late Telychian (Llandoverian C5 or C6) age. 

East of the type section, the Merritton is not present in 

outcrops and has not been recognized (except for a possible 

2- to 3-in. limestone remnant) in the Niagara River Gorge. 

As noted above, however, a featheredge of the unit is probably present in two of the USGS drill cores (Niagara Falls-1 

and Grand Island-2). The unconformity between the Merritton and the tongue of the Williamson Shale apparently truncates the Merritton eastward within the approximately 

10-mi distance between the type area and the vicinity of the 

Niagara River Gorge. This pinchout could also be interpreted as depositional. 

Age: The Merritton is of late Telychian (Llandoverian 

C5) age, as indicated by Pentameroides brachiopods and 

conodont species typical of the upper celloni Zone (Berry 

and Boucot, 1970; Mark Kleffner, Ohio State University, 

oral commun., 1991). 

Summary of Change: Rickard (1975) does not extend 

the Merritton Limestone from Ontario into western New 

York. The Merritton Limestone is herein geographically 

extended (tentatively) from Thorold, Ont., where it was 

traced by Kilgour (1963), into the southern Niagara County 

subsurface. 

WILLIAMSON SHALE 

(geographic extension herein) 

First Usage of Nomenclature: Hartnagel (1907) proposed the term Williamson Shale for the Second Clinton 

Shale designated by Hall (1843). The Williamson Shale, as 

used by Hartnagel in the Rochester area, included what are 

now referred to as the Williamson and the juxtaposed lower 

part of the Sodus Shale. Hartnagel (1907) stated that the 
36 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Williamson Shale is underlain by the Wolcott Limestone 

and overlain by the Irondequoit Limestone. 

Type Section: Exposures at Salmon Creek, about 160 ft 

south of Route 104, town of Williamson, Wayne County, 

N.Y. (Williamson quadrangle) (Hartnage1, 1907). 

Reference Sections: Browncroft Creek, in east Rochester, N.Y.; Genesee River Gorge, also in Rochester. 

Thickness: The Williamson Shale ranges from a featheredge in Niagara County to a maximum thickness of 78.5 

ft at Lakeport, Oneida County, N.Y. 

Lithologic Description: The Williamson Shale is a 

greenish-gray to black, fissile to platy, graptolite-bearing 

shale (fig. 188). At its base is a thin (0.75 to 8 in.) quartz 

and phosphate-pebble bed designated the Second Creek 

Bed by Linand Brett ( 1988) (geographical extension 

herein). Fossil assemblages in the Williamson Shale are discussed in Lin and Brett ( 1988). 

Contacts: Both the lower and upper contacts of the 

Williamson Shale are sharp and unconformable (Lin and 

Brett, 1988). The lower contact is marked by the Second 

Creek Phosphate Bed, a major regional angular unconformity that overlies various formations in the lower to middle 

parts of the Clinton. The upper contact with the Rockway 

Dolomite is sharp and disconformable and is marked by a 

quartz and phosphate-pebble bed designated the Salmon 

Creek Bed by Lin and Brett (1988); this bed is discussed in 

the following section on the Rockway Dolomite. 

Regional Correlations: Regional stratigraphic correlations and relations of the Williamson Shale are shown in 

figures 9, 15, and 1 7. East of the study area, the Williamson 

Shale thickens to a maximum of 65 ft near Oneida Lake, 

then thins and grades laterally into the Willowv.ale Shale of 

the Clinton type area, near Utica, N.Y. The Williamson is 

the westward stratigraphic equivalent of the Willowvale 

Shale-both are bounded by the same biostratigraphically 

dated discontinuity surfaces (Lin and Brett, 1988). Westward across the study area, the Williamson thins and the 

shale ultimately pinches out between Lockport and St. 

Catharines, Ont. In the Niagara County area, the Williamson is exceptionally thin and is confined to the basal Second 

Creek Phosphate Bed and a few inches of greenish shale. In 

the Hamilton, Ont., region, thin remnants of the Williamson 

locally overlie the Merritton Limestone. 

Age: The Williamson Shale is of latest Llandoverian, 

late Telychian (C6) age on the basis of the rugose coral 

Palaeocyclus, monograptid graptolites (Ruedemann, 1947; 

Berry and Boucot, 1970), Pterospathodus amorphognathoides Zone conodonts, and Mastigobolbina typus Zone 

ostracodes (Ulrich and Bassler, 1923; Gillette, 1947; Rickard, 1975; Lin and Brett, 1988). 

Summary of Changes: Rickard's (1975) correlation 

chart shows the Williamson Shale extending as far west as 

the Albion, N.Y., area. Lin and Brett (1988) recognized the 

Williamson Shale as far west as Lockport, N.Y. It is herein 

geographically extended westward to the Niagara Falls 

area, where a thin erosional remnant has been observed in 

the USGS cores. The Second Creek Phosphate Bed of the 

Williamson apparently also extends into Ontario. 

SECOND CREEK PHOSPHATE BED 

(geographic extension, minor modification of unit name herein) 

First Usage of Nomenclature: The basal phosphaticquartz pebble bed of the Williamson Shale was designated 

the Second Creek Bed by Lin and Brett (1988). It is a thin 

but widespread bed. Lin and Brett ( 1988) present evidence 

that the Second Creek is laterally equivalent to the Westmoreland Iron Ore at the base of the Willowvale Shale. The 

Second Creek Bed overlies a major regional angular unconformity; it truncates over 150 ft of shales, carbonates, and 

hematite beds that are exposed in west-central New York, 

and bevels progressively lower stratigraphic units to the 

west (Brett and others, 1991). The bed is herein termed the 

Second Creek Phosphate Bed. 

Type Section: Exposures on Second Creek, near Red 

Mill Road, north of Alton, Wayne County, N.Y. (Rose quadrangle) (Lin and Brett, 1988). 

Reference Sections: Genesee River Gorge in Rochester, N.Y.; railroad cut at Lockport, N.Y.; Niagara River 

Gorge. 

Thickness: The Second Creek Phosphate Bed ranges 

from 0.1 to 0. 7 ft thick. At the type section, the bed ranges 

from 0.1 to 0.25 ft thick. In the USGS cores, the Second 

Creek Phosphate Bed is thin (0.1-0.2 ft) but distinctive. 

Lithologic Description: The Second Creek Phosphate 

Bed is a thin but laterally persistent quartzose and phosphatic granule-to-pebble-sized conglomeratic-lag deposit 

(fig. 18B). The bed can be pyritic, locally calcareous, and 

fossiliferous, with abundant Eoplectodonta brachiopods 

(Lin and Brett, 1988). The Second Creek Phosphate Bed 

represents relict sediments reworked during a widespread 

(late Llandoverian, C6) marine transgression (Lin and Brett, 

1988). 

Contacts: The lower contact is sharp and erosional, 

particularly where the Second Creek Phosphate Bed 

directly overlies a broad, regional, low-angle unconformity. 

In Ontario, where the Merritton Limestone is above this 

same unconformity, the Second Creek Phosphate Bed 

seems to disconformably overlie the Merritton. The upper 

contact of the Second Creek Phosphate Bed is gradational 

where the green shales of the Williamson overlie the bed, 

but where the shales are absent, the contact with the overlying Rockway Dolomite is unconformable. 

Regional Correlations: At the type section, the Second 

Creek Phosphate Bed lies at the unconformable contact 

between the Wolcott Furnace Iron Ore and the overlying 

shales of the Williamson (Lin and Brett, 1988). Farther east 

in the Clinton type area, the sequence becomes increasingly 

conformable, and the Second Creek Phosphate Bed lies at 
REVISED STRATIGRAPHY AND CORRELATIONS 37 

the paraconformable contact between the Willowvale Shale 

(lateral equivalent of the Williamson) and the Westmoreland Iron Ore. 

Westward from the Clinton type area, the appearance 

of successively older stratigraphic units beneath the Second 

Creek Phosphate Bed illustrates that the bed marks a significant, low-angle, regional unconformity that increases in 

magnitude from east to west (Lin and Brett, 1988). For 

example, at Rochester, the Second Creek Phosphate Bed 

immediately overlies the Sodus Shale, whereas in the Niagara River Gorge, it overlies the Reynales Limestone. The 

pattern of northwestward overstep is reversed in the Bruce 

Peninsula of Ontario; a succession of beds emerges below 

the lower contact of the Fossil Hill to the northwest and 

these strata are laterally continuous between the western 

flank of the Appalachian Basin and the southeastern flank 

of the Michigan Basin. From St. Catharines to Hamilton, 

Ont.,the Second Creek Phosphate Bed lies at the upper contact of the Merritton Limestone. North of Hamilton, it most 

likely would be present at the top of the Fossil Hill Limestone. 

Age: The Second Creek Phosphate Bed lies above the 

Pentameroides-bearing Merritton Limestone, which has 

been considered to be of Llandoverian late Cs to C6 age. 

Conodont assemblages confirm a Llandoverian C6 age (Lin 

and Brett, 1988). 

Summary of Change: Lin and Brett (1988) recognized 

the Second Creek Bed as far west as Lockport, N.Y. It is 

herein geographically extended westward to at least the St. 

Catha.D.nes area. It has been recognized in the USGS cores, 

in the Niagara River Gorge, and in outcrops in the Niagara 

Peninsula of Ontario. A minor modification of the name has 

been made from Second Creek Bed as formally named by 

Lin and Brett (1988) to Second Creek Phosphate Bed. 

ROCKWAY DOLOMITE 

(revised herein) 

Brief History of Nomenclature: The Rockway Dolomite Member of the Irondequoit Limestone was named by 

Kilgour (1963) (fig. 13), who assigned it to the Irondequoit 

on the basis of his interpretation of fossil content and stratigraphic relations. It had previously been considered the 

upper part of the Reynales Formation. Kilgour (1963) stated 

that at the type locality, the Rockway disconformably overlies the Merritton Limestone Member of the Reynales; 

between Middleport, N.Y., and the Niagara River Gorge, the 

Rockway overlies the Hickory Comers Limestone Member 

of the Reynales. 

Discussion of Change in Rank: Although Kilgour 

(1963) removed the Rockway Dolomite from the Reynales 

Formation, the Ontario Geological Survey has continued to 

map the Rockway, together with the underlying Merritton, 

as Reynales. Neither of these units belongs with the Reynales Limestone, however, because they overlie the major 

sequence boundary that, in tum, overlies and locally truncates the Reynales. In southern Ontario, where the type sections are located, the Merritton and Rockway are 

lithologically distinctive-the former is more calcareous, 

glauconitic, and fossiliferous, and the latter is dolomitic, 

pyritic, and only sparsely fossiliferous. The distinct lithofacies of these units warrant their rank as formations as 

opposed to their incorporation as members into the much 

older Reynales Limestone. In addition, a very thin, brownish phosphatic shale between the two units at the Merritton 

type section may represent the featheredge of an intervening unit; therefore, the Williamson Shale (see discussion 

under Williamson Shale and Merritton Limestone), the 

Merritton, and the Rockway cannot be construed as contiguous members of a single formation. 

Formation rank for the Rockway Dolomite, therefore, 

is proposed herein. Kilgour (1963) designated the Rockway 

as a member of the Irondequoit Formation, recognizing that 

the argillaceous dolomicrites and the overlying crinoidal 

grainstones that had previously been designated as Irondequoit were similar in age-approximately early Wenlockian. The dolomicrites and grainstones, however, belong to 

different (although successive) conodont zones; the dolomicrites of the Rockway contain a fauna typical of the 

Pterospathodus amorphognathoides Zone, whereas most, if 

not all, of the grainstone of the Irondequoit is in the Kockelella ranuliformis Zone (Kleffner, 1991). Rickard (1975) 

also shows the Rockway as a member of the Irondequoit in 

the Niagara area. 

The Rockway Dolomite always appears to be separated 

from the ovrrlying crinoidal packstones and grainstones of 

the Irondequoit Limestone by a sharp, disconformable contact. In the Niagara region, this contact is typically an irregular surface at the top of the highest dolomicrite bed of the 

Rockway. This uppermost bed of the Rockway is welded to 

the base of the overlying grainstones. Clasts of the Rockway Dolomite .in the basal grainstone of the Irondequoit 

indicate a period of erosion between deposition of these two 

units. Regional correlation of this contact indicates that it is 

an extensive disconformity that corresponds to the contact 

between the Dawes Formation16 and the overlying crinoidal, hematitic Kirkland Limestone17 in the Clinton type area 

and to the contact between the Rose Hill Shale1

8 and the 

Keefer Sandstone in central Pennsylvania (Brett and others, 

1990a). The greatest amount of erosion of the Rockway 

observed in the Niagara region is in eastern Niagara County 

and in Orleans County, where the upper half of the Rockway is truncated by the unconformity below the !ronde16Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

17Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 18Designated "Rose Hill Formation" by the U.S. Geological Survey. 
38 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

quoit. At the Irondequoit type locality (near Rochester), the 

Rockway-Irondequoit contact shows little or no evidence of 

erosion but is sharp and is at least a diastem. A disconformity is therefore recognized between the Rockway Dolomite and the Irondequoit Limestone (Brett and others, 

1990a), and these units are consequently considered to be 

discrete formations. The Rockway Dolomite is herein elevated to formation rank, and the Irondequoit is reestablished 

herein to its previous usage (for example, Gillette, 194 7) 

and is restricted to the massive packstone and grainstone 

lithology in the Niagara area. 

Type Locality: Gorge at Fifteen Mile Creek at Rockway, Ont. (Fonthill, 30M/3c, Canadian NTS) (Kilgour, 

1963). 

Reference Sections: Genesee River Gorge in Rochester, N.Y.; Niagara River Gorge; Route 403 roadcuts in 

Hamilton, Ont. 

Thickness: At the type locality, the Rockway is 12 ft 

thick. In the USGS cores, its thickness ranges from 6.6 to 

9.2 ft. 

Lithologic Description: In Niagara County, the lithology of the Rockway closely resembles that at its type locality in that it consists of medium gray, pale buff-weathering, 

thin- to medium-bedded, dolomitic wackestones separated 

by medium-gray, very thin dolomitic shales (figs. 18B, 19). 

The dolomitic shale interbeds thicken eastward from Niagara County. In cores, much of the rock appears burrowmottled, and the trace fossils Chondrites and Planolites are 

observed on some bedding planes. Minor amounts of pyrite 

are associated with the burrows. 

In the Niagara River Gorge and throughout the Niagara 

region, the Rockway contains a distinctive succession of 

beds. A lower shale-rich zone about 1 ft thick at the base 

grades upward into medium-bedded dolomite. A thick, 

blocky bed of dolomitic wackestone typically is present 

about 3 ft above the base of the unit and is, in tum, overlain 

by a succession of thin to medium beds and an upper shaly 

zone up to 6 in. thick. The uppermost bed is a thin (2-6 in.) 

dolomicrite bed that is typically welded to the base of the 

overlying Irondequoit Limestone. The upper contact of this 

bed is irregular and darkly stained in some outcrops. 

In most of southwestern Ontario and western New 

York, the Rockway Dolomite is barren to sparsely fossiliferous. The observed macrofauna consists of a few taxa. 

Between St. Catharines and Hamilton, Ont., poorly preserved molds of the brachiopod Costistricklandia and rare 

F avosites corals are found on bedding planes low in the 

Rockway. At the Niagara River Gorge, nautiloids, gastropods, and dendroid graptolites occur sporadically. Scattered 

pelmatozoan ossicles and brachiopod valves are evident in 

the USGS cores. 

Contacts: Both the lower and upper contacts of the 

Rockway Dolomite are sharp and disconformable. The 

Rockway appears to onlap progressively older units across 

the Niagara region of Ontario. Inspection of the USGS 

cores has shown that a thin tongue of greenish-gray phosphatic shale (beneath the Rockway) extends into the Niagara area; this indicates that at least the Second Creek 

Phosphate Bed of the Williamson Shale extends as far west 

as the Niagara River Gorge. At Niagara River Gorge, the 

disconformable contact between this green shale and the 

overlying Rockway is marked by an interval of argillaceous 

dolomite up to 1.5 ft thick that contains scattered phosphate 

and quartz grains. This rather diffuse zone probably correlates with the more compact phosphate and quartz granule 

bed designated the Salmon Creek Bed by Lin and Brett 

(1988). Near St. Catharines, Ont., the Rockway disconformably overlies the Merritton Limestone. The contact between 

these units is a phosphatic hardground that probably correlates with the amalgamated Second Creek Phosphate Bed 

and Salmon Creek Phosphate Bed. The upper contact of the 

Rockway with the Irondequoit represents at least a minor 

unconformity. In addition, the grain size changes abruptly 

from the very fine-grained dolomite of the Rockway to the 

medium- to coarse-crystalline limestone of the Irondequoit. 

Regional Correlations: Regional stratigraphic correlations and relations of the Rockway Dolomite are shown in 

figures 15 and 17, respectively. The Rockway becomes 

increasingly shaly east of the study area. At the Genesee 

River Gorge in Rochester, N.Y., the Rockway is about 50 

percent green shale and is interbedded with thin limestones 

(wackestones). In Madison County, the Rockway and its 

distinctive basal bed can be traced directly into dolomitic 

sandstones and shales of the Dawes Formation of the Clinton type area. Rhythmic carbonate-shale and sandstoneshale bedding patterns in the Rockway have facilitated correlations between the Rockway and the Dawes Formation 

across New York. Northwest of the study area, the Rockway 

Dolomite appears to grade laterally into beds assigned to 

the Lions Head Member of the Amabel Formation at the 

north tributary of the Nottasawaga River near Orangeville, 

Ont. 

Age: The Rockway Dolomite is assigned to the upper 

Pterospathodus amorphognathoides conodont Zone (Rexroad and Rickard, 1965; Kleffner, 1991) and is therefore 

earliest Wenlockian in age. 

Summary of Revision: The Rockway Dolomite is 

herein raised in rank from a member of the Irondequoit 

Limestone, as originally proposed by Kilgour (1963) and as 

shown in Rickard (1975), to formation status. It is recognized as separated from the Irondequoit Limestone by a disconformity (Brett and others, 1990a). In most of New York, 

it is underlain at a minor disconformity by the Williamson 

Shale, but in parts of Niagara County where the Williamson 

is extremely thin, the Rockway may directly overlie the 

Second Creek Phosphate Bed of the Williamson. 
REVISED STRATIGRAPHY AND CORRELATIONS 39 

SALMON CREEK PHOSPHATE BED 

(geographic extension, minor modification of unit name herein) 

First Usage of Nomenclature: The Salmon Creek Bed 

was named by Lin and Brett (1988). It is best developed at 

the type section of the Williamson Shale. Lin and Brett 

( 1988) assigned the Salmon Creek Bed to the base of the 

Rockway Member (herein considered the Rockway Dolomite, a formation-level unit) of the Irondequoit Limestone. 

It probably correlates with the conglomeratic basal bed of 

the Dawes Formation in the type area of the Clinton Group 

(Lin and Brett, 1988). The Salmon Creek Bed was traced by 

Lin and Brett (1988) from its easternmost exposure at Second Creek to west of Lockport, N.Y. The bed is herein 

termed the Salmon Creek Phosphate Bed. 

Type Section: Exposures at Salmon Creek, about 160ft 

south of Route 104, town of Williamson, Wayne County, 

N.Y. (Williamson quadrangle) (Lin and Brett, 1988). 

Reference Sections: Genesee River Gorge in Rochester, N.Y.; Lockport Glen railroad cut in Lockport, N.Y. 

Thickness: The Salmon Creek Phosphate Bed ranges 

from 0.25 to 0.5 ft in thickness. 

Lithologic Description: The Salmon Creek Phosphate 

Bed is a buff-weathering, light greenish-gray, pyritic, bioturbated dolomicrite that contains small pebbles of quartz 

and phosphate (fig. 18B). 

Contacts: The lower contact with the Williamson Shale 

is sharp and disconformable. The upper contact with the 

Rockway Dolomite is more gradational and apparently conformable. 

Regional Correlations: To the east, the Salmon Creek 

Phosphate Bed can be traced into the basal hematitic ore 

bed of the Dawes Formation in the Clinton type area (Lin 

and Brett, 1988; Brett and others, 1990a). To the west, in the 

Niagara region of Ontario, the Williamson Shale appears to 

pinch out; as a result, the Second Creek Phosphate Bed 

merges with the Salmon Creek Phosphate Bed to form a 

complex phosphatic zone at the top of the Merritton Limestone. 

Age: The Salmon Creek Phosphate Bed is of latest 

Llandoverian age (Telychian C6) to earliest Wenlockian, on 

the basis of upper Pterospathodus amorphognathoides 

Zone conodonts and Mastigobolbina typus Zone ostracodes. 

Summary of Change: Lin and Brett (1988) recognized 

the Salmon Creek Bed as far west as Lockport, N.Y. It is 

herein geographically extended westward to the Niagara 

Falls area, where it has been recognized in the USGS cores. 

A minor modification of the name has been made from 

Salmon Creek Bed as formally named by Lin and Brett 

( 1988) to Salmon Creek Phosphate Bed. 

IRONDEQUOIT LIMESTONE 

(revised herein) 

Brief History of Nomenclature: Hartnagel (1907) 

named the Irondequoit Limestone Member of the Clinton 

Formation for the town of Irondequoit, just north of Rochester, in Monroe County, N.Y. He defined the Irondequoit 

as the top member of the Clinton Formation in the Rochester and Ontario Beach quadrangles and stated that it is 

underlain by the Williamson Shale and overlain by the 

Rochester Shale. Chadwick (1908) classified the Irondequoit as the basal member of the Rochester Shale, on the 

basis of faunal similarities. Hartnagel (1912) excluded the 

Irondequoit from the Rochester Shale and traced the Irondequoit to the Niagara River. Ulrich and Bassler (1923) and 

Goldring (1931) placed the Irondequoit between the Williamson Shale and the Rochester Shale. Although Gillette 

(1947) restricted the term Irondequoit to the massive packstone and grainstone found in the Niagara area, Kilgour 

( 1963) designated the underlying Rockway Dolomite as a 

member of the Irondequoit Formation (fig. 13). Rickard 

( 197 5) considered the Rockway to be a member of the 

Irondequoit in the Niagara region (fig. 14 ). The Rockway 

Dolomite is herein elevated to formation rank, and the 

Irondequoit is reestablished to its previous usage (Gillette, 

1947), which is restricted to the massive packstone and 

grainstone (fig. 14). See "Discussion of Change in Rank" in 

the preceding section on the Rockway Dolomite. 

Type Locality: None is specifically given but the unit 

was probably named for exposures in tributaries of Irondequoit Creek, in the town of Webster, Monroe County, N.Y. 

(Rochester East quadrangle) (Hartnagel, 1907). 

Reference Sections: Irondequoit Creek in Webster, 

N.Y.; Genesee River Gorge in Rochester, N.Y.; Niagara 

River Gorge; Route 403 roadcuts in Hamilton, Ont. 

Thickness: In the USGS cores, the thickness of the 

Irondequoit Limestone ranges from 11.5 to 22.4 ft and generally increases southward. The maximum observed thickness is 22.4 ft in the USGS Wheatfield-2 core; the minimum 

is less than 5 ft near Albion, Orleans County, N.Y. 

Lithologic Description: In Niagara County, the Irondequoit Limestone is a thick- to massive-bedded, medium 

greenish-gray to pinkish-gray, buff-weathering, dolomitic, 

crinoidal- and brachiopod-rich packstone to grainstone (fig. 

19). Laterally persistent stylolitic surfaces are prominent 

within the unit. The Irondequoit contains pink calcite crystals and pyrite, gypsum, and pyrolusite (Kilgour and Liberty, 1981 ). The lower 1-2 ft are typically altered to 

aphanitic dolomite. Upper beds of the Irondequoit consist of 

medium- to massive-bedded crinoidal limestone. Thin 

tongues of green shale, commonly with small (less than 1/3 

in.) micritic intraclasts, are common. The brachiopods 

Atrypa and Whitfieldella and the rugose coral Enterolasma 

are commonly observed in core and outcrop. 
40 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Toward the top of the Irondequoit, thin greenish shale 

layers become increasingly numerous, and the upper 1-2 ft 

is an argillaceous, brachiopod-rich packstone. A distinctive 

green shale and an overlying grainstone rich in the brachiopod Whitfieldella are present about 10 ft above the base of 

the Irondequoit in the USGS Grand Island-2 core. This 

interval appears to correlate with a Whitfieldella-rich 

marker bed that is traceable eastward to Wayne County. 

Small bioherms (3-10ft across and up to 6.5 ft high) 

are common in the upper beds of the Irondequoit. These 

bioherms are sparsely fossiliferous, pale greenish-gray, nonbedded micrite masses that commonly contain internal crinkly surfaces and partings associated with microstylolites. 

The mounds consist partly of foliose fistuliporoid bryozoans and locally contain pockets filled with trilobite and nautiloid material. These bioherms have been described in 

detail by Sarle (1901) and by Hewitt and Cuffey (1985). 

Contacts: At the lower contact, a dark-stained erosional surface separates coarse crinoidal packstones of the 

Irondequoit from a thin dolomitic wackestone bed of the 

underlying Rockway Dolomite. This stained contact is pronounced everywhere in the study area. In the Hamilton, 

Ont., area, it is so distinctive that many workers (for example, Bolton, 1957) have perceived it as the significant stratigraphic break between the lower and upper parts of the 

Clinton Group and used it as the boundary between the 

"Reynales" as defined in Ontario (actually the Rockway 

Dolomite) and the Irondequoit Limestone. Although the 

surface underwent relatively little erosion, the relatively 

deep-water shales and dolomites of the Rockway change 

abruptly to the shallow, crinoidal grainstones of the Irondequoit (Brett and others, 1990b ). 

A transitional interval of argillaceous, shelly limestone 

that ranges from a few inches to a few feet thick is typically 

found at the contact of the Irondequoit with the overlying 

Rochester Shale. The Irondequoit-Rochester contact is 

apparently conformable in the Niagara region but becomes 

disconformable in the Hamilton, Ont., region. 

Regional Correlations: Regional stratigraphic correlations and relations for the Irondequoit Limestone are shown 

in figures 15 and 17, respectively. The Irondequoit Limestone grades eastward from massive grainstones at Niagara 

River Gorge to thin- and medium-bedded wackestones and 

packstones and thin shales in Monroe County. At the Genesee River Gorge in Rochester, N.Y., the Irondequoit consists 

of interbedded, thin- to medium-bedded, dolomitic wackestones and packstones with abundant thin shale partings and 

micritic bioherms. The Irondequoit extends eastward from 

the Rochester area to the Clinton type area, where it grades 

laterally into the Kirkland Limestone (Brett and others, 

1990a). To the northwest, in the Bruce Peninsula region, the 

Irondequoit grades into the lower part of the Colpoy Bay 

Member of the Amabel Formation (Bolton, 1957). 

Age: The Irondequoit Limestone contains Mastigobolbina typus Zone ostracodes and Kockelella ranuliformis 

Zone conodonts (Swartz, 1923; Gillette, 1947; Kleffner, 

1991 ). The presence of these conodonts and ostracodes 

indicates that the Irondequoit is of earliest Wenlockian 

(early Sheinwoodian) age. 

Summary of Revision: The unit that Kilgour (1963) and 

Rickard (1975) considered to be the Rockway Member of 

the Irondequoit Limestone is herein removed from the 

Irondequoit and raised to formation rank and is termed the 

Rockway Dolomite. This reestablishes previous usage 

(Gillette, 1947) of the Irondequoit, and restricts it in the 

Niagara area to the massive packstone and grainstone. 

ROCHESTER SHALE 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: The Rochester Shale 

was named by James Hall (1839), probably for exposures in 

the Genesee River Gorge near Rochester, N.Y., of calcareous shales underlying the Lockport Limestone and the overlying green shale and iron ore. It was the first formally 

designated stratigraphic unit in North America. Hall (1842, 

1843) proposed the Niagara Group, which included the 

Rochester Shale and Lockport Limestone. In 1843, Hall 

abandoned the term Rochester Shale and replaced it with 

Niagara Shale. When Clarke and Schuchert (1899) introduced the Niagaran Period or Group to include the Clinton 

beds, Rochester Shale, Lockport Limestone, and the Guelph 

Dolomite, they revived the term Rochester Shale with its 

original meaning and subsequent workers have accepted 

this name. 

Type Locality: As originally designated by Hall (1839), 

the type locality is near Rochester, N.Y., probably in the 

Genesee River Gorge, Monroe County, N.Y. (Rochester 

East and West quadrangles). 

Reference Sections: The Rochester Shale is exposed in 

many creek sections along the Niagara Escarpment, 

although relatively few complete exposures are known. 

Exposures in cliffs of the Niagara River Gorge near 

Lewiston, both north and south of the Robert Moses Powerplant (south haul road), and sections at DeCew Falls, near 

St. Catharines, Ont., are the best local reference sections for 

the entire formation (Bolton, 1957; Brett, 1983a,b). 

Thickness: The Rochester Shale ranges from 1.5 to 

more than 120ft thick. In the Niagara region, it ranges from 

58 to 65 ft thick, with an average thickness of about 60 ft. 

Lithologic Description: The Rochester Shale consists 

of medium-dark gray to black calcareous mudstone with 

thin interbeds of calcareous to dolomitic calcisiltite (pelletal 

grainstone) and calcarenite (fossil packstone and grainstone) (figs. 17, 19). Carbonate interbeds are particularly 

concentrated near the base, middle, and upper third of the 

formation. The Rochester has been divided into the 

Lewiston and Burleigh Hill Members in the Niagara region 
REVISED STRATIGRAPHY AND CORRELATIONS 41 

(Brett, 1983a,b ). The division was made at the top of a 

series of skeletal packs tones to grains tones that are typically 

rich in bryozoans and (or) brachiopod-shell fragments. The 

altitude of this unit above the lower contact increases 

steadily southward as the amount of section between the 

bryozoan-rich packstone interval and the lower contact of 

the formation increases (Brett, 1983a,b ). This generalization has been confirmed through examination of the USGS 

cores. Lithologic subdivisions (informal units A-E) of the 

Lewiston Member as originally proposed by Brett ( 1983a,b) 

have been modified slightly, as discussed below. Facies are 

traceable without substantial change in fossil content or 

lithology from east to west for distances exceeding 95 mi, 

but abrupt lateral facies changes occur along short (3-8 mi) 

north-south distances (for example, along the Niagara River 

Gorge); this suggests that the facies belts are elongated 

east-west, parallel to both a northern paleoshoreline and to 

the present outcrop belt along the Niagara Escarpment 

(Brett, 1983a,b). 

Contacts: In western New York, the basal contact with 

the Irondequoit Limestone is gradational over intervals 

ranging from several inches to 2 ft. In Ontario, this contact 

becomes increasingly sharp and disconformable westward. 

Regional Correlations: Regional stratigraphic correlations and relations for the Rochester Shale are shown in figures 15 and 17, respectively. The Rochester Shale is 

exposed from Waterdown (north of Hamilton, Ont.) eastward to the area of Verona, in Oneida County, N.Y. Shale of 

the same name and approximately the same age is exposed 

in the central Appalachians from Pennsylvania to northern 

Virginia. East of Verona, N.Y., the Rochester Shale becomes 

sufficiently arenaceous that strata equivalent to the Rochester are assigned to the Herkimer Sandstone19 • 

Age: Early to middle Wenlockian, as indicated by 

Paraechmina spinosa Zone ostracodes (Berdan and Zenger, 

1965), and by conodonts of the Kockelella ranuliformis and 

Ozarkodina sagitta Zones (Kleffner, 1991). 

Summary of Revisions or Changes: Not revised or otherwise changed herein except for minor refinement of informal subdivisions of the Lewiston Member. 

LEWISTON MEMBER 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: The term Lewiston 

Member of the Rochester Shale was introduced by Brett 

(1983a,b) to designate the shales and fossiliferous limestones of the lower unit of the Rochester Shale from Hamilton, Ont., to west-central New York. The Lewiston is 

typified by bryozoan- and brachiopod-rich mudstones and 

thin limestones at the base and top (units A, B, D, E), which 

19Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

are separated by an interval of sparsely fossiliferous shales 

and calcisiltites (unit C) (Brett, 1983b). 

Type Section: Cliff in the east wall of Niagara River 

Gorge about 0.3 mi north of Robert Moses Powerplant and 

1.4 mi south of Artpark, in Lewiston, Niagara County, N.Y. 

(Lewiston quadrangle) (Brett, 1983b ). 

Reference Sections: South haul road (access for Robert 

Moses Powerplant) in the Niagara River Gorge; site of the 

old Schoellkopf Powerplant in the east wall of the gorge; 

partial sections at Lockport Gulf (Eighteen Mile Creek 

gully) and along a tributary of Jeddo Creek in Middleport, 

N.Y. (Brett, 1983a,b). 

Thickness: The Lewiston Member thickens regularly 

and rapidly southward along the Niagara River Gorge. The 

member is about 26-30 ft thick in the north end of the Niagara River Gorge at Lewiston, but more than 45 ft thick in 

the gorge near Niagara Falls. It is 38 ft thick in the USGS 

Niagara-1 core, 43 ft thick in the USGS Niagara Falls-1 

core, and 55 ft thick in the USGS Grand Island-2 core. 

Most of this thickening involves a middle interval of 

sparsely fossiliferous shale that has been informally designated unit C by Brett (1983b ). 

Lithologic Description: The Lewiston Member consists of medium- to dark-gray, calcareous mudstone with 

interbedded fossiliferous lenses and beds (figs. 17, 19). Fossiliferous wackestones and packstones are particularly 

abundant in the lowermost and uppermost parts of the unit. 

Several traceable units can be recognized within the 

Lewiston Member at most localities; these intervals have 

been designated informally as units A through E by Brett 

(1983b) and are described below. 

UNIT A 

This unit consists of highly fossiliferous, typically brachiopod-rich, argillaceous limestone (packstone to grainstone) and very calcareous shale. Unit A forms a transition 

from the underlying Irondequoit Limestone in the Niagara 

region. In some sections this interval is marked at its top by 

a relatively compact shell-rich limestone band overlain by 

less fossiliferous mudstone. Unit A is thin; it is only 1-2 ft 

thick in the USGS cores. 

UNITB 

Unit B is characterized by calcareous mudstone interbedded with lenses (biostromes) of ramose bryozoans and 

brachiopods. Its facies range from argillaceous wackestone 

to packstone. The rhombiferan Caryocrinites and the coronoid (Brett and others, 1983) Stephanocrinus are common 

in unit B. The contact between unit B and unit C marks a 

relatively at1rupt decrease in fossil content; the mudstones 

of unit C are only sparsely fossiliferous. Unit B ranges in 

thickness from about 12ft in the north Niagara River Gorge 

to about 27 ft in the USGS Grand Island-2 core. On the 
42 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

basis of detailed examination of the USGS cores, unit B is 

subdivided (informally) into lower and upper bryozoan biostromal units (B-1, B-3) that are separated by an interval of 

relatively sparsely fossiliferous mudstone (B-2). The B-2 

interval is quite thin in northern areas ( 1-2 ft thick in the 

northern Niagara River Gorge) but thickens to the south 

(7.5 ft thick in the USGS Grand Island-2 core). The upper 

bryozoan biostromal unit, B-3, becomes sparsely fossiliferous and is indistinct in the USGS Grand Island-2 core. It 

appears to grade into the sparsely fossiliferous unit C. 

UNITC 

This unit is a sparsely fossiliferous zone characterized 

by thin shell pavements, thin laminated calcisiltites, and a 

lack of bryozoan lenses. The thickness of this interval 

ranges from about 4 ft in the north to more than 25 ft in the 

USGS Grand Island-2 core. It displays major southward 

thickening that could be partly due to loss of resolution of 

the B-3 unit. 

UNITD 

The lithology of this unit is variable, but it is easily recognized in the northern end of the Niagara River Gorge as a 

bryozoan- and brachiopod-rich facies resembling unit B. 

The northern facies is replaced south of the Whirlpool area 

in the Niagara River Gorge by a 3-4-ft-thick interval of 

laminated and typically contorted dolomitic calcisiltites that 

closely resemble the DeCew Dolomite (discussed below). 

In outcrop, this interval weathers as a series of resistant 

bands with low-angle, hummocky cross stratification and 

soft-sediment deformation structures. These beds are overlain by a few feet of calcareous mudstone containing thin, 

shell- and bryozoan-rich bands. The thickness of unit D 

ranges from about 10 ft in the north end of the Niagara 

River Gorge to about 3 ft near Grand Island. This trend of 

northward thickening is opposite to that of unit C, into 

which unit D probably grades to the south. 

UNITE 

This unit is a thin but widespread interval containing 

calcareous, fossil-rich shales and interbeds up to 5 in. thick 

of bryozoan- and brachiopod-rich calcarenite. Although this 

interval is thin, it is recognizable in all USGS cores and 

crops out in the Niagara region. Above the top surface of 

unit E, there is generally a sharp change into barren shales 

that characterize the overlying Burleigh Hill Member. The 

unit E packstone to grainstone interval is as much as 4 ft 

thick at the Niagara Escarpment but is only 1 ft thick in the 

Wheatfield-Grand Island area. 

Contacts: The contact of the Lewiston Member with 

the underlying Irondequoit Limestone is gradational in the 

Niagara region; unit A represents the transition beds. The 

upper contact of the Lewiston Member is drawn at the typically distinct top of the uppermost thick grainstone-packstone bed of unit E. At some localities, this bed is pyrite 

coated and might reflect a minor discontinuity. At a few 

localities, however, the few inches of mudstone above the 

last substantial unit E bed contain one or two thin shell 

pavements that might represent a thin, transitional interval 

from unitE into the overlying Burleigh Hill Member. 

Regional Correlations: Regional stratigraphic correlations and relations for the Lewiston Member are shown in 

figures 15 and 17, respectively. Regional correlations of the 

Lewiston Member have been established by Brett 

(1983a,b ). The Lewiston Member can be recognized from 

at least the Sodus area of central New York westward to the 

Hamilton, Ont., area. Probable correlatives have been identified in the Rochester Shale of Pennsylvania, Maryland, 

and West Virginia (Brett and others, 1990a). The key carbonate interval that marks the top of the Lewiston Member, 

unit E, is apparently correlative with a zone of calcareous 

sandstones and sandy hematitic limestones in the Herkimer 

Sandstone of east-central New York. 

The Lewiston is everywhere underlain by the Irondequoit Limestone and is bounded above by a sharp contact 

between a thin (0.7-4.0 ft) interval of bryozoan- and 

brachiopod-rich wackestone to packstone (unit E), and the 

overlying sparsely fossiliferous Burleigh Hill Member. As a 

result of basal onlap of beds onto the Irondequoit, depositional pinchout, and probable truncation at the top, the 

Lewiston Member generally thins to the northwest. Its maximum thickness ranges from 90 ft in the Sodus-Wolcott 

area; more than 70 ft near Rochester; about 40 ft near 

Albion; 35 ft in northern Niagara County; 20 ft near Stoney 

Creek, Ont.; and about 10 ft or less at Hamilton, Ont. In 

addition to thinning westward, the unit also thins abruptly 

northward; its thickness is about 54ft in the Grand Island-2 

core, 46 ft in the Wheatfield-! core, 40 ft near Niagara 

Falls, and 30 ft at Lewiston. Most of this change is due to 

the northward thinning of the middle, sparsely fossiliferous 

shale intervals (units B-2 and C). 

The lowest interval of the Rochester Shale in the Niagara region, unit A of Brett (1983a), is a 1-2-ft-thick transitional, brachiopod- and pelmatozoan-rich argillaceous 

packstone to calcareous shale. This interval thins to the west 

and is absent west of St. Catharines; to the east, it thickens 

slightly to about 4 ft near Rochester. 

The lower 10-17 ft (unit B) are highly fossiliferous at 

almost all outcrops between Grimsby, Ont., and Rochester, 

N.Y. In the Niagara Peninsula of Ontario, as well as Niagara 

and Orleans Counties in New York, this interval is typified 

by ramose bryozoan colonies; eastward, near Rochester, the 

fauna becomes increasingly dominated by brachiopods. The 

proportion of sparsely fossiliferous shales in unit B 

increases markedly to the south and east of Niagara River 

Gorge; as the upper biostromal beds (informal unit B-3) 

become thinner and sparsely fossiliferous, this interval 
REVISED STRATIGRAPHY AND CORRELATIONS 43 

appears to merge with unit C, which ranges from sparsely 

fossiliferous to nearly barren. It typically contains thin, laminated calcisiltite beds that decrease in number to the south. 

Dramatic regional changes occur in the fossil content 

of units D and E. These units are highly fossiliferous and 

contain thin, bryozoan-rich limestones in sections along the 

Niagara Escarpment from Grimsby, Ont., east to near 

Medina, N.Y., but the fossil content decreases rapidly to the 

south and east. Unit D becomes sparsely fossiliferous and 

contains thick, laminated calcisiltite beds. This interval is 

well developed near the south end of Niagara River Gorge, 

where it contains several thick to massive ledges of dolomitic calcisiltite. These beds, which are apparently confined 

to broad channellike areas, resemble the DeCew Dolomite 

and show similar soft-sediment deformation. Unit E, the 

limestone that caps the Lewiston Member, thins southward 

and eastward from about 3 to 5 ft of bryozoan- and 

crinoid-rich pack- and grainstone to a bed less than 6 in. 

thick composed of compact fossil packstone. In Ontario, 

this interval displays a sharp to erosional base and becomes 

a thin, compact, and commonly heavily mineralized bed of 

crinoidal grainstone resembling the Gasport Dolomite. To 

the east, only a single, thin, crinoid- and brachiopod-rich 

packstone bed persists as a continuous unit to Brockport; 

near Rochester, it is lenticular and locally absent. 

Age: The Lewiston Member is early to middle Wenlockian (Sheinwoodian), on the basis of Paraechmina spinosa Zone ostracodes (Berdan and Zenger, 1965) and 

Kockelella ranuliformis Zone conodonts (Kleffner, 1991). 

Summary of Revisions or Changes: Not revised or otherwise changed herein except for minor refinement of informal subdivisions of the Lewiston Member. These include 

subdivision of unit B into intervals B-1, B-2, and B-3. 

Minor changes are also made in the definition of the upper 

and lower boundaries of unit D. 

BURLEIGH HILL MEMBER 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: The term Burleigh Hill 

Member was introduced by Brett (1983a,b) for the upper 

member of the Rochester Shale in the Niagara region, 

between Grimsby, Ont., and the Monroe County, N.Y., area. 

The Burleigh Hill consists of sparsely fossiliferous, calcareous to dolomitic shale. 

Type Section: Roadcut in Niagara Escarpment (locally 

called Burleigh Hill) along Burleigh Hill Drive, in Thorold, 

Ont. (St. Catharines, 30M/3g, Canadian NTS) (Brett, 

1983b). 

Reference Sections: Many creeks and rivers that cut 

through the Niagara Escarpment, such as the Niagara River 

and the Genesee River, expose at least the upper part of the 

Burleigh Hill Member. The Burleigh Hill is exposed at 

DeCew Falls on Twelve Mile Creek and is exposed in its 

entirety along the cliffs adjacent to the Robert Moses 

Powerplant on the east side of Niagara River Gorge. An 

outcrop on Gasport Road in the town of Gasport, Niagara 

County, N.Y., also exposes the entire member. 

Thickness: The Burleigh Hill Member is about 30 ft 

thick in the north end of the Niagara River Gorge and 

includes transitional dolomitic beds toward its top. It thins 

toward the south, in contrast to the Lewiston Member 

(Brett, 1983b). The Burleigh Hill is 23ft thick in the USGS 

Niagara-1 core, 16.5 ft thick in the USGS Wheatfield-! 

core, and only 10.4 ft thick in the USGS Grand Island-2 

core. 

Lithologic Description: The Burleigh Hill Member 

consists of rather uniform dark- to medium-gray, pale- and 

platy-weathering, highly calcareous to dolomitic mudstone 

(figs. 17, 19). It contains abundant thin interbeds of medium 

gray, pale-buff weathering, laminated calcisiltites (pelletal 

grains tones) that become thicker (2-4 in.) and more closely 

spaced in the upper 5-10 ft of the unit. The Burleigh Hill 

becomes increasingly calcareous to dolomitic upward and 

grades into argillaceous limestone and dolomite near the top 

(Brett, 1983b ). In contrast to the Lewiston Member, the 

Burleigh Hill contains a sparse fossil assemblage of low 

diversity but locally contains scattered Dalmanites and Trimerus trilobites, Coolinia and Resserel/a brachiopods, and 

the bivalve Cornellites (Brett, 1983b). A few thin (1-2 in.) 

coquinites rich in crinoids, ostracodes, and trilobites are 

common in the upper few feet of the Burleigh Hill. A thin 

but persistent marker bed about 15 ft below the contact with 

the DeCew Dolomite at the north end of Niagara River 

Gorge locally contains an abundance of the brachiopod 

Dalejina. This bed has been traced eastward from St. 

Catharines, Ont., to the Sodus, N.Y., area. 

Contacts: The lower contact of the Burleigh Hill Member is typically sharp and is at the top of the last thick 

bryozoan- and brachiopod-rich packstone (or grainstone) of 

unit E of the Lewiston Member. The upper contact with the 

DeCew Dolomite is sharp but probably conformable in outcrops at the north end of the Niagara River Gorge and gradational at most localities along the Niagara Escarpment. In 

contrast, the contact is sharp and erosional in the southern 

Niagara River Gorge near Niagara Falls (see discussion 

below of DeCew Dolomite). Nonetheless, this contact is 

difficult to locate precisely in most of the USGS cores 

because the Burleigh Hill Member and the DeCew Dolomite are similar in grain size, texture, and color. 

Regional Correlations: Regional stratigraphic correlations and relations for the Burleigh Hill Member are shown 

in figures 15 and 17, respectively. The Burleigh Hill Member is traceable westward to near Stoney Creek, Ont., where 

it grades into argillaceous dolomites and dolomitic shales of 

the Stoney Creek Member (introduced by Brett, 1983a,b). 

The Burleigh Hill Member is traceable eastward toward the 
44 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

Brockport, N.Y., area, where the upper part of the member 

is replaced by the Gates Dolomite20. 

Age: The Burleigh Hill contains the boundary between 

the Kockelella ranuliformis and Ozarkodina sagitta conodont Zones (Kleffner, 1991). The unit therefore straddles 

the middle Wenlockian Sheinwoodian-Homerian Stage 

boundary. 

Summary of Revisions or Changes: Not revised or otherwise changed herein. 

DECEW DOLOMITE 

(not revised or otherwise changed herein) 

First Usage of Nomenclature: The term DeCew Limestone was introduced by Williams (1914a,b) for the 

8.5-ft-thick, fine-grained, dark-gray, argillaceous limestone 

overlying the Rochester Shale and underlying the Lockport 

Dolomite at DeCew Falls on Twelve Mile Creek, near St. 

Catharines, Ont. Williams ( 1914a) suggested that the 

DeCew represents reworked Rochester Shale to which lime 

has been added. He considered the DeCew a transitional 

unit between the Rochester Shale and the Lockport but 

thought it was more closely related to the overlying carbonates and included it (Williams, 1919) as the basal bed of his 

Lockport Member of the Niagara Formation in the Niagara 

Peninsula. 

Type Section: DeCew Falls on Twelve Mile Creek, 

western St. Catharines, Ont. (Fonthill, 30M/3c, Canadian 

NTS) (Williams, 1914a). 

Reference Sections: Several excellent sections of 

DeCew Dolomite are exposed along the Niagara River 

Gorge, especially at the south haul road (access to Robert 

Moses Powerplant), at the adjacent Devils Hole State Park, 

and at the abandoned Niagara Falls sewage-treatment plant. 

Other good exposures are at Lockport Junction Road (Route 

429) west of Lockport, N.Y., and at the Burleigh Hill Drive 

roadcut in Thorold, Ont. 

Thickness: Outcrops of the DeCew Dolomite in the 

Niagara region range in thickness from about 8 to 12ft. In 

the Gasport area of Niagara County, however, the DeCew is 

unusually thin and locally absent. In the USGS cores, it 

ranges in thickness from 4.5 to 11.8 ft. The considerable 

variation in thickness of the DeCew in the Niagara Peninsula of Ontario could be partly the result of erosion (Bolton, 

1957). 

Lithologic Description: The DeCew Dolomite consists 

of variably bedded, dark-gray to olive-gray, argillaceous to 

sandy, fine-grained dolomite that locally contains shaly 

partings and interbeds up to a few inches thick (figs. 17, 

19). A middle bed of dolomitic shale up to 3 ft thick is 

20Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 

present in the southern Niagara River Gorge. The DeCew 

weathers to a distinctive light olive gray. Stringers of 

crinoid ossicles are present locally near the base of the unit. 

Zones of intraformational conglomerate and planar to hummocky cross lamination are typical. The most distinctive 

feature of the DeCew is pervasive soft-sediment deformation features (possibly enterolithic ), which include flame 

structures and overturned and isoclinal folds. Contorted 

bedding is seen in nearly all outcrops of the DeCew and is 

visible (although subtle) in the USGS cores. Solution cavities have formed in several outcrops along the Niagara 

River Gorge, particularly at Devils Hole State Park. 

The DeCew Dolomite is barren in many sections 

except for crinoidal stringers and scattered ossicles. Planolites and Chondrites burrows are prominent at some levels. 

Lingulid brachiopods and trilobites have also been observed 

but are rare. 

Contacts: As noted above (see discussion of the Burleigh Hill Member of the Rochester Shale), the base of the 

DeCew Dolomite appears gradational at most outcrops 

along the Niagara Escarpment and is difficult to distinguish 

in all the USGS cores. In contrast, the base of the DeCew is 

sharp at the southern end of the Niagara River Gorge, where 

it shows channellike scours up to 3 ft across and 1-2 ft in 

relief that have been cut into the underlying Rochester 

Shale. The upper contact with the Gasport Dolomite is 

sharp nearly everywhere in the Niagara region (except in 

the USGS Niagara Falls-1 core). In many areas the uppermost bed of the DeCew, which is a few inches thick, is a 

laminated, greenish-gray calcisiltite or dolosiltite. The 

Gasport Dolomite has a sharp and commonly stylolitic contact with this bed and the basal Gasport contains clasts of it. 

Bolton (1957) speculated that the thin, greenish-gray clay 

bands that separate the DeCew from the overlying Gasport 

could be due partly to seepage along this pronounced surface. Whether this surface underwent major erosion is 

uncertain. This unconformity cuts out the DeCew entirely 

near Hamilton, Ont., however, and further truncates the 

upper beds of the Rochester Shale northwest of that area 

(Brett and others, 1991). To the east, a fossiliferous shale 

(Glenmark Member21 of the DeCew [Brett and others, 

1990a]) is juxtaposed between beds equivalent to the basal 

DeCew and to the Gasport. 

Regional Correlations: Regional stratigraphic correlations and relations for the DeCew Dolomite are shown in 

figures 15 and 17, respectively. The DeCew Dolomite is 

distinctive in outcrop and is traceable from near Stoney 

Creek, Ont., eastward at least to the vicinity of Penfield, 

N.Y. It appears to be thin or absent, however, near Gasport 

(Niagara County) and Fancher (Orleans County), N.Y. 

21 Usage of the New York State Geological Survey; nomenclature not 

formally accepted by the U.S. Geological Survey. 
REVISED STRATIGRAPHY AND CORRELATIONS 45 

AUTHOR OR SOURCE 

BOLTON (1957) ZENGER (1965) RICKARD (1975) THIS REPORT 

GUELPH GUELPH 

FORMATION OAK DOLOMITE 

ORCHARD GUELPH 

MEMBER DOLOMITE 

z ERAMOSA 

0 DOLOMITE 

a.. ERAMOSA ~ a.. ::> a.. 0 :2 ::> ::> a: MEMBER a: ERAMOSA 0 ERAMOSA 0 VINEMOUNT ~ z 0 MEMBER a: FORMATION a: Ow 0 u. ~ ~ zl- MEMBER 

w ~ 1- 1- <C1- .....1:2 ....I 

a: :2 a: a: a: ~0 AN CASTER <( a: 0 0 0 ....J 

:2 0 GOAT a.. GOAT a.. GOAT a.. !;;co MEMBER w u. ~ ~ ~ oo ISLAND (.) ISLAND (.) ISLAND co 0 0 (.) ~ ....I 1- MEMBER MEMBER FORMATION 0 NIAGARA FALLS 

<( a: ....I ....I ....I 

0 MEMBER 

a.. 

~ 

(.) PEKIN 

0 f-W MEMBER ....I GASPORT GASPORT GASPORT a: I0:2 

MEMBER MEMBER FORMATION a..o 

(f) .....I 

<Co GOTHIC HILL ~0 MEMBER 

Figure 21. Historical summary of Lockport Group nomenclature in the Niagara region. 

Age: Middle Wenlockian: sagitta Zone conodonts were 

obtained from the DeCew by Rexroad and Rickard (1965); 

included in Ozarkodina sagitta Zone by Kleffner (1991). 

Summary of Revisions or Changes: Not revised or otherwise changed herein. 

LOCKPORT GROUP 

(revised herein) 

As defined herein, the Lockport Group in the Niagara 

region consists of about 160-175 ft of massive- to 

medium-bedded, argillaceous dolomite with minor amounts 

of dolomitic limestone and shale. The outcrop belt of the 

Lockport Group in New York extends from Niagara Falls 

200 mi east to Ilion, where it pinches out (Zenger, 1965). 

Because the carbonates of the Lockport Group are more 

resistant to weathering than the rocks of the Medina and 

Clinton Groups, they form the most prominent part of the 

Niagara Escarpment. Hall (1839) designated the Lockport, 

N.Y., area as the type locality for this group, but the best reference outcrop section is the more recently excavated Niagara Stone Quarry in the town of Niagara, N.Y. No field 

exposures display the entire Lockport Group succession, 

but three of the USGS cores (Grand Island-2, Pendleton-!, 

and Wheatfield-2) include the entire Lockport section. 

The Lockport carbonates have long been collectively 

treated as a formation, beginning with Hall ( 1839) and have 

continued to be considered a formation as recently as 

Zenger ( 1965). A historical summary of nomenclature for 

the Lockport Group is shown in figure 21. A comprehensive 

summary of the nomenclature is presented in Bolton ( 1957) 

and in Zenger (1965). The internal stratigraphy and paleontology of the Lockport Group has been refined and revised 

by many workers, including Hall (1839, 1840, 1843, 1852), 

Vanuxem (1839, 1842), Logan (1863), Arey (1892), Clarke 

and Schuchert (1899), Grabau (1901), Clarke and Ruedemann (1903), Hartnagel (1907), Kindle and Taylor (1913), 

Chadwick (1917), Ulrich and Bassler (1923), Goldring 

(1931), Howell and Sanford (1947), Fisher (1954, 1960), 

Bolton (1957), Zenger (1962, 1965), Crowley (1973), Rickard (1975), and LoDuca and Brett (1991). 

As previously defined in New York, the Lockport 

interval either was assigned no formal group designation 

(Zenger, 1965), or the name Lockport was used for both the 

formation and the group, in violation of the NASC. The 

Lockport is considered a group in Berry and Boucot (1970) 

but divisions such as the Gasport are given only member 

status, leaving open the question of the proper stratigraphic 

rank. The NYSGS considers the Lockport to have group 

status (Fisher, 1960; Rickard, 1975) and to include all units 

between the Clinton and Salina Groups. The Lockport is 

also given group status herein for the following reasons. 

Several subdivisions of the Lockport that were formally 

termed members (for example, Gasport, Goat Island) 
46 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

contain consistently recognizable, widely traceable internal 

units. These internal units would be termed beds under the 

constraints of the NASC. Raising major Lockport units to 

formation status resolves the problem because these smaller 

units can then be termed members. The thicknesses of the 

formations of the Lockport Group are mappable on 

1:24,000-scale quadrangle sheets (except where the Lockport crops out on the nearly vertical Niagara Escarpment). 

Although the term group could be considered inappropriate 

for such a lithologically consistent package as the Lockport, 

its thickness is comparable to those of the Medina and Clinton Groups and of other somewhat uniform carbonate 

sequences (for example, Helderberg Group) in New York 

that have been given group status. 

As defined herein, the base of the Lockport Group is 

sharply marked at the abrupt unconformity at the base of the 

Gasport Dolomite. In most outcrops and USGS cores, this 

contact between the DeCew Dolomite (of the Clinton 

Group) and the massive crinoidal grains tones of the Gothic 

Hill Member of the Gasport Dolomite can be located without ambiguity. This contact is similar to that between the 

Rockway Dolomite and the Irondequoit Limestone but it is 

a more extensive and more regionally eroded angular 

unconformity (Brett and others, 1991). This contact is sharp 

and commonly stylolitic in the Niagara region. To the west, 

this unconformity truncates the DeCew near Hamilton, 

Ont., and the upper beds of the Rochester Shale are cut out 

northwest of that area (Brett and others, 1991 ). 

The upper contact of the Lockport Group is gradational, with an interfingering of lithologies typical of the 

upper part of the Guelph Dolomite with the greenish and 

black shales of the overlying Vernon Shale (lowest unit of 

the Salina Group). This interval, observed in the USGS 

Grand Island-2, Pendleton-I, and Wheatfield-I cores, is 

termed the transition zone, which is herein recognized as 

unit C of the Guelph Dolomite. It is unclear whether these 

transition beds were included by Rickard (1975) (or by 

Zenger, 1965) in the uppermost part of the Lockport Group 

or in the lowermost part of the Salina Group (fig. 22). Inclusion of this transition zone herein adds 22-29 ft to the overall thickness of the Lockport Group. The authors arbitrarily 

place the Lockport-Salina contact, which does not crop out 

anywhere in the study area, at the first thick (greater than 1 

in.) black shale interbed. This bed might not be stratigraphically equivalent in all sections, however. 

As revised herein, the Lockport Group consists of the 

following four formations: the Gasport Dolomite, Goat 

Island Dolomite, Eramosa Dolomite, and Guelph Dolomite. 

The Eramosa Dolomite includes the lower and middle parts 

of the unit previously designated the "Oak Orchard Member"22 by Zenger (1965), and the Guelph Dolomite includes 

the upper part of Zenger's "Oak Orchard Member." The 

name "Oak Orchard" is not used in this report because little 

or none of the interval generally ascribed to the "Oak 

NOMENCLATURE FROM 

RICKARD (1975) 

§) GUELPH 

0 DOLOMITE a: 

<.9 

fa: 

0 

a.. 

~ 

(.) 

0 

...J 

ERAMOSADOLOMITE 

GOAT ISLAND 

DOLOMITEGASPORT 

LIMESTONE~ 

REVISED 

NOMENCLATURE 

GUELPH DOLOMITE- INFORMAL 

UNITSA-C 

(It is not clear whether Rickard (1975) 

included the unit C beds of the Guelph 

in the Lockport Group or in the Salina 

Group.) 

ERAMOSA DOLOMITE- INFORMAL 

UNITS A-F 

VINEMOUNT MEMBER 

ANCASTER MEMBER GOAT ISLAND 

AND DOLOMITE 

NIAGARA FALLS MEMBER 

PEKIN MEMBER 

GOTHIC HILL MEMBER 

GASPORT 

DOLOMITE 

EXPLANATION 

a.. 

::I 

0 

0:: 

<.9 

fa: 

0 

a.. 

~ 

(.) 

0 

...J 

'331 Average unit thickness, in feet, based on data from nine U.S. Geological 

~ Survey cores, two Canadian core!i and several outcrops 

* The maximum thickness of the Vernon Shale observed in the U.S. 

Geological Survey cores is 54 feet. In areas where the section is more 

complete (farther to the south in Ontario and western New York), the 

thickness of the Vernon ranges from about 150 to 400 feet (Rickard 1969) , E9 Dolomite ~ Limestone f~~ Shale 

Figure 22. Stratigraphic nomenclature from Rickard (1975) and 

revised nomenclature for the Lockport Group in the Niagara 

region. Formation contacts and lithologic shading of units are 

based on the revised nomenclature. 

Orchard Member" (Zenger, 1965) is present at the type 

locality along Oak Orchard Creek in Orleans County, N.Y. 

In addition, the term "Oak Orchard" overlaps in usage with 

the Canadian terms Eramosa and Guelph. 

Stratigraphic contacts have been revised for the 

Gasport Dolomite, Goat Island Dolomite, Eramosa Dolomite, and Guelph Dolomite. The Gasport Dolomite consists 

of two newly proposed members-a lower grainstone unit 

termed the Gothic Hill Member and an upper, argillaceous, 

fine-grained carbonate termed the Pekin Member (fig. 4 ). 

The Goat Island Dolomite contains three newly proposed 

members: a lower biohermal grainstone unit termed the 

Niagara Falls Member (with two informal units); a middle, 

cherty, fine-grained dolomite termed the Ancaster Member 

22Recognized as "Oak Orchard Dolomite" by the New York State 

Geological Survey; this nomenclature is not formally accepted by the U.S. 

Geological Survey. 
REVISED STRATIGRAPHY AND CORRELATIONS 47 

WEST ~ E' 

e ~ 0 0 riJ Q) Q) u .!II: 

Q) ~ El c _r~~ M Q) 't: 0 .s 

co ... ..9l ~ " u CJ)= ~~ ! '=$ i 12 12 :c ·a Q) 

c.:; ;§ u ~ ~ c ~ 0 0 s Ol ~~ uo:: <i) ci5 ~ ... Q) 

CJ) zo.. 

12 3 4 5 6 7 8 

Ill ~I 

ERAMOSA[ &~ DOLOMITE 

Member , ~ .,....._ "'""--.. .--., - - -- .--., --... ....... .,....._ ~ ,, GOAT 

ISLAND 

DOLOMITE 

. ~~. 

GASPORT 

DOLOMITEL,W 

Niagara 

Falls 

Member 

t: 

0 

c. 

.!II: 

(,) 

.s 

9 

t: 

0 

c. 

~ 

riJ ~ ~ " 10 11 

~ ~1 Ancaster 

Member 

Gothic Hill 

Member 

... 

~ c 

0 ~ "8 c 

Q) 

d "t:: 

~ 12 13 

Pekin _ 

·Member-

... 

~ :s! Q) 

..c .:! (,) c ~ ~ 

14 15 

EAST 

~J·ERAMOSA ~~ DOLOMITE 

·-

PENFIELD 

FORMATIOr'-' 

NOT TO SCALE 

~ 

EXPLANATION 

~ SHALE ~ ARGnLACEOUSDOLOMITE - -

20 ~BIOHERM Ill ARGnLACEOUS LIMESTONE 

m LIMESTONE Ill BIOTURBATED LIMESTONE ~ 

42°30' 

LOCATION MAP ~ DOLOMITE • ARENACEOUS DOLOMITE 

Figure 23. Diagrammatic stratigraphic relations in the Lockport Group, with regional correlations between Clappison's Comers, Ont., and 

Penfield, N.Y. Reference datum is the contact between the Gasport Dolomite and the Goat Island Dolomite. 

(name used informally in Ontario); and an upper, argillaceous, fine-grained dolomite and shale unit termed the 

Vinemount (name used informally in Ontario) Member (fig. 

4 ). The Vinemount Member was formerly miscorrelated 

with the Eramosa Member as defined by Zenger (1965). 

The Eramosa and Guelph Dolomites are not formally subdivided although several informal units are recognized herein 

within each formation. The relation between stratigraphic 

nomenclature from Rickard ( 197 5) and the revised nomenclature for the Lockport Group is shown in figure 22. 

These revised stratigraphic units are described in the 

following sections. A stratigraphic correlation chart for the 

Lockport Group is shown in figure 15. A geologic section 

for the Lockport Group, with regional correlations between 

Clappison's Comers, Ont., and Penfield (Wayne County), 

N.Y., is shown in figure 23. A descriptive stratigraphic column for the Lockport Group is shown in figure 24. 

Natural-gamma logs and stratigraphic correlations for units 

within the Lockport Group are presented in figures 12 and 

20. 

Summary of Revisions: Lockport Group as used herein 

refers to the stratigraphic interval identified as Lockport 

Group on Rickard's (1975) correlation chart (fig. 22) in that 

it also encompasses all units between the Clinton and Salina 

Groups. It is unclear, however, whether the transition beds 

that are herein recognized as unit C of the Guelph were 

included by Rickard (1975) (or by Zenger, 1965) in the 

uppermost part of the Lockport Group or in the lowermost 

part of the Salina Group. The authors arbitrarily place the 

Lockport-Salina contact, which does not crop out anywhere 

in the study area, at the first thick (greater than 1 in.) black 

shale interbed. The contact between the DeCew Dolomite 

and the Gothic Hill Member of the Gasport Dolomite is designated herein as the basal contact of the Lockport Group. 

Stratigraphic contacts have been revised for the Gasport 

Dolomite, Goat Island Dolomite, Eramosa Dolomite, and 

Guelph Dolomite. These major subdivisions of the Lockport Group were previously referred to as members of the 

Lockport Formation by Zenger ( 1965) but are treated herein 
48 

w 

1-

~ 

0 

__J 

0 

0 

I 

a_ 

__J 

w 

:::J 

C) 

w 

1-

~ 

0 

__J 

0 

0 

<( 

U) 

0 

~ 

<( 

a: 

w 

REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

w 

z 

0 

N 

I 

~ 0 

a: 

<.9 

lL 

w 

w 

a: 

(/) 

lL 

w 

w 

a: 

Laminated, fine grained, generally oolitic dolomite. 

Transitional beds contain partings of dark 

greenish-gray to nearly black shale. Shale and 

dolomite facies are petroliferous 

Biostromal, bituminous, medium- to massivebedded dolomite. Some vuggy and chert-rich 

horizons. Intervals of digitate stromatolites that 

locally form small biostromes or bioherms 

Medium- to thin-bedded, argillaceous dolomite 

with thin shale partings. Some chert 

Thin- to medium-bedded, fine-grained dolomite. 

Typically contains abundant chert nodules 

Sucrosic, medium-grained, thick- to massivebedded, commonly porous and vuggy dolomite 

Three facies:"A" is bioturbated dolomudstone; 

"B" contains bioherms; "C" consists of biohermal 

flank debris 

Thick- to massive-bedded, dolomitic crinoidal 

grainstone and crinoidal dolomite. Laminations 

and cross-bedding are common 

~ 

Ill 

D 

CJ . 

. 

. 

CJ 

~ 

~ 

EXPLANATION 

CLADOPORID CORALS 

FAVOSITID CORALS 

STROMATOLITES 

TABULAR THIN WACKETO PACKSTONE 

BIOHERMAL BRYOZOAN 

WACKESTONE 

COARSE CRINOIDAL 

GRAINSTONE 

TROUGH CROSS-BEDDED 

GRAINSTONE 

BIOTURBATED, MUDDY 

MICRITIC DOLOMITE 

STROMATOPOROIDS 

INTRACLASTS 

CHERTY, FINE-GRAINED 

DOLO MICRITE 

Figure 24. Descriptive stratigraphic column for the Lockport Group. Composite section for Niagara County is shown. (Modified from 

Brett and others, 1991, fig. 15.) 
REVISED STRATIGRAPHY AND CORRELATIONS 49 

as formations within the Lockport Group, in accordance 

with the usage of Rickard (1975). 

The Gasport Dolomite is divided into two new members, the Gothic Hill Member and the overlying Pekin 

Member. The term Goat Island Dolomite is retained but the 

Goat Island is herein split into three new members: the Niagara Falls Member, the Ancaster Member (also revised and 

extended geographically), and the Vinemount Member (also 

revised and extended geographically). The latter unit was 

previously miscorrelated with the Eramosa Member of 

Zenger (1965). The Eramosa Dolomite as defined herein 

includes parts of the unit termed the "Oak Orchard Member" by Zenger (1965). The term "Oak Orchard" is not used 

in Rickard's (1975) correlation chart for western New York; 

Guelph is used instead. The authors are in agreement with 

this usage; the name "Oak Orchard" is not used in the 

present work because little or none of the interval pre viously assigned to the Oak Orchard Member (Zenger, 1965) 

is present at the type locality along Oak Orchard Creek in 

Orleans County, N.Y. The Guelph Dolomite as defined 

herein is the uppermost formation of the Lockport Group 

and includes strata previously considered as the upper part 

of the Oak Orchard Member of Zenger ( 1965). 

GASPORT DOLOMITE 

(revised herein) 

Brief History of Nomenclature: The Gasport Limestone 

Member of the Lockport Dolomite was named by Kindle 

and Taylor (1913) for exposures near Gasport, Niagara 

County, N.Y. This interval had previously been referred to 

as the Encrinital Limestone by Hall (1843) and as the 

Crinoidal Limestone by Grabau (1901). Howell and Sanford ( 194 7) regarded the DeCew Waterlime Member rather 

than the Gasport as the basal member of the Lockport Formation. Fisher ( 1960) stated that the Gasport is the basal 

formation in the Lockport Group and that it underlies the 

Goat Island Limestone and overlies the DeCew Dolomite. 

Zenger (1965) referred to the Gasport Member of the Lockport Formation. The Gasport is given formation-level status 

in Rickard's (1975) correlation chart (fig. 21), although he 

refers to it with two lithologic modifiers, as the Gasport 

limestone and dolomite. The Gasport is herein referred to as 

the Gasport Dolomite. The formal revisions to the Gasport 

Dolomite ma9e herein have been informally introduced by 

the authors (Brett and others, 1990a,b, 1991; Tepper and 

others, 1990; and LoDuca and Brett, 1991). 

Type Locality: Unspecified exposures near Gasport, 

Niagara County, N.Y. (Kindle and Taylor, 1913) (Gasport 

quadrangle). 

Reference Sections: Many sections along the Niagara 

River Gorge; Niagara Stone Quarry, town of Niagara, N.Y.; 

Route 429 roadcut in Pekin, N.Y.; roadcut on Townline 

Road at the Lockport-Cambria, N.Y., town line; Frontier 

Stone Quarry, Lockport, N.Y.; and Frontier Stone Quarry, 

immediately south of Route 31, village of Gasport, town of 

Royalton, Niagara County, N.Y. (Gasport quadrangle). 

Thickness: The Gasport Dolomite ranges in thickness 

from a minimum of 19.5 ft in the USGS Lewiston-I core to 

a maximum of 37.2 ft in the USGS Wheatfield-2 core, 

where much of the unit consists of dark-gray, argillaceous 

dolomite and shale. The average thickness of the unit in the 

USGS cores is 33.8 ft. Local biohermal buildups cause the 

thickness of this unit to vary considerably. Both members of 

the Gasport typically decrease in thickness to the west along 

the Niagara Escarpment (Brett and others, 1991). 

Lithologic Description: The Gasport Dolomite consists 

of two members named herein: the Gothic Hill Member, a 

light pinkish-gray, crinoidal- and brachiopod-rich dolograinstone to dolopackstone; and the Pekin Member, a dark 

olive-gray, argillaceous, fine- to medium-grained dolomicrite that grades laterally into bioherms and flanking 

dolorudites (figs. 23, 24 ). These members of the Gasport are 

described in detail below. The occurrence of patch reefs in 

the Gasport is discussed in detail by Crowley (1973) and in 

Crowley and Poore (1974). 

Contacts: As noted above, the basal contact of the 

Gothic Hill Member with the underlying DeCew Dolomite 

is generally sharp and locally erosional. At many localities 

along the outcrop belt between Brockport, N.Y., and Hamilton, Ont., the contact is sharp and commonly stylolitic, and 

the lowest foot of the Gothic Hill Member contains rip-up 

clasts of DeCew Dolomite. At sections from Brockport 

eastward, however, the contact is typically gradational and 

contains fine-grained sandy dolomite of the DeCew interbedded with crinoidal sandy dolomite of the lower part of 

the Gothic Hill. 

The contact of the Gasport with the overlying Goat 

Island Dolomite is also typically sharp, stylolitic, and p!'obably erosional in many sections. At some localities, the 

pale-buff grainstones of the lower part of the Goat Island 

rest abruptly on dark-gray, tabular to biostromal beds of the 

upper part of the Pekin Member. The Wenlockian-Ludlovian boundary is placed at or slightly above the Gasport -Goat 

Island contact by LoDuca and Brett (1991). 

Regional Correlations: The Gasport caps the Niagara 

Escarpment in western New York. It can be traced as a distinct unit for 110 mi along the escarpment from just west of 

Hamilton, Ont., to Brockport, N.Y. (figs. 15, 23) (Crowley, 

1973). The Gasport Dolomite is recognizable westward to 

near Dundas, Ont. With the truncation of the Rochester 

Shale beneath the sub-Gasport unconformity at Waterdown, 

Ont., the massive crinoidal dolomite of the Gasport directly 

overlies the lithologically similar Irondequoit Limestone. 

The unconformity between these units is typically obscure 

and they are not differentiated northwest of this area. The 

term Amabel Formation is used in Ontario for the resulting 

massive dolograinstone unit. The beds equivalent to the 

Gasport on the Bruce Peninsula have been identified as 
50 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

belonging to the Wiarton Member of the Amabel (Bolton, 

1957). 

From Hamilton, Ont., eastward to near Clarendon, 

N.Y., the lower part of the Gasport (Gothic Hill Member) is 

traceable as a distinct crinoidal grainstone. The upper part 

of the Gasport (Pekin Member) is a distinctly more argillaceous, dark-gray, thinly bedded dolomite that is thin to 

absent near Hamilton, Ont. Near Stoney Creek, virtually the 

entire Gasport is missing; its absence could be attributed to 

erosion prior to deposition of the Goat Island Dolomite. 

Age: The Gasport Dolomite is of latest Wenlockian 

age, as indicated by the presence of Ozarkodina sagitta 

Zone conodonts (Rexroad and Rickard, 1965; LaDuca and 

Brett, 1991 ). 

Summary of Revisions: The Gasport Dolomite is herein 

divided into two new members, the Gothic Hill Member 

and the overlying Pekin Member. The Gasport as defined 

herein includes the "crinoidal," "small bioherms," and 

"dark, bedded" facies of Zenger (1965), and the "crinoidbar," "reef," and "interreef' facies identified by Crowley 

(1973). The upper contact of the Gasport Dolomite is 

revised herein. The "stromatoporoid-cap" facies of Crowley 

is considered herein as part of the Niagara Falls Member of 

the Goat Island rather than as part of the Gasport because it 

is separated from the Gasport by a minor unconformity at 

many localities. 

GOTHIC HILL MEMBER 

(new unit, proposed herein) 

Background: The term Gothic Hill was first informally 

introduced by the authors (Brett and others, 1990a,b, 1991~ 

Tepper and others, 1990; LaDuca and Brett, 1991). It is formally proposed as a new unit herein. Zenger (1965) informally recognized this unit as the "crinoidal" facies and 

classified it as a calcirudite or dolorudite because it contained abundant, coarse-grained crinoid and brachiopod 

fragments. This unit also corresponds to the "crinoidal-bar" 

facies of Crowley (1973), who states that it is the most 

widespread facies of the Gasport between Hamilton, Ont., 

and Brockport, N.Y. 

Type Locality: Roadcut along the northeast-facing Niagara Escarpment on Gothic Hill Road, about 0.1 mi south of 

the intersection of Lower Mountain Road and Gothic Hill 

Road, about 2 mi west of the city of Lockport, Niagara 

County, N.Y. (Lockport quadrangle). 

Reference Sections: Excellent reference sections are 

exposed in the Niagara Stone Quarry, Niagara; the Niagara 

River Gorge; the Frontier Stone quarries at Lockport and 

Gasport; and the roadcut on Townline Road at the 

Lockport-Cambria, N.Y., town line. 

Thickness: The Gothic Hill Member ranges in thickness from 3 ft in the USGS Lewiston-I core to over 21 ft at 

the Lockport Junction roadcut; its average thickness is 

about 15 ft. The thickness of this unit varies considerably 

depending on local biohermal buildups. 

Lithologic Description: The Gothic Hill Member, 

which is similar to the Irondequoit Limestone in terms of 

lithology and fauna, consists of thick- to massive-bedded, 

dark olive-gray to light-pink, dolomitic limestone (primarily crinoidal grainstone and crinoidal dolomite) and weathers to a light olive-gray (figs. 23, 24). Laminations and 

cross bedding are common within the unit; trough crossstratification and possible bimodal ("herringbone") crossstratification are particularly well developed at the northern 

end of the Niagara River Gorge. The Gothic Hill Member 

corresponds to the "crinoidal-bar" facies of Crowley 

(1973). Near St. Catharines, Ont., and Lockport, N.Y., the 

Gothic Hill Member contains small bioherms composed of 

crinkly weathering, pale-gray to greenish-gray micrite with 

abundant crustose fistuliporoid and ramose bryozoans; 

alveolitid, favositid, and colonial rugosan corals~ and pelmatozoan holdfasts (Zenger, 1965~ Crowley, 1973; Brett, 

1985). 

The Gothic Hill Member can be subdivided into three 

parts: (1) a basal crinoidal- and brachiopod-rich grainstone 

that typically contains dolomicrite clasts, especially near the 

bottom of the unit; (2) a middle zone, generally 1-2 ft thick, 

of thinner bedded, more argillaceous, and darker gray dolomite that locally contains small bioherms; and (3) an upper, 

coarse grainstone unit that typically forms about one-third 

of the total thickness of the Gothic Hill. Large bioherms that 

extend upward into the overlying Pekin Member commonly 

originate near the top of the upper grainstone unit. 

Contacts: The lower contact between the massive 

crinoidal grainstones of the Gothic Hill Member and the 

DeCew Dolomite is sharp, commonly stylolitic, and erosional nearly everywhere in the Niagara region. In most outcrops and in the USGS cores, this contact can be located 

without ambiguity. It is similar to the contact between the 

Rockway Dolomite and the Irondequoit Limestone but is 

more extensive and more regionally eroded (Brett and others, 1991). In many areas, the uppermost bed of the DeCew 

is a few inches thick and is a laminated, greenish-stained 

calcisiltite or dolosiltite. The Gothic Hill has a sharp and 

commonly stylolitic contact with this bed and contains 

clasts of it. Bolton (1957) noted thin, greenish-gray clay 

bands that he speculated could be due partly to seepage 

along the pronounced surface that separates the DeCew 

from the overlying Gasport. Whether this surface underwent major erosion is uncertain. To the west, however, this 

unconformity cuts out the DeCew entirely near Hamilton, 

Ont., and further truncates the upper beds of the Rochester 

Shale northwest of that area (Brett and others, 1991 ). To the 

east, a fossiliferous shale (Glenmark Member of the 

DeCew~ Brett and others, 1990a) is juxtaposed between 

beds equivalent to the basal DeCew and to the Gasport. The 

upper contact of the Gothic Hill Member with the Pekin 

Member is conformable but relatively sharp, although it can 
REVISED STRATIGRAPHY AND CORRELATIONS 51 

be gradational over several inches. Pronounced changes in 

color, grain size, and bedding style are typical from the 

pinkish, coarse-grained, thick- to massive-bedded Gothic 

Hill Member to the dark-gray or black, fine-grained, thin- to 

medium-bedded Pekin Member. 

Regional Correlations: According to Crowley (1973), 

the Gothic Hill Member is laterally continuous with, and 

lithologically similar to, the crinoid-rich Wiarton Member 

of the Amabel Formation west of Hamilton, Ont. The typical facies of the Gothic Hill Member is recognized from 

Hamilton, Ont., eastward to McCargo Lake, near Fancher, 

N.Y. (figs. 15, 23). The unit generally thins to the northwest 

near Hamilton and, at East Stoney Creek roadcut, it is 

nearly absent as a result of truncation beneath the Goat 

Island Dolomite. At most localities, the Gothic Hill is 

readily recognizable as a pinkish-gray, massive crinoidal 

grainstone, although in a few outcrops near St. Catharines 

and in the USGS Lewiston-I core, the interval consists of 

finer-grained dolopackstone or wackestone with interbedded shales, which could represent infilling of local minor 

depressions or intershoal areas. To the east, in eastern 

Orleans County, N.Y., a relatively abrupt change occurs in 

the 2.5 mi between McCargo Lake and the Genesee-LeRoy 

Stone Quarry at Clarendon. At McCargo Lake, the Gothic 

Hill Member is represented by about 10 ft of coarse, 

stromatoporoid- and coral-bearing dolopackstones and 

grainstones. In contrast, this interval at the Genesee-LeRoy 

Stone Quarry is represented by about 12 ft of interbedded 

laminated and bioturbated crinoidal dolowackestone resembling the DeCew Dolomite, and by thin beds of crinoidal 

grainstones. In eastern Monroe County, this facies grades 

into the laminated sandy dolomites and dolomitic sandstones of the lower part of the Penfield Member23 of the 

Lockport Formation (Zenger, 1965). To the south, as indicated in the USGS Grand Island-2 core, the grainstones 

are thin and grade into interbedded packstones and 

wackestones. 

Age: Late Wenlockian; Ozarkodina sagitta conodont 

Zone (Rexroad and Rickard, 1965; LoDuca and Brett, 1991; 

Kleffner, 1991 ). 

Summary of Revision or Change: The Gothic Hill 

Member is a new unit, proposed herein. It is the lowermost 

member of the Gasport Dolomite and is underlain by the 

DeCew Dolomite and overlain by the Pekin Member of the 

Gasport. 

23Rickard (1975) considers the Penfield to be a formation-level unit 

although he refers to it as the Penfield sandstone and dolomite. Because the 

lithology of this unit is mixed, the authors will herein refer to it as the Penfield Formation. This nomenclature is not formally accepted by the U.S. 

Geological Survey. 

PEKIN MEMBER 

(new unit, proposed herein) 

Background: The term Pekin Member was first informally introduced by the authors (Brett and others, 1990a,b, 

1991; Tepper and others, 1990; LoDuca and Brett, 1991 ). It 

is formally proposed as a new unit herein. The Pekin Member includes both the "small bioherms" facies and the "dark, 

bedded" facies informally recognized by Zenger (1965). 

The "dark, bedded'' facies grade laterally into the "small 

biohenns'' facies (Zenger, 1965). Between the margins of 

some bioherms and the "dark, bedded" facies, Zenger 

(1965) observed dark dolomitic layers that contain a profusion of coral and stromatoporoid fragments, which represent flanking debris. These dark beds south of Gasport were 

referred to as the "Gasport shaly channel" by Ruedemann 

(1925). The "small bioherms" and "dark, bedded'' facies of 

Zenger were referred to as the "reef' and "interreef facies" 

respectively, by Crowley (1973). 

Type Section: Roadcuts on Route 429 at the overpass 

of Upper Mountain Road, village of Pekin, Niagara County, 

N.Y. (Ransomville quadrangle). This exposure was 

described in detail by Crowley and Poore (1974). 

Reference Sections: Excellent reference sections are 

exposed in the Niagara Stone Quarry in Niagara, N.Y.; the 

southern Niagara River Gorge; and the Frontier Stone quarries at Lockport and Gasport, N.Y. 

Thickness: The Pekin Member, like the underlying 

Gothic Hill Member, is highly variable in thickness, partly 

as a result of local biohermal buildups. The interval attains a 

maximum thickness of about 33ft in the USGS Lewiston-2 

core but thins considerably northward. The Pekin averages 

about 23 ft in thickness in the USGS cores. 

Lithologic Description: The reef-bearing Pekin 

Member is an argillaceous, dark-gray, fine-grained, thinto medium-bedded dolomicrite (figs. 23, 24). Bioherms 

locally extend from the top of the grainstones of the Gothic 

Hill up into the Pekin or from the Pekin itself up into the 

overlying Goat Island. The Pekin Member consists of three 

distinct facies assemblages. Facies assemblage A, which is 

predominant, consists of nonreefal deposits that accumulated east and west of a region containing many bioherms 

(fig. 23). To the west, facies assemblage A is a medium- to 

dark-gray, thin- to medium-bedded and slightly nodular, 

bioturbated dolomudstone to slightly fossiliferous dolowackestone with scattered crinoid ossicles and small rugose 

corals (Enterolasma). To the east, facies assemblage A consists primarily of argillaceous to arenaceous dolomite. 

Facies assemblage B consists of coral-stromatoporoid 

framestones forming bioherms up to 20ft high. The dominant facies consist of pale-buff to greenish-gray, crinklyweathering micrite with abundant tabulates (Favosites, 

Heliolites, Halysites), colonial rugosans (Diplophyllum), 

and stromatoporoid heads. Facies assemblage Cis a darkgray, coarse, rubbly dolorudite composed of fragments of 
52 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

corals and stromatoporoids in a dark micritic matrix and 

represents biohermal flank debris. Facies assemblage C 

contains small-scale, localized halos of abraded reefal material. The dolorudite facies typically extend only a few yards 

laterally from the bioherms. 

Contacts: The lower contact of the Pekin Member with 

the Gothic Hill Member can be gradational over several 

inches. Although the upper contact with the Niagara Falls 

Member of the Goat Island locally appears gradational, it is 

sharp to gently undulatory in the northern and western parts 

of the study area. Even in the USGS cores in which the contact is obscure, clusters of celestite crystals in vugs at the 

top of the Pekin Member suggest possible early diagenetic 

alteration of this contact. In some areas, the Pekin is truncated beneath the undulatory base of the Niagara Falls 

Member. At the type locality in Pekin, N.Y., for example, 

the upper contact with the Goat Island is highly irregular, 

with as much as 10 ft of relief. This contact appears channelized, and the Pekin Member is completely truncated in 

parts of the outcrop (Brett and others, 1990b ). 

Regional Correlations: The Pekin Member is recognized from the Niagara River Gorge eastward to Brockport, 

N.Y. (figs. 15, 23). In southern Niagara County, as at Lockport, Gasport (in most places), and eastward at least as far 

as Oak Orchard Creek, the Pekin Member is well developed 

and ranges from 15 to more than 30ft thick. East of Brockport, the Pekin Member grades into the laminated sandy 

dolomites and dolomitic sandstones of the Penfield Formation. West of the Niagara River Gorge, the Pekin Member is 

partly to completely truncated by an erosional surface 

beneath the Goat Island Dolomite. At the Highway 403 

roadcut near Hamilton, Ont., and at the Highway 20 roadcut 

in Stoney Creek, Ont., only a thin remnant of the Pekin 

crops out, which consists of a few inches of shale and 

argillaceous dolomite. Small (3-5-ft diameter, 1-2-ft high) 

bioherms with corals and bryozoans protrude upward into 

this unit. East of Stoney Creek, Ont., the Pekin is apparently 

missing, as is most of the Gasport, but the Pekin reappears 

as a thin interval in the Vinemount Quarry. 

About 10ft of dark-gray argillaceous dolomite apparently representing the Pekin Member overlies grainstones 

of the Gothic Hill in drill cores from Smithville, Ont., 

southeast of Grimsby, but the Pekin appears to be absent in 

sections from St. Catharines eastward to the northern end of 

the Niagara River Gorge. Along the south haul road immediately south of the Robert Moses Powerplant in Lewiston, 

N.Y., about 7 ft of typically argillaceous dolomite of the 

Pekin Member underlies the undulatory base of the Niagara 

Falls Member of the Goat Island Dolomite. In cliffs just 

north of the powerplant and less than 1 mi north of the outcrop on the south haul road, however, the Pekin is absent, 

and the basal vuggy bed of the Goat Island, again with a distinctly undulatory basal contact, rests directly on grainstone 

of the Gothic Hill. Similarly, in parts of the type-section 

roadcut at Pekin Hill on Route 429 in Pekin, N.Y., the Pekin 

ranges up to 15ft thick, but at the southern end of this roadcut, it appears to be completely truncated beneath biohermal 

beds of the Niagara Falls Member of the Goat Island Dolomite. A similar undulatory contact between the Pekin Member and the Niagara Falls Member is observed at the 

Frontier Stone Quarry in Gasport. 

Age: The Pekin Member is late Wenlockian (Homerian) because it is within the Ozarkodina sagitta conodont 

Zone (Rexroad and Rickard, 1965; LoDuca and Brett, 1991; 

Kleffner, 1991). 

Summary of Revision or Change: The Pekin Member is 

a new unit, proposed herein, as the upper member of the 

Gasport Dolomite. It is underlain by the Gothic Hill Member and is overlain by the Goat Island Dolomite. 

GOAT ISLAND DOLOMITE 

(revised herein) 

Brief History of Nomenclature: The Goat Island Dolomite was originally named the Suspension Bridge Dolomite 

Member of the Lockport Dolomite by Cumings (1939), who 

defined it as the middle member of the Lockport, overlying 

the Gasport Dolomite Member and underlying the Eramosa 

Dolomite Member. Because the name Suspension Bridge 

was preoccupied (used for a Lower Ordovician formation in 

New Brunswick), the term was replaced by Goat Island 

Member of the Lockport Formation by Howell and Sanford 

(1947). This unit is named for Goat Island, the small island 

on the brink of Niagara Falls. Bolton ( 1957) retained the 

term Goat Island Member of the Lockport Formation in 

southern Ontario (fig. 21). The same unit was referred to as 

the Goat Island Member of the Lockport Formation by 

Zenger (1965) but is considered a formation-level unit by 

Rickard (1975) (fig. 21). The interval identified herein as 

the Goat Island Dolomite corresponds to Rickard's (1975) 

Goat Island and Eramosa intervals (fig. 22). The formal 

stratigraphic revisions of the Goat Island Dolomite made 

herein have previously been informally introduced by the 

authors (Brett and others, 1990a,b, 1991; Tepper and others, 

1990; LoDuca and Brett, 1991 ). 

Type Locality: Cliffs on the north escarpment of Goat 

Island, slightly below the level of the brink of Niagara Falls 

and between the American and Horseshoe Falls (Niagara 

Falls quadrangle) (Howell and Sanford, 1947). This type 

section is poor because it is largely inaccessible. 

Reference Sections: Access road for the Sir Adam 

Beck Powerplant at Queenston, Ont.; south haul road for 

the Robert Moses Powerplant, Lewiston, N.Y. (designated 

as the primary reference section by Zenger, 1965); Niagara 

Stone Quarry, Niagara, N.Y.; Frontier Stone Quarry, Lockport, N.Y. 

Thickness: The Goat Island Dolomite has a minimum 

thickness of 26 ft in the USGS Lewiston-2 core and reaches 
REVISED STRATIGRAPHY AND CORRELATIONS 53 

a maximum thickness of 55.9 ft in the USGS Wheatfield-2 

core. It averages about 42 ft in thickness in the nine USGS 

cores. 

Lithologic Description: The lithology of the Goat 

Island Dolomite is highly variable (figs. 23, 24), but in general, the unit is finer grained and thinner bedded than the 

Gothic Hill Member of the Gasport Dolomite. The Goat 

Island Dolomite is divided into three distinct members that 

are discussed in the next sections: (1) the Niagara Falls 

Member, a gray to buff, biohermal grainstone; (2) the 

Ancaster Member24, a buff, thin-bedded, fine-grained, 

chert-rich dolomite; and (3) the Vinemount25 Member, a 

light to dark gray, thin-bedded, shaly dolomite with some 

chert. 

Contacts: The Niagara Falls Member of the Goat 

Island Dolomite is underlain by the Pekin Member of the 

Gasport Dolomite. The Pekin is locally truncated beneath 

the undulatory base of the Niagara Falls Member. The upper 

contact of the Vinemount Member of the Goat Island with 

the Eramosa Dolomite is typically sharp, although 

fine-grained, argillaceous dolomite resembling the Vinemount lithology is locally present as thin beds in the Eramosa Dolomite. 

Regional Correlations: The Goat Island Dolomite has 

been traced from outcrops northwest of Hamilton, Ont., to 

Brockport, N.Y. (figs. 15, 23). East of Brockport, the Goat 

Island appears to be represented by a medium- to thick-bedded interval of relatively fine-grained, sandy dolomite in the 

upper part of the Penfield Formation. 

Age: The Goat Island Dolomite is probably of latest 

Wenlockian to earliest Ludlovian age (LoDuca and Brett, 

1991); see "Age" discussion in next section. The Goat 

Island spans the uppermost part of the Ozarkodina sagitta 

Zone, and the Ozarkodina crassa and Ancoradella ploeckensis conodont Zones. 

Summary of Revision: The interval identified herein as 

the Goat Island Dolomite corresponds to Rickard's (1975) 

Goat Island and Eramosa intervals. The term Goat Island is 

retained but the upper and lower contacts have been revised. 

The Goat Island is herein split into three new members, 

which are discussed in the following sections: (1) the Niagara Falls Member; (2) the Ancaster Member (also revised 

and extended geographically); and (3) the Vinemount Member (also revised and extended geographically). 

24Name used in Ontario and not previously formally used in New 

York; named formally herein. 25Name used informally in Ontario and not previously formally used 

in New York; named formally herein. 

NIAGARA FALLS MEMBER 

(new unit, proposed herein) 

Background: The term Niagara Falls Member was first 

informally introduced by the authors (Brett and others, 

1990a,b, 1991; Tepper and others, 1990; LoDuca and Brett, 

1991) and is formally proposed as a new unit herein. This 

unit includes the "stromatoporoid-cap" facies of Crowley 

(1973) that he considered to be part of the Gasport although 

Zenger (1965) assigned it to part of the Goat Island. 

Type Section: Outcrop at old sewage-pumping station 

on the east wall of Niagara River Gorge, west of the intersection of Ashland Avenue and the Robert Moses Parkway, 

city of Niagara Falls, N.Y. (Niagara Falls quadrangle). 

Reference Sections: Niagara River Gorge at various 

locations, including Goat Island slightly below the caprock 

of Niagara Falls; Niagara Stone Quarry in Niagara, N.Y.; 

Frontier Stone quarries at Lockport and Gasport, N.Y. 

Thickness: The thickness of the Niagara Falls Member 

ranges from less than 3 ft at the north end of the Niagara 

River Gorge to more than 15 ft at the Frontier Stone Quarry 

in Lockport, N.Y. 

Lithologic Description: In the Niagara River Gorge, 

the Niagara Falls Member is a prominent light-olive to 

brownish-gray, sucrosic, medium-grained, thick- to massive-bedded, commonly porous and vuggy dolomite (figs. 

23, 24). The vugs commonly are filled with sphalerite, gypsum, calcite, and dolomite crystals. Some of these mineralfilled vugs are found in coral and stromatoporoid heads 

(Brett and Calkin, 1987). The Niagara Falls Member weathers to very light gray (whitish) and is a conspicuous unit 

near the top of Niagara River Gorge. In the Niagara region, 

the Niagara Falls Member is similar to the Gothic Hill 

Member of the Gasport because it locally consists of very 

coarse, pinkish-gray, crinoidal grainstone with bioherms 

containing stromatoporoids and favositid and cladoporid 

corals (Tepper and others, 1990). The small patch reefs of 

the Niagara Falls Member grade laterally into extensive 

nonreef areas, where the contact between the Niagara Falls 

Member and the underlying Pekin is typically obscure (Tepper and others, 1990). From the type locality eastward to 

Brockport, the Niagara Falls Member typically is biostromal and is characterized by an abundance of stromatoporoids. This interval was referred to as the "stromatoporoid 

cap facies" by Crowley (1973), although he assigned it to 

the Gasport Dolomite rather than to the Goat Island Dolomite. East of the Niagara River Gorge, two distinct lithologic units that are informally termed units A and B and are 

of subequal thickness form the Niagara Falls Member. 

UNIT A 

The base of unit A can be sharp and form an irregular 

contact with the underlying Pekin Member of the Gasport 

Dolomite. At the Route 429 roadcut at Pekin Hill, local 
54 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

channels of the Niagara Falls Member cut through at least 

6-7 ft of the Pekin Member. These channeled areas are 

infilled with a stromatoporoid-rich micritic bioherm that 

Crowley and Poore (1974) referred to as the "Pekin reef' of 

the Gasport Formation. The relation of this channel-fill to 

adjacent facies is complex, but the bioherm clearly rests 

unconformably atop the Gasport strata (Brett and others, 

1990b). 

Unit A of the Niagara Falls Member consists of two 

locally developed facies. One facies consists of pale pinkish-gray to olive-gray, crinoidal, dolopackstone and grainstone that weather to a very light gray color. Stromatoporoids and cladoporid corals are abundant, and small, low 

(up to 7ft high) bioherms are locally present that consist of 

pale micrite with abundant rugose and tabulate corals, pelmatozoan holdfasts, and stromatoporoids. The crinoidal 

grainstone is closely associated with the bioherms and 

could represent a halo of debris around them. The other 

facies of unit A is best developed at the northern end of the 

Niagara River Gorge and in the adjacent Queenston-St. 

Catharines area. It consists of thin- to thick -bedded, paleolive-gray, fine-grained dolowackestone and is extremely 

vuggy, with yellowish dolomite and sphalerite crystals lining the vugs. 

A thin, argillaceous dolomite bed immediately overlies 

unit A at several localities (for example, Lockport, Clarendon, Brockport) and contains a distinctive Medusaegraptus 

and dendroid graptolite fauna (LaDuca, 1990; LaDuca and 

Brett, 1991). 

UNITB 

The upper interval of the Niagara Falls Member, unit 

B, is a dark-gray to pale-pinkish-gray massive dolorudite 

that typically contains a profusion of stromatoporoid heads 

and favositids. Brett and others (1990b) describe the outcrop of unit Bat the Niagara Stone Quarry in Niagara, N.Y., 

although they refer to what is termed unit B herein as the 

Niagara Falls C unit. 

Contacts: The basal contact of the Niagara Falls Member with the underlying Pekin Member of the Gasport Dolomite is commonly sharp and locally erosional. The upper 

contact of the Niagara Falls Member is marked by an abrupt 

change to pale olive-gray, thin-bedded, fine-grained cherty 

dolomite of the Ancaster Member (new unit, proposed 

herein), which weathers to light tan. This contact is generally sharp but conformable. 

Regional Correlations: The Niagara Falls Member has 

been traced from Brockport, N.Y., westward to Hamilton, 

Ont. (figs. 15, 23). West of Hamilton, the Niagara Falls 

Member grades into the massive carbonates of the Amabel 

Formation; to the east, it grades into the sandy dolomites of 

the Penfield Formation. The Niagara Falls Member is a 

stromatoporoid- and cladoporid-rich packstone and crinoidal grainstone at the southeastern rim of the Frontier 

Dolomite Quarry in Gasport. At Oak Orchard Creek, the 

correlative interval is represented by a 3-ft-thick, reddish, 

hematitic crinoidal packstone (Zenger, 1965). The Niagara 

Falls Member is represented by a complex interval exposed 

in the Genesee-LeRoy Stone Quarry at Clarendon. On the 

southeastern wall of the quarry, the Niagara Falls Member 

consists of two massive grainstone beds, each about 8 ft 

thick, split by the Medusaegraptus-bearing argillaceous 

dolomite. In contrast, the northern face of the same quarry 

displays only a single 8-ft-thick crinoidal grainstone bed. At 

the Iroquois Stone Quarry (Sweden-Walker Quarry) in 

Brockport, a 5-6-ft-thick crinoidal grainstone with small 

coral-stromatoporoid bioherms represents the Niagara Falls 

Member. 

Age: Latest Wenlockian to early Ludlovian; contains 

the Ozarkodina sagitta/Ozarkodina crassa conodont Zonal 

boundary (LaDuca and Brett, 1991). 

Summary of Revision: The Niagara Falls Member is a 

new unit, proposed herein as the lowermost member of the 

Goat Island Dolomite. Two informal units of the Niagara 

Falls, units A and B, are introduced herein. 

ANCASTER MEMBER 

(revised herein and geographic extension) 

Brief History of Nomenclature: Nowlan (1935) considered the Eramosa to be a formation in the Lockport Group 

and included within it the entire section above the Gasport 

Dolomite and below the Guelph Dolomite. Shaw (1937) 

recognized two members, the Ancaster and Speedwell, and 

stated that the Ancaster Member comprised the lower, 

chert-rich part of the "expanded" Eramosa Formation. 

Cumings (1939) redefined Eramosa in its original, restricted 

sense and substituted the name Suspension Bridge for the 

interval that overlies the Gasport and underlies the Eramosa. Because the term Suspension Bridge was preoccupied, Howell and Sanford ( 194 7) changed the name to Goat 

Island. The term Ancaster has been used informally in 

Ontario by Bolton (1957), who stated that the beds immediately above the Gasport at the base of the Goat Island contain plentiful chert nodules and lenses and are consistent 

throughout the Niagara Peninsula, and he referred to them 

as the Ancaster chert beds. These chert beds are traceable 

from Clappison's Comers roadcut east to DeCew Falls; the 

concentration of chert is greatest in the Hamilton, Ont., area 

and decreases eastward (Bolton, 1957). Zenger ( 1965) notes 

that the lower strata of the Goat Island in the Niagara Peninsula of Ontario are characterized by an abundance of chert 

nodules and are referred to informally as the Ancaster chert 

beds. Although he comments that the cherty beds in the 

lower part of the Goat Island at Albion are probably equivalent to the Ancaster chert beds of Ontario, he does not further discuss their occurrence in western New York. Sanford 

(1969) informally divides the Goat Island into two members, a lower cherty member termed Ancaster and an upper 
REVISED STRATIGRAPHY AND CORRELATIONS 55 

member, similar to the Ancaster but containing little or no 

chert. The term Ancaster Member has been used informally 

by the authors (Brett and others, 1990a,b, 1991; Tepper and 

others, 1990; LoDuca and Brett, 1991). The Ancaster Member of the Goat Island Dolomite is proposed herein as a formal unit and is geographically extended into the study area 

from the Niagara Peninsula of Ontario (fig. 4). 

Type Locality: Highway 403 roadcut, town of 

Ancaster, Ont. (Dundas, 30M/5d, Canadian NTS) (Bolton, 

1957). 

Reference Sections: North end of the Niagara River 

Gorge; Niagara Stone Quarry, Niagara, N.Y.; GeneseeLeRoy Quarry, Clarendon, N.Y. 

Thickness: The Ancaster Member, like the Niagara 

Falls Member below it, is variable in thickness, and these 

two units appear to have a compensatory thickening/thinning relation (that is, where the Ancaster is thick, the Niagara Falls is thin, and vice versa). The Ancaster Member 

ranges in thickness from a minimum of 2 ft at the south end 

of the Niagara River Gorge to a maximum of 25 ft at the 

type locality. It thins rapidly in areas where the Niagara 

Falls Member is a thick, massive grainstone. The unit averages about 12ft in thickness. 

Lithologic Description: The middle part of the Goat 

Island, herein formally termed the Ancaster Member, is a 

medium ash-gray, thin- to medium-bedded, fine-grained 

dolomite (figs. 23, 24). The unit weathers to light tan and 

typically contains abundant nodules (up to 5 in. across) of 

distinctive pale, cream-colored chert. The chert nodules 

commonly contain better preserved original sedimentary 

fabrics than do the surrounding dolomites and frequently 

incorporate well-preserved silicified fossils, including the 

rugose coral Enterolasma; the brachiopods Stegerhynchus, 

Leptaena, and Howellella; gastropods; and, rarely, trilobites. The Ancaster Member is generally cherty throughout 

its lateral extent, although at the Niagara Stone Quarry in 

Niagara, N.Y., chert is rather scarce and is absent at the 

Frontier Stone Quarry in Lockport, N.Y. At several field 

exposures, a thin, laterally continuous cherty band about 5 

ft above the base of the unit contains a profusion of Whitfieldella brachiopod valves. The upper 1-2 ft of the 

Ancaster Member are typically biostromal and contain 

abundant Whitfieldella, corals, and small stromatoporoids. 

Contacts: As noted above, the basal contact of the 

Ancaster Member with the Niagara Falls Member is generally sharp· but conformable. Color and texture typically 

change from dark gray and medium grained below this 

boundary to pale buff and finer grained above it. 

The upper contact of the Ancaster Member with the 

Vinemount Member is typically sharp, though conformable. 

A shaly interval with a ground-water seepage zone is recognized at this contact in many outcrops. In the USGS cores, 

an abrupt upward change to a darker gray and finer grain 

size is discernible at this contact. As noted above, one or 

more beds of coarse crinoidal debris are typically observed 

near the top of the Ancaster Member. 

Regional Correlations: Regional stratigraphic correlations and relations for the Ancaster Member are shown in 

figures 15 and 23, respectively. The Ancaster Member has 

been traced from Hamilton, Ont., east to Clarendon, N.Y. 

West of Hamilton, it grades into the massive carbonates of 

the Amabel Formation, and east of Clarendon, it merges 

with the thinly bedded, sandy dolomite facies of the Penfield Formation. Although cherty facies appear in the northem and southern extremes of the Niagara River Gorge, the 

Ancaster Member is largely absent from gorge sections in 

which a massive Niagara Falls Member occupies most of 

the thickness of the Goat Island. In contrast, the Ancaster 

Member, with well-developed chert beds, is predominant in 

the Niagara Stone Quarry, which is only 2-3 mi east of the 

Niagara River Gorge sections in which the Ancaster is 

absent. In drill cores from a hazardous-waste-disposal site 

in Niagara Falls (near the intersection of Pine Avenue and 

Packard Road), the cherty facies is largely replaced by dark, 

argillaceous dolomite. This lateral facies change suggests 

that a narrow, troughlike depression could have been 

present in central Niagara County during deposition of the 

lower part of the Goat Island. In all outcrop sections northeast of this area (Pekin roadcut, Lockport Quarry, Oak 

Orchard Creek, Clarendon Quarry), a relatively uniform 

interval of fine-grained, brownish-gray, and generally 

cherty Ancaster Member overlies grainstones of the Niagara Falls Member. At Oak Orchard Creek, an interval of 

more than 7 ft of brownish-gray, thinly bedded dolomite 

with abundant elongate, white chert nodules was misidentified by Zenger (1965, p. 174) as the "Oak Orchard Member" (herein termed Eramosa Dolomite). Zenger notes (p. 

67) that the presence of chert nodules is atypical for the 

"Oak Orchard Member." The anomaly is resolved if this 

unit at Oak Orchard Creek is recognized as the Ancaster 

Member of the Goat Island instead of the "Oak Orchard 

Member." The easternmost exposure of typical An caster 

facies crops out at the Genesee-LeRoy Stone Quarry, 15 mi 

east of Oak Orchard Creek. This outcrop consists of a 15-ftthick, thinly bedded, brownish-gray cherty dolomite that 

closely resembles the outcrop at Oak Orchard Creek. 

Age: Early Ludlovian, above the top of the Ozarkodina 

sagitta Zone conodonts. 

Summary of Revisions or Changes: The term Ancaster 

was previously used (beginning with Shaw, 1937) as an 

informal name for thinly bedded dolomite with distinctive 

white chert nodules found near Hamilton, Ont. The 

Ancaster Member is herein defined as a formal unit of the 

Goat Island Dolomite and is geographically extended eastward to Clarendon, N.Y., from the Niagara Peninsula of 

Ontario. 
56 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

VINEMOUNT MEMBER 

(revised herein and geographic extension) 

Brief History of Nomenclature: Hewitt (1960) was first 

to make informal reference to the Vinemount shale beds, a 

section of argillaceous dolomite with abundant shale partings that is 17 ft thick in the Armstrong Brothers Company 

Limited Vinemount Quarry, in Vinemount, Saltfleet Township, Ont. In the Hamilton, Ont., area, Telford and others 

(1975) considered this shaly dolomite interval as a distinct 

mappable unit but referred to it only as an unnamed member. On a map of the Paleozoic geology of the Grimsby, 

Ont., area by Liberty and others (1976a), the Lockport Formation consists of four members: Gasport Member, Goat 

Island Member, unnamed member, and Eramosa Member. 

This unnamed member is identified as argillaceous dolostone and shale of the Vinemount shale beds. On a geologic 

section across the Niagara Peninsula in Ontario, Telford 

(1978) shows the Vinemount shale beds pinching out 

between Hamilton and Niagara Falls. The Vinemount shale 

beds are referred to as an informal member of the Lockport 

Formation in Derry Michener Booth and Wahl and Ontario 

Geological Survey (1989). The stratigraphic interval herein 

termed the Vinemount Member of the Goat Island Dolomite 

is the same as that assigned to the Eramosa Dolomite on 

Rickard's (1975) correlation chart. The term Vinemount 

Member has been used informally by the authors (Brett and 

others, 1990a,b, 1991; Tepper and others, 1990; LoDuca 

and Brett, 1991 ). The Vinemount Member of the Goat 

Island Dolomite is proposed herein as a formal unit and is 

geographically extended into the study area from the Niagara Peninsula of Ontario (fig. 4). 

Type Section: Vinemount Quarry, north of Green 

Mountain Road, in Vinemount, Saltfleet Township, Ont. 

(Winona, 30M/4g, Canadian NTS). 

Reference Sections: Niagara River Gorge; Niagara 

Stone Quarry, Niagara, N.Y.; Frontier Stone Quarry, Lockport, N.Y. 

Thickness: The Vinemount Member in the Niagara 

region is relatively uniform in thickness-about 17 ft in 

outcrops, 20ft in the USGS Grand Island-2 core, and 19 ft 

in the Wheatfield-I core. It is anomalously thin (10ft) in the 

USGS Niagara-1 core and near Niagara Falls, Ont. (9ft). At 

the type section at the Vinemount Quarry near Vinemount, 

Ont., it is about 18 ft thick. 

Lithologic Description: In the Niagara region, the 

Vinemount Member consists of light- to dark-gray, 

medium- to thin-bedded, very fine-grained, argillaceous 

dolomite with thin shale partings (figs. 23, 24). The Vinemount is commonly bituminous and yields a petroliferous 

odor from fresh surfaces. It locally contains vugs lined with 

gypsum, sphalerite, calcite, dolomite, fluorite, and galena. 

Pyrite is locally disseminated throughout this unit. White to 

bluish-gray chert, typically with a distinctly banded or 

wood-grained appearance, is found in the upper 5 ft of the 

unit in several of the USGS cores, and near the base of the 

Vinemount Member along the south haul road in Niagara 

River Gorge. On both sides of the gorge near Niagara Falls, 

the Vinemount consists of about 7 ft of thin-bedded, 

brownish-gray dolomite with alternating bands (up to 6 in. 

thick) of bluish-gray chert. Fossils are sparse in the Vinemount Member but include small rhynchonellid brachiopods, gastropods, nautiloids (large Dawsonoceras), and 

small rugose corals. Favositids and stromatoporoids generally are lacking. Farther west, at the type section near Vinemount, Ont., the unit becomes increasingly argillaceous and 

consists mainly of dark -gray, unfossiliferous shale and 

highly argillaceous dolomite. 

Contacts: At many localities, the contact of the Vinemount Member with the underlying Ancaster Member is 

conformable but abrupt and is typically demarcated by a 1-

2-in. layer of black shale. In some sections within the Niagara Falls area, however, this contact is gradational and difficult to establish. The contact of the Vinemount Member 

with the overlying Eramosa Dolomite appears gradational 

in areas where fine-grained argillaceous dolomites of the 

Vinemount are interfingered with cleaner carbonates over 

an interval of several feet. In other areas, however, this contact is sharp between the thin-bedded argillaceous dolomites 

and shales of the Vinemount and the massive, biostromal, 

vuggy dolomite of the basal Eramosa beds. 

Regional Correlations: Regional stratigraphic correlations and relations for the Vinemount Member are shown in 

figures 15 and 23, respectively. The Vinemount Member 

has been traced westward from Orleans County, N.Y., to the 

Steetly quarries near Dundas, Ont. West of Hamilton, Ont., 

it grades into the massive carbonates of the Amabel Formation. The Vinemount extends eastward at least to Orleans 

County, N.Y. At Oak Orchard Creek, the Vinemount is represented by the uppermost 4-5 ft of dark brownish-gray, 

carbonaceous dolomite assigned by Zenger (1965, p. 174) 

to the "Oak Orchard Member" (unit 12). This unit is the 

source of the upper Guelph fauna or upper Shelby beds of 

Clarke and Ruedemann (1903). This unit, however, is actually lower in the section than the interval previously 

referred to as the "Oak Orchard Member" in the Niagara 

region. At the Genesee-Le Roy Stone Quarry in eastern 

Orleans County, the Vinemount consists of about 10 ft of 

thin-bedded, slightly cherty, fossiliferous gray dolomite. 

The basal contact is gradational with the underlying cherty 

Ancaster Member, but the upper contact with the overlying 

massive lower unit of the Eramosa Dolomite is sharp. Correlation of the Vinemount Member east of Orleans County 

is difficult, primarily because outcrops are sparse, but this 

interval probably correlates with an upper fossiliferous 

interval of the Penfield Formation that is well exposed on 

roadcuts along Route I-490 near the town of Gates, west of 

Rochester, N.Y. If this interval is correlative, then the Vinemount is much more widely traceable than previously 

suspected. 
REVISED STRATIGRAPHY AND CORRELATIONS 57 

Age: Early Ludlovian. 

Summary of Revisions or Changes: The stratigraphic 

interval herein termed the Vinemount Member is the same 

as that assigned to the Eramosa Dolomite on Rickard's 

(1975) correlation chart. The Vinemount Member of the 

Goat Island Dolomite is herein made a formal unit. lt is geographically extended eastward to at least Orleans County, 

N.Y., from the Niagara Peninsula of Ontario, where it has 

been considered an unnamed member of the Lockport Formation. 

ERAMOSA DOLOMITE 

(revised herein) 

Brief History of Nomenclature: Williams (1915) proposed the term Eramosa Member for the bituminous dolomites at the top of the Lockport Formation on the Eramosa 

River between Rockwood and Guelph, Ont. Williams 

(1919) considered the Eramosa to be conformably overlain 

by the Guelph Dolomite, which he treated as a separate formation, and underlain by an unnamed dolomite that separated the Eramosa from the Gasport Member. Nowlan 

(1935) and Shaw (1937) redefined the Eramosa to include 

the entire section between the Gasport and the Guelph. 

Cumings (1939) recognized the Eramosa as the uppermost 

member of the Lockport Dolomite and stated that it is 

underlain by the Suspension Bridge Member (a name he 

introduced) and overlain by the Guelph Dolomite. Howell 

and Sanford (1947) stated that the Eramosa Member overlies the Goat Island Member (a name they introduced) and 

underlies the Oak Orchard Member (a name they introduced). Bolton (1957) included the bituminous dolomites of 

Williams (1915) and thin, nonbituminous horizons at or 

near the top of the Amabel Formation (lateral equivalent of 

the Lockport Formation) in his Eramosa Member (fig. 21 ). 

Zenger (1965) considered the Eramosa a member of the 

Lockport Formation (fig. 21), overlain by the Oak Orchard 

Dolomite and underlain by the Goat Island Dolomite, and 

extending only as far east as the Tonawanda-Lockport area 

of New York. The Eramosa Dolomite is considered a formation-level unit on Rickard's (1975) correlation chart; it is 

underlain by the Goat Island Dolomite and overlain by the 

Guelph Dolomite (figs. 21, 22). The Eramosa Dolomite, as 

revised herein, corresponds with the lower and middle sections of the Guelph Dolomite as shown on Rickard's (197 5) 

correlation chart (fig. 22). The term Eramosa Dolomite as 

revised herein has been informally introduced by the 

authors (Brett and others, 1990a,b, 1991; Tepper and others, 

1990; LoDuca and Brett, 1991). It is formally revised 

herein. 

Type Locality: Banks of the Eramosa River between 

Rockwood and Guelph, Ont. (Guelph-Rockwood, 40P/9b, 

Canadian NTS), Williams (1915). 

Reference Sections: Niagara River Gorge, old sewagetreatment plant access road in Niagara Falls, N.Y.; south 

haul road (access to Robert Moses Powerplant); Niagara 

Stone Quarry in Niagara, N.Y.; and the Vinemount Stone 

Quarry in Vinemount, Ont. 

Thickness: The thickness of the Eramosa Dolomite in 

the Niagara Falls, N.Y., area ranges from about 38 ft to 

slightly over 50 ft. 

Lithologic Description: As originally defined by 

Williams (1915), the Eramosa Dolomite included at least 50 

ft of upper beds of the Lockport in southern Ontario. At its 

type locality, the Eramosa consists of thick- to thin-bedded, 

dark-brownish-gray, bituminous dolomite that emits a 

petroliferous odor. Some horizons contain small white chert 

nodules. 

As defined herein, the Eramosa Dolomite is separate 

from, and immediately overlies, beds in western New York 

designated as "Eramosa" by Zenger (1965) that are 

regarded herein as the Vinemount Member, the uppermost 

member of the Goat Island Dolomite. The Eramosa Dolomite of western New York, as defined herein, consists of 

about 50 ft of biostromal, bituminous, medium- to massivebedded, brownish weathering dolomites (figs. 23, 24) that 

have previously been assigned to the lower part of the Oak 

Orchard Member (Zenger, 1965). As noted above, little or 

none of this unit is present along Oak Orchard Creek; therefore the name "Oak Orchard" is formally abandoned 

her~in. Because part of the interval formerly named "Oak 

Orchard" is laterally continuous with the Eramosa Dolomite 

in Ontario, the term Eramosa Dolomite is herein applied, 

although the Eramosa facies typically ·found in western 

New York differ somewhat from those in Ontario. The eastem facies of the Eramosa Dolomite is characterized by 

massive, pale-brownish-weathering, vuggy, commonly biostromal dolomite with some intervals of sparsely fossiliferous, medium bedded, flaggy-weathering, brownish-gray, 

bituminous dolomite and intervals of digitate stromatolites 

that locally form small biostromes or bioherms. This interval, including several traceable subdivisions, is overlain by 

a thin, persistent band of light -gray stromatolitic dolomite 

that forms the base of the Guelph Dolomite, as recognized 

herein. Equivalence of the Eramosa Dolomite, as revised 

herein, with Canadian units has been supported by lateral 

correlations of cores and outcrops between the Niagara and 

Guelph, Ont., areas. Six major units are recognizable rather 

consistently in the Niagara region and are designated herein 

as informal units A through F, as described below. 

UNIT A 

The basal Eramosa, unit A, is a rather uniform, 7-

8-ft-thick, massive, biostromal dolomite. It is characterized 

by thickets vf the ramose tabulate coral Cladopora, which 

are commonly packed together with favositids and (rarely) 

stromatoporoids in a dark-brownish-gray dolomitic matrix. 

In some areas, white chert nodules are abundant, particu-
58 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

larly in the lower part of this unit. Weathered blocks of this 

interval are massive and have a distinctive pitted appearance. Although unit A is quite vuggy, it is highly resistant 

and tends to form overhangs in outcrop. 

UNITB 

Unit B is relatively uniform; it is fine grained, sparsely 

fossiliferous, and bituminous. It is rarely slightly argillaceous and vuggy. It weathers medium bedded to flaggy and 

tends to form a slight reentrant in cliff profiles. This interval 

ranges in thickness from about 13 ft to more than 20 ft. 

UNITC 

Unit C is a recurrent Cladopora-rich biostromal interval (as in unit A) in some localities, but elsewhere it is characterized by distinctive bunlike masses of digitate 

stromatolites up to 5 ft thick that are sometimes associated 

with favositid corals. The rock tends to be massive- or 

thick-bedded, brownish-weathering, saccharoidal dolomite 

with abundant large vugs, many of which occupy fossil 

voids. The vugs are typically lined with sphalerite, galena, 

fluorite, calcite, or dolomite. The variation in the thickness 

of unit C primarily reflects the distribution of algal 

buildups. 

UNITD 

In outcrop, a flaggy-weathering zone in the lower part 

of this unit typically forms a reentrant. In outcrop, unit D is 

a tripartite interval consisting of lower and upper flaggyweathering, dark-brownish-gray, nonfossiliferous, saccharoidal dolomites that commonly are separated by a somewhat more massive 3-4-ft-thick bed that is locally packed 

with a distinctive branching form of Favosites. This interval, which averages 16.8 ft thick in the USGS cores, is 

sharply overlain by unit E. 

UNITE 

Unit E consists of a regionally widespread, 1-2-ftthick marker bed of light-gray, laminar, stromatolitic 

dolomite. 

UNITF 

Unit F is a medium-grained, olive-gray dolomite that 

locally contains scattered oolites and Favosites. It averages 

7.4 ft thick in the USGS drill cores. Because it resembles 

unit D, it is included within the Eramosa. 

Contacts: The basal contact of the Eramo sa Dolomite 

with the underlying Vinemount Member of the Goat Island 

Dolomite is relatively sharp in most weathered exposures; 

locally the contact is gently undulatory. In Niagara County, 

the contact is at the top of a 1-2-ft-thick bed of crinoid-rich, 

coarse-grained dolomite at the top of the Vinemount Member. The upper contact of the Eramosa Dolomite with the 

basal stromatolite marker bed of the overlying Guelph 

Dolomite is sharp. 

Regional Correlations: Regional stratigraphic correlations and relations of the Eramosa Dolomite are shown in 

figures 15 and 23, respectively. The Eramosa Dolomite is 

traceable in cores westward to Guelph, Ont. At the Vinemount Quarry near Stoney Creek, Ont., the lower part of the 

unit is well exposed. No complete exposures of the Eramosa 

(as defined herein) crop out between Stoney Creek and the 

Niagara River. In Niagara County, the Eramosa is partly 

exposed along the Niagara River, and all units are exposed 

in the Niagara Stone Quarry. 

To the east, the Eramosa Dolomite is poorly exposed 

but the massive basal biostromal beds (4-6 ft thick) crop 

out in the Clarendon Quarry and along Route I -490 near the 

junction with Route 531. The basal biostromal beds are 

present in exposures along Aliens Creek near Rochester, 

N.Y., and at the top of the Penfield Quarry in Rochester. 

Age: Ludlovian (Berry and Boucot, 1970, p. 181; 

LoDuca and Brett, 1991), on the basis of Ancyrodella 

ploeckensis and Polygnathoides siluricus Zone conodonts 

(LoDuca and Brett, 1991; Kleffner, 1991). 

Summary of Revisions: The upper and lower contacts 

of the Eramosa Dolomite have been revised to include 

about 50 ft of strata that were previously assigned to the 

lower part of the "Oak Orchard Member" as defined by 

Zenger (1965) and shown as belonging to the Guelph Dolomite by Rickard (1975). The Eramosa Dolomite, as defined 

herein, is separate from and directly overlies beds in westem New York previously designated as Eramosa by Zenger 

(1965), and regarded herein as the Vinemount Member of 

the Goat Island. This revision allows uniformity of nomenclature across the border with Ontario. Six informal units of 

the Eramosa, units A through F, have been introduced 

herein. 

GUELPH DOLOMITE 

(revised herein) 

Brief History of Nomenclature: The Guelph Formation 

was originally designated by Logan (1863); he did not specify a precise type section although he stated that the Guelph 

was developed in the area of Guelph and Galt, Ont. He also 

stated that the Guelph Formation appears to be absent in 

New York. Although Hall (1867) considered the Galt or 

Guelph Limestone of Canada to be above the Niagara 

Limestone of Niagara Falls, he included the Galt or Guelph 
REVISED STRATIGRAPHY AND CORRELATIONS 59 

in the Niagara Group. Arey (1892) discovered strata of the 

Guelph Formation in Rochester, N.Y., where 4ft of it overlie typical Niagara Limestone. Clarke and Schuchert ( 1899) 

included the Guelph Dolomite in the Niagaran but excluded 

it from the Lockport Dolomite. Clarke and Ruedemann 

(1903) recognized strata containing two invasions of 

Guelph fauna into New York as the Upper and Lower 

Shelby Dolomite. Kindle and Taylor (1913), in their folio 

on the Niagara quadrangle, recognized Guelph fauna in the 

upper part of the Lockport Dolomite, which they considered 

a formation-level unit. Schuchert (1914) observed the precursors of the Guelph fauna in the highest beds of the Lockport Dolomite in Niagara River Gorge. Ulrich and Bassler 

( 1923) included the rocks containing the Guelph fauna in 

the Lockport Dolomite. Zenger ( 1965) stated that the "~ak 

Orchard Member" of the Lockport Formation extends westward into Ontario, where it is called the Guelph Formation. 

He emphasized that east of Hamilton, in the Niagara Peninsula of Ontario, the Guelph is closer lithologically to the 

"Oak Orchard" than to the buff, saccharoidal dolomite of 

the true Guelph. The Guelph is shown on Rickard's (1975) 

correlation chart as the westward lateral equivalent of the 

"Oak Orchard Dolomite." The Guelph as revised herein 

encompasses only the upper part of the stratigraphic interval referred to as the Guelph Dolomite on Rickard's (1975) 

correlation chart (fig. 22). The term Guelph Dolomite, as 

formally revised herein, has previously been introduced 

informally by the authors (Brett and others, 1990a,b, 1991; 

Tepper and others, 1990; LoDuca and Brett, 1991). Discussions of the Guelph in Ontario are provided by Williams 

(1919), Shaw (1937), Caley (1940, 1941), Bolton and Liberty (1955), Bolton (1957), and Sanford (1969). The Guelph 

Formation, which overlies the Eramosa Member of the 

Lockport Formation, is poorly exposed in the Niagara Peninsula of Ontario (Liberty and others, 1976a,b). The Guelph 

is described in its type area by Telford (1976). 

Type Locality: The name Guelph was first proposed by 

Logan ( 1863). Although the Guelph Dolomite is an 

accepted unit in Canadian literature, the precise type section 

is not specified. 

Reference Sections: The lower beds and the contact 

with the underlying Eramosa Dolomite are well exposed in 

the old Penitentiary Quarry near Speedwell Station, 0.5 mi 

northeast of Guelph (Guelph-Rockwood, 40P/9b, Canadian 

NTS). Upper parts of the succession are exposed along the 

Eramosa River at Elora Gorge, north of Guelph (GuelphRockwood, 40P/9b, Canadian NTS). Reference sections for 

the eastern facies of the Guelph in the Niagara River Gorge 

area include cuts along the east access road to the Robert 

Moses Powerplant, just west of Military Road, near the 

Route I -190 underpass in Lewiston, N.Y. 

Thickness: The Guelph Dolomite in Ontario probably 

forms a "great lentil thinning to the southwest toward the 

Niagara River and to the northwest at Manitoulin Island" 

(Sanford, 1972). In the intervening region (for example, 

near Guelph) it attains an unknown thickness, estimated to 

be between 200 and 300 ft. Only a thin wedge of the 

Guelph, previously identified as upper beds of the Oak 

Orchard Member by Zenger (1965), extends into Niagara 

County; the upper part is replaced by the Vernon Shale. 

Guelph strata are nowhere exposed in entirety, but the 

complete thickness of the unit as defined herein is present in 

the following USGS cores: Grand Island-2, where it is 37.2 

ft thick, including transitional beds into the Vernon Shale; 

and in the Pendleton-I core, where it is 35.9 ft thick, including the transition beds. 

Lithologic Description: In Niagara County, the Guelph 

is medium-gray to dark-gray, light-gray to tan weathering, 

laminated, fine-grained, commonly oolitic dolomite (figs. 

23, 24). It is divided herein into three informal units: A, B, 

and C. The upper transitional beds (herein designated as 

informal unit C) contain partings of dark greenish-gray to 

nearly black shale; the shale content increases upward 

toward the top of the formation. The shale and dolomite 

facies are petroliferous. The Guelph in Niagara County, 

N.Y., is sparsely fossiliferous, except for stromatolites. 

Favositids, small Whitfieldella and Howe/leila brachiopods, 

and possible ostracodes have been identified. 

UNIT A 

Unit A consists of very light gray, fine-grained, 

stromatolitic dolomite and is marked by a distinctive and 

apparently continuous biostromal bed of LLH-SH type 

stromatolites (based on classification scheme of Logan and 

others, 1964). These stromatolites form large rounded 

mounds up to 10ft across. Lower parts of the stromatolites 

are laterally linked; laminae are subhorizontal but are gently 

convex upward with wavy surfaces. Upper (and outer) parts 

of the mounds display a digitate fabric (0.75-1.25 in. 

across) and contain columnar stromatolites up to 6 in. high, 

with dolomicrite and flat-edgewise dolomicrite clasts in 

narrow interstices. The stromatolites are capped by thrombolites, which can be surrounded by fossil debris, typically 

Whitfieldella and ostracodes. Unit A can be locally oolitic. 

Part of this interval ( 6-7 ft) is exposed along the east access 

road to the Robert Moses Powerplant, just west of Military 

Road, near the Route 1-190 underpass in Lewiston, N.Y. 

The thickness of unit A in the USGS cores averages 4.0 ft. 

UNITB 

Unit B is a 4-6-ft-thick interval of contorted, darkgray, laminated, oolitic dolomite with partings of black 

shale. This interval appears to represent stromatolitic sediment that has undergone soft-sediment deformation. The 

middle beds of this unit are more uniform, medium bluishgray, oolitic dolomite with thin, dark, shaly partings and 
60 REVISED STRATIGRAPHY AND CORRELATIONS OF THE NIAGARAN PROVINCIAL SERIES 

beds of small (1-2 in.) intraclasts of dolomicrite. The beds 

show weathering in outcrop. 

UNITC 

Unit C, at the top of the Guelph Dolomite, forms a 

transition zone between lithologies typical of the Guelph 

and those of the overlying Vernon Shale of the Salina 

Group. Unit C averages 28 ft thick and is similar to unit B 

but contains minute (1/32-1/8 in.) pits or vugs that apparently are remnant from dissolved evaporite crystals. Unit C 

also contains many interbedded zones up to several inches 

thick of fine-grained, olive-gray to greenish-gray, argillaceous dolomite and thin, black or dark-gray, shaly partings. 

Although the latter closely resemble the dominant lithologies of the overlying Vernon Shale, the predominance of 

medium-gray oolitic dolomite justifies placement of this 

transition zone with the underlying Lockport Group. 

Contacts: The lower boundary of the Guelph Dolomite 

with the Eramosa Dolomite is placed at the sharp base of 

the thick laminar stromatolite zone (unit A). This interval 

normally lies 7-9ft above unitE, a thin stromatolite bed of 

the Eramosa Dolomite. In addition to field and core relations, the basal stromatolitic marker horizon of the Guelph 

has a distinctive signature (an abrupt positive deflection) on 

natural-gamma logs (figs. 12, 20). The upper boundary of 

the Guelph Dolomite in Niagara County is indistinct and 

difficult to place as a result of the gradual upward transition 

into the Vernon Shale. The authors have arbitrarily placed 

the boundary at the base of the first black shale bed that is 

greater than 1 in. thick, but emphasize that this stratigraphic 

horizon might not be equivalent in all sections. As such, the 

Guelph Dolomite contains a higher proportion of gray dolomite than dolomitic shale. In the overlying Vernon Shale, 

the proportions are more equal. 

Regional Correlations: Regional stratigraphic correlations for the Guelph Dolomite are shown in figure 15. The 

thin tongue of rock herein tentatively assigned to the 

Guelph Dolomite is atypical of the unit as exposed in 

Ontario but is apparently the lateral equivalent of it, as indicated by transitional facies at intermediate localities near 

Hamilton, Ont. The beds herein assigned to the eastern 

facies of the Guelph Dolomite were previously assigned to 

the upper part of the "Oak Orchard Member" by Zenger 

(1965). The basal stromatolite beds are distinctive and 

traceable into the more typical Guelph facies of Ontario. 

The thick stromatolitic bed (unit A) is a distinctive marker 

and is present in all of the USGS cores. Unit A is traceable 

westward into Canada (Robert Blair, Golder Associates, 

written commun., 1988). This stromatolitic zone appears in 

outcrop in a section near the base of the Guelph Dolomite 

on Highway 403 at Hamilton, Ont. This outcrop and intervening cores appear to establish the continuity of the 

stromatolitic facies at the base of the Guelph Dolomite west 

to Hami1ton, where it is developed in typical Guelph facies 

(very light tan-weathering, saccharoidal dolomites). To the 

north, near Guelph Township, however, the basal layer loses 

its stromatolitic character and, instead, contains biostromes 

of small, branching favositids that closely resemble those 

seen in the upper part of the Eramosa in Niagara County. 

The Guelph Dolomite therefore appears to grade into more 

open marine facies to the northwest. 

Age: Late Ludlovian, on the basis of Polygnathoides 

siluricus Zone conodonts (Berry and Boucot, 1970; Kleffner, 1991; LoDuca and Brett, 1991). 

Summary of Revisions: The lower contact of the 

Guelph Dolomite is revised herein to be at the base of a 

thick, regionally extensive stromatolite bed (informal unit A 

of the Guelph). In Niagara County, the Guelph as revised 

herein includes about 35 ft of strata previously included in 

the upper part of the Oak Orchard Member as defined by 

Zenger (1965), and only the upper part of the stratigraphic 

interval referred to as the Guelph Dolomite on Rickard's 

(1975) correlation chart. This revision allows uniformity of 

nomenclature across the border with Ontario. Three informal units of the Guelph, units A through C, are introduced 

herein. 

SUMMARY AND CONCLUSIONS 

A revised stratigraphic nomenclature for the Niagaran 

Provincial Series has been developed that establishes uniform nomenclature across the Niagara region. This revised 

nomenclature is primarily intended to apply to the type area 

in western New York but is applicable to the adjacent 

regions between Hamilton, Ont., and Rochester, N.Y 

This study builds upon and partly revises the stratigraphic column of Rickard (1975), the most recent correlation of rocks of Silurian age for western New York to be 

published by the New York State Geological Survey. 

Changes include establishment of 6 new units, revision of 

13 units, and geographical extension of 6 units. Although 

all of the group names have remained the same, the boundaries of the Medina, Clinton, and Lockport Groups have 

been revised. Changes at the formation level include use of 

Canadian nomenclature (for example, Guelph Dolomite) to 

establish uniformity across the international border; geographical extensions of two formations (Merritton Limestone and Williamson Shale) that had previously been 

recognized beyond Niagara County but have now been recognized as actually extending into Niagara County; and 

proposal of two new formations (Devils Hole Sandstone 

and Cambria Shale). The rank or stratigraphic contacts of 

eight formations have been revised. In addition to these 

changes at the formation level, three new members are proposed and two are revised, extended geographically, and 

proposed as members of the Goat Island Dolomite. Of 
REFERENCES CITED 61 

particular importance to regional correlations are four distinctive, laterally traceable, phosphate-pebble horizons, 

which are given formal bed-level status. Some new informal units are included in the revised column. 

Names for all of the newly established units have been 

formally reserved through the Geologic Names Committee 

of the U.S. Geological Survey, and all revisions have been 

made in accordance with the North American Stratigraphic 

Code. 

As revised herein, the Medina Group consists of the 

following seven formations, in ascending order: the Whirlpool Sandstone, the Power Glen Shale, the Devils Hole 

Sandstone, the Grimsby Formation, the Thorold Sandstone, 

the Cambria Shale, and the Kodak Sandstone. New formations proposed herein include the Devils Hole Sandstone 

and the Cambria Shale. In addition, a newly recognized distinctive, laterally traceable phosphate-pebble bed at the base 

of the Grimsby Formation is herein formally proposed as 

the Artpark Phosphate Bed. Stratigraphic contacts of the 

Power Glen Shale and the Grimsby Formation have been 

revised. The Thorold Sandstone and the Kodak Sandstone 

are herein included in the Medina Group rather than in the 

Clinton Group. 

The Clinton Group has been divided into the following 

eight formations: the Neahga Shale, the Reynales Limestone, the Merritton Limestone, the Williamson Shale, the 

Rockway Dolomite, the Irondequoit Limestone, the Rochester Shale, and the DeCew Dolomite. The Merritton Limestone, the Second Creek Phosphate Bed, the Williamson 

Shale, and the Salmon Creek Phosphate Bed have been 

extended into the Niagara Falls area from areas to the east 

in which they were previously recognized. Stratigraphic 

contacts of the Irondequoit Limestone have been revised. 

The Rockway is raised herein to formation rank. 

As revised herein, the Lockport Group consists of the 

following four formations: the Gasport Dolomite, the Goat 

Island Dolomite, the Eramosa Dolomite, and the Guelph 

Dolomite. The Gasport Dolomite consists of two newly proposed members: a lower grainstone termed the Gothic Hill 

Member and an upper, argillaceous, wackestone termed the 

Pekin Member. The Goat Island Dolomite contains three 

newly proposed members: a lower biohermal and grainstone unit termed the Niagara Falls Member; a middle, 

cherty, wackestone termed the Ancaster Member (also 

revised and geographically extended); and an upper, argillaceous, wackestone and shale unit termed the Vinemount 

Member (also revised and geographically extended). The 

Eramosa and Guelph Dolomites are not formally subdivided, although several informal units are recognized herein 

within each formation. Stratigraphic contacts of the Gasport 

Dolomite, Goat Island Dolomite, Eramosa Dolomite, and 

Guelph Dolomite have been revised. 

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