Definition of 

Wisconsinan Stage

By JOHN C. FRYE, H. B. WILLMAN, MEYER RUBIN, and ROBERT F. BLACK

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1274-E

The Wisconsinan Stage and its Altonian, 

Farmdalian, Woodfordian, Twocreekan, 

and Valderan Substages are described as 

time-stratigraphic units of the Pleistocene 

of Illinois and Wisconsin
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

U.S. GOVERNMENT PRINTING OFFICE, WASHINGTON: 1968

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

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

Page

Abstract ........................................... ...................................................... ............ El

Introduction ..........................................,.._................._................................-..... . 1

Wisconsinan Stage .............................................................................................. 1

Historical review .. .......... .................-.................................................... 3

Deposits and age ...................................................................................... 9

Substages of Wisconsinan Stage ............. .... -. ..... .......... .........-_. 13

Altonian Substage ...................................................................................... 14

Farmdalian Substage ......._....................................................................... 15

Woodfordian Substage ... .........................._............................ ................ 16

Twocreekan Substage ................................................................................ 18

Valderan Substage ...................................................................................... 18

Application of the Stratigraphic Code .I......................................................... 18

References cited .................................................................................................. 20

ILLUSTRATIONS

Page

FIGURE 1. Map showing locations of type localities of the 

Wisconsinan substages and geologic reference sections 

described in this report ............................................................ E2

2. Chart showing evolution of the time-stratigraphic classification of the Wisconsinan Stage in the type region .......... 5

III

CONTRIBUTIONS TO STRATIGRAPHY

DEFINITION OF WISCONSINAN STAGE

By JOHN C. FRYE,1 H. B. WiLLMAN,1 MEYER RUBIN, and ROBERT

F. BLACK 2

Abstract

The Wisconsinan Stage of the Pleistocene is described and defined as a 

time-stratigraphic unit for use in Illinois and Wisconsin. The Wisconsinan 

includes all deposits from the contact of the Roxana Silt on the A-horizon of 

the Sangamon soil at the base to the top of the Cochrane till and its contact 

with the overlying post-Cochrane deposits in the James Bay Lowland of 

Ontario, Canada. The substages of the Wisconsinan Stage also are described 

and defined; these are (from the base upward) the Altonian, Farmdalian, 

Woodfordian, Twbcreekan, and Valderan. Correlations from type areas 

throughout this region are based on physical stratigraphy, abundant radiocarbon age determinations, and paleontology.

INTRODUCTION

It is our intent herein to clarify the definition of the Wisconsinan 

Stage, in keeping with the prescribed procedures of the Code of 

Stratigraphic Nomenclature (American Commission on Stratigraphic Nomenclature, 1961), for use in Illinois and Wisconsin. 

Correlations from type areas throughout this region are based 

on physical stratigraphy, abundant radiocarbon age determinations, and paleontology. The adoption of Wisconsinan Stage by 

the U.S. Geological Survey represents the Survey's first usage of 

stage as a time-stratigraphic term in the Pleistocene.

WISCONSINAN STAGE

We here define the Wisconsinan Stage to include all deposits 

from the contact of Roxana Silt on the A-horizon of the Sangamon 

soil to the top of the Cochrane till and its contact with the overlying thin discontinuous post-Cochrane deposits in the James Bay 

Lowland of Ontario, Canada. As thus defined, the Wisconsinan 

Stage includes (in successive order upward) the Altonian, Farmdalian, Woodfordian, Twocreekan, and Valderan Substages; the

i Illinois State Geological Survey, Urbana, 111. 61801. 

-' University of Wisconsin, Madison, Wis. 68508.

El
E2 CONTRIBUTIONS TO STRATIGRAPHY

deposits and limits of each substage will be described. Geographic 

locations of described geologic reference sections and type localities of substages are shown in figure 1.

WISCONSIN

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V

Wedron section (

/ 1 WOODPORD 

'-, ,1 COUNTY

°Farmdale

n Cottonwood 

School section INDIANA

 -& Alton

' Pleasant Grove 

i School section /

I

\I

I

MISSOURI N,

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KENTUCKY

FIGURE 1. Locations of type localities of the Wisconsinan substages 

and geologic reference sections described in this report.
DEFINITION OF WISCONSINAN STAGE E3

HISTORICAL REVIEW

The term Wiscorisinan Stage has evolved from the term "EastWisconsin formation," which was used by T. C. Chamberlin 

(1894). Chamberlin's original description (p. 763) was in part,

Overlapping the preceding formation there comes a very complex sheet of 

drift, characterized by much more pronounced glacial features, along which 

are massive terminal moraines, not only denning the outer edge of the 

sheet, but marking various stages of its development, some of which are 

connected with imbricating overlaps. For present convenience, all this complex is grouped under a single term the East-Wisconsin formation because 

the grounds for a formal subdivision are not yet clear. Eastern Wisconsin 

is selected as the denominative locality because the formation there takes on 

a very pronounced development and assumes some of its most striking 

characteristics.

* * * In Illinois, Indiana and Ohio the outermost moraines, together with 

one to five of the succeeding ones, constitute a group somewhat distinctly 

separable from a later group, which embraces from five to seven or more 

successive terminal moraines.

Chamberlin further stated (1894, p. 764),

A very notable feature of the East-Wisconsin formation is presented by 

the loops of its terminal moraines, which indicate strong lobation of the icesheet * * *. The accompanying map presents to the eye something of the 

extent and nature of this lobation * * *

The differentiation of a younger glacial drift, the "Second 

Glacial Epoch," in the drift-covered region of the Central States 

resulted from recognition that the "Kettle Range" in Wisconsin 

represented a terminal moraine of the Green Bay and Lake Michigan glaciers (Chamberlin, 1877, 1878, 1883). Chamberlin placed 

the boundary of the younger drift in Illinois approximately at 

the Minooka moraine (1878), but later placed it nearer the 

Valparaiso moraine (1883). By the time he introduced the "EastWisconsin" in 1894 (fig. 2), the area of the younger drift had 

been extended to the margin of the Shelbyville moraine in central 

and eastern Illinois, and the drift was considered to be divisible 

into two units at the front of the Valparaiso moraine. The "preEast-Wisconsin" unit was differentiated into an "East-Iowan" 

drift and a "Kansas drift" (older), and the "East-Wisconsin" 

unit became the third glacial epoch.

Concerning the boundary below his East-Wisconsin formation, 

Chamberlin stated (1894, p. 762):

Between the East-Iowan formation and the overlapping sheet of till, 

presently to be described, occurs a second horizon marked by soils, vegetal 

accumulations, oxidation, ferrugination, erosion, and other indications of a
E4 CONTRIBUTIONS TO STRATIGRAPHY

TIME, IN RADIOCARBON YEARS BEFORE PRESENT 

B 8 8 8 S $

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East lowan Formation

(of northern Illinois 

and southern Wisconsin)

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WISCONSIN 

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WISCONSIN

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substages

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Altonian Farmdalian Woodfordian |r

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Intraglacial St.Charles 

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WISCONSINAN STAGE

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Substage

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Laighton Frye Leighton Leighton Leverett Chamberlin and Willman 

(1929)33 (1950) (1957)60 (1899) report (1878)94 Willman This 
DEFINITION OF WISCONSINAN STAGE E5

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E6 CONTRIBUTIONS TO STRATIGRAPHY

notable interval. These are not traceable 59 far back beneath the upper 

formation as in the preceding instance * * *. Nevertheless, even under great 

depths of morainic debris, soils, beds of peat, and remains of trees are found 

at many localities. The interval, however, is best shown by the marked 

differences between the erosion of the preceding and succeeding surfaces.

It seems clear that in the southern Wisconsin and northern 

Illinois region, with which he was concerned, Chamberlin was 

referring primarily to the widespread peats that have since been 

widely recognized, radiocarbon dated, and placed in the unit now 

called Farmdale. This conclusion is supported by the fact that 

the till he called "East-Iowan" adjacent to the Illinois-Wisconsin 

State line has been radiocarbon dated as Altonian in age; the 

Altonian is the unit just below the Farmdale.

Later, Chamberlin (1895, p. 275) changed his East-Wisconsin 

formation to Wisconsin formation.

Leverett (1899, p. 191-417) gave the first comprehensive description of the Wisconsin drift sheets in Illinois. By this time, 

Leverett had described the Illinoian glacial stage, and its overlying Sangamon soil, as underlying the deposits now classed as 

Wisconsinan (East-Iowan plus Wisconsin of Chamberlin) and, 

in southeastern Iowa, overlying the Kansan drift. Leverett stated 

(1899, p. 191):

The northeastern fourth of Illinois and adjacent portions of Indiana are 

covered by a sheet of drift, somewhat fresher than the lowan, which has its 

terminus in the Shelbyville moraine, but which embraces several morainic 

systems of considerable prominence that lie between the Shelbyville moraine 

and the border of Lake Michigan. The term "early Wisconsin" is restricted 

to the moraines which lie outside the bulky moraine that encircles the head 

of the lake * * *. The moraines included in the late Wisconsin are not 

concentric with the earlier group * * *. In Illinois the early Wisconsin is well 

exposed outside the late Wisconsin series, probably better than in any other 

part of the glaciated district.

Concerning the base of the Wisconsin drift, Leverett (1899, 

p. 141) stated:

The Wisconsin drift may usually be readily separated from the older sheets 

which underlie it. Its uniform blue color and the ease with which it may be 

penetrated by auger or spade enable the well drillers to distinguish it readily 

from the underlying deposits, which are brown or gray color and more 

difficult to penetrate. There is also in many places a black soil at the junction 

of this sheet with the underlying drift which furnished additional evidence 

of the passage from the Wisconsin to an older drift * * *. There is often 

considerable peat at this lower soil horizon * * *.

It is, of course, now impossible to reexamine the we'll sections 

Leverett cited as evidence for the above statements. However,
DEFINITION OF WISCONSINAN STAGE E7

several dozen core holes that have penetrated a similar sequence 

within Illinois and more than a dozen radiocarbon dates on peat 

and wood from the same stratigraphic position within core 

samples and outcrop sections seem to leave little doubt that the 

black soil and peat are the unit now called Farmdale Silt. Leverett 

therefore probably intended to exclude from the Wisconsin those 

deposits now classed as the Farmdalian and Altonian Substages. 

His intent on this point is not clear, however, because in central 

Illinois, he assigned the loess (Morton Loess of the present classification) above the peaty zone (Farmdale Silt) and below the 

Shelbyville till to the "lowan" glaciation.

Leighton (1931) included the "lowan" in the Wisconsin glacial 

stage and thus redefined the base of the Wisconsin in Illinois by 

including the "lowan" loess (Morton Loess) within it.

The lower boundary of the Wisconsin was later modified again 

by the inclusion of the Farmdale Silt (named by Leighton in a 

footnote in Wascher and others, 1948, p. 300) as the earliest 

substage of the Wisconsin. Leighton and Willman (1950) regarded the Farmdale as pro-Wisconsin and described it as follows 

(p. 602):

A silt deposit which lies on the weathered zone and erosional slopes of the 

Illinoian drift and which has a very youthful profile of weathering beneath 

the Peorian loess was recognized as loess by Leighton in 1920 and described 

in a publication by him in 1926. He called it "Late Sangamon loess" but 

later renamed it "Farmdale" from the exposures in the Farm Creek section, 

near Farmdale, Tazewell County, Illinois * * * [p. 603], This, in turn, implies 

an extension of an ice sheet during the Farmdale substage into the drainage 

basin of the ancestral Mississippi prior to the lowan substage but not yet 

recognized in the series of drift sheets because it fell short of subsequent 

ice lobes.

Immediately following the introduction of the term, Farmdale 

was extended westward into the Great Plains (Frye and 

Leonard, 1951, 1952) and, in the loess sequence, was generally 

accepted as representing the basal unit of the Wisconsinan Stage.

Contradictory evidence as to the age and correlation of the base 

of the Wisconsinan, however, was introduced by radiocarbon 

dating of the "lowan" in Iowa and Illinois. In Illinois the term 

"lowan" had been applied to a loess (Morton Loess of present 

classification) for which a radiocarbon age of 19,500-22,000 years 

B.P. (before present) has been firmly established. This loess 

occurs stratigraphically below the Shelbyville till and above the 

Farmdale Silt. To date, 21 radiocarbon age determinations have 

been made from the Farmdale deposits of Illinois; these ages
E8

range from 22,450*1,000 (W-334 and 1-2518 3 ) to 27,200+1,000- 

900 (1-2220). In eastern Iowa on the other hand, radiocarbon 

dates (greater than 34,000 (W-534) to greater than 38,000 (W139)) indicated that "type-Iowan" till was significantly older than 

the Farmdale Silt (Rune and others, 1957). Because of this 

difference in the radiocarbon dates and because of the desirability 

to base the classification on the continuous sequence of deposits in 

the Lake Michigan Lobe, the term "lowan" was dropped from the 

classification of the Illinois State Geological Survey (Frye and 

Willman, 1960). The confusion concerning the placement of the 

"lowan" has been resolved by Ruhe and others (Friends of the 

Pleistocene [Midwest Group], 16th Annual Meeting, 1965), who 

demonstrated that "lowan" till in the type areals actually eroded 

Kansan till and therefore cannot be correlated with the so-called 

"lowan" of Illinois.

Shaffer (1956) studied the drift in central-northern Illinois, 

including that called "lowan" by Chamberlin and by Leverett 

prior to 1900, but which was subsequently assigned to the Illinoian 

by Alden (1918). Shaffer concluded that much of the drift of the 

area was older than Shelbyville but younger than Illinoian, a 

relationship suggested by Leverett (1899), and Shaffer therefore 

assigned the drift to the Farmdale, which was at that time considered the earliest Wisconsin glacial substage. Shortly thereafter, 

Black (1958) reported a radiocarbon date of 31,800*1,200 (W628) from comparable till in southern Wisconsin, and Kempton 

(1963, 1966) reported additional radiocarbon dates from centralnorthern Illinois. To date, eight finite and 12 off-scale radiocarbon 

age determinations have been made on materials from Altonian 

deposits in Illinois, and six finite and four off-scale radiocarbon 

determinations have been made on Altonian deposits from Wisconsin.

Acting on Moore's (1947) recommendation to the American 

Commission on Stratigraphic Nomenclature, Frye, Swineford, 

and Leonard (1948) applied the adjectival ending to Wisconsinan 

Stage to identify it as a time-stratigraphic unit.

From the foregoing historical review, it is apparent that the 

base of the Wisconsinan has been revised downward from the 

base of the Valparaiso drift, to the base of the Shelbyville drift,

3 Radiocarbon samples throughout paper are numbered with a prefix denoting the laboratory 

in which they were analyzed: W, U.S. Geological Survey; I, Isotopes, Inc.; GrN, Groningen, 

Netherlands. The ages are given in years B.P. (before present) ; "present" is arbitrarily chosen as A.D. 1950.
DEFINITION OF WISCONSINAN STAGE E9

to the base of the Morton Loess (then called "lowan"), and 

finally to the base of the Roxana Silt (formerly included within 

the Farmdale).

DEPOSITS AND AGE

At present, the base of the Wisconsinan Stage is defined as 

the contact of Roxana Silt on the A-horizon of the Sangamon soil. 

Beyond the limit of Wisconsinan glaciers in Illinois, the relation 

is well shown in many geologic reference sections. Within the 

Pleasant Grove School section (given below), which contains the 

type section of Roxana Silt (Frye and Willman, 1960, p. 10; 

Schultz and Smith, 1965b, p. 13), the Sangamon soil is developed 

in thin Loveland Silt and also laterally in till of Illinoian age; 

within the Cottonwood School section (Leonard and Frye, 1960, 

p. 27) given below, the Sangamon soil is developed in till. Much 

of the Wisconsinan Stage is represented in the above listed 

reference sections and adjacent described sections (for example, 

French Village and Collinsville sections, Frye and others, 1962); 

fossil molluscan faunas have been described from several faunal 

zones within these sections (Leonard and Frye, 1960). Radiocarbon dates on both wood and snail shells from these sections in 

Illinois demonstrate contemporaneity with the larger number of 

radiocarbon dates on wood and peat intercalated within the sequence of the glacial tills northward in Illinois and Wisconsin.

Reference section of Pleistocene deposits at Pleasant Grove School, 

including the type section of Roxana Silt

[Measured in nearly vertical face of large pit for earthnll material in center SE % sec. 20,

T. 3 N., R. 8 W., Madison County, 111. The uppermost 25 feet was measured in excavations

above the main pit and about 50 yards to the northeast]

Thicknenn 

 « . (ft) Pleistocene Series: 

Wisconsinan Stage: 

Woodfordian Substage: 

Peoria Loess:

9. Loess, medium to coarse; loose and friable in upper part; 

calcareous except in very thin surface soil at top; 

light yellow tan including some streaks and mottling 

of tan brown and gray; contains several very weakly 

developed A-horizons in upper part ................................ 25.0

8. Loess, medium to coarse, massive, compact, calcareous, 

gray-tan to yellow-tan; contains fossil snail shells 

throughout (Leonard and Frye, 1960); radiocarbon 

date from one-fourth mile south, 17,950±550 (W-1055),. 

determined on wood; radiocarbon data from 1 mile 

north, 17,100±300 (W-730), determined on fossil snail 

shells --..-.-....-.............._............ .............. ....................... 15.0
E10 CONTRIBUTIONS TO STRATIGRAPHY

Reference section of Pleistocene deposits at Pleasant Grove School, 

including the type section of Roxana, Silt Continued

Thickness 

(ft)

Pleistocene Series Continued 

Wisconsinan Stage Continued 

Altonian Substage: 

Roxana Silt:

7. Loess, medium to coarse, massive, pink-tan, non-fossiliferous; leached in part but weakly calcareous in 

lower part; sharp erosional contact at top, but gradational at base . _..........-.....,.._.... --. .. ......-.....-..... ...... 11.0

6. Loess, medium to coarse, massive, gray-tan to gray; 

weakly calcareous throughout; contains fossil snail 

shells in lower part....-............... ............................... . 12.0

5. Loess, coarse, massive, pink-tan, calcareous; contains 

fossil snail shells throughout (Leonard and Frye, 

1960); radiocarbon date on shells from upper part of 

this zone, 35,200^1,000 (W-729); when the face was 

exposed in the pit, a zone of fine sand was seen in the 

middle of this bed ............I................................................... 20.0

4. Silt, coarse, massive, gray; leached in upper part, but 

weakly calcareous in lower part where bed has maximum thickness; locally contains a humic A-horizon 

at top, but a well-developed B-horizon was not observed ______________.______________ 5.0 

Sangamonian and Illinoian Stages of Frye, Willman, and Black 

(1965):

3. Sangamon soil; developed in silt, coarse, massive, noncalcareous; A-horizon, tan-brown, granular, threefourths-foot thick, grading downward to B2-horizon, 

red-brown, clayey, columnar structured, 2-foot thick; 

Ba-horizon and C-horizon, friable, tan to light-brown, 

gradational downward .......................................................... 3.5

2. Silt, massive, gray to gray-tan; contains streaks of 

yellow brown; leached; at north end of exposure this 

unit is 15 feet thick and is calcareous in the lower 

part. (This silt is judged to be equivalent to the Roby 

Silt, Buffalo Hart Substage of Frye, Willman, and 

Black (1965) of central Illinois.) ...................................... 7.0

Illinoian Stage of Frye, Willman, and Black (1965): 

Liman Substage of Frye, Willman, and Black (1965):

1. Till, having truncated soil at top; weakly developed 

B-horizon exposed only at the highest point on the 

erosional contact surface, leached in upper part and 

calcareous in lower part. At the erosional contact between beds 1 and 2 at the north end of the pit, 

calcareous silt overlies calcareous till ............................ ,11.5

Total thickness of Pleistocene deposits .._......._._............... 110.0
DEFINITION OF WISCONSINAN STAGE Ell 

Reference section of Pleistocene deposits at Cottonwood School

[Measured in readouts on the valley bluff at center of east border, 

sec. 11, T. 18 N., R. 11 W., Cass County, 111.]

Thickness

(ft) 

Pleistocene Series:

Wisconsinan Stage: 

Woodf ordian Substage: 

Peoria Loess:

9. Loess, coarse, gray-tan to pale-yellow-tan; massive to 

indistinctly bedded and laminated; calcareous except 

in thin surface soil at top; sparsely fossiliferous in 

lower and middle part; contains two weakly developed 

A-C soil profiles in upper part ........................................ 25.0

8. Loess, coarse to medium, gray-tan, massive, calcareous; 

indistinct streaks of pale pink throughout; contains 

fossil snails listed in Leonard and Frye (1960) ............ 15.0

Altonian Substage: 

Roxana Silt:

7. Loess, coarse, massive; dark pink in lower part grading 

upward to pink gray; leached in upper part to weakly 

calcareous in lower part; contains a few snail shells 

except in uppermost part; sharp contact at top suggests erosional truncation .................................................. 15.0

6. Loess, medium, neutral-gray, massive, weakly calcareous; contains limonite tubules throughout .................. 10.0

5. Loess, medium, pink-tan, massive, weakly calcareous, 

nonfossiliferous; sharp contact at base, but gradational 

with bed above; contains limonite tubules and small 

calcium carbonate concretions throughout .................... 8.0

4. Silt containing some sand and dispersed small chert 

pebbles in lower part; gray with some tan mottling; 

leached; the fabric of the deposit and presence of 

angular chert fragments and clay pellets suggesting 

derivation from the underlying Sangamon soil indicate that the lower part of the deposit is colluvium.... 5.0 

Sangamonian and Illinoian Stages of Frye, Willman, and Black 

(1965):

3. Sangamon soil developed in till; contains pebbles and 

cobbles; grades downward into calcareous, gray, compact till; soil profile in upper part has an A-horizon, 

thin, brown, gradational with a B-horizon, red-brown, 

clayey, about 2 feet thick ................................................ 8.0

2. Silt, gray- and tan-banded, compact, blocky, calcareous;

contains some sand and a few small pebbles ........._..... 3.0

1. Till, gray to gray-brown, massive, compact, calcareous, 

pebbly; rests on shale and siltstone of Pennsylvanian 

age ............................................................................................ 5.0

Total thickness of Pleistocene deposits .......................................... 94.0
E12 CONTRIBUTIONS TO STRATIGRAPHY

At the southern extremity of Wisconsinan glaciers, the younger 

Woodfordian glaciers considerably overlapped the earlier Altonian 

glaciers; therefore, here also the basal Wisconsinan deposit on 

Sangamon soil is Roxana Silt (for example, Richland Creek and 

Varna sections, Frye and others, 1962, p. 5.4-55). Radiocarbon 

dates have been obtained from peat and wood in the Farmdale 

Silt that overlies the Roxana Silt in several such sections (for 

example, Danvers section, Frye and others, 1962, p. 50).

In extreme northern Illinois, the pre-Farmdale (Altonian) part 

of the Wisconsinan Stage is represented by glacial tills interbedded with silt, sand, and peat. In Wisconsin only the youngest 

pre-Farmdale till has been studied (Black, 1958, 1959, 1962; 

Black and others, in Schultz and Smith, 1965a, p. 56-81), and in 

northeastern Illinois detailed data from the older units are derived primarily from a series of core borings that penetrated to 

a depth of as much as 400 feet (Kempton, 1963, 1966; Kempton 

and Hackett, 1963). Radiocarbon dates have been obtained on 

peat between tills from several of these cores, but attempts to 

date the lowest peats in the Wisconsinan sequence have been 

futile because they are too old for the method currently used.

Although essentially all the Wisconsinan Stage is represented 

in the loess sequence above Illinoian till, most exposures within 

the area of Wisconsinan glacial deposits contain only a small 

fraction of the sequence (note the Wedron section in this report), 

and the type area of the Wisconsinan Stage must include sections 

occurring through several hundred miles from central Illinois to 

the Door Peninsula of Wisconsin. However, the stratigraphic 

relations of the glacial sequence to the loess sequence can now 

be demonstrated by physical stratigraphy, and, except for the 

earliest part of the Wisconsinan, by more than 100 radiocarbon 

dates in Illinois and Wisconsin.

The upper boundary of the Wisconsinan Stage is denned with 

less precision than the lower boundary. In recent years this upper 

boundary has been placed at several different stratigraphic positions by various workers. Frye and Willman (1960) used a radiocarbon date of 5,000 B.P. as the end of the Wisconsinan on the 

basis that this date represents the approximate return of sea 

level to its present position following the final dissipation of a 

continental ice cap from the interior of the continent. The return 

of sea level, however, has been interpreted to have taken place as 

recently as 3,500 years B.P. As a boundary of this type cannot 

be defined in a stratigraphic sequence in compliance with the
DEFINITION OF WISCONSINAN STAGE E13

Code of Stratigraphic Nomenclature (American Commission on 

Stratigraphic Nomenclature, 1961), we now define the upper 

boundary of the Wisconsinan Stage as the contact between the 

Cochrane till and the post-Cochrane deposits in the Ontario, 

Canada, region (Karlstrom and Rubin, 1955; Karlstrom, 1956; 

Hughes, 1956, p. 5). The Stratigraphic sequence and dating of 

the deposits have been described (Terasmae and Hughes, 1960a, 

1960b; Hughes, 1965), and withdrawal of the ice from the 

Cochrane moraine is dated at approximately 7,000 radiocarbon 

years B.P.

SUBSTAGES OF WISCONSINAN STAGE

Chamberlin (1894), Leverett (1899), and Alden (1918) considered their Wisconsin stage (Shelbyville and younger) to be 

divisible into two substages (fig. 2) at the front of the Johnstown 

and Valparaiso moraines. Leverett (1929) introduced early, middle, and late subdivisions by dividing the pre-Valparaiso drift at 

the front of the Bloomington moraine. Leighton (1931) introduced Hudsonian substage for the late Wisconsin, Quebecan 

substage for the early and middle Wisconsin, and Manitoban 

substage for his "lowan." Leighton (1933) withdrew these three 

names and in their place proposed Mankato (late Wisconsin), 

Gary (middle Wisconsin), Tazewell (early Wisconsin), and 

"lowan" (earliest Wisconsin). The classification was expanded to five substages by Leighton and Willman (1950) when 

they added the Farmdale as a substage next older than 

"lowan" (fig. 2).

Thwaites (1943) proposed the name Valders for the youngest 

till in Wisconsin (his Wisconsin stage), that till lying above the 

Two Creeks forest bed (Goldthwait, 1907); he also proposed that 

the name be a replacement for Mankato in the Wisconsin region. 

Thwaites doubted, however, the contemporaneity of his Valders 

with the Mankato of northern Iowa and southern Minnesota, and 

his doubts have been amply justified by radiocarbon dates (Wright 

and Rubin, 1956; Ruhe and others, 1957). Subsequently, Leighton 

transposed the term Mankato, as used in Wisconsin and Illinois, 

from the Valders till above the Two Creeks deposits to the upper 

part of the Gary below the Two Creeks deposits, thus restricting 

the span of the Gary.

Frye and Willman (1960) proposed a new five-fold classification of the Wisconsinan Stage, introducing the Altonian (oldest), 

Farmdalian, Woodfordian, Twocreekan, and Valderan Substages. 

Shortly thereafter, Leighton (1960) modified his 1957 classifi-
E14 CONTRIBUTIONS TO STRATIGRAPHY

cation to eleven units by recognizing Valders as the youngest 

unit, by applying the term Mankato to the upper part of the 

former Gary, by restricting the Gary, by placing the organic-rich 

silts of the typical Farmdale in the Farm Greek, by redefining 

Farmdale, and by recognizing Gardena, St. Charles, Bowmanville, 

and Two Creeks as interstadials (fig. 2).

It is our purpose here to review the definitions of the substages 

now in most common use in Wisconsin and Illinois (Frye and 

Willman, 1960; Frye and others, 1965).

ALTONIAN SUBSTAGE

The Altonian Substage was named for the city of Alton, 111., 

and is defined on the basis of the Roxana Silt. The Roxana Silt 

is well exposed in the overburden of the abandoned quarry in 

the Mississippi River Bluffs at the north edge of Alton and in 

the Reliance Whiting Company quarry within the city limits 

(Frye and Willman, 1963, p. 17; Schultz and Smith, 1965b, p. 11). 

The Roxana also is well exposed at the Pleasant Grove School 

section (p. E10; Frye and Willman, 1960, p. 10), which is the 

type locality for the Roxana Silt. As previously described, the 

Roxana Silt rests on the top of the well-developed Sangamon 

soil and is bounded at the top by its contact with the organic-rich 

Farmdale Silt; in the absence of the Farmdale Silt, the top of 

the Roxana is bounded by a zone of leaching and soil formation 

or an eroded unconformable contact. The Roxana Silt is overlain 

by calcareous and fossiliferous Peoria Loess. The distinctive 

molluscan fauna from the upper units of the Roxana Silt has 

been described (Leonard and Frye, 1960). Radiocarbon dates 

from these fossiliferous upper units (35,200±1,000 (W-729) and 

37,100±1,500 (W-869)) show an equivalence to dates obtained 

from peats between the tills below the Farmdale Silt in core borings and outcrops in northern Illinois: 32,600*520 (GrN-4408), 

35,000*2,500 (W-1450), 38,000*3,000 (1-847), and 41,000*1,500 

(GrN-4468). In southeastern Wisconsin, dates on spruce (31,800* 

1,200 (W-638), 30,800*1,000 (W-901), 29,000*900 (W-903)) 

in till and outwash are slightly younger. These samples are interpreted as dating a short-lived ice advance immediately preceding the Farmdalian. These dates, together with abundant 

radiocarbon dates from the overlying Farmdale Silt, indicate that 

the age of the upper boundary of the Altonian Substage is 28,000 

radiocarbon years B.P., or somewhat more. A radiometric date 

is not yet obtainable for the lower boundary of the substage; 

however, on the basis of the dates reported by Dreimanis,
DEFINITION OF WISCONSINAN STAGE E15

Terasmae, and McKenzie (1966) from Ontario, Canada, an age 

of about 75,000 radiocarbon years B.P. seems reasonable.

The drift that Shaffer (1956) assigned to the Farmdale in 

northern Illinois is now included in the Altonian Substage, and 

the local rock-stratigraphic name, Winnebago drift, has been 

applied (Frye and Willman, 1960, p. 5). Black (1962) has proposed the term Rockian for the uppermost part of the Altonian 

Substage.

FARMDALIAN SUBSTAGE

The Farmdalian Substage is based on the Farmdale Silt, which 

is typically exposed near Farmdale, Tazewell County, 111. (Frye 

and Willman, 1960, geol. section 2, p. 11; Frye and others, 1962, 

Danvers section, p. 50), where it consists of organic-rich silt and 

peaty silt overlying the Roxana Silt and overlain by calcareous 

fossiliferous Morton Loess. Within the Wedron section given below (see also Leonard and Frye, 1960, p. 31; Schultz and Smith, 

1965a, p. 88, 89), the Farmdale Silt is a lacustrine deposit, from 

which an extensive fossil molluscan fauna has been described in 

association with two radiocarbon dates. In Illinois, 21 radiocarbon 

dates have been obtained from peat and wood in Farmdale Silt 

from outcrop sections and core borings. These dates range from 

21,950±500 (1-2517) and 22,450*1,000 (W-334) to 26,800*700 

(W-871) and 27,200+1,000-900 (1-2220). On the basis of these 

dates, it is considered reasonable to place the time span of the 

Farmdalian Substage, in radiocarbon years, from 22,000 B.P. to 

28,000 B.P.

In its original description, the Farmdale Substage included all 

silt deposits overlying the Sangamon soil as high as, and including, the top of the organic-rich silts below the "lowan" (Morton) 

loess. In the type area, however, most of this interval was occupied by organic-rich silts, from which radiocarbon dates in the 

range of 22,000 B.P.-27,200 B.P. were obtained, and only a few 

feet of organic-free loess separated these dated silts from the 

top of the Sangamon soil below. In contrast, along the lower 

Illinois and middle Mississippi River valleys, thick loess deposits 

that contain a leached zone at an erosionally truncated top occur 

below the calcareous fossiliferous Peoria Loess. On the basis of 

this relationship in the loess sequence, Frye and Willman (1960) 

restricted the term Farmdale to the organic-rich radiocarbondated silts at the type locality and denned the Roxana Silt as the 

thick unit of loess, silts, and sands that occur below the Farmdale 

and rest on the A-horizon of the Sangamon soil. Leighton (1960)
E16 CONTRIBUTIONS TO STRATIGRAPHY

subsequently redefined the Farmdale, but chose the alternative 

of proposing a new name, Farm Creek, for the deposits of the 

original Farmdale type section in order to retain the name Farmdale for the glacial substage represented by the loess deposition.

WOODFORDIAN SUBSTAGE

The Woodfordian Substage was named for Woodford County, 

111. (Frye and Willman, 1960), and was defined as embracing the 

succession of rocks from the contact of Morton Loess on Farmdale 

Silt (note reference sections listed above) upward to the base of 

the Two Creeks deposits typically exposed in east-central Wisconsin. No soils, leached zones, or widely traceable key horizons occur 

within the Woodfordian sequence. Although no single exposure 

contains the entire succession of Woodfordian deposits, the 

Wedron section described below is representative of much of the 

substage. It is also the type section for the unit herein named the 

Wedron Formation. The upper boundary of the Woodfordian 

Substage is the contact of till with the water-laid silt, clay, and 

sand, including the forest bed (Thwaites and Bertrand, 1957, 

p. 856) typically exposed at Two Creeks, Wis. Beyond the limit 

of Woodfordian glaciation, the substage is well represented in 

sections of Peoria Loess along the bluffs of the Illinois and 

Mississippi valleys; the Cotton wood School and Frederick South 

sections (Leonard and Frye, 1960, p. 27, 28) should be considered 

supplementary reference sections. The Peoria Loess forms from 

the merging, beyond the Woodfordian glacial limit, of Morton 

Loess from below the Shelbyville till with the Richland Loess 

from the top of the Woodfordian tills.

The fossil molluscan fauna, although sparse in the glacial succession, has been amply described from.the contemporary loess

Reference section of Pleistocene deposits at Wedron, including the 

type section of the Wedron Formation

[Measured in overburden in southwest part of No. 1 Pit of Wedron Silica Co., 

SE& SWi4 sec. 9, T. 34 N., R. 4 E., LaSalle County, 111., as exposed in 1964]

Thickness 

(ft)

Pleistocene Series: 

Wisconsinan Stage: 

Woodfordian Substage: 

Richland Loess:

15. Loess, leached; largely included in surface soil ............ 3.0

Wedron Formation:

14. Sand and gravel, poorly sorted, lenticular _........_.......__ ... 3.0

13. Till (Farm Ridge), silty, yellow-gray, calcareous .......... 4.0

12. Sand and gravel, calcareous .. ........................................ 2.0

11. Till (Cropsey), silty, bouldery, gray, calcareous .......... 3.0

10. Sand, calcareous, tan ........... ....-..-......._......................... 0.5
DEFINITION OF WISCONSINAN STAGE E17

Reference section of Pleistocene deposits at Wedron, including the 

type section of the Wedron Formation Continued

Thickness

(ft)

Pleistocene Series Continued 

Wisconsinan Stage_c0ntinued 

Woodfordian Substage Continued 

Wedron Formation Continued

9. Till (Cropsey), tan, oxidized, calcareous ........................ 5.0

8. Silt and some sand, laminated, gray, calcareous ............ 2.0

7. Till (Normal), silty, gray, calcareous; contains sparse

pebbles ................................................................................. 3.0

6. Sand and silt, gray, calcareous ......................... ................ 1.0

5. Till (Bloomington), pink, bouldery, massive, tough, 

calcareous; indistinct boulder pavement in middle 

part ...................................................................................... 15.0

4. Till (Shelbyville), gray and tan, bouldery, compact, 

calcareous; sharp contact and indistinct boulder pavement at top .......................................................................... 3.0

3. Sand and gravel (pro-Shelbyville outwash), tan, loose, 

calcareous; locally crossbedded and generally well 

bedded; irregular erosional contact at base; thickness 

varies (maximum thickness given here) .................... 20.0

Farmdalian Substage: 

Farmdale Silt:

2. Silt, clayey, pink to red and red-brown, calcareous; 

massive to indistinctly bedded, but locally thin bedded 

and blocky; locally contains small lenses of fine 

sand; radiocarbon date of 24,000^700 (W-79) determined on wood; conformable on unit below, but upper 

contact erosional and irregular; thickness varies 

(maximum thickness given here) ................................ 20.0

1. Silt, blue-gray and tan, massive, compact, calcareous; 

contains some clay and fine sand, and locally sandy 

streaks near the top; contains molluscan fauna described by Leonard and Frye (1960); radiocarbon 

date of 26,800±700 (W-871) determined on twigs and 

wood fragments from upper part; some zones 

strongly contorted by frost action; basal contact is 

irregular on eroded surface of St. Peter Sandstone 

(Ordovician); thickness varies (maximum thickness 

given here) .......................................................................... 25.0

Maximum total thickness of Pleistocene deposits .................... 109.5

sequence. The radiocarbon dates from the underlying Farmdale 

Silt place a limit on the maximum age of the substage, and those 

from the overlying Twocreekan deposits, a limit on the minimum 

age. Dates determined on fossil shells from the Peoria Loess in 

Illinois have ranged from 20,300*400 (W-870) to 13,700*230 

(1-1720). The oldest known radiocarbon date from the Woodfordian in Illinois, 20,700±650 (W-399), was determined on wood
E18 CONTRIBUTIONS TO STRATIGRAPHY

from the upper part of the Morton Loess. The many dates from 

the Two Creeks deposits of Wisconsin (Broecker and Farrand, 

1963) serve to limit the end of the substage and give it an 

approximate range, in radiocarbon years from 22,000 B.P. to 

12,500 B.P.

TWOCREEKAN SUBSTAGE

The Twocreekan was defined as a substage by Frye and 

Willman (1960), who used Thwaites and Bertrand's (1957) description of the typical Two Creeks deposits of east-central Wisconsin as the type. Thwaites and Bertrand (1957, p. 856) stated 

that more than 10 feet of lake clay overlies a till and is overlain 

locally by silt and sand, on which occurs the well-known forest 

bed. This succession of deposits is the type for the Twocreekan 

Subtage (Black and others, in Schultz and Smith, 1965a, p. 66- 

70). More than a dozen radiocarbon dates have been determined 

for the forest bed by Chicago, Washington, and Lamont laboratories (Broecker and Farrand, 1963). On the basis of the sediments below the dated forest bed and the range in radiocarbon 

dates obtained, it seems reasonable to consider that the radiocarbon years of the Twocreekan Substage span from about 

12,500 B.P. to about 11,000 B.P.

VALDERAN SUBSTAGE

The Valderan Substage was named by Frye and Willman 

(1960) and was based on the Valders till of eastern Wisconsin 

as described by Thwaites (1943) and Thwaites and Bertrand 

(1957). The base of the substage was defined as the contact of 

Valders till on the Two Creeks deposits in east- central Wisconsin, 

but the upper limit was defined as an arbitrary radiocarbon age 

of 5,000 B.P. It was judged that at about that time, the return 

of sea level approximately to equilibrium near its present position 

indicated that the continental ice cap had completely dissipated. 

Because such a definition does not meet the requirements of the 

Stratigraphic Code (American Commission on Stratigraphic Nomenclature, 1961), we here define the upper limit of the Valderan 

Substage as the top of the Cochrane till and its contact with 

overlying thin discontinuous post-Cochrane deposits in the James 

Bay Lowland of Ontario, Canada (Hughes, 1956, p. 5; 1965).

APPLICATION OF THE STRATIGRAPHIC CODE

Among American students of the Pleistocene, there have been 

differences in interpretations of the Stratigraphic Code (American Commission on Stratigraphic Nomenclature, 1961) as it is ap-
DEFINITION OF WISCONSINAN STAGE E19

plied to the glacial succession. These differences, or misunderstandings, may have been prompted by a statement about the 

misuse of the term "Stage." The statement is as follows (American Commission on Stratigraphic Nomenclature, 1961, p. 659):

The terms "stage" and "substage" were authorized for climatic subdivisions of the Quaternary Period by the 1933 Code. This usage has led to 

confusion and is here specifically rejected. "Stage" and "substage" are timestratigraphic terms and should be used for Quaternary rocks as for other 

parts of the column. 

It has been our intention here to adhere strictly to this admonition.

The Code clearly specifies (American Commission on Stratigraphic Nomenclature, 1961, p. 657, 658) (1) that time-stratigraphic units must be based on actual sections or sequences of 

rocks, (2) that the upper and lower limits should be defined in the 

rock succession of the type area and should set the unit apart as 

representing a significant geologic episode, but that the boundaries 

of time-stratigraphic units in other than the type area may fall 

within rock-stratigraphic or biostratigraphic units, (3) that timestratigraphic units can be extended geographically from their type 

areas only as criteria of time equivalence are available, and (4) 

that the radiocarbon dating method is applicable to Quaternary 

rocks.

It is our judgment that the time-stratigraphic units described 

herein more fully meet all the requirements of the Stratigraphic 

Code than do a great many of the generally accepted units in the 

older part of the rock column. The top surface of a buried soil 

(top of the A-horizon) defines beyond argument an unconformable 

contact, and, furthermore, we may be sure that such a surface 

was exposed to the action of weather,, plants, and animals for a 

sufficient period of time to alter the sediments a significant distance below the surface. The Code does not clearly state whether 

such a soil profile properly classed as a soil-stratigraphic unit 

may be used as a basis to define a time-stratigraphic unit, but 

its upper surface clearly is appropriate to define the boundary of 

a time-stratigraphic unit.

Although the Code states that ideally the boundaries of timestratigraphic units are isochronous surfaces (and thus independent of lithology, fossils, or other physical criteria), it also states 

that in actual practice the geographic extension of the unit is 

generally controlled by Stratigraphic features (American Commission on Stratigraphic Nomenclature, 1961, p. 658). The geographic extension of the Wisconsinan Stage by using many 

radiocarbon dates seemingly permits a closer approach to the
E20 CONTRIBUTIONS TO STRATIGRAPHY

ideal stated in the Code than is true for any other time-stratigraphic unit so far defined.

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DEFINITION OF WISCONSINAN STAGE E21

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E22 CONTRIBUTIONS TO STRATIGRAPHY

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* U.S. GOVERNMENT PRINTING OPFICE : 1968 O 315-694