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557 IL6gu
no. 20

iuidebook 20

Quaternary records of central and
northern Illinois

Leon R. Follmer
Dennis P. McKenna
James E. King

Ninth Biennial Meeting, American Quaternary Association
University of Illinois at Urbana-Champaign, May 31 -June 6, 1986

Sponsored by the Illinois State Geological and Water Surveys, the Illinois State Museum,
and the University of Illinois Departments of Geology, Geography, and Anthropology

Digitized by the Internet Archive

in 2012 with funding from

University of Illinois Urbana-Champaign

http://archive.org/details/quaternaryrecord20foll

Quaternary records of central and
northern Illinois

Leaders

Leon R. Follmer
Dennis P. McKenna
Illinois State Geological Survey, Champaign, Illinois

James E. King
Illinois State Museum, Springfield, Illinois

Contributors

John M. Masters
E. Donald McKay
Richard C. Berg
Ardith K. Hansel
Illinois State Geological Survey, Champaign, Illinois

Alan D. Ham
Francis F. King
Illinois State Museum, Springfield, Illinois

W. Hilton Johnson
University of Illinois, Urbana-Champaign, Illinois

Richard G. Baker
Amy E. Sullivan
University of Iowa, Iowa City, Iowa

Alan V. Morgan
Anne Morgan
University of Waterloo, Waterloo, Ontario, Canada

American Quaternary Association

Ninth Biennial Meeting, May 31 -June 6, 1986

Urbana-Champaign, Illinois

ISGS Guidebook 20
Reprinted 1990

ILLINOIS STATE GEOLOGICAL SURVEY
Morris W Leighton, Chief

615 East Peabody Drive
Champaign, Illinois 61820

Contents

Introduction v

Acknowledgments vi

Stopl TheWisconsinan Glacial Margin 1

Leon R. Follmer

Stop 2 Athens Quarry Sections: Type Locality of the Sangamon Soil 5

Leon R. Follmer, E. Donald McKay, James E. King and Francis B. King

Stop 3 Dickson Mounds 19

Alan D. Ham

Stop 4 Farm Creek: A Notable Pleistocene Section 21

Leon R. Follmer and E. Donald McKay

Stop 5 Review of the Green River Lowland 29

Leon R. Follmer

Stop 6 The Farmdaleand Sangamon Soils at the Wempletown Southeast Section 33

Dennis R McKenna and Leon R. Follmer

Stop 7 Rockford Terrace: A Late lllinoian Outwash Surface 43

Leon R. Follmer, Richard C. Berg, and John M. Masters

Stop 8 A Review of the Esmond Till 51

Leon R. Follmer

Stop 9 Wedron Type Section 61

W. Hilton Johnson, Ardith K. Hansel, and Leon R. Follmer

Stop 10 Chatsworth Bog : A Woodfordian Kettle 71

James E. King

Bibliography 76

Appendix 1. A Preliminary Note on Fossil Insect Faunas from Central Illinois 83

Alan V. Morgan and Anne Morgan

Appendix 2. Comparison of the Complete Soil Profile and a Weathering Profile 86

(from Follmer, 1984)

This guidebook was prepared for the Ninth Biennial Meeting of the American Quaternary Association
held in Urbana-Champaign, Illinois, May 31 -June 6, 1986. Much of the material was taken from previous
guidebooks, and new material was added to complete the tour itinerary for the AMQUA meeting. Our
purpose in compiling this guidebook was to provide the newest information and interpretations and
to stimulate discussion. The guidebook was reviewed internally, but not by outside reviewers; the
articles reflect the thinking of the individual authors at the time of preparation of the guidebook, not
necessarily the current opinions or positions of the Illinois State Geological Survey.

Printed by the authority of the State of Illinois/1990/475.

INTRODUCTION

Field trips are designed to allow us to view the scope and scale of the
objects of interest and to develop an appreciation of the infinite number of
surrounding factors. This trip is intended to focus on many aspects of
Quaternary Science, a science that is concerned with surficial processes and
human activities over the last several million years.

However, the range of interests of Quaternarists is very large and all
topics cannot be equally addressed within the scope of a two-day trip.
Therefore, we will concentrate on the geological aspects of the conference
theme of Glacial Margins: Processes and Environments. Pedological, paleo-
floral and f aunal , paleoclimatic and archaeological subjects have been worked
in where practical .

On this trip we will see many parts of the classical Wisconsinan glacial
margin of Illinois (see trip route map on back cover). At stop 1 the
morphological expression of the moraine is one of the best that can be seen
along the margin. In many other places the margin is subdued but can be
easily determined from soil patterns and stratigraphic evidence. Stop 2 is
the type locality of the Sangamon Soil, where the present-day exposures in
limestone quarries reveal the sequence of silt deposits and buried soils
that became the basis for naming the Sangamon Soil.

Stop 3 will be at the Illinois State Museum's Dixon Mounds park and
museum, where features of early Mississippian culture can be seen in a natural
setting. On the way to Stop 3 we will cross the Mason County sand plain where
the ancestral "Ohio" and Mississippi Rivers once joined. Wisconsinan glacio-
fluvial and eolian sand deposits now cover this lowland (the "Havana"
Strath"?).

Stop 4 is located at the original site of the Farm Creek Section, if the
slope retreat of a cut bank on Farm Creek is taken into consideration. This
section was one of the first exposures of late Pleistocene deposits to be
described in Illinois and has been very useful to glacial geologists
attempting to formulate stratigraphic concepts and interpret glacial
history in the Midwest.

Stop 5 is in the Green River Lowland where Twocreekan wood has been
recently found under "Holocene" alluvium. The ancient Mississippi River once
crossed this lowland, which has a very complex history, including large-scale
erosion linked to the building of the moraines at the Wisconsinan margin. End
of first day.

Stop 6 is at one of the rare locations in northern Illinois where we can
see a relatively complete stratigraphic record of Wisconsinan deposits
overlying a Sangamon Soil developed in a reddish brown till. The extensive
erosion on this till removed the Sangamon in most places and led many
geologists to interpret this till as early Wisconsinan in age.

Stop 7 is a gravel pit on the Rockford Terrace, which was subjected to
periglacial processes during late Illinoian time. Sangamon Soil development
exploited fossil ice wedge casts and produced large pendants. The exact age
of the gravel is uncertain, but the soil in it appears to be overlain in places
by a complete sequence of Wisconsinan deposits.

Stop 8 is in a "till plain" area between the Wisconsinan margin and the
Rock River where large-scale erosion greatly modified the landscape during the
construction of the moraines of the Wisconsinan margin. The type of erosion
is thought to include periglacial processes that removed the Sangamon Soil
from most of the "Esmond Till plain" (except for rare sites of preservation
such as at Stop 8).

Stop 9 is the Wedron type section, located within a series of quarry
exposures in the St. Peter Sandstone. The quarry has been operating for more
than 80 years and has provided excellent exposures for the study of late
Wisconsinan glacial deposits designated as the Wedron Formation. Most of the
concepts of the stratigraphic units in the Wedron in Illinois during about
1950 to 1970 were based on or directly related to features observed in the
quarry exposures.

Stop 10 is a rare bog in central Illinois that formed in a kettle that by
coincidence is crossed by a thalweg of a former glacial river that carried
water from a stagnated Wisconsinan ice margin. Pollen studies on marl and
organic deposits in the bog reveal a complete record back to about 14,000
years ago.

End of trip.

ACKNOWLEDGMENTS

During the preparation for this field trip, we received the cooperation
and assistance from many landowners and organizations. We want to express our
appreciation to Jack Brown, Superintendent of Indian Point Quarry, Material
Service Corporation; Farmdale Park, Tazewell County; Porter Brothers, Inc.;
Cooling and Sons Sod Farm; Dan Fisher, Rockford Blacktop Construction Company;
Ronald Lentz; Charles Fowler and Spencer Zitka, Wedron Silica Company; Delmar
Ford, Loren Hodgson and Roger Farney.

Faith Stanke, Jack Masters and Stephen Zu Hoene assisted us with field
work and trip organization. Many staff members of the Illinois State
Geological Survey assisted in the preparation: Herb Glass, clay mineralogy
and interpretation; Mike Miller, Becky Roeper, and Bill Westcott, particle
size analysis; Jack Liu and Barry Fisher radiocarbon analysis; Joanne
Klitzing, Gloria Merrick, and Kathy Cooley, typing; Sandy Stecyk, drafting;
and Gail Taylor, typesetting.

THE WISCONSINAN GLACIAL MARGIN

Leon R. Follmer

STOP 1 . View of the Shelbyville Morainic System at Warrensburg

Sec. 10 and 11, T17N, R1E, Macon County IL (Warrensburg Quadrangle)

The crest ot the outer moraine of the Shelbyville System at Warrensburg rises about 100 ft above the
outwash plain to the west.

The city of Warrensburg is located on the crest of the Shelbyville
Moraine, providing an excellent view of the outwash plain to the north and
west. The Shelbyville Moraine was named by Leverett in 1897 and discussed in
detail in his monograph (Leverett, 1899). The Shelbyville marks the margin of
the classic or late Wisconsinan (Woodfordian) glaciation in this area.
Because it is made up of multiple ridges in many places, Willman and Frye
(1970) changed the formal name to Shelbyville Morainic System. The morainic
system can be traced from Indiana to Peoria, Illinois, where it is overlapped
by the Bloomington Morainic System.

At Warrensburg the moraine has about 90 ft (27 m) of relief in about a
mile along a line to the northwest. On the basis of available water well
records, most of the height of the moraine can be accounted for by the
thickness of the Wedron Formation. The E-W alignment of the moraine at
Warrensburg reflects a reentrant relationship of the multiple advances during
the construction of the morainic system. In the regional view, a reorienta-
tion of the system occurs here. From Warrensburg south, a younger advance
appears to have overridden the earlier margin. The younger advance deposited
a gray drift that contains a relatively high amount of illite; it has been
recognized as the Piatt Till Member of the Wedron Formation. The older
deposits to the north are pinkish gray and have an intermediate content of
illite; they have been mapped as the Fairgrange Till Member (Lineback, 1979).

The age of these advances has not been determined at this location but
can be estimated to be in the range of 20,000 to 21,000 years old on the basis
of radiocarbon dates on organic material at the base of the outer moraine in
many other locations.

M Modern Soil
F Farmdale Soil
S Sangamon Soil

Glasford Formation

Figure 1-1. Stratigraphic units in region of Wisconsinan margin in central Illinois.

One of the largest and best developed Woodfordian outwash plains in
Illinois is the lowland to the northwest of Warrensburg. All of the outwash
of Woodfordian age occurring above Woodfordian tills or older deposits are
included in the Henry Formation (Willman and Frye, 1970).

The stratigraphic relationships of the glacial deposits in the area are
reasonably simple (fig. 1-1). For practical reasons, the surficial loess is
divided by a vertical cutoff at the margin of the Wedron Formation. The part
of the Woodfordian loess covered by the Wedron Formation is the Morton
Loess. The overlying loess is the Richland Loess. Where these units converge
beyond the limit of the Wedron Formation they become indistinguishable for
mapping purposes and are grouped together to form the Peoria Loess. As a
matter of convention the Woodfordian outwash is recognized as Henry Formation
only if it overlies or extends beyond the Wedron Formation. Where inter-
calated with till, the outwash is included in the Wedron Formation. Where the
Henry outwash overlies Woodfordian loess, the loess is treated as an unnamed
silt (bed). Therefore, the Peoria Loess thickness depends on the presence or
absence of the Henry Formation (fig. 1-1).

Under the Woodfordian deposits is a sequence of geosols (buried soils in
a known stratigraphic sequence) developed in silt, organic deposits, and
glacial diamictons. The Farmdale Soil, developed in a thin Roxana Silt (early
Wisconsinan) , underlies the Wedron Formation in most places. In low or
depressional locations on the paleolandscape, the Farmdale is an organic soil
that has developed on the Robein Silt, an accretionary deposit derived
principally from the Roxana Silt. The Roxana conformably overlies the
Sangamon Soil developed in accretionary deposits (post-Illinoian) and the
glacial deposits of the Glasford Formation (Illinoian). The Roxana is
commonly difficult to differentiate from the underlying deposits because of
bioturbation (pedogenic mixing). The Sangamon Soil and complexities of the
overlying deposits will be discussed in detail at the next stop.

TYPE LOCALITY OF THE SANGAMON SOIL

Leon Ft. Follmer, E. Donald McKay, James E. King, and Francis B. King

STOP 2. Athens Quarry Section

Sec. 18 and 19, T18N, R5W Menard County, IL (Greenview Quadrangle)

The sequence of materials in the overburden of this limestone quarry matches very closely Worthen's description
(1873) of an organic-rich zone later named the Sangamon Soil.

INTRODUCTION

The limestone quarries north of Athens, Illinois, are located within the
central portion of the type area of the Sangamon Soil. Type section concepts
are not directly applicable to soils (pedostratigraphic units) as they are to
lithostratigraphic and chronostratigraphic units because for soils, all of the
necessary information for establishing type section concepts are not available
at one designated location. For soils, the necessary information for refer-
ence and definition involves a catena (a sequence of soil profiles ranging
from well drained to poorly drained) in a minimum lateral distance of gener-
ally 100 ft (30 m) or more. North Quarry, an active quarry, provides the
necessary information for a reference section. The open pit exposures are
generally more than 1,000 ft (300 m) long and serve well as a type locality
exposure of the Sangamon Soil.

Most of the material used in the discussion of this stop is taken from a
guidebook prepared for the 1979 Midwest Friends of the Pleistocene Field Con-
ference (Follmer et al . , 1979). New results from C-14 studies have been added.

BACKGROUND

Much of the study of the glacial stratigraphy in Illinois has been
directly or indirectly related to the Sangamon Soil. In a general sense, the
Sangamon became known as a zone of weathering on glacial deposits about the
same time that the drift upon which the Sangamon Soil developed was recognized
as the Illinoian till sheet (Leverett, 1898a). Leverett and others recognized
the need for a term to identify the interruption in the glacial record between
the Illinoian and Iowan (Wisconsinan) Stages of glaciation.

The Sangamon Soil was first recognized as a soil by Worthen in 1873 in
the fifth volume of his report to the Illinois General Assembly on the geology
and paleontology of Illinois. Worthen had not recognized the existence of a
buried soil until his fourth volume (Worthen, 1870), when he reported a soil
zone or "bed resembling the surface soil was observed below the Drift" in a
coal mine shaft in Adams County in western Illinois.

In his report on Sangamon County, Worthen summarized the common observa-
tions on the sequence of materials found in northwestern Sangamon County and
the adjoining part of Menard County. All of the units described by Worthen
can be seen in the Athens Quarries today (Table 2-1).

Table 2-1. Correlation of terminology in type locality of the Sangamon Soil.

Worthen (1873) Present

Soil Peoria Loess, A horizon

Yellow clay Peoria Loess, B horizon

Whitish gray clay with shells Peoria Loess, C horizon, calcareous

Black muck with wood Peoria Loess, basal organic zone

Robein Silt, Farmdale organic horizon
Bluish colored boulder clay Diamicton, Sangamon Soil Bg horizon

Gray hard pan Diamicton, calcareous Illinoian till

Soft blue clay Undetermined paleosol, till or

lacustrine material

Between 1873 and 1898, resolution of many complexities of the Quaternary
progressed considerably. The idea of multiple glaciations separated by inter-
glaciations and characterized by episodes of nonglacial erosion and weathering
of the surficial materials had been largely accepted. The U.S. Geological
Survey furthered progress with a program directed by Frank Leverett on the
study of the glacial formations of the Midwest.

During his work in the Midwest, Leverett discovered that one soil
occurred above and another below a formation of glacial deposits that he named
the "111 inoian till sheet" in 1896. In 1897, Leverett gave these
soils formal status by naming them the "Sangamon soil" and "Yarmouth soil,"
respectively (Leverett, 1898a and 1898b). By 1898 the concept of the Sangamon
Soil was reasonably well understood, as indicated in Leverett's paper
introducing the Sangamon as "the weathering zone between the (Wisconsinian)
loess and the Illinoian till sheet . . . found from central Ohio westward to
southeastern Iowa, i.e., to the limits of the Illinoian till sheet" (1898a, p.
75). The first use of the term "Sangamon soil" by Leverett in 1898 restricted
it to the black soil, muck, or peat that contains remains of coniferous wood
occurring at the base of the loess. The purpose of naming the Sangamon was to
formalize a term so that an interval of geologic time could be named "the
Sangamon interglacial stage," to separate the "Illinoian and Iowan stages" of
glaciation. The Iowan was later included in the Wisconsinan and eventually
dropped as a time term (Ruhe, 1969).

Perhaps Leverett's most astute observation was that the type of organic
matter in the "black soil," particularly the coniferous wood, is not
characteristic of conditions during an interglacial climax, but of "the close
of that stage when glacial conditions were being inaugurated." Probably all
of the woody deposits that Leverett observed below the loess in central
Illinois are post-Sangamonian by present definition, but were interpreted to
be the Sangamon Soil by Leverett.

In 1930, Leighton and MacClintock published their classic paper on the
"Weathered zones of the drift-sheets of Illinois." Leighton and MacClintock
reached a very important point in the understanding of the Sangamon Soil.
They recognized a type of catena: the gumbotil profile in poorly drained
areas, the siltil profile in well-drained areas, and the mesotil profile in
intermediate areas. They did not call them types of Sangamon Soil, but
weathering profiles on Illinoian drift. They used the term "Sangamon" only in
a time-stratigraphic sense.

In 1931, the stratigraphic position of the Sangamon Soil was adjusted
when Leighton (1931) reinterpreted the loesslike silt described at the "Farm
Creek exposure" (Leighton, 1926) to be the "Late Sangamon loess." This
exposure was considered by Leighton to be a "type Pleistocene section," and,
in effect, became the reference section for the Sangamon Soil. The inference
that can be drawn from Leighton (1931) is that the Sangamon Soil transgresses
from interglacial to glacial conditions and consists of two parts:

(1) Illinoian gumbotil (a product of intense weathering) in the lower part and

(2) a youthful soil profile formed in the Late Sangamon loess which may have
developed during the "Iowan," the first glacial stage of the "Wisconsin."

After 1931, no significant modification of the two-part concept of the
Sangamon Soil was made for about 20 years. Then Leighton eliminated the

"upper Sangamon" by changing the name of the "Late Sangamon loess" to the
Farmdale loess (Wascher, Humbert, and Cady, 1948) and placing it into the
"Wisconsin" stage (Leighton and Willman, 1950). During the 1940s, Leighton
and others came to realize that the Farmdale loess was a deposit related to
glacial conditions. But the Sangamon peat described by Leverett (1899) at the
"Farm Creek exposure" overlies the Farmdale loess. Therefore, by placing the
peat and Farmdale loess into the Wisconsinan, the peat bed containing the
boreal remains (coniferous wood) was deleted from the Sangamon Soil as
conceived by Leverett.

The most controversial change in the concept of the Sangamon Soil
occurred in 1960 when Frye and others published the paper, "Accretion-gley and
the gumbotil dilemma." They criticized the dualism of the empirical and
genetic definition of gumbotil and suggested that gumbotil be restricted to
the truly in situ, gleyed soil. They reviewed the term gley, a product of
reduction in a wet environment, and defined "accretion gley," a product of
"slowly accumulating deposits of surficial clay" in a wet soil environment.

Shortly after publishing their paper on the gumbotil dilemma, Frye and
others (1960b) presented the first broad analysis of the physical features of
the Sangamon Soil in Illinois, but did not describe any soil profiles. The
significant conclusions drawn by Frye and others (1960b) are: (1) the degree
of mineral decomposition in accretion-gley profiles is less than in the in
situ profiles and much less than ascribed to the gumbotil, and (2) the term
gumbotil is not a good scientific term and "should be used only in a general
sense to refer to those plastic and sticky surficial clays resting on till."
Leighton and MacClintock (1962) disputed much of the work of Frye and others
but acknowledged that some deposits are accretion gleys.

Frye and Willman (1963) countered by commenting on what they considered
to be archetypical gumbotil sections that "At every reported exposure that we
have recently examined the 'gumbotil' is accretion-gley." The dilemma can be
explained by considering a conceptual catena. Given a nearly level ground
surface with an occasional rise and isolated depressions, an in situ, poorly
drained gleyed soil can exist on the level ground between the accretion gley
in the depression and the better-drained, in situ soil on the rise. In fact,
this sequence is typical on a large part of the flat 111 inoi an till plain. In
a soil-geomorphic sense, disregarding the chemical and mineralogic require-
ments, the in situ, gleyed profile could be called gumbotil; however, Willman
and others (1966) did not approve of differentiating a poorly drained, in situ
soil from the better drained, in situ soils because they did not consider it
practical .

Because the Sangamon Soil is time-transgressive, its recognition in a
sequence of deposits does not necessarily establish that the beginning of
Wisconsinan time is marked by the top of the soil. The Wisconsinan time
boundary commonly lies within the A horizon of the Sangamon Soil and has been
determined in Illinois by detailed analyses of grain sizes (Follmer, 1970,
summarized in Johnson and others, 1972) or by mineralogical analysis (Frye and
others, 1974). The beginning of Wisconsinan time has been estimated by Frye
and others to be about 75,000 years ago. Studies in Iowa (Rune, 1976) and in
Indiana (Kapp and Gooding, 1964) suggest that the Wisconsinan begins at a
younger age.

A general evaluation of all known published descriptions of the Sangamon
Soil in central Illinois has been summarized by Follmer (1978). Only 7 of the
88 described sections included detailed description of the Sangamon Soil. At
17 other sections, only the major horizons were noted. The general appear-
ances of the profile were described at 52 sites; at the remaining 12 sites the
Sangamon Soil was noted as occurring in the described section, but was not
described. The type area of the Sangamon Soil had not been designated until
the central portion of the Illinoian till plain was proposed (Follmer, 1978).

The major concepts of the origin and stratigraphic position of the
Sangamon Soil in Illinois have evolved into a reasonably clear picture in the
88 years since the introduction of the Sangamon Soil by Leverett (1898a).
Some of the details remain to be resolved, however. The details pertaining to
the Sangamon Soil and its age have become increasingly important as more
precise correlations to other areas, particularly the oceanic record, are
being attempted.

The need for more precise information has always been recognized.
Leighton initially went to the Farm Creen Section in 1926 because he thought a
"detailed examination" was needed. Even after the great amount of work
Leighton accomplished himself, he described the need for a comprehensive study
of the weathering profiles (1962) and made recommendations that the "Farm
Creek Section should be opened up" and studied again (1965). In more recent
work, Willman and Frye (1970) thought that paratype sections of two types of
Sangamon Soil profiles were needed because none had existed before. At the
present time the status of the Sangamon Soil in central Illinois can be
generalized by the following: (1) It has been used successfully to separate
the Wisconsinan and Illinoian deposits; (2) the mineralogy has been satis-
factorily characterized; (3) its morphology and parent material have not been
studied in sufficient detail; (4) its catenary members have been character-
ized at Athens North and South Quarries, but more work needs to be done; (5)
the top of one accretionary profile has been dated at 41,770 + 1100 RCYBP
(ISGS 684).

ATHENS NORTH QUARRY SECTION

The section was measured at the east end of the operating Material
Services Indian Point limestone quarry, August 1978.
Pleistocene Series
Wisconsinan Stage

Woodfordian Substange
Peoria Loess

Depth Sample Thickness

Horizon (m) no (m)

Loess; dolomitic, light olive-gray (5Y 6/2)
silt loam, common 10YR 6/8 mottles, common
dark stains and small iron concretions;
massive to weak platy, very weak aggregation;
porous, common small channels with thin dark
argillans; friable; upper 1.0 m disturbed. 2.1

1.02

NQA43

2.05

NQA35

Depth Sample Thickness

Horizon (m) no (m)

Oa 2.18 NQA34 Silt, organic rich; dolomitic, very dark

Oe to to grayish brown to black (10YR 3/2 and 2/1)

A 3.28 NQA17 color-stratified muck and silt loam, few

to common 5/6 mottles, few pipestem
concretions in upper part; few continuous
small channels; weak platy "bedded" structure
with ragged vertical fracture faces and felted
horizontal surfaces; well-preserved spruce
needles and charred-carbonized wood fragments
in upper part, zones of highly decomposed
organic material between zones of moderately
well preserved woody fragments, generally more
decomposed downward; abundant wood remains in
lower 5 cm (wood at 2.25 m, 22,170 ^450 RCYBP
(IS6S-534). 1.2

Farmdale Soil

irmdalian Su

bstage

Robein Silt

3.37
3.40
3.47

NQA16
NQA15
NQA14

3.53
3.60

NQA13
NQA12

Gley
zone
I

3.66
3.73
3.98
4.14
4.30

NQAll

NQAIO

NQA9

NQA8

NQA7

Muck; leached, black (10YR 2/1) mucky silt,

rare 5/4 mottles in upper part; massive to

very weak platy; firm when moist, hard and

punky when dry (wood at 3.35m, 25,170 +_ 200

RCYBP [ISGS-536]). 0.2

Silt; leached, black (10YR 2/1) silt loam;

massive, very weak aggregation, fracture

surface rough with small rounded forms;

somewhat friable. 0.1

Silt; leached, very dark gray to dark gray
(5YR 3/1-4/1) silt loam, more sand at base;
nearly massive, healed platy (bedding?);
rare pores and small channels; few very
thin argillans; few thin bleached silt
lenses; traces of organic matter, stratiform
light and dark layers; somewhat friable, hard
when dry; a few krotovina filled with
2/1 or 3/1 silt; common large-scale involu-
tions (differential compaction or cryoturba-
tion?); very gradational boundaries (C-14
dates on muck from adjacent pits in lower
half of unit, 35,750 + 620, 37,100 +_ 1200
[ISGS 870 and 883], respectively). 0.7

Horizon

Depth
(m)

Sample
no

Altonian Substage
Roxana Silt

Bg/A

4.46

NQA6

61 ey

zone

5.27

NQA1

4.45

NQB22

5.25

NQB18

Sangamonian Stage
Glasford FormaTi on
Berry Clay Member

5.45

NQB17

Gley

5.65

NQB16

zone

5.85

NQB15

III

6.05

NQB14

6.25

NQB13

6.45

NQB12

6.65

NQB11

Illinoian Stage
Glasford

Thickness
(m)

Silt; leached, gray (5Y 5/1) heavy silt loam,
rare 5/6-6/8 mottles; B horizon superimposed
on A horizon, structures largely healed, breaks
into blocks with rounded forms (welded aggre-
gates) on fracture surfaces, distinct platyness
and traces of degraded charcoal; few small
channels, porous in places; few thin argillans
in pores; rare silans separating platy forms;
friable to plastic; occasional krotovina
filled with Robein material; very gradational
boundaries (C-14 date on humus from preserved
Ab from top of unit from adjacent pit 38,900
+ 654 RCYBP [ISGS 654]). 1.0

Sangamon Soil

Clayey silt; leached, dark gray to greenish gray
(5Y 4/1 to 5GY 4/1), silty clay loam, some sand,
few pebbles; few 7.5YR 6/6 mottles, few 2/1 stains
and small concretions; rare degraded charcoal in
upper sample; nearly massive when wet, weak blocky
with irregular aggregate forms when dry; few thin
to large dark argillans; few silans; few pores
(channels, planar voids and vugs); more firm than
above; plastic when wet, hard when dry; few
krotovina; local masses of vivianite, white, turn
blue on exposure; clear lower boundary
(C-14 date on seeds, charcoal and humus from
preserved Ab from top of unit from adjacent
pit, 41,770 + 1100 RCYBP (ISGS 684). 1.4

Formation
Vandal ia Till Member

Bg 6.75 NQB10 Till; leached, dark greenish gray (5GY 4/1)
6.90 NQB9 loam, common pebbles, many 5Y 6/6 mottles;
Gley few stains and small concretions; nearly

zone massive when wet, healed weak blocky with

IV moderate aggregate expression when dry; few

5Y 4/1 argillans; firm to plastic;
occasional krotovina; gradual irregular lower
boundary.

0.3

7.50

NQB5

7.65

NQB4

7.85

NQB1

7.95

NQB2

8.05

NQB3

9.20

NQBB9

10.10

NQBB1

Depth Sample Thickness

Horizon (m) no (m)

B3 7.05 NQB8 Till; leached, olive (5Y 5/4) loam, common
(BC) 7.20 NQB7 pebbles, common 5G 6/1 and 10YR 6/8 mottles,
(CI) 7.35 NQB6 few manganese concretions; weakly blocky with

few argillans on healed ped surfaces, few
pores; firm to plastic; gradual to distinct
lower boundary. 0.4

C2 7.50 NQB5 Till; dolomitic, light olive-brown (2.5Y 5/4)

loam, common pebbles, gravel -rich zone at
base, common 1CYR 5/8 and rare 5G 6/1
mottles; weak coarse platelike blocks; rare
small argillans; brittle, hard somewhat friable;
common vertical stained joints; gradual lower
boundary. 0.4

Till; dolomitic, pebbly loam, olive (5Y 5/4-5/3)
grading down to dark gray (5Y 4/1), oxidizes to
4/2 on exposure, common 5/8 mottles at top and
base; middle part uniform gray with coarse blocky
to platy fracture pattern on drying, massive when
wet: breaks with smooth to hackly conchoidal
surfaces; dense, firm, brittle (dry), plastic (wet);
rests upon glacially polished Pennsylvanian
limestone in most places. 2.1

Total 10.2

EXPLANATION OF TERMINOLOGY

Geologists and pedologists have historically used different styles in
describing weathering profiles in surficial materials. In this description
the two styles are combined to illustrate relationships of terminology. The
first word of the description is a lithogenetic term used by geologists; the
second is a term that describes a condition of leached (of carbonate minerals)
or dolomitic ("unleached"). Much of the terminology, concepts, and horizon
designations is from Soil Taxonomy (Soil Survey Staff, 1975). Recent trends
are replacing lithogenetic terms with simple descriptive terms, such as
diamicton for till and silt for loess. When these descriptive terms are
encountered, it is important to keep in mind the differences between general-
izations made by geologists and specific definitions offered by the USDA Soil
Taxonomy. For example, what a geologist may call silt could include a range
of textures from silt to loam or silty clay as defined by the USDA. In the
main body of the description, the USDA definitions for texture have been
followed. The C horizon has been differentiated on morphogenetic criteria and
is explained in the appendix.

DISCUSSION

The Peoria Loess at North Quarry is dolomitic and 3.3 m thick; it con-
tains dolomite zones p-1, p-2, p-3, and p-5 (McKay, 1979). The clay-mineral

composition of the Peoria increases in expandable clay minerals and decreases
in kaolinite and chlorite upward from the base (fig. 2-1).

The lower 1.2 m of the Peoria Loess (zones p-
of p-3) contain well-preserved spruce wood, needle
Wood and muck at the base of the Peoria and at the
the Farmdale Soil yielded a radiocarbon date of 25
536). This date supports the interpretation that
Peoria Loess is about 25,000 years old. The upper
(sample NQA33) yielded a date on wood of 22,170 +
date is from just below the middle of zone p-3, wh
range from about 20,500 to about 24,000 years old

1, p-2, and the lower half
s, and other plant debris.

top of the 0a horizon of
,170 +_ 200 RCYBP (ISGS-
the aye of the base of the

part of the organic zone
450 RCYBP (ISGS-534). This
ich has been estimated to
(McKay, 1979).

ISGS 1979

Figure 2-1. Grain sizes, carbonate-mineral content, and clay mineralogy of profiles A, B, and BB of the
Athens North Quarry Section. Subdivisions of the C horizon are designated in the clay mineral column; see
appendix 2 for explanation.

The Oa horizon of the Farmdale Soil is more compact than the overlying
organic-rich zone and stands out in the exposure as a more resistant bed. As
organic-rich as this horizon appears, it only contains 6.3 to 7.3 percent
organic carbon. It is leached of carbonates and contains about 85 to 90
percent silt. This horizon has the greatest amount of vermiculite in the
profile; the presence of vermiculite causes large reductions in the calculated
values for expandable clay. An A horizon occurs below the Oa, and from that
point downward, the clay-mineral trends change very little until the till is
encountered. This indicates a similarity of the materials, or of the soil-
forming environment, or both. The environmental conditions may be the more
important of the two.

The parent material of the Farmdale Soil here is interpreted to be the
Robein Silt. The upper part is organic-rich silt and the lower part is an
involuted gleyed silt loam (gley zone I). This gley appears to have a wavy
bedding and a few soft-sediment penetration structures. The clay content
gradually increases downward and sand becomes noticeable in the lower part.
The lower boundary is placed where the color becomes lighter and the apparent
bedding stops. All other features are very gradational across the boundary
into gley zone II. In more recent exposures an abrupt boundary with an
organic horizon at the top of gley zone II has been found.

Passing down into gley zone II at the site of the original description,
the small soil features change somewhat and become more granular or have a
welded granular aggregation within a weak blocky or platy structure. Mottling
becomes apparent and the clay and sand content continues to increase down-
ward. Gley zone II is interpreted to be the Roxana Silt because of the silt
content and stratigraphic position. The Roxana (massive gleyed silt) appears
to be the source for the overlying Robein (stratified gleyed silt).

The lower boundary of gley zone II with gley zone III is very gradational
at most places. Blocky aggregates with argil lans and internal granularity
help distinguish zone III. Pebbles become apparent and texture becomes a
silty clay loam in zone III. Traces of charcoal and other organic fragments
present in the upper sample of this zone indicate a ground surface. In a more
recent exposure, a distinguishable, dark-colored A horizon has been
observed. Gley zone III is interpreted to be the Berry Clay (accretion-gley)
and the upper part of the Sangamon Soil. The principal argument for Berry
Clay is based on the conformable relationships it has with the Vandal i a Till
below and the Roxana-derived material above. For practical purposes, the top
of the Sangamon Soil is arbitrarily placed at the top of the Berry Clay. An
alternative is to place the top of the Sangamon at the top of the Farmdale
Soil, as did Leverett in 1898; however, Leverett did not realize that a
glacial deposit (Roxana) separated the weathered till (Sangamon) from the
Farmdale organic horizon.

A third alternative interpretation for gley zone III comes from the silt
fraction data (Follmer et al., 1979). The medium silt content is about 10
percent higher than in the underlying till; this suggests that a loessial
component is in zone III; the admixture of some Roxana Silt in the Sangamon
Soil is common in all profiles that have been examined.

The lower boundary of gley zone III with gley zone IV is clear in
comparison to the other zone boundaries. Pebbles are more common, the sand

content is higher, and the zone takes on the appearance of gleyed till. The
boundary position is commonly gray with many "orange" mottles. The blocky
aggregates are more distinctive, but in a fresh exposure the zone is usually
wet and plastic, and appears massive, as in zone III. In places a coarse
layer is found at the top of the till. The sand content of zone IV (about 40
%) is the same as the till below. Also, the clay mineralogy shows a genetic
relationship to the underlying till. The gleying has caused some increase in
the values of the expandables and kaolinite and chlorite, and a decrease in
illite values. Therefore, gley zone IV is interpreted to be the upper part of
the Vandalia Till .

The olive B3 beneath the gley zone IV is a normal pedologic feature in
gleyed soil profiles. The solum thickness of the Sangamon in this profile is
2.1 m, and the B3 is in sharp contact with a calcareous C2 horizon in the
Vandalia in most places. Average carbonate content of the C2 is slightly
lower (27.4 %) than the C4 (28.5 %) . Grain size is essentially the same for
both horizons, averaging 38 percent sand and 27 percent clay (20% <2 ym). The
C4, but is largely destroyed in the C2. This causes the warp in the illite to
kaolinite and chlorite depth-function between 8 to 9 m (fig. 2-1). The value for
kaolinite and chlorite is about 20 percent in the C4. When oxidation alters
the chlorite, the value for kaolinite and chlorite drops to about 10 percent,
and the difference is largely made up by the apparent increase in illite from
about 71 percent to 77 percent. This difference in illite content shows the
value of recognizing subdivisions of the C horizon so that the degree of
weathering can be considered when till correlations are made.

NEW INFORMATION

Since 1979, the quarry operations have continued to work northward and
have produced one or two new exposures each year. Each open pit is about 1000
to 1300 ft long with a width of 265 ft. Each new pit is parallel to the
former pit and is separated by a 15-ft buffer zone. The pit studied in 1978
was designated pit 1. The Midwest Friends of the Pleistocene (Follmer et al . ,
1979) examined pit 2.

After the Friends trip in 1979, a new exposure in pit 3 revealed an
organic-rich A horizon in the top of the Roxana (fig. 2-2). The age of this
horizon is 38,920 ^ 1100 RCYBP (ISGS-654). Later in 1980 a careful search for
a preserved Sangamon A horizon revealed one isolated location in which dark
blotches containing seeds, plant fragments and carbonized wood were present.
A combination of these materials with extracted humus gave an age of 41,770 +_
1100 RCYBP (ISGS-684, Follmer, 1983). The humus alone yielded an age of
35,560 +_ 900 RCYBP (ISGS-688), which indicates that a small amount of con-
tamination probably affected the age of the residue sample. This allows us to
project the age of the top of the accretionary Sangamon Soil at this location
to be about 45,000 years old.

In pit 4 and in all succeeding exposures up to the present, multiple
couplets of A and Bg horizon have been found in the lower part of the Robein
Silt. Each A/Bg couplet is interpreted as a soil that developed in accreted
silty material. Samples collected from the two most prominent A horizons, the

lower one (5 cm thick) from the top of the Roxana and the upper
thick) about 0.5 m above the Roxana, gave ages of 37,100 +_ 1200
35,750 +_ 620 (ISGS 870) RCYBP respectively. No formal name has
to these soils, but they have been referred to as splits in the
geosol .

one (15 cm
(ISGS 883) and
been assigned
Indian Point

The greater thickness of the Peoria Loess in pit 3 suggests that the
Farmdale Soil in Roxana may have been lower on the paleolandscape and buried
at an earlier time than the equivalent horizon in pit 4. Also, sampling from
different stratigraphic levels could account for the apparent different age.
The pit 1 profile was sampled nearer a modern drainage way that appears to be

PIT 1

PIT 3

PIT 4

O-i

1 -

2 -

4 -

5 -

10 -

11 -I

Modern
Soil

Farmdale
Soil

organic
horizons
unnamed
geosols

Sangamon
Soil

H60±nH

Figure 2-2. Stratigraphic correlations of North Quarry pit exposures.

related to the thinner Peoria Loess at that location. The C-14 dates from pit

1 indicate that the base of the Peoria is intact there and that headward

erosion by the modern drainage way has eroded about 1 m or more of the younger
parts of the Peoria Loess.

SUMMARY OF PALEOBOTANICAL STUDIES

Bulk samples for pollen and plant analyses were collected from the North
Quarry pit exposures in 1978 (J. King, 1979). Because of the continued quarry-
ing operations the same exposure is no longer present, but a similar exposure
is expected to be available in 1986. The pollen samples were collected from a
cleaned face at the east end of the north wall in pit 1 near the site of the
profile description. At the east end of this pit, the upper horizon of the
Farmdale Soil is a compact muck that grades upward into a 50-cm-thick, dark
peatlike, silty deposit in the lower part of the Peoria Loess. Abundant wood
fragments, plant macrofossils, and small logs are present at the base of the
Peoria (table 2-2).

Table 2-1. Macrofossils from Athens North Quarry (F. King, 1979).

Wood

Picea

spruce

Pinus

pine

Larix laricina

larch

Needles

Picea

spruce

Abies balsemea

balsam fir

Cones

Picea mariana

black spruce

Seeds

Cyperus

sedge

Hypericum

St. John's-wort

Viola

violet

Pollen in the Athens North Quarry section was preserved only in a 50-cm
section above the Farmdale Soil in the lower part of the organic-rich Peoria
Loess (fig. 2-3). Spruce wood at the Peoria Loess/Robein Silt contact (the
base of the pollen column) was radiocarbon dated at 25,170 + 200 RCYBP. Wood

ATHENS NORTH QUARRY

*$wW^0y

10 20 30 40%

Figure 2-3. Relative frequency of pollen from Athens North Quarry.

from near the top of the oryanic-rich silt and 80 cm above the uppermost
pollen sample is dated at 22,170 +_ 450 RCYBP. The dark organic-rich silt with
the preserved pollen therefore dates between about 23,000 and 25,000 8. P.

The pollen in this section is dominated by Pinus (pine) and Picea
(spruce); together these two types comprise about 70 percent of the total
pollen. Other taxa commonly present throughout the section include Quercus
(oak), Gramineae (grass), and Tubuliflorae (the sunflower group). Yfie
variations in the percentages of individual taxa between samples is relatively
small within the range of confidence limits of percentages based on N_ of 200
(Rohlf and Sokal , 1969). Thus, the fluctuations between levels of pine and
spruce, the major plant types, are not statistically significant. A possible
shift to slightly colder climatic conditions toward the top of this short
pollen section may be suggested by the disappearance of Betula (birch), Salix
(willow), and Morus (mulberry). Overall, however, the pollen evidence
indicates rather stable vegetational conditions during the deposition of this
portion of the lower Peoria Loess which occurred over approximately a 2000-
year period.

The pollen in the Athens North Quarry section appears to reflect a forest
composed of pine and spruce with a grass and herb understory. The presence of
<10% oak pollen indicates that it was not growing near the site; the oak
pollen in the section apparently drifted in on the prevailing winds from
source areas to the south and southwest. The pollen does not suggest any type
of major climatic change between 23,000 and 25,000 years ago in this area.

DICKSON MOUNDS

Alan D. Harn

STOP 3. The Dickson Mounds Museum

Along the Illinois River, west of Havana IL, Fulton County (Havana Quadrangle)

A modern museum has been developed in an area rich in remains of a Mississippian culture abandoned about A.D.
1300.

Dickson Mounds, a branch of the Illinois State Museum and a National
Historic Site, is one of the few on-site archaeological museums in
the Midwest. It developed as the result of a carefully planned private
excavation undertaken nearly 60 years ago by Or. Don F. Dickson on land owned
by his family. First opened to the public in 1927, this excavation was
operated as a private museum until 1945 when it was sold to the State of
Illinois. Additional excavations and research by the Illinois State Museum
over the last three decades have greatly increased knowledge of the site and
its importance in interpreting Midwestern prehistory during the Woodland and
Mississippian archaeological periods.

Between A.D. 800 and 1200, important changes were taking place in
lifeways over a large area of North America. At the beginning of this time
period, people lived in small, scattered settlements supported primarily by
fishing, gathering, and hunting of large animals such as deer. Some wild,
starchy seed plants also were being domesticated through cultivation. By the
end of the period, people were concentrated around fortified towns and were
part of a highly controlled, structured society partially dependent upon
horticulture for its food. The development of such economically important
crops as corn and beans can be attributed to these later groups. These
innovations and changing lifestyles can be traced especially well at Dickson
Mounds, which stands at the margins of several major culture areas.

A thousand years ago, bands of Late Woodland people in the Illinois River
valley were beginning to come increasingly under the influence of a strong
Mississippian culture which had developed downriver near the present East St.
Louis. Within a century, Mississippian people had established a small
habitation site (Eveland) on the terrace at the bluff base below Dickson
Mounds. Here the Woodland and Mississippian populations merged, and by A.D.
1250 this settlement and the Dickson cemetery had become a part of a large
Mississippian community of villages, camps, homesteads, and work stations
extending for several miles along the river. Its center was a fortified town
on the blufftop near Dickson Mounds. This grouping of over 40 sites
represented a seasonal interplay of human activity which articulated with the
natural environment in a delicate attempt to support a rapidly expanding
population. Growth in population and intensive exploitation of the
environment gradually resulted in a depletion of resources, and by A.D. 1300
the inhabitants had abandoned the area.

Dickson Mounds Museum offers a variety of learning experiences for the
scientist as well as for the general public. In addition to its mandate of
public education, the Museum serves as an active research center for Illinois
State Museum archaeologists and as a repository for regional archaeological
collections. Outside at the Eveland village site, remains of three original
structures from an early Mississippian village are preserved for viewing.
Within the museum complex at Dickson Mounds are the original 248 human burials
and their accompanying possessions which were excavated by the Dickson family
between 1927 and 1932. Modern museum displays and programs interpret the
unique prehistory of the area and relate it to human cultural development in a
regional perspective.

FARM CREEK: A NOTABLE PLEISTOCENE SECTION

Leon R. Follmer and E. Donald McKay

STOP 4. Farm Creek Section and adjacent sections

Sec. 30, 31, and 32, T26N, R3W, Tazewell County IL (Peoria East and Washington Quadrangles)

First described by Leverett in 1899, The Farm Creek Section has been much studied ever since by glacial geologists.

No exposure in Illinois has drawn more attention from glacial geologists
than has the Farm Creek Section. Since Leverett's discovery of this creek
bluff in 1897, this exposure has stimulated much research into the late
glacial history of the area. The Farm Creek Section was one of the featured
stops on the 1979 Midwest Friends of the Pleistocene Field Conference (Follmer
et al . , 1979). The following summary and discussion are modified from
material prepared for the Geological Society of America Decade of North
American Geology--Centennial Field Guides.

The Farm Creek Section, located east of Peoria near the margin of the
late Wisconsinan (Woodfordian) glacial margin, is a large cut bank of Farm
Creek in the Farmdale Recreation Area.

The Farm Creek Section and nearby exposures appear to be complete with
respect to most stratigraphic elements of the late Pleistocene in central
Illinois, and continue to be the best and most accessible exposures in the
area. The Farm Creek Section is the type section for the Farmdale Soil, the
Farmdalian Substage, and the Robein Silt. Many geologists have used this
section as a type or reference section for litho-, chrono-, and pedostrati-
graphic units. A discontinuous organic paleosol within a sequence of loess
that overlies Illinoian till and underlies Wisonsinan till is a principal
reference point for Pleistocene researchers in Illinois. The organic soil
was first thought to be the Sangamon Soil but later was determined to
stratigraphically overlie the Sangamon Soil developed in Illinoian till.

BACKGROUND

Leverett (1899) first described and interpreted the Farm Creek Section in
terms of the meaning of the organic soil and weathering zone on the Illinoian
till. He related both features to the Sangamon Soil and considered them to be
evidence for an interglacial stage (Follmer, 1978). Leighton (1926) was so
impressed with the exposure that he referred to it as "a notable type Pleisto-
cene section." His general interpretation of the sequence between the over-
lying Wisconsinan till (Shelbyville) and the Illinoian till below agree with
Leverett's (fig. 4-1). Leverett's Farm Creek description indicates that he
did not resolve the detail that was later found to be present. The terms
Iowan and Peorian, first introduced by Leverett, have been confused or mis-
interpreted and have since been dropped (see McKay in Follmer et al . , 1979).
The Iowan was interpreted as a glacial event between the Illinoian and
Wisconsinan, represented here by a calcareous loess; the Peorian was thought
to be a loess deposited at the end of a glacial event and weathered during an
interglacial event.

Leighton and Leverett agreed that the "Sangamon" (the organic zone)
contains coniferous wood and overlies a loesslike silt. The boreal vegetation
present caused interpretation problems because the Sangamon was thought to be
a time of warmth similar to the present climate. They concluded that the
cold-climate indicators reflected either the close of the Sangamon time or the
result of the subsequent glaciation. By 1948, Leighton had decided that the
loesslike silt had been generated by glacial conditions, and consequently he
renamed the unit the Farmdale loess. Leighton and Willman (1950) interpreted

this loess as representing the Farmdale substage, the oldest part of the
Wisconsin stage. They did not name the organic soil at this time but recog-
nized it as a youthful profile of weathering not sufficient to be designated
as an interglacial soil. This interpretation removed the confusion between
the organic soil and the profile of weathering on till below the loess, both
of which had been called Sangamon. This change brought the basic strati-
graphic interpretations into alignment with present concepts, but no agreement
on terminology was reached at this time.

In 1960 Frye and Willman proposed a major revision of the Wisconsinan
terminology because new data could not be reconciled with the old models.
Much new information was developed from their study of the Farm Creek area.
Their work culminated with the publication of a comprehensive study of the
Pleistocene stratigraphy of Illinois (Willman and Frye, 1970). They cor-
related and renamed most stratigraphic units present at Farm Creek and desig-
nated the section as the type section for the Farmdale Soil, the Farmdalian
Substage, and the Robein Silt. A new railroad cut south of the Farm Creek
Section (plate 4) was designated the type section of the Morton Loess (Frye
and Willman (1960). Most of the changes resulted from the implementation of a
system of multiple classification allowing litho-, chrono-, and pedostrati-
graphic units to be treated independently. In effect, the previous classifi-
cation system was monotaxonomic, in that all aspects were considered interre-
lated; this led to confusion of the terms used for materials, time intervals,
and paleosols.

The study of Follmer et al . (1979) provides the most recent information
for the Farm Creek Section. In this study, the classic Farm Creek Section was
described, using the terminology of Willman and Frye (1970); figure 4-2 shows
a generalized sketch of the main section. Profiles A and C are in the general
area that had been previously studied. The area where profile B was taken had
probably not been studied before, but the materials present there appear to be
similar to those Leverett had found in the old railroad cut about 0.8 km (0.5
mi) upstream (east). All profiles show the location of detailed sampling and
description. The results are presented in Follmer et al . (1979) and are
summarized here on table 4-1.

LEVERETT (1899)

LEIGHTON
(1926)

WILLMAN and
FRYE (1970)

FARM CREEK

FC RR*

FARM CREEK

Shelbyville till

Delavan Till

_ 4-

lowan loess

Peorian loess

Morton Loess

to O
to O _
0)

Sangamon peat

Sangamon Soil

(Farmdale Loess)

(1948)

Robein Silt

thick

silt

Roxana Silt

> 16-

lllinoian till

leached
lllinoian till

gumbotil

Sangamon Soil
in till

u 20-

0/1-

calcareous
lllinoian till

'railroad cut near Farm Creek Section

Figure 4-1. Development of stratigraphic classifications of Farm Creek Section.

FARM CREEK SECTION

The top of the Farm Creek Section is quite irregular and nearly vertical
in places. A late Wisconsinan loess (Richland Loess), continuous across the
top, ranges from 1 to 2 m (3 to 7 ft) thick. In most places a modern soil
(Hapludalf) has developed through the loess into the underlying gravel of the
Henry Formation. The alteration due to soil formation caused clay enrichment
and reddening, particularly in the upper part of the gravel. The gravel is
part of the terrace deposits formed by the outwash from the Bloomington
Morainic System to the east. Under the gravel is the Delavan Till Member of
the Wedron Formation, which is about 7 m (25 ft) thick; it contains large
lenses of sand and gravel. The Delavan (the name for basal Woodfordian till
in the area) forms the terminal Wisconsinan moraine south of Peoria.

Table 4-1. Averages of common lithologic parameters.

Grain size

Carbonate

ay mi nerals

(<2mm)*

(

<74lm)**

(<2nn) +

Section

Cal

Dol

K+C

Unit

(%)

{%)

(%)

[%)

(%)

Horizon

Farm Creek

Richland Loess

Henry (sand & gravel )

Delavan Ti 1 1

Morton Loess

"Robe in Silt"

30tt

Roxana Silt

Radnor Ti 1 1

E (C/A) horizon

35tt

Bt horizon

C (oxidized)

C (unaltered)

Gardena

Delavan Ti 11

Morton Loess

"Robein Silt"

32tt

Roxana Si It

Farmdale Park

Radnor Till

C2 (oxidized)

C4 (unaltered)

"Vandal i a Till"

C2 (oxidized)

*Gravel excluded, <4un clay on tills, <Z\tn clay on silts and soil horizons.
**Weight percent of fine fraction (Chittick method).

tPercentages based on sum

ttHigh vermiculite causing

Abbreviations: Sd = sand,

expandable clay minerals

(7A).

of three peak heights.

K+C value to be relatively high.

Si = silt, C = clay; Cal = calcite, Dol = dolomite; E =

(17A), I = illite (10A, K + C = kaolinite and chlorite

The gray Delavan Till forms a sharp contact with the underlying light
colored Morton Loess that can be easily traced across the outcrop. The Morton
is calcareous and appears to be undisturbed except for local, indistinct shear
disturbances. Leverett (1899) and Leighton (1926) thought a soil surface
or eroded soil surface might be present here. No evidence for a soil has
been found in recent studies, but one can be seen at the Gardena Section
about 1.0 km to the southeast of the Farm Creek Section. The Morton is an
early (classic or late Wisconsinan) Woodfordian loess that was overridden by
the advancing glacier. Beyond the margin of the late Wisconsinan moraine
west of Peoria, the Richland and Morton Loess converge to form the Peoria Loess

In the main section at Profile A, about 1.5 m (5 ft) of Morton Loess lies
over a leached brown silt (the Roxana), which is about 5 feet thick and
contains the fossil remnants of the Farmdale Soil. The main body of the
Roxana Silt is eolian and can be traced across the upland of much of Illinois
(McKay, 1979). The Roxana Silt is considered to represent the Altonian
Substage or early Wisonsinan in Illinois. At Profile E the Morton-Roxana
contact is somewhat masked by organic matter, including wood fragments,
carbonized wood, and charcoal. Rounded pods form the organic-rich zone
here. Over time, diagenic processes (biogeochemical degradation) eliminated
the organic matter, leaving large bleached zones and segregations of secondary
iron and manganese minerals. The organic-rich remnants in this occluded form
indicate that the Morton was deposited on an organic-rich soil that continued
to develop upwards. Therefore, it is likely that most of the Morton and
Roxana at this section was initially humic-rich and that most of the humic
material was removed by diagenic processes, leaving most of the Morton and
Roxana exposed in the outcrop, free of humic material.

At Profile B much of the organic material of the 0 horizon of the
Farmdale Soil has been preserved because of the environment of burial. Pollen
is present in the richest portion, but it is poorly preserved. The pollen
assemblage is dominated by pine and spruce, indicating a cool climate during

West

100

120

140

160

Distance (m)

Figure 4-2. Diagram of the Farm Creek Section. Datum point is stream level.

the formation of the Farmdale Soil (see J. King, Stop 2). Radiocarbon analy-
sis of samples near the top and bottom of the organic-rich zone, designated by
Willman and Frye (1970) as Robein Silt, yielded ages of 26,680 _+ 380 and
27,700 +_ 770 RCYBP, respectively. The Robein Silt is defined as a resedi-
mented silt derived from the Roxana, but no evidence for resedimentation was
found in recent studies reported in Follmer et al . (1979). It appears that
organic matter accumulated on the surface of the Roxana Silt during the forma-
tion of the Farmdale Soil; this presents a technical problem because although
this is the type section for the Robein, no evidence for waterlain stratifica-
tion can be demonstrated here. Because stratified Robein deposits are present
in other localities, a new reference section needs to be designated.

The Roxana was calcareous when deposited, but is leached of its carbonate
minerals in the present exposure. The base of the Roxana is gradational into
the top (A horizon ?) of the Sangamon Soil developed in Illinoian till. The
boundary is hard to identify because it has been blurred by bioturbation or
pedogenic processes. The sand content increases downward and the color
becomes lighter. Characteristics of fossil A horizons commonly are poorly
preserved and organic matter (analogous to soft parts of fossils) is often not
preserved. The distinguishing characteristics are the biogenic pores and
structures in the probable A and underlying E horizon of the Sangamon Soil
profile. The relative high porosity in a bleached (light-colored) matrix
serves to identify the "topsoil" of many Sangamon Soil profiles as well as
other soils that have developed in a deciduous forest environment. The
E horizon overlies a greenish gray Bt horizon that is recognized by the abrupt
increase in clay, changes in soil structures from small to large, and the
abundant clay skins coating the soil structures. In most places in the out-
crop the Sangamon Soil is poorly drained (gleyed); it was formerly referred to
as gumbotil. Because of the gleyed condition, it has been confused with
accretion-gley (Follmer, 1978). In recent years the relatively slow bluff
erosion has exposed a reddish brown Sangamon Bt horizon near the center of the
exposure, revealing a Sangamon catena from a poorly drained profile to a
moderately-well drained profile.

The B-horizon characteristics of the Sangamon Soil fade with depth into
unaltered calcareous, gray Radnor Till of the Illinoian age. The top of the
Illinoian till must be placed at the top of the Sangamon Soil at this site
because no sedimentologic unit can be demonstrated to exist between the Roxana
and the till. Lithologic studies (Follmer et al . , 1979) support the interpre-
tation that the Sangamon soil is the highly altered portion of the till.
Further study is needed to resolve some remaining problems concerning till
correlations. The relationship of the till exposed at profile A to that at
profile H is not yet clear. The clay content at H is about 10% higher than
average (table 4-1), but the till contains the amount of illite characteristic
of the Radnor. At profile A the texture of the C horizons is characteristic
of the Radnor, but the illite content of the unaltered Radnor is about 5%
lower than average (table 4-1). Two rows of data presented in Follmer et al .
(1979) are misprinted; all parameters for samples FCA-1 and FCA-3 must be
inverted in order to put them into correct stratigraphic order. Lower illite
values and higher sand content are regional characteristics of the Vandal ia
Till Member, which occurs stratigraphically below the Radnor Till in this area
and to the south. The till at profile H was at one time assigned to the
Hulick, a middle Illinoian unit known in western Illinois (Will man and Frye,
1970); however, recent lithologic studies in the Farm Creek area suggest that

the best correlation is with the Radnor, the youngest 111 inoi an till in
Illinois. The differences between A and H raise the question of equivalency,
but the till at both locations is more like Radnor than Hulick.

Farmdale Park Section

The Farmdale Park Section was studied near the west ford on the north
side of the creek (Stop 4 map) and presented in Follmer et al . (1979). The
same strati graphic units seen at the Farm Creek Section are present here from
the top of the section down to the Radnor Till. The Sangamon Soil here is a
complete profile of an oxidized, well -drained soil developed in the Radnor
Till. The redness of the Sangamon Soil contrasts with the greenish gray
colors that dominate the Sangamon at the main section. Color and other
physical characteristics indicate that the Sangamon landscape had topo-
graphically high (oxidized) and low (wet) landscape positions. This infor-
mation is used to reconstruct paleolandscapes.

Two Illinoian tills are visible in the lower part of the exposure. The
upper unit is correlated to the Radnor on the basis of stratigraphic position
and lithologic characteristics. Most of the Radnor is calcareous and oxidized
to a yellowish brown. At the north side of the exposure, the base of the
Radnor is unoxidized and gray. Here the gray till forms a distinct boundary
with an underlying oxidized, olive brown, calcareous, more sandy till. The
textural boundary continues across the outcrop, but the color contrast disap-
pears to the south because of oxidization. On the basis of texture and
stratigraphic relationships, the lower till is correlated to the Vandalia Till
Member. But the clay mineral assemblage of the lower unit is typical of oxi-
dized Radnor Till; it is higher in illite than is typical for Vandalia Till to
the south. The two units of Illinoian till at the Farmdale Park Section may
represent a more complex sequence within the Radnor or the lower unit could be
a till older than the Vandalia. Other exposures in the area have not been
studied in detail and may contain the stratigraphic information that can
resolve the question.

Garden a Section

One can hike across the park or along the new T.P. and W. Railroad track
to this rare exposure of a soil developed in the top of the Morton Loess under-
lying the Delavan Till (Stop 4 map) described in Follmer et al . , 1979. A
moss layer at the top of the soil was dated 19,680 +_ 460 RCYBP. Five species
of mosses were found that now range from the northern United States to the
Arctic. Spruce pollen was the dominant pollen in this soil, indicating that this
short-lived soil formed during the coldest interval this area experienced during
the advance of the Woodfordian (late Wisconsinan) glaciers (appendix 1). A few
centimeters of lacustrine clay separate the Delavan Till from the moss
layer. The lacustrine clay probably represents the derangement of drainage
caused by the advancing glacier to form a lake that was soon overridden.

About 2.1 m (7 ft) of Morton is present west of the railroad bridge just
above the creek level. The lower 0.6 m (2 ft) is dolomitic, and is black from
all the decomposed organic matter it contains. The C-14 age of wood in the

base of this zone is 25,370 +_ 310 RCYBP. Under this is a leached organic zone
that yielded an age of 25,960 +_ 280 RCYBP and is interpreted to be Farmdale
Soil developed in Robein Silt. Below water level is the gray (gleyed) horizon
of the Farmdale Soil in Robein Silt. The ages of the organic samples and the
litho- and pedostratigraphic relations confirm the interpretations drawn from
the study of the Farm Creek Section. The analytical data (table 4-1) support
the correlations between sections and illustrate the value of using lithic
parameters in the correlation of glacial deposits. The contrasts within and
between sections create problems and questions when geologists attempt to make
litho-, chrono-, and pedostratigraphic correlations. Appropriate features at
each section are correlated, using stratigraphic and pedologic principles, and
lithologic similarities.

REVIEW OF THE GREEN RIVER LOWLAND

Leon R. Follmer

STOP 5. Normandy Profile Section

SE SW NE Sec. 8, T18N, R7E, Bureau County IL (New Bedford Quadrangle)

Wood found in a soil profile at 1 .5 m depth was determined to be Twocreekan-age black ash underlying
alluvium younger than 1 1 ,400 ± 90 RCYBP.

The route between Farm Creek (Stop 4) and the Green River Lowland site
(Stop 5) is on the complex topography of the Bloomington Morainic System for
about 50 miles (fig. 5-1). The Bloomington Moraine was first recognized by
Leverett in 1897 and formally renamed a Morainic System by Willman and Frye
(1970) because of its multiple ridge characteristics. Older deposits of the
early Woodfordian (late Wisconsinan) are buried by the Bloomington advance
along this portion of the Wisconsinan glacial margin.

The Green River Lowland area has been an area of interest over the years.
The complex glacial history of the lowland has led to some unresolved issues
and controversies. Most of the early interpretations concluded that the first
advance of the classic (Woodfordian) Wisconsinan glaciation occupied some,
part, or all of the lowland (Frye et al . , 1969; Willman and Frye, 1970).
Studies of terraces and drainage patterns in the Rock Island area support the
interpretation of a glacier in the lowland that could explain the terraces
along the Rock River and the abandoned channels of the Mississippi River
(Anderson, 1968).

The age of glaciers occupying the lowland west of the Bloomington is
still in doubt because of complexities and a dependence on physical correla-
tion parameters. In recent work till in the lowland interpreted to be
Woodfordian by Willman and Frye (1970), and formerly correlated to Shelbyville
Drift, has been found to support Farmdale and Sangamon Soils in critical loca-
tions (Follmer and Kempton, 1985). The till has lithic characteristics of the
Radnor Till, the youngest till under the 111 i noi an till plain.

South of Stop 5 we cross the former channel (s) of the Mississippi River
that once traversed the Green River Lowland on a diagonal from the abandoned
channels shown in the northwest part of figure 5-1 (between the loess hills)
to the present Illinois River at the "big bend" (in the middle of the east
edge of figure 5-1). The Woodfordian advance blocked the Mississippi and
caused a large lake to form in the Green River Lowland. Ultimately, water
found a passage to the west, which established the present-day course of the
Mississippi. The release of lake water may have been catastrophic and related
to evidence down the Mississippi for short-lived floods that produced clay
beds in the lower part of the Peoria Loess near St. Louis.

The age of the construction of the Bloomington System and associated lake
and flood features is about 20,000 BP. This was the time when severe
landscape erosion occurred in the area adjacent to the Bloomington (Follmer
et al . , 1978), and this erosional event in Illinois correlates to the time of
maximum erosion on the Iowan erosion surface (Ruhe, 1969). The discussion at
Stop 8 will cover additional details of this event.

During the late Woodfordian large sand dunes up to 50 ft high were formed
on many parts of the lowland. East of Stop 5 sand was blown up and over the
dissected outer Bloomington Moraine to form sheet deposits on the back side of
the moraine. Dominant winds appear to have been from the west. Stop 5 is
located just east of a dune complex and adjacent to the present channelized
Green River. Before the channel was created the Green River did not have
a continuous channel, but passed through large areas of marsh.

During the mapping of soils in the area, wood was found in a test pit at
Stop 5. The wood found was detrital fragments of black ash, which dated at

Iowa

20 mi

__i

20 30 km

Peoria^

5TOP

^Shelbyville\ ;•

Figure 5-1. Surficial geology between Farm Creek and the Green River Lowland.

11,410 _+ 90 RCYBP (ISGS 1112). The wood was collected from the upper part of
a stratified sand at 1.5 m depth. The overlying silty alluvium contains a
normal poorly-drained Haplaquoll of the area.

The alluvium appears to be one unit that shows slight evidence of a
fining-upward sequence. For practical reasons the Holocene boundary for this
area is placed at the contact of the silty alluvium with the stratified sand.

The age of the wood corresponds to Twocreekan, which means that this area
did not experience any sedimentological impact of the younger glacial advance
(Valderan/Greatlakean) in Wisconsin. Black ash is typically the first decid-
uous species to increase significantly after the decline of glacial condi-
tions. Oak, elm, and hackberry wood has been found in alluvium near Mahomet,
west of Champaign, which also date at about the same time. In the Chicago
region, all of the wood of Twocreekan age found has been coniferous.

These observations, combined with data from pollen studies in the
Midwest, indicate that when the conditions for vegetation change were met, the
change was rapid.

FARMDALE AND SANGAMON SOILS

AT THE WEMPLETOWN SOUTHEAST SECTION

Dennis P. McKenna and Leon R. Follmer

-I- ' M

V/2 km

STOP 6. Wempletown Southeast Section

NW NW Sec. 5, T44N, R1E, Winnebago County, IL (Winnebago Quadrangle)

This section exposes a sequence of Peoria Loess and Roxana Silt over a Sangamon Soil
developed in the Argyle Till Member of the Winnebago Formation. The Argyle Till is now
thought to be lllinoian rather than early Wisconsinan.

INTRODUCTION

The Wempletown Southeast Section is an exposure in a quarry on the
uplands above the North Fork of Kent Creek in Winnebago County. This stop was
developed for the 1985 Midwest Friends of the Pleistocene Field Conference
(Berg et al . , 1985). The material is reproduced here with only a few
modifications.

This section is the first described in the
Silt is recognized over a paleosol formed in a W
In earlier studies, the absence of the Roxana Si
developed" paleosols were often cited as reasons
Formation tills to the Altonian Substage (early
the 111 inoian Stage (Shaffer, 1956; Leighton and
Frye, 1970). This section is the most complete
area previously considered to be underlain by ea
includes an unnamed organic soil dated at 20,150
formed in the lower part of the Peoria Loess, a
Roxana, and a Sangamon Soil formed in Argyle Til
at this section and at the Oak Crest Bog (McKenn
lower Winnebago Formation deposits are late II li

literature in which the Roxana
innebago Formation deposit.
It and absent or "weakly

for assigning the Winnebago
Wisconsinan) rather than to

Brophy, 1966; Willman and
stratigraphic section in the
rly Wisconsinan deposits; it

+ 500 RCYBP (ISGS-1302)
Farmdale Soil formed in the
1. From the evidence found
a, 1985), we conclude that the
noian in age.

The following profile is measured in a vertical exposure in the northeast
corner of the quarry. The upper portion of the section was apparently removed
for sale as topsoil .

PROFILE DESCRIPTION

Pleistocene Series
Wisconsinan Stage
Woodfordian Substage
Peoria Loess

Modern Soil
(truncated Argiudoll)

Soil
horizon

3tl

Bt2

BC
(B3)

Depth
cm

0-32

Sample

32-87

no.

PB-1

PB-2

87-110

PB-3

Silt; dark yellowish brown (10YR 4/6)
silty clay loam, subangular blocky
structure, numerous roots, gradual
lower boundary, leached

Silt; dark yellowish brown (10YR 4/6)
silty clay loam with few pale brown
(10YR 6/3) mottles, weak subangular
blocky structure, few roots, abrupt
lower boundary, leached

Thickness
(cm)

Silt; brown (7.5YR 3/4) silt loam,
blocky structure, few small roots,
abrupt lower boundary; leached

weak

Soil Depth Sample Thickness

horizon cm no. (cm)

CB 110-120 PB-4 Silt; light yellowish brown (10YR 6/4)

(CI) silt loam, massive to weak blocky

structure, few lenses of fine sand,
few small root channels, fairly
porous, dolomitic 10

(C2) and yellowish brown (10YR 5/6) silt

loam, massive to stratified, few root

channels, some vertical fracturing,

wavy abrupt lower boundary, dolomitic 25

Unnamed Soil

2A/Cg 145-175 PB-6 Silt; alternating dark grayish brown

P6-7 (10YR 4/2) organic-rich silt loam and

light gray (10YR 7/1) dolomitic silt loam,
massive structure, root channels, few
thin oxidized layers of yellowish brown
(10YR 5/6) silt, few snail shells,
wavy abrupt lower boundary, organic-
rich silt; leached 30

2A 175-187 PB-8 Silt; very dark brown (10YR 2/2)

organic-rich silty clay loam, massive

structure, few fine roots, slight

oxidation around small channels,

porous, wavy abrupt lower boundary,

dolomitic (humic material dated

20,150 + 500 RCYBP, ISGS-1302) 12

Altonian Substage
Roxana Silt, sandy silt facies Farmdale Soil

3E 187-207 PB-9 Silt; yellowish brown (10YR 5/4)

silt loam, few light brownish gray

(10YR 6/2) and yellowish brown

(10YR 5/6) mottles, granular,

porous, gradual lower boundary;

leached 20

3AE 207-257 PB-10 Silty sand; dark brown (7.5YR

3/4) loam, coarse pinkish gray
(7.5YR 6/2) mottles and silans,
granular to platy, porous,
gradual lower boundary; leached 50

Soil
horizon

3-4AE

Depth
cm

257-340

Sample

no.

P8-11
PB-12

Diamicton; brown (7.5YR 4/4)
loam to sandy loam; dries out
very light, weak platy structure
breaking to granular, highly
porous, abrupt lower boundary,
leached, fewer mottles than above
but more black concretions, more
brittle than above, few pebbles,
stone line at bottom

Thickness
(cm)

The profile description continues 25 ft to the southwest at the silt contact
with the stone line 200 cm below the new surface (depths in parentheses are a
continuation of the original profile).

Illinoian Stage

Winnebago Formation

Argyle Till Member

4EBt 200-215
(340-355)

PB-13

4Btl 215-282
(355-422)

PB-14
Pb-15

4Bt2

4Bt3

4C1

282-360
(422-500)

360-390
(500-530)

390-450
(530-590)

PB-16
PB-17

Sangamon Soil

Stone line, zone of mixed
material, disrupted strata
of gray sandy loam and reddish
loam

Diamicton; strong brown
(7.5YR 4/6) sandy loam, weak
blocky structure, few roots,
moderate porosity, few dark
brown skins, few white spots
(salts?), few pebbles, leached

Diamicton; strong brown
(7.5YR 4/6) sandy loam, weak
large blocky structure, few
roots, few vertical fractures,
few clay skins along macropeds,
numerous rotten rocks, gradual
lower boundary, leached

PB-18 Diamicton; strong brown

(7.5YR 5/6) sandy loam, weak
blocky structure, few roots,
abrupt lower boundary, leached

PB-19 Diamicton; dark yellowish brown
(10YR 4/6) sandy loam, coarse
platy to blocky structure,
gradual lower boundary, leached

Soil
horizon

4C2

Depth
cm

450-510
(590-650)

Ordovician System

5R 510+
(650+)

Sample
no.

PB20 Diamicton; light yellowish brown
PB21 (10YR 6/4) sandy loam, numerous
pebbles, dolomitic

Ordovician dolomite, yellowish
brown (10YR 7/4)

Thickness
(cm)

RESULTS AND DISCUSSION

During our initial field investigation, we had concluded that this
section consisted of a straightforward sequence of Peoria Loess, a Farmdale
Soil in Robein Silt, Roxana Silt, and a Sangamon Soil formed in the Argyle
Till. After determining the particle size, clay-mineral composition, and a
radiocarbon date of the organic materials (fig. 6-1), we recognized (1) that
there is an additional soil in the Peoria Loess, and (2) that the Roxana

100

Figure 6-1 Grain-size distribution, clay-mineral composition, and carbonate
data for the Wempletown Southeast Section.

pedogenically welded with the Sangamon Soil during formation of the Farmdale
Soil .

Our field description had placed the lower boundary of the Peoria Loess
at 120 cm, on the basis of the stratification in the 120- to 145-cm interval
and an abrupt decrease in sand content and increase in clay. The marked
change in clay-mineral composition indicates, however, that the boundary is
between samples PB-7 and PB-8 at approximately 175 cm, and that all the
overlying material has a clay-mineral composition characteristic of the Peoria
Loess. Textural data further complicate the interpretation. Samples PB-5
through PB-8 (120 to 187 cm) have a significantly higher clay content than the
samples immediately above or below; this suggests there were similar pedogenic
or sedimentological conditions throughout the interval respresented by samples
PB-5 to PB-8. Although the analytical data as well as the morphology of this
unit are somewhat inconsistent, we consider the upper 187 cm of this profile
to be Peoria Loess.

Humic material from the thickest and darkest organic-rich layer of the 2A
horizon at 175 to 187 cm (PB-8) was dated at 20,150 ^500 RCYBP (ISGS-1302).
The fact that this date is slightly younger than expected may be due to con-
tamination. There were modern roots in the sample and they may not have been
completely removed during pretreatment ; however, a 20,000-BP age is reasonable
if the Peoria Loess is the parent material for this soil. This date also
indicates that the soil formed just before the main body of the Peoria Loess
was deposited. Deposition of the loess terminated the soil-forming
processes. We have classified the soil within the interval represented by
samples 6, 7, and 8 in the basal portion of the Peoria Loess as an unnamed
soil after considering its morphological characteristics, organic content,
stratigraphic position, and the radiocarbon date of 20,150 +_ 500 RCYBP.

The source of the clayey silts and the causes of the alternating light
and dark bands in the unnamed soil are uncertain. The apparent paleo-
landscape position of this section would lead to the conclusion that the silty
layers are primarily slopewash, although there was undoubtedly some eolian
deposition. The organic-rich layers could either have formed in place or
could have been derived from an A horizon of an adjacent soil. Both
explanations suggest intervals of landscape stability alternating with
intervals of erosion and deposition. The high clay content of this silt is
also problematic. Preferential lateral transport of eroded clays and fine
silt may explain this situation. There is no evidence that the clays formed
in situ or were translocated from overlying horizons.

A distinct increase in sand content marks the upper boundary of the
Roxana Silt; the boundary does not coincide with the boundary between
materials with different clay-mineral compositions. The sample (PB-8) showing
the change in clay-mineral content was taken above the sample (PB-9) showing
the change in sand content. Sample PB-8 could be interpreted as a silty,
uppermost layer of the Roxana but has been included here with the Peoria
because of the physical similarities.

The Roxana is much sandier here than in other described sections of the
Roxana in the area. However, it is similar to the Roxana sandy silt facies
described by Johnson et al . (1972) in east-central Illinois. They interpreted
the sandy silt facies as a pedogenic mixing of eolian silt with underlying

Sangamon Soil developed in a sandy parent material. We correlate the Roxana
here to this sandy silt facies not only because of its stratigraphic position,
but also because of its similar physical properties and evidence of pedogenic
alteration. The increase in the kaolinite plus chlorite values in samples PB-
10 through PB-12 actually reflects an increase in vermiculite. The abundant
vermiculite in the Roxana reflects its A-horizon characteristics; the
vermiculite is sometimes referred to as "soil chlorite" and is found in most
soils.

In the Wempletown Southeast Section, a stone line serves as a marker for
the base of the Roxana; however, it appears that soil development after
deposition of the Roxana Silt welded the Roxana with the Sangamon Soil. Well
developed characteristics of A and E horizons (granular and platy structure,
pores, and light color) are present in the Roxana, and the particle-size data
show only a gradual transition across the stone line into the Bt horizon of
the Sangamon Soil. We have classified the soil interval above the stone line
as the Farmdale Soil because it is buried by the Peoria Loess. It is likely,
however, that the soil began to form in Altonian time.

The Sangamon Soil is morphologically less well developed than other
Sangamon profiles on Winnebago Formation tills observed in recent studies in
the area. Many types of buried soils have been observed during the soil
survey of the area underlain by Argyle Till. Commonly, paleosol B-horizons
contain 25 to 40 percent clay in soils mapped by the Soil Conservation Service
(Grantham, 1980). The clay content in the Bt horizon is only 15 to 18
percent, which is lower than our field estimates of 25 to 30 percent. Whether
this discrepancy is due to an overestimation of clay content relative to the
high sand content or to the failure of our methods to completely disperse
iron-bound clay aggregates is unknown.

The data on clay-mineral composition also do not agree with the data from
other studies on the Sangamon Soil. The illite shows only a slight decrease
upwards in the weathering profile in contrast to the 50 to 60 percent decrease
reported by Frye et al . (1969) for typical profiles in Winnebago and Glasford
Formation deposits in northwestern Illinois. However, in the upper portion of
the Bt (samples 14, 15, and 16), the increase in kaolinite values is strong
evidence that soil kaolinite was formed. In Illinois, soil kaolinite has
never been observed in soil profiles younger than the Sangamon Soil (H. D.
Glass, personal communication, 1985). The comparatively low clay content and
the presence of only a few thin argil lans may indicate that the Bt of the
original Sangamon Soil is not preserved in this exposure. The horizon
classified as Bt in this profile could be the BC(B3) or some lower horizon
that survived the erosional event (late Sangamonian) and then re-formed into a
Bt(B2) at a later time. On the basis of the evidence at the Oak Crest Bog
(McKenna, 1985), there may have been as much as 25,000 years of a cool moist
climate during which the Farmdale Soil was subject to weathering. Assuming
those conditions, the morphology of the presently exposed polygenetic paleosol
is more understandable.

The diamicton in which the Sangamon Soil has formed is the Argyle Till
Member of the Winnebago Formation. The lowermost samples from the exposure
(PB-20 and PB-21) are dolomitic. Their average grain sizes are 57 percent
sand, 31 percent silt, and 12 percent clay; the average clay-mineral

composition is 28 percent expandables, 63 percent illite, and 9 percent
kaolinite plus chlorite.

CONCLUSIONS

This section and the surrounding hi
events, three significant erosional inte
(fig. 6-2). A transect in any direction
encounter a variety of modern and paleo-
primarily the results of erosion and dep
The morphologies of modern soils formed
are similar, a fact that supports an ear
recent erosional interval. The lack of
below thick Peoria Loess on many slopes
intensive erosion also occurred prior to

llslopes reflect th
rvals, and four soi

from this section
soil profiles; the
osition interruptin
in both thin and th
ly post-Woodfordian
both the Roxana Si 1
throughout this reg

deposition of the

ree depositional
1 -forming intervals
would likely
variations are
g soil formation,
ick Peoria Loess
time for the most
t and a paleosol
ion indicates that
Peoria Loess. The

Stratigraphy

Landscape stability

Soil formation
(stronger-*- )

Deposition

Erosion

Time

Figure 6-2. Duration and approximate dates of intervals of erosion, deposition, and soil
formation since late lllinoian time in area of the Wempletown Southeast Section.

evidence at the Oak Crest Bog for erosion prior to 47,000 RCYBP (McKenna,
1985), in addition to the sandy silt facies of the Roxana Silt and the stone
line at the top of the Sangamon Soil in this profile, suggest that the most
intensive erosional event occurred in early Wisconsinan time. It is
neccessary to reconize these erosional episodes to properly interpret the
soil- and rock-stratigraphic record in this region.

In summary, the important observation at this section is that a distinct
paleosol is present under early Wisconsinan silt and is developed in the upper
part of the till. This sequence of materials and soil horizons is commonly
found on the Illinoian till plain of Illinois; however, late Sangamonian and
Wisconsinan erosional events have removed much or all of the argi Uic-type
paleosol over large areas of northern Illinois. On the basis of the character
of the paleosol and its stratigraphic position, we interpret the paleosol to
represent soil formation of the last interglacial --the Sangamon Soil.
Although the soil at this site appears to be an exception because of its low
clay content, the regional stratigraphic equivalent is continuous throughout
the areas of Glasford and Winnebago Formations. On this basis we interpret
both formations to be Illinoian. At this time, we have no evidence for
weathering profiles on the Glasford where it is overlain by the Winnebago
Formation.

ROCKFORD TERRACE: A LATE ILLINOIAN OUTWASH SURFACE

Leon R. Follmer, Richard C. Berg, and John M. Masters

STOP 7. Simpson Road Sand and Gravel Pit

SE Sec. 4, T43N, R1 E, Winnebago County IL (Rockford South Quadrangle)

The Rockford Terrance, buried by Wisconsinan loesses, is a rare occurrence of an lllinoian glaciofluvial surface.
The outwash deposits contain ice-wedge casts that have been altered by Sangamon Soil formation.

INTRODUCTION

The information for Stop 7 has been taken from a guidebook prepared for
the 1985 Midwest Friends of the Pleistocene Field Conference (Berg et al.,
1985). The highest terrace-forming glaciofluvial deposit along the Rock River
in northern Illinois is the Rockford Terrace. Anderson (1967) described its
distribution, sedimentological , and geomorphic aspects, and Anderson and
Masters (1985) formalized its name.

Rockford

R 2 E

Simpson Road|

gravel pit

Rockford Terrace deposits

Wisconsinan and Holocene gravel,

sand, and silt deposits in Rock River valley

Bedrock exposures
Upland surficial diamictons

j Winnebago Co.
■I Ogle Co.

R 1 E

1 mi

1 km

ISGS 1985

Figure 7-1. Distribution of the Rockford Terrace (modified from Anderson, 1967).

Two large and rare remnants of the Rockford Terrace are found near
Rockford on the west side of the Rock River (fig. 7-1). These remnants nearly
merge with the upland to the west and are about 5 to 9 m above the highest
Wisconsinan age terrace. The Rockford Terrace is more hummocky and dissected
than the Wisconsinan terraces. Soil maps of the area can be used to delineate
the boundary between the uplands and the Rockford Terrace (Grantham, 1980). On
the terrace, soils developed in sand and gravel predominate, whereas the
uplands are dominated by loess underlain by paleosols that have formed in
glacial diamictons.

SIMPSON ROAD GRAVEL PIT

The materials of the Rockford Terrace are best displayed at an exposure
in a gravel pit (the Hoogie Pit) on the north side of Simpson Road (Stop 7 map)
The Rockford Sand and Gravel Company operates the pit. Our discussion here
emphasizes (1) the characterization of the deposits, (2) the fossil ice wedges
in the gravel with a superimposed paleosol, (3) litho- and chronostratigraphic
relationships and (4) depositional environments of the gravel.

North of Simpson Road, the terrace scarp has a local relief of about 3 m.
West of the scarp is the small pit in the terrace gravel. The overburden of
loess is at most times stripped from the gravel exposure or covered by vegeta-
tion. The noticeable feature at the pit is an irregular spacing of dark
reddish brown pendants of a paleosol penetrating the upper part of the gravel
(figure 7-2). The distribution of the pendants is irregular: some are large
and singular; others have wide, complex, and multiple downward projections.
The large individual pendants and complexes are numbered on figure 7-2 for
convenience. In places the reddish horizon pinches out between pendants.

PROFILE DESCRIPTION

Pleistocene Series
Wisconsinan Stage
Woodfordian SuoTtage
Peoria Loess

Modern Soil (Mollic Hapludalf)

Horizon

Depth
0-.29

.29-. 42

.42-. 63

Thickness

Silt loam, very dark grayish brown

(10YR 3/2), many roots, friable, abrupt

lower boundary; leached .29

Silt loam, very dark grayish brown (10YR
3/2), few roots, fine thin platy structure,
irregular lower boundary; leached .13

Silt loam, dark brown (10YR 3/3), slight

bleached appearance, few fine roots,

very gradual lower boundary; leached .21

Depth Thickness

Horizon (m) (m)

Btl .63-1.07 Silty clay loam, brown (10YR 4/3), common

roots, subangular blocky structure,
gradual lower boundary; leached .44

Bt2 1.07-1.60 Silty clay loam, brown (10YR 4/3),

many yellowish-red (5YR 4/6) mottles, few
sand grains on ped faces, few lower chroma
mottles, strong subangular blocky structure,
gradual lower boundary; leached .53

BC 1.60-2.08 Silty clay loam, brown (10YR 4/3),

many 2-chroma mottles, subangular
blocky structure, siltier with depth,
clayey silt at base; leached .48

Illinoian Stage
Pearl Formation Sangamon Soil

2BC 2.08-2.21 Medium sand mixed with silt, at top

yellowish brown (10YR 5/4-5/6), lower
part brown (7.5YR 4/3), few layers
of pea gravel and coarse sand, abrupt
lower wavy boundary, 18-cm diameter gray
silt-clay ball (rip-up clast) at base of
unit, few fine roots in joints; leached .13

3Btl 2.21-4.10 (Pendant #16 description) (infilling);

alternating dark reddish brown (5YR 3/3) to
yellowish red (5YR 4/6) sandy clay within
wedges protruding downwards into sandy gravel;
curved horizontal bands (lamellae) of clay
and iron-rich sand, textural boundaries
stained red and higher in clay content,
some clay bands have wavy appearance and
dip downward in the middle of the pendant,
some bow up near the edges; abrupt lower
boundary; leached 1.89

3Bt2 4.10-5.04 Diamicton; very dark reddish brown to

black (5YR 3/3 to 2/1) clayey gravel,
black clay accumulations at edges of
pendant, some black clay passing into
underlying and adjacent calcareous
gravel, many rotten dolomite pebbles,
abrupt lower boundary; leached .94

Depth Thickness

Horizon (m) (m)

4C 5.04-8.0+ Stratified layers of gravelly

sand and sandy cobbly gravel ,
grayish brown to pale brown (10YR
5/2 to 6/3), calcareous, lower
part covered by talus 2.96

Wi nnebago Formati on
Argyle Till Member

5C 8.0 Diamicton; brown to pale brown

(10YR 5/3-6/3) sandy loam with 5 to
15 percent gravel, exposed in base of
pit; calcareous; probable basal till.

Total 8.0

DISCUSSION

A modern soil (Mollic Hapludalf) was described in the bank about 5 m east
of the northeast corner of the exposure. For convenience we moved to pendant
16 to describe the lower part of the exposure (fig. 7-2). The modern soil
here is typical of soils found on terraces and uplands. If it were well
drained, as one might expect for a soil overlying gravel, it would be bright
colored, without mottles. However, the iron-stained mottles in the lower part
of the soil indicate prolonged wetness.

The bottom of the modern solum appears to terminate in horizon 2BC, which
is a yellow to brown medium sand in most places. It is quite evident, how-
ever, that much reddish brown to black clay has moved down into the reddish
clay horizons (3Bt). This illuvial clay amassed along boundaries, and in
places, in the dolomitic gravel. The lower boundary of the 3Bt, which is very
irregular, defines the pendant shapes. In most places, pendants have formed
where sand has infilled a wedge-shaped area opening upwards. These forms are
interpreted to be fossil ice-wedge casts, although they might be sand wedges.
The main distinction between an ice wedge and a sand wedge is that ice wedges
cause compressional upwarping of adjacent strata, and while sand wedges are
fillings in cracks caused by tension.

The tops of the wedges flare out in a horn shape in most cases. A few
have structures that indicate disruption or a spreading of the wedge and sub-
sequent collapse. Most show a draping of sand layers above the outer parts of
the wedges and a bowing downward of sand layers over the midsection of the
wedge. This reflects the filling process and perhaps downwarping due to dis-
solution of underlying carbonate minerals. The layering is easily confused
with "layers" of clay enrichment or subsoil lamellae. The clay enrichment
either follows bedding planes or cuts across them. Pedogenic clay bands are
also present in the wedges.

The flanks and bottoms of most wedges are filled with clay-enriched
gravel. Some appear distinctly layered. The margins of the wedges are
difficult to delineate because the outer parts of the infilling are derived

from the wall material, and in most places, the reddish to black illuvial clay
passes beyond the margin of the wedge into the gravel. The dolomite cobbles
surrounded by the clay are soft and generally leached of their carbonate
content (ghosts). Beyond the zone of clay enrichment, the cobbles may have
softened rims, but are generally competent.

In 1983 an area in the northeast corner of the pit was stripped down to
the top of the gravel, exposing polygonal tops of the wedges. The yellowish
sand of the 2BC horizon appears to be the same sand that is permeated with
reddish clay in the center of the wedges; this relationship, however, has not
been studied in detail and remains uncertain.

The top of the gravel appears to be an erosion surface. The yellowish
sand above the gravel is missing in places. A clayey silt and a sandy silt
are frequently present above the gravel. The Peoria Loess uniformly overlies
them both, and in places, directly overlies the gravel. The sandy silt has
upper solum soil characteristics and is restricted to a position above a stone
line at the top of the 3Bt in the gravel as well as above the reddish, sandy
clay, wedge infilling. These relationships suggest that the sand predates the

South Facing Wall

West

Talus

Cobbly gravel
East (corner wall)

— i —
70

60 50

North End East Wall

curved
segment

NE corner
ft ^/Spoil

covered p*or',a Loess Clayey silt (lacustrine?)

40
curved segment

6-
8

10-1
12

Center Part East Wall

-A

light sicKloessL
heavy sicf ( lacustrine?)
^TnrTgling AE

— « as O

Coarse gravel

Fine gravel
Coarse gravel

North

South

-1
-2

210 220 230

5 | Sand permeated with clay
°-y | Gravel permeated with clay

ISGS 1985

Figure 7-2. Sketch of soil pendants in highwall of Simpson Road gravel pit. Pendants are exaggerated
up to 1 .5 and numbered for convenience.

paleosol, while the sandy silt postdates it. This means that the gravel
surface probably was subjected to at least two episodes of erosion.

About 54 m south of Pendant 16, above Pendant 28 (fig. 7-2), 10 to 20 cm
of clayey silt (lacustrine) comformably underlies the Peoria Loess; this
clayey silt is the same material that forms the "clay-ball clasts" described
in a contact zone between loess and sand. Where the clayey silt is present,
the paleosol has upper solum horizons (A, EA, and EB) overlying a stone line
on the top of the clayey 3Bt. The upper solum horizons are sandy silt that
can be correlated to the Roxana Silt; this sandy silt is comparable to the
sandy silt facies at the Wempletown Southeast Section (McKenna and Follmer,
Stop 6). The sequence here is interpreted to represent a late Sangamonian
erosion followed by (1) early Wisconsinan deposition of a silt, (2) early to
middle Wisconsinan pedogenesis, (3) late Wisconsinan deposition of lacustrine
clayey silt, (4) fluvial scour, (5) covering by Peoria Loess, and (6) Holocene
pedogenesis.

With the Wisconsinan events accounted for, the character and strati -
graphic relationships of the materials here strongly suggest that the reddish
paleosol is the Sangamon Soil developed in the top of the gravel.

Underlying the gravel is diamicton of the Argyle Till Member, a late
Illinoian unit. The diamicton here is uniform in appearance and is inter-
preted to be basal till. It has an average grain size distribution of
65 percent sand, 30 percent silt, and 5 percent clay. Its clay-mineral com-
position averages 26 percent expandables, 63 percent illite, and 11 percent
kaolinite plus chlorite. The diamicton at the Simpson Road gravel pit is
somewhat more sandy than Argyle described elsewhere in the area (Berg et al . ,
1985).

The terrace deposits consist of a poorly sorted, coarse cobble and pebble
gravel about 3 m thick, having crude horizontal bedding and cross strata.
Clasts up to 20 cm in median diameter are common. About 70 percent of the
cobble- to granule-size material is dolomite. Other rock types include about
10 percent chert, 10 percent other sedimentary rocks, and 10 percent igneous and
metamorphic rocks. Many carbonate and crystalline cobbles are deeply weathered;
some have completely disintegrated to sand. The gravel is a clast-supported
deposit that varies from open-to-closed framework. Most of the matrix (silty
sand) filling the interstices of the closed-framework gravel probably dropped
out of the meltwater as flow decreased following gravel deposition.

One of the beds is a poorly sorted cobble gravel about 1 meter thick.
The underlying bed (about 1 m thick) contains low-angle crossbedding, and
consists mostly of pebbles to fine cobbles; the crossbeds dip to the south of
open framework, well graded, fining-upward deposits of pebble or pea gravel.
Both of these beds were probably deposited in a high-velocity, braided stream
system on an outwash plain or a kame terrace during peak melt-water discharge
close to an ice margin.

INTERPRETATIONS

The exposure of the sand and gravel in the Rockford Terrace at the
Simpson Road pit and the available subsurface information in the area show

that these deposits are thin. We think that the high degree of weathering in
the upper part of the terrace deposits represents the Sangamon Soil; thus, the
sand and gravel correlates with the Illinoian age Pearl Formation, and makes
the Rockford Terrace an Illinoian glaciofluvial landform.

A probable correlation of the Rockford Terrace gravel can be made to a
site beyond the Rock River Valley 80 km northeast of Rockford. Near East
Troy, Wisconsin, Schneider and Follmer (1983) described a Sangamon Soil in
coarse gravel of Illinoian age that underlies the Tiskilwa Till of late
Wisconsinan age. No ice-wedge casts or other evidence of periglacial condi-
tions are present. The Sangamon profile described at the exposure contains an
unusually large clay pendant (beta horizon development) that penetrates the
dolomitic gravel. The appearance of the pendants and the red and clayey
paleosols at both locations is similar; however, at the Simpson Road pit the
pattern of soil horizons follows the structural feature (wedges in the gravel
infilled with sand) interpreted to be ice wedge casts. In general the
pendants at both locations cut across horizontal bedding planes in a similar
manner.

The formation of the ice wedge casts observed at the Simpson Road pit
would require that periglacial conditions existed at some time during the
Illinoian Stage. These periglacial conditions could only have occurred prior
to the Sangamonian, because the pedogenic features follow the form of the
wedges. The age of the Rockford Terrace is still somewhat in question.
Because the gravels overlie the Argyle Till, they may be closely associated
with the Argyle degl aciation, or they may be the result of an event after the
Argyle event but still during the Illinoian. However, the poorly sorted large
boulders and cobbles in the terrace and lack of distinct stratification, plus
the absence of fine-grained constituents, suggest proximity to an ice margin
and deposition in a high-velocity, braided glacial stream system.

REVIEW OF THE ESMOND TILL

Leon R. Follmer

STOP 8. Monroe Profile Site

NE NE Sec. 3, T42N, R2E, Ogle County IL (Cherry Valley Quadrangle)

Recent work has shown that a Sangamon Soil in the Esmond Till at this site has been removed by large-scale erosion.

INTRODUCTION

The age of the Esmond Till has been reinterpreted many times because of
incompatible arguments based on landform appearance, glacial history, paleosol
relations and stratigraphy. Some geologists thought the Esmond was deposited
during the Iowan, a glaciation between 111 inoi an and Wisconsinan; others
considered it Illinoian, early Wisconsinan, or late Wisconsinan in age.
Although many studies have been made of glacial deposits that included the
Esmond, most appear unrelated to the Esmond because of nomenclatural and
conceptual changes over the years. This paper will (1) review the history of
the previous concepts of the Esmond; (2) present information concerning its
age and stratigraphic relationships with paleosols and other glacial deposits
in the region; and (3) discuss the Esmond at a rare site where the Sangamon
Soil is preserved.

The Esmond Till was informally named by Frye et al . (1969) for the
Village of Esmond in De Kalb County, Illinois. Their recognition of the
Esmond Till was based on detailed study of the Greenway School cores taken
near Esmond. Later, the Esmond was formalized by Willman and Frye (1970) as a
member of the Wedron Formation (late Wisconsinan). Recent work has shown the
Esmond to be late Illinoian. The background information for this stop is
reproduced from a guidebook prepared for the Midwest Friends of the Pleisto-
cene Field Conference (Berg et al . , 1985).

BACKGROUND

In a study of the tills of northwestern Illinois, Frye et al . (1969)
introduced the term Esmond Till to denote a loam to silty clay diamicton that
they believed to be the oldest till member of the Wedron Formation. They
showed the Esmond as the surface diamicton, extending westward as the Dixon
Lobe from the Bloomington Morainic System to the vicinity of Dixon (fig. 8-1).
They considered a region to the south to be an interlobate area dividing the

Figure 8-1. Glacial lobes of northern
Fryeet al., 1969).

linois beyond the Bloomington Morainic System (modified from
52

Esmond from a time-equivalent unit they called Lee Center Till. According to
Frye et al . (1969), the Lee Center forms the Green River Lobe that extends to
the eastern border of Rock Island County covering the Green River Lowland.
The drift of the Bloomington System overlaps both the Esmond and the Lee
Center Tills, but at the present time the distribution of these materials in
the subsurface is uncertain.

Frye et al . (1969) summarized the interpretations of many previous
studies on the tills of northwestern Illinois. The interpretations are quite
confusing because stratigraphic concepts and mapping criteria differ among the
researchers. Examples include

• the presence or absence of a paleosol ; a Sangamon Soil was required for
recognition of Illinoian deposits. A weak paleosol (Farmdale) was con-
ceptually associated with Farmdale deposits (Winnebago Formation) and no
paleosol was allowed on deposits interpreted to be Shelbyville or Esmond,

• landscape characteristics; Illinoian areas were recognized where thick,
weathered drift was dominant, Farmdale was conceptually associated with
less weathering and less stream drainage development, and the Esmond
and equivalents were recognized on "youthful landscapes."

• the presence or absence of a silt (Roxana, previously called Farmdale)
below the Peoria Loess.

• stratigraphic position, the least developed but the most important
theoretical criterion; stratigraphic concepts differed mainly on the
number of glacial stages (fig. 8-2). Erosional events were recognized
in most studies but were not integrated into the stratigraphic
framework. Early workers were only able to recognize 'bundles' of
Illinoian and Wisconsinan deposits separated by the Sangamon Soil.

Much of the confusion is eliminated when the stratigraphic concepts are
separated from the mapping problems. Although the names and numbers of
stratigraphic units, as well as the basis of definition, have been changed in
several cases, the units fall into a relatively simple stratigraphic framework
(fig. 8-2).

Stratigraphy and Lithology

The composition of the Esmond Till is relatively easy to distinguish from
that of other surficial diamictons in the area. The Esmond belongs to the
gray-olive family and oxidizes to a brown. Other diamictons in the area are
gray brown in the subsurface and oxidize to a pinkish brown or yellowish
brown. The pinkish hue indicates a distant source material while the
yellowish brown indicates a local source. The underlying Galena-Plattevil le
Dolomite is light yellowish brown.

The most diagnostic property of the Esmond Till is its clay-mineral
composition. Its illite content is commonly about 76 to 80 percent, which
contrasts with that of other diamictons in the area that generally have less
than 70 percent. The grain-size characteristics of the Esmond are also rela-
tively distinctive. In a complete sequence, the Esmond has a downward-fining

texture. The Esmond is commonly a heavy loam, low in sand, that grades
downward into a silty clay, clay, or a heavy clay loam (fig. 8-3).

In accretion-gley (gleyed accretionary soil) sites, lacustrine silt and
clay commonly overlie Esmond diamicton. Under the Esmond diamicton a silt
unit up to 3 m thick is common; it usually has a silt loam texture but becomes
more clayey and stratified where thick. The silt loam appears to be eolian;
the stratified portions are obviously waterlaid. This silt underlying the
Esmond was recognized by previous researchers and correlated with the Morton
Loess by Willman and Frye (1970). The time-stratigraphic placement of the
Morton, however, is no longer valid because snails from this silt at the Byron
Power Plant site 30 km to the southwest were dated >36,500 RCYBP (ISGS 378),
(Follmer et al ., 1978).

Soil Geomorphology

The soil geomorphology of the area was described by Follmer et al .
(1978). Most of the soils are formed in eolian silt, sand, or loam over
Esmond Till. The eolian silt is the Peoria Loess. The eolian material that
ranges from loam to sand is designated the Parkland Sand. Several soil types
(Acker et al., 1980) are developed into the silty upper Esmond; one soil that
by definition requires a fine-textured parent material is found where the
lower Esmond is within 1 m of the ground surface. Another group of soils is
mapped where the underlying sandy diamicton outcrops on hill slopes. In a few

Leverett
(1899)

Leighton
(1923)

Shaffer
(1956)

Leighton

and Brophy

(1961)

Frye et al.
(1969)

Present

Wisconsin

Wisconsinan

Bloomington

Woodfordian

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Farmdale

Altonian

Sangamon

Sangamonian

lllinoian

Sterling

Esmond

NR — Not Recognized

Figure 8-2. Relative order and correlation of important names used in discussion of the Esmond Till.

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places on high parts of the Harrisville Moraine (terminus of the Esmond,
(page 51), soils are developed in the gravels of the ice-contact deposits. On
gentle slopes south and east of lowlands, stratified layers of eolian sand,
loam, and silt often attain thicknesses of more than 1.5 m.

The eolian loam originated from prograding sand moving onto a loess-
covered surface (Follmer et al., 1978). Small eolian dunes are visible in the
affected areas. A sandy lag material (pedisediment or solifluction debris),
sometimes similar to the eolian loam, is present in places above Esmond.

Regional Relationships

Follmer et al . (1978) reported the Esmond in most of northeastern Ogle
County; however, it was quite discontinuous within the areas mapped west of
U.S. 251 and to the south. An early Woodfordian erosion surface under an
eolian cover forms a band-shaped area paralleling the front of the Bloomington
Morainic System. This erosion surface extends from eastern Ogle County north-
ward into southeastern Winnebago and southern Boone Counties and southward to
Lee County. Frye et al . (1969) mapped the Green River Lowland area to the
south as Lee Center, a time equivalent and in some places, a lithic equivalent
to the Esmond. Erosion in many places has removed the upper coarser textured
Esmond, exposing its finer grained components; in many places to the west and
south, the Esmond has been entirely removed by erosion. Thus, the substratum
of the Modern Soil formed in eolian deposits and Esmond Till may vary from
loam to clay. This is a factor that made soil mapping difficult in Ogle
County.

Follmer et al . (1978) concluded that early Woodfordian erosion exposed a
wide variety of older deposits and generally removed the paleosol (Sangamon
Soil) from the top of the Esmond and Lee Center Tills. Generally, no stone
line is present on the Esmond or Lee Center surface; however, a sand lag
deposit is commonly found. The lack of a stone concentration above the trun-
cated Esmond or Lee Center surface indicates a mass movement (solifluction) of
the entire paleosol mantle, which was later covered in places by slope wash
(lag or pedisediment).

In the areas east of the Rock River where maximum erosion occurred, sandy
eolian deposits are found more or less continuously eastward to the
Bloomington Morainic System. In places the sandy deposits terminate in low-
lying sand-rich dunes. No dune crest is more than 1 m higher than the inter-
dune areas; however, contrasting soil color patterns clearly reveal the dune
positions (Acker et al., 1980). Beyond dune crests, the sand content drops to
essentially zero; here loess-derived soils are found. Follmer et al . (1978)
concluded that following the erosional event during Woodfordian time, the
Peoria Loess was deposited on a barren landscape. Sand was then blown out of
the Rock River valley, forming dunes that migrated across the loess-covered
landscape. The migration of this dune sand entrained loess, locally producing
large areas of loamy deposits that attain thicknesses of at least 150 cm. The
loamy soils are always associated with dune-sand soils, indicating a clear
genetic relationship. In places the upper horizons in the loamy soils are
high in silt, suggesting that loess was deposited during the final phase of
eolian activity. At the close of this event, the Modern Soil began to form.
For classification purposes, the eolian loam is included in the Parkland Sand,
a dune sand of Wisconsinan age.

Near Holcomb, 12 km southwest of Stop 8 and within the Esmond Till plain,
a paleosol was studied by Follmer et al . (1978). On the basis of soil
characteristics, this paleosol "outlier" was judged to be a Sangamon Soil.
The area around Holcomb appears to be a ground moraine because of the smooth,
gently rolling landscape; however, it would be quite anomalous for a wide
variety of parent materials, including paleosols, to subcrop beneath the
Peoria Loess on what appears to be a constructional geomorphic surface such as
a ground moraine. The stratigraphy and geomorphology of the Holcomb site
indicate that widespread erosion was associated with the building of the
Bloomington Morainic System. A combination of solifluction, and fluvial and
eolian activity resulted in a discontinuous distribution of Esmond Till, rare
occurrences of a paleosol in or above the Esmond Till, and an outcropping of a
variety of older deposits. These materials are now all covered by late
Woodfordian eolian sediments.

Age and Correlation of the Esmond Till

For several reasons, Frye et al . (1969) interpreted the Esmond Till to be
Woodfordian in age: (1) the landforms appear youthful; (2) Woodfordian eolian
deposits commonly rests upon calcareous Esmond Till (i.e., no accretion-gley
paleosol); (3) the apparent stratigraphic position is above the Altonian
Winnebago Formation; and (4) one radiocarbon date of 23,750 ± 1000 RCYBP on
material found beneath the Esmond was Farmdalian in age. The first two
reasons can now be explained by erosion and eolian deposition. The strati-
graphic problem has been resolved with the recognition of two similar diamic-
tons overlying and underlying the Esmond (Berg et al . , 1985). Thus the
strength of the argument depends on one radiocarbon date.

The age of the Esmond was not seriously questioned until Frye et al .
(1969) recognized the I llinoian-age Sterling Till adjacent to the Esmond to
the west. They reported that the clay-mineral composition of both units was
very much alike; (illite values of about 80%). Although they were unable to
demonstrate stratigraphic relations between them, they concluded that the two
units did not correlate because (1) the Roxana Silt and the Sangamon Soil were
present above the Sterling but not above the Esmond; and (2) Winnebago Forma-
tion till members were recognized below the Esmond and above the Sterling.

The rare observations of the Sangamon Soil on the Esmond were not
explainable using the old model. The strength of the old model rested on one
radiocarbon date of 23,750 ± 1000 RCYBP (1-2784) from organic material beneath
the Esmond Till in the Greenway School Cores (Frye et al., 1969). Because
they expected the Esmond to be younger than Farmdalian (22,000 to 28,000 BP)
and the age of the organic material fell into this range, the date appeared to
confirm their model. Later a conceptual conflict arose between the growing
pedo-stratigraphic evidence that a Sangamon surface was above the Esmond and
the evidence for a younger interpretation.

On the basis of stratigraphic position and the lack of a paleosol, the
units in cores 2 through 6 appeared to fit the young Esmond model (fig. 8-3).
However, the accretion-gley (Sangamon) soil occurs above the Esmond in core 1.
Cores 2 through 6 were taken in a close-spaced traverse with a length of about

2.0 km. Core 1 was located about 5.1 km to the south. Unfortunately, core 1
was excluded because it did not appear to relate to the other five cores.

The organic material below the Esmond was re-examined (Follmer and
Kempton, 1985) to resolve the question of whether the Esmond is young (based
on its youthful appearance and one radiocarbon date) or old (based on soil
stratigraphy). To confirm or counter the significance of the single radio-
carbon date, a revaluation was undertaken. A sampling plan was designed to
collect field replicates of the organic material. Five cores were made
between the original cores 3 and 6; however, recovery of organic material was
so small that the material from cores 2 and 3, and cores 4 and 5, were
combined. The coarse fraction (e.g. twigs) was separated from the silt and
the clay fraction; the clay fraction was discarded to ensure against con-
tamination. The silt fraction and coarse organic fragments were combined,
then leached with HC1 and NaOH. The residue was burned to produce the carbon
(benzene synthesis method) for dating. The results were >41,000 RCYBP for
both samples (IS6S-722 and -724). The agreement between dates and the fact
that both were equally dead (equal background activity) indicate success in
avoiding contamination and the likelihood that the dates are valid. Thus, the
Esmond Till does not have to be Woodfordi an in age.

Summary of Background Material

The recognition that the Esmond Till belongs in the sequence of 111 i noi an
till members rather than in the early Wisconsinan sequence was the key to the
stratigraphic reorientation that separates till members of the Winnebago
Formation from those of the Glasford Formation in northern Illinois. The
occurrence of an "interglacial " soil on the Esmond, the realization that the
youthful appearance of the Esmond Till plain was due to erosion and not to
recent deposition, and two new radiocarbon dates of >41,000 RCYBP, all
indicate an 111 inoi an age for the Esmond. In the regional perspective, the
Esmond is believed to be correlative with the Sterling to the west and the Lee
Center and Radnor to the south. On the basis of the widespread distribution
and available information on the Radnor, Follmer and Kempton (1985) selected
Radnor for the name of this correlated unit.

NEW INFORMATION

Soil mapping by the Soil Conservation Service in the early 1970s revealed
the rare occurrences of a strongly developed paleosol on the Esmond till plain
and led to the investigation by Follmer et al . (1978). On the basis of local
stratigraphy and correlations the best interpretation of the paleosol is
Sangamon. For this field trip, we attempted to find a better example of this
paleosol than has previously been reported. An important factor in the
old controversy was the uncertain relation of the Esmond Till at its type
section (page 51) to the paleosol observed at other locations. Three sites
were found a short distance to the south; we selected one for Stop 8; the
others dre designated with a "P" (see p. 51). The soil-geomorphic relation-
ships behind the farmstead of Ronald Lentz at Stop 8 have many of the features
that are associated with sites of Assumption soil (a Modern Soil that contains
a poorly drained, accretion-gley paleosol in the present solum). Composites

of many hand borings were used to sketch the stratigraphic relations around
the Monroe Profile (fig. 8-4). Superposed on figure 8-4a is a reconstruction
of the paleolandscape showing the position of former lithostratigraphic units
that were stripped from the landscape during a major erosional event about
20,000 years ago. Relics of poorly drained paleosols in sites such as this
indicate an inversion of topography that was caused by deeper erosion of the
surrounding materials in comparison to the paleo-gley sites.

4 -

6 -

8 -

1 -

-^Bt
2C^

A^
^^Bt

\2Btb""
3C\

Monroe
Profile

A
^^ Bt

2Bt
3C "

2 -

■ —
Berry Clay

2Ab "^\^

2Bgb

3 -

3C lacustrine
4C

Esmond Till

"N. '/;

4 -
R

former geologic boundary

common soil and geologic boundary

- — — soil horizon boundary

Figure 8-4. Idealized sketch of Monroe profile area stratigraphy.

The Sangamon Soil at this site is correlated to the 2Ab and 2Bgb hori-
zons. The Roxana Silt (early Wisconsinan) and the Robein Silt (mid-
Wisconsinan) may be contained in the 2Ab. The solum (2Ab and 2Bgb) is a
fining-upward sequence representing slow accretion in a wet pedogenic environ-
ment. Pedogenic features effectively mask all but the textural trends. At
one location the thickness of the dark gray 2Ab and the gray 2Bgb are each
about 1 m thick. The 2Ab is a silty clay that grades downward to a clay
loam with pebbles at the base of the 2Bgb. The underlying lacustrine
deposits are thin-bedded silt loam and silty clay. Towards the base, the
lacustrine unit contains thin lenses of diamicton from the Esmond Till, which
indicates that at the close of Esmond glaciation (Illinoian) a lake existed at
this location.

In many other locations to the west the Robein and Roxana overlie a
paleosol that closely resembles the one here. Because the 2Ab is silty clay
and contains much highly weathered material, the Robein and Roxana were
probably removed by erosion. The same erosion event probably removed the
early Peoria Loess that is commonly found in the area underlying the Parkland
loam, a sand-silt facies of the Parkland Sand that is middle to late Woodfordian
in age.

The landform expression here is close to ideal for this type of sequence.
A bench observed on the lower part of the upland is caused by the relatively
flat surface of the paleosol. The main erosion of this paleosol created two
forms in front view (fig. 8-4a): one is where total removal of the solum
occurred (left side); the other is a beveled surface (right side). In the
side view (fig. 8-4b) both ends of paleosol are beveled. The bevelling can be
caused by any type of overland erosion, whereas the whole profile removal next
to a "scarp" indicates mass wasting. Here, mass wasting during a time of
coldest climate can be interpreted as the result of solifluction processes.
In many places on the Esmond Till plain the Sangamon Soil appears to have been
"melted off" the landscape leaving little trace on a youthful appearing
landscape. In support of the solifluction interpretation, many parts of the
erosion surface do not have a stone line that would indicate a fluvial
process. Instead, the late Woodfordian eolian silt, loam, or sand commonly
rests directly on Esmond Till (usually calcareous). On the beveled surfaces a
sandy lag deposit is relatively common.

Most of the Parkland loam is eolian in origin except for possible
resedi mentation in alluvial positions. The dominant wind direction was from
the west-northwest, and dune forms were built on north facing slopes of east-
west trending valleys and in lowlands between the Rock River valley and the
Bloomington Morainic System. Here at Stop 8 the major landforms trend more
north-south, and dune forms are absent or poorly formed. Some build-up is
evident on the beveled surface, and blow-over covered the "scarp" area. The
surface horizon of most Modern Soil in the region is relatively silty, which
suggests that dune formation had slowed or ceased before the end of the
Woodfordian. For all practical purposes, Modern Soil formation began at this
time, estimated to be about 13,000 years ago.

WEDRON TYPE SECTION

W. Hilton Johnson, Ardith K. Hansel, and Leon R. Follmer,
with contributions by R. G. Baker and A. E. Sullivan

STOP 9. Wedron Silica Company Quarry

Sec. 8, 9, 10, and 16, T34N, R4E, La Salle County IL (Wedron Quadrangle)

Studies of exposures in this quarry have led to the development of a detailed, evolving interpretation of the late
Wisconsinan glacial history of the area.

INTRODUCTION

The Wedron Section is the type section of the Wedron Formation, which
consists of glacial diamictons and intercalated stratified deposits of the
late Wisconsinan (Woodfordian Subage) glaciation in Illinois, and of the
Peddicord Formation. The exposures in the five pits at this quarry are the
thickest, most complete exposures of the Wedron Formation in Illinois: they
include complex succession of deposits representing multiple glacial events.
Observations and interpretations of these deposits have been important in
developing the history of the last glaciation.

Researchers have been studying at 'Wedron for more than 70 years. Early
studies were focused on the stratigraphy of the multiple diamictons,
originally all called tills, and their relationship with Woodfordian moraines
down-ice to the west. These studies have led to the recent work on the
sedimentology of the deposits, which has generated some new interpretations
described in detail by Johnson et al , (1985).

The following summary and discussion is modified from material prepared
for the Geological Society of America Decade of North American Geology--
Centennial Field Guides. New information on the paleobotanical record has
been added.

STRATIGRAPHY AND INTERPRETATIONS

Exposures in the quarry were first described by Sauer (1916), who
recognized one main till unit and several units of sand and gravel, and silt
and clay. The early work placed strong emphasis on morphology as a basis for
subdividing and interpreting the glacial deposits. End moraines were
interpreted as representing still-stands of an otherwise fluctuating ice
margin, and it was assumed that each end moraine would have a sheet of till
associated with it. The Wedron Section supported this concept because several
till units of the last glaciation were exposed, and several end moraines of
the last glaciation had been mapped to the west. Thus, the till units were
named for the end moraine with which they were assumed to be related; for
example, Willman and Payne (1942) recognized Shelbyville drift, Bloomington
drift, Farm Ridge drift, and Marseilles drift at the Wedron Quarry.

Frye and Willman (1960), Frye et al . (1968), and Willman and Frye (1970)
introduced formal lithostratigraphy into the classification of Pleistocene
deposits in Illinois, revised the chronostratigraphic classification, and
formalized the practice of morphostratigraphic classification. The Wedron
Formation, as defined by Frye et al . (1968), includes the deposits of glacial
till and intercalated outwash and silt of the Woodfordian Substage. Wedron
was designated the type section, and three till members, Lee Center, Tiskilwa
and Maiden, were described in the section. Although the younger members are
not present at the quarry, Wedron was selected by Willman and Frye (1970) as
the best available exposure for the type section. The age of the Wedron
Formation at the quarry is in the range of 15,000 to 25,000 BP. The top of
the Wedron Formation is defined as bounded by the Two Creeks deposits in
Wisconsin, which have an age of about 11,800 RCY8P. The youngest members were
defined by Lineback et al . (1974).

Willman and Frye also formalized a system of morphostratigraphic clas-
sification in 1970. In the sequence at Wedron they recognized six morpho-
stratigraphic units that are named after moraines and are called drifts.
Nomenclature used in Willman and Frye (1970), as well as that used earlier
(Frye et al . , 1968) and in this guidebook, is summarized in table 9-1.

The quarry operation exposes the Starved Rock Sandstone Member of St.
Peter Sandstone, a thick, quartz sandstone that is Champlainian Series middle
Ordovician). The sandstone is medium grained, crossbedded, and friable except
for an outer case-hardened surface. More than 30 m of St. Peter is exposed in
Pit 1. Because it is almost pure Si02, the St. Peter is mined here and
elsewhere in the area for silica sand.

Several pits have been worked in the quarry (page 61); Pits 1, 4, and 6
currently are active. 1 11 i noi an and pre-IUinoian deposits are exposed in

Table 9-1. Current and recent nomenclature used for Wisconsinan glacial deposits at Wedron Quarry.

1968
(Frey et al .)

1970
(Willman and Frye)

1985
(Johnson et al .)

Richland Loess

Wedron Formation
Sand and gravel

Henry Formation
Batavia Mbr.

Henry Formation

Wedron Formation
Maiden Till Mbr.

Wedron Formation
Maiden Till Mbr.*

Farm Ridge Drift (till )
Sand and gravel

Till (Farm Ridge)
Sand and gravel

Till (Cropsey)
Sand

Mendota Drift (till)
Sand

Unit 3

Till (Cropsey)
Silt, some sand

Arlington Drift (till )
Silt, some sand

Unit 2

Till (Normal)
Sand and silt

Dover Drift (till)
Sand and silt

Unit 1

Till (Bloomington)

Till (Shelbyville)

Tiskilwa Till Mbr.

Bloomington Drift (till)

Lee Center Till Mbr.
Atkinson Drift (till)

Tiskilwa Till Mbr.
Main Unit

Lower unit

Sand and gravel
(pro-Shelbyville)

Farmdale Silt

Sand and gravel

Farmdale Silt

Peddicord Formation
Sand unit

Silt unit

Robe in Silt

♦Correlations between the Maiden units of this guide and drift units of
earlier workers are uncertain.

Maiden T.M., Unit 3, Henry Fm.,
Richland Loess (undifferentiated)

Figure 9-1. Sketch of southwestern corner of Pit 1, Wedron Quarry, 1984, destroyed in 1985 (not to scale).

Dm diamicton, massive

Cm clay, massive

Cmp clay, massive, pebbly

CI clay, laminated

STm silt, massive

STI silt, laminated

Sh sand, horizontal bedding

Sx sand, crossbedding

Gh gravel, horizontal bedding

evidence for

(p) pedogenesis

(d) soft sediment deformation

(r) resedimentation

(s) shearing

Maiden Till Member

Unit 2

Sh, Sx

Peddicord Formation

St. Peter Sandstone

Figure 9-2. Sketch of west wall exposure of Pit 6, Wedron Quarry, 1984, destroyed 1985 (not to scale).

Pits 3 and 4. The following description and discussion focuses on Pits 1 and
6, and is organized by stratigraphic unit. The nongenetic term diamicton is
used to describe poorly to unsorted deposits. The genetic term ti 1 I is "
restricted to those diamictons that are interpreted to have been deposited
directly from glacier ice with little or no modification after deposition.
Other diamictons are interpreted to have been deposited from sediment (mud)
flows in the glacial environment.

The bedrock surface contains several valleys that are tributaries of the
Ticona Bedrock Valley (Willman and Payne, 1942). These are exposed in Pit 1
(Fig. 9-1) and are filled with Wisconsinan alluvial and lacustrine deposits.
Although the alluvial deposits vary, they are silty for the most part and are
included in Robein Silt. The Farmdale Soil, about 1.3 m thick, is developed
in the top of Robein Silt (Fig. 9-1). The A horizon of the Farmdale is dark
and cumulic, and contains abundant organic debris and wood. It overlies a
weakly developed, gleyed B horizon.

Peddicord Formation

Willman, Leonard, and Frye (1971) defined the Peddicord Formation as
including gray and pink silt that had accumulated in a Farmdalian lake
confined to valleys of the Ticona drainage system. We recognized these
deposits as a silt unit of the Peddicord, and also tentatively include in the
Peddicord overlying sand deposits that we think are related to the same
drainage system.

The silt unit consists of massive and laminated silt containing sub-
ordinate beds and laminae of clay and sand. These materials are calcareous
and vary in color from gray to reddish brown. Coniferous wood fragments and
organic-debris laminae are common, particularly near valley and gully margins.
The unit varies in thickness; up to 13 m has been described at Wedron (Willman
and Frye, 1970). It is particularly thick in buried canyons where the silt
beds grade to and are interbedded with sandy colluvium derived from St. Peter
Sandstone. The unit has the same clay mineral composition as the Tiskilwa
Till Member. Radiocarbon dates on detrital wood from this facies are 24,370 +_
310 (ISGS 863), 24,900 +_ (ISGS 862), 24,000 ^700 (W-79) and 26,800 +_ 700
(W-79) RCYBP.

The deposits are interpreted as typical proglacial lake beds that
accumulated in a dammed drainage system during the initial Woodfordian glacial
advance in northern Illinois. The color and clay mineral composition suggest
that the system was dammed by the Tiskilwa ice margin or by outwash from that
ice sheet. Lake Peddicord inundated the Farmdale Soil, which had formed in
the valleys, and wood and organic debris were washed into the lake from valley
sides and adjacent uplands. The lake probably existed in latest Farmdalian
and earliest Woodfordian time.

Previous interpretations related the silt deposits either to Lake
Kickapoo, interpreted as postdating the initial Woodfordian ice margin advance
and hence to be younger (Willman and Payne, 1942), or to Lake Peddicord,
interpreted as predating the earliest Woodfordian glaciation and thus older
than the Farmdale Soil (Willman, Leonard, and Frye (1971). The latter inter-
pretation of the age of the lake is rejected because of stratigraphic rela-
tionships at Wedron. Additional regional studies will be required to

determine possible relationships between deposits of Lake Kickapoo and Lake
Peddicord.

A sand unit comprising up to 6 m of relatively well -sorted sand and some
fine gravel overlies the silt unit of the Peddicord Formation. The sands are
calcareous and tan to yellow brown. Beds vary in thickness from about 0.2 to
1.0 m, and are planebedded and trough and planar crossbedded. The sand unit
is more extensive than the silt unit and appears to be continuous across the
bedrock surface at Wedron.

This unit is interpeted as representing glaciofluvial sedimentation that
occured as the Woodfordian ice margin approached the quarry area. The
proglacial origin agrees with earlier interpretations (table 1), except that
we relate the unit to the ice sheet that deposited the Tiskilwa Till Member
and not the Lee Center Till Member or Shelbyville till.

Wedron Formation

The Wedron Formation, which consists of glacial deposits, overlies the
Peddicord Formation. Initially it was subdivided into three members at
Wedron; currently, only two members are recognized, although both consist of
multiple lithologic units. In addition, Willman and Frye (1970) recognized
six morphostratigraphic units (table 1). The latter classification is not
utilized in this guide because correlations to end moraines to the west are
uncertain. The Wedron Formation is exposed in all pits, but currently is best
exposed in Pits 1 and 6 (Figs. 9-1, 9-2).

Tiskilwa Till Member. The lower unit of diamicton and intercalated sand and
silt is related here to the Tiskilwa glacial advance, not an earlier
advance. The unit is thin, rarely more than 1 m thick, and discontinuous. It
is highly variable in character. In most places it consists of thin diamicton
layers interbedded with stratified sand or silt. The lenticular beds thicken
and thin abruptly. In some places, the unit is uniform pebbly loam
diamicton. The diamicton, which is generally oxidized, has a yellow-brown to
pinkish color, similar to the pinkish diamicton in the main body of the
Tiskilwa; where unoxidized, it is distinctly grayer. Its clay fraction
contains slightly more illite than does the main part of the Tiskilwa. We
interpret the unit to be till and material that has undergone resedimentation
and deformation in the subglacial environment.

Willman and Frye (1970) included this unit in the Lee Center Till Member;
earlier it had been called Shelbyville till (table 1). Subsequent work by
Follmer and Kempton (1985) has demonstrated that the Lee Center Till in the
type area is II 1 i noi an; thus the name is inappropriate for this unit at
Wedron. Although the contrasting color and composition suggested to earlier
geologists that the unit had been deposited during an earlier glacial event,
materials with these characteristics are not unusual in the lower portion of
the Tiskilwa Till Member. We believe the unit was deposited by the Tiskilwa
ice sheet and that the contrasting characteristics are the result of
incorporation of older drift and local Paleozoic source material.

The lower unit is overlain by 2 to 4 m of typical Tiskilwa Till. The
contact is distinct and locally marked by a concentration of boulders. The

main body of the Tiskilwa is a massive, relatively uniform loam to clay loam
diamicton that weathers to a distinct pinkish color. This unit is interpreted
as till, but in some places the upper portion contains interbedded stratified
sands, silts, and diamicton layers of sediment flow origin. In Illinois, the
Tiskilwa is one of several reddish-brown till units; its color and composition
reflect late Precambrian source materials that occur in the Lake Superior
region north of Lake Michigan. The unit is extensive in northern Illinois and
forms several large end moraines along the western margin of Woodfordian
glaciation.

Maiden Till Member. At Wedron the Maiden Till Member is complex, consisting
of various lithologic materials. Three main units, numbered upward, are
tentatively recognized; each is variable.

Maiden unit 1 is a gray to gray-brown diamicton that oxidizes to a
reddish brown hue and has a variable color and clay mineral composition. The
latter characteristics generally are intermediate between those of the main
Tiskilwa and Maiden unit 2. A discontinuous boulder pavement occurs at the
lower contact, and azimuths of striae commonly range from 70° to 80°; a
boulder pavement also is present within the unit. The diamicton has a pebbly
loam texture and the upper part of the diamicton locally is interbedded with
stratified deposits. These deposits are overlain by a bed of well-sorted silt
to fine sand, that is laminated and continuous in exposures at Wedron. The
unit is 1 to 3 m thick and consists primarily of till and sediment flow and
lacustrine deposits.

Maiden unit 2, about 3 m thick, consists of a lower silty clay that
gradates upward to pebbly, silty clay diamicton, and an upper pebbly loam
diamicton. The lower subunit ranges from massive to faintly laminated and is
interpreted to be lacustrine in origin. The increased sand and sparse pebble
content in the silty clay diamicton may be from ice-rafted material. The
overlying gray, pebbly loam diamicton is about 2 m thick; it is generally
massive, but locally contains thin streaks of fine sand, block inclusions of
older pinkish and clayey diamicton, and interbedded sorted deposits of sand
and silt. Although mainly gray, locally the upper part contains pinkish
diamicton that has a lower illite content. The diamicton subunit is
interpreted as consisting of basal till and deposits that have undergone
resedimentation in the supraglacial environment.

Maiden unit 3 consists of a lower sand subunit and a discontinuous,
overlying fine-grained diamicton subunit. The sand unit is stratified and
crossbedded, and locally it contains multiple coarsening-upward sequences.
Local lenticular bodies of pea gravel are present at the base or within it.
The sand is best exposed in Pit 6, where it is up to 2 m thick. The overlying
diamicton, which contains few pebbles, has a clayey texture, its maximum
thickness, observed in recent exposures, is 1.5 m. The upper surface of the
diamicton has been truncated and locally is marked by a thin lag (a concentra-
tion of pebbles). The diamicton and subjacent sand and gravel are weathered
and locally are part of the solum of the Modern Soil. The regional signifi-
cance of unit 3 is not known; it may consist of outwash and sediment flow
deposits derived from the Yorkville Till Member, which forms the Marseilles
Morainic System located immediate east of the Fox River, or it may have been
the result of a younger Maiden ice margin advance that extended west of Wedron.

Henry Formation

Several deposits of sand and gravel found at or near the ground surface
are assigned to in the Henry Formation: they include the sand of Maiden unit
3, where it has been exhumed, and thin sand that locally overlies the clay
diamicton of Maiden unit 3. The deposits, interpreted as outwash, have been
weathered in the Modern Soil.

Richland Loess

The uppermost unit at Wedron, Richland Loess, is weathered silt; it is
thin (usually about 0.5 m thick), but locally approaches 1.0 m. This eolian
deposit was derived from valley trains and drift surfaces during the middle
and latter portions of the Woodfordian Subage. The A and locally the E
and/or B horizons of the Modern Soil are developed in the loess. The soils,
which developed in a well-drained position under forest or grass vegetation,
are classified as Udalfs or Udolls, respectively.

PALEOBOTANICAL RECORDS ROM BIGGSVILLE AND WEDRON: NEW INFORMATION

Richard G. Baker and Amy E. Sullivan, Department of Geology, University of Iowa.

Pollen studies from several areas in Illinois and Iowa indicate that a
spruce-pine forest that prevailed in the region from at least 28,000 to
25,000 BP gave way to a spruce-larch forest that lasted until about 22,500 BP
(Baker et al., 1986; Hallberg, Baker, and Legg, 1980; Hallberg, Van Zant, and
Baker, 1980; F.B. King, 1979; J.E.King, 1979; Mundt and Baker, 1979).
Detailed pollen and plant macrofossil work from Biggsville in western
Illinois, an area well beyond the Woodfordian glacial margin, indicates that
spruce pollen percentages and influx drop off sharply between about 22,500 and
21,500 BP, and spruce needles disappear from the record. The pollen spectra
are dominated by high percentages of spruce and sedge, with lesser amounts of
pine. However, low pine pollen influx suggest that pine was already absent
from the area. As spruce and larch disappear from the record, megaspores and
microspores of the Selaginella selaginoides (spikemoss), a subarctic plant,
appear for the first time. Loess deposition apparently mantled the entire
landscape after 21,500 BP, and organic deposition ceased.

Preliminary pollen and plant macrofossil analysis of sediments in a small
swale fill in the Wedron Quarry (Pit 6) indicates that the subarctic to arctic
conditions existed as Woodfordian glaciers approached the Wedron area 21,400 +_
470 RCYBP, shortly after the record at Biggsville ended. The pollen spectrum
consists of a spruce-pine-sedge assemblage, much like the uppermost samples at
Biggsville dated at 21,410 RCYBP (Sullivan, 1985). Plant macrofossils of the
arctic plants Dryas intergri folia (arctic avens) and Vaccinium uliginosum var.
alpinum (arctic blueberry) , and the subarctic Selaginella selaginoides and
Betula glandulosa (dwarf birch) indicate that the environment was very open
and tundralike. Other plant macrofossils include a number of pioneer aquatic
plants, wetland plants, and several taxa whose identification is still
incomplete. This is the first arctic-plant assemblage from Illinois, and it
is similar to the plant assemblage from the arctic biota at Conklin Quarry,

dating from about 16,700 to about 18,000 BP (Baker et al . , 1984; manuscript
in review).

In summary, fossiliferous sediments of full-glacial age have seldom been
found in Illinois. Oata from new sites, especially the Wedron site, suggest
that the full -glacial environment was much more open and tundralike than
previously thought.

CHATSWORTH BOG: A WOODFORDIAN KETTLE

James E. King

I T~nr?mr'C<iTirn

STOP 10. Chatsworth Bog

SWV4 Sec. 32, T26N, R8E, Livingston County IL (Sibley Quadrangle)

The sediment record found in this rare bog in central Illinois provides significant information on the floral history
from about 14,000 years ago to the present.

Chatsworth Bog is a marl bog situated within a roughly circular 25-ha
depression dissected by an outwash channel that originated in the late
Wisconsinan Chatsworth Moraine (Willman and Frye, 1970) 4 km to the north
(see p. 51). A small permanent stream flows in the channel and through the
bog. In the 1930s the organic-rich marl was commercially mined from the east
half of the bog for agricultural lime, producing a pit that is now occupied by
a small lake. Although the bog was probably surrounded by forest in the 19th
century, the primary vegetation on the rolling morainic topography was tall-
grass prairie (Anderson, 1970).

The fossil pollen in Chatsworth Bog was first investigated by John Voss
(1937) who sampled the vertical walls of the open pit during the period of
active mining at the site. He reported 60% spruce pollen at a depth of 11.2
m. This analysis included only the arboreal pollen types and was completed
only on sediments below 6.5 m depth. Leonard (1974), who referred to the site
as Strawn Northeast, studied the snails recovered from the fossiliferous marls
at the edge of the basin in sediments dated younger than 9000 RCYBP and
reported no evidence of climatic change. The snails indicated a uniform
environment with some fluctuations in water levels. A pollen study of Turtle
Pond, 3 km east of Chatworth Bog (Griffin, 1951), did not include herbaceous
pollen types.

A 5-cm diameter continuous core, 1275 cm long, was collected from the
southwestern side of the Chatsworth basin in the remaining unmined area. The
stratigraphy is shown in figure 10-1. Volumetric pollen samples were recovered
from the core at 20 cm intervals. Additional samples were later analyzed from
selected parts of the core at 5 and 10 cm intervals in areas of rapid changes in
pollen frequency and/or influx. The extraction methods and a detailed discus-
sion of this and other Illinois pollen sites are described by King (1981).

Radiocarbon dates from the core are shown in figure 10-1 along with a
plot of sedimentation rates throughout the sequence. The radiocarbon dates of
3370 +_ 75 RCYBP from the top of the marl and 2640 +_ 75 RCYBP (Leonard, 1974)
from near the base of the overlying surface peat bracket the stratigraphic
contact between the organic marl and the surface peat.

Pollen concentration, Figure 10-1, fluctuates widely below 1000 cm depth,
then slowly declines in the upper portion. There is no appreciable change
across the marl/peat stratigraphic boundary at 100 cm. Total pollen influx
(Fig. 10-2) remains relatively low, about 2000 grains/sq cm/yr between 14,300
BP and 11,000 BP when it increases to 5000 grains/sq cm/yr. Between 10,200
and 9100 BP, it again declines to about 1000 grains/sq cm/yr. At 9100 BP the
pollen influx begin a rapid increase to 28,000 grains/sq cm/yr, remains high
until about 7500 BP when it declines to about 7000 grains/sq cm/yr, and then
continues to decline to the top of the marl at 100 cm depth, about 3400 BP
(fig. 10-2).

The pollen record from Chatsworth Bog, Figure 10-3, is dominated by
spruce (Picea) in the lower Pleistocene levels and oak (Quercus) in the upper
Holocene sections. The pollen record is divided into 4 assemblage zones.

ZONE I. Zone I is dominated by up to 76% spruce with lesser amounts of fir,
larch, alder, birch and oak. Also present are grass and sage. Pollen influx

-s

».

■c:

Peat

? ■

Organic

Marl

3 H

4
5

Orgonic
Silty
Clay

Organic
Marl
9 -

Gyttjo

Clay

II
12

0 3lmm/yr

'3370=75

- 10,855=75
0 94mm/yr /

'♦ 11,280=110

/0 32inm/yr

~'l4,38o:=i50

I l l — l — r— l — l — l l l — I — i — i — i — i

14 13 12 II 10 9 8 7 6 5 4 3 2 I 0 0

A I03 Radiocarbon Years BP n

A. B.

— i — i — i — i — i — i — i — i — i — i — i — i — i

5 10 15

I04 Grains/cm3

Figure 10-1. Stratigraphy, sedimentation rates, and pollen concentration for the Chatsworth Bog
core: (A) sedimentation rates calculated from adjacent pairs of dates and the bog surface; (B)
pollen concentration (grains/cu cm).

CHATSWORTH BOG

/ /</ /// /

S //

0 -,

0 —

I000 -

2000 -

I -

JOOO -

4000 -

4 -

5000 -

»-

6000 -

7000 -

» -

8000 -

10 -

9000 -

10.000 -

II -

11.000 -

12.000 -

It -

13.000 -

14.000 -

/a.7-

15.0 0 0 —

> '

■

1
1

r lv

)

i 1Mb

)

r Ilia

I — ' — I — ' — I

-I — ' — I — ' — I — ' — I — ■ — I — ' — I — ' — I — ■ — I — ' — I — ' — I — I — I — I — I —

2 3 1 5 6 7 6 9 10 II 12 13

-I — i — I — i — I I — ■— I-

Pollen Influx — 103 Grains cm"2 • yr"'
Figure 1 0-2. Pollen influx of selected taxa from Chatsworth Bog plotted as a function of years BP.

05
O

.c
r
o

.C
O

i—

O)
CO

C
0)

CD
O)

c
o
o

i_
o

I I I

(uu) 4(d»o | — r— i — i | i l i — | — i — i—i — [— i — i—i— | — i I i | i l i | — i— r

O - oj ki <)■ m u>

sauoz U3||0<j >

~i — I — i — I — I — 1 — I — I — i — I — i — I — I — I — i — I — I — I — r

T^^

values range from 1000 to 2100 grains/sq cm/yr. Based on the sedimentation
rate curve (Fig. 10-1), Zone I dates from the base of the core, about 14,700
BP to 13,800 BP. Although oak comprises up to 17% of the total pollen in Zone
I, its influx ranges only from 80 to 400 grains/sq cm/yr. This is consider-
ably less than the 2000-12,000 grains/sq cm/yr in areas where oak trees
presently occur, indicating that the late Pleistocene oak component was
from long-distance wind transport rather than from the presence of sig-
nificant quantities of local oak trees. Zone I is interpreted as reflecting a
mosaic of open spruce woodland and tundra, perhaps similar to the modern
forest-trundra transition.

ZONE II. This zone contains much lower spruce percentages and increases in
ironwood, elm, oak, and ash, particularly black ash. There is little pine
pollen present, less than 2%. Pine is never prominent at Chatsworth Bog
suggesting that pine did not occupy an important place in the late-glacial
vegetation of central Illinois as it did in areas to the north. Total pollen
influx increases slightly to maximums of 2400 grains/sq cm/yr. Most of this
increase is due to ash pollen; oak remains about 500 grains/sq cm/yr. Zone II
dates between 13,800 and 11,600 BP. This zone is interpreted as a rapid
expansion of black ash in the wet lowlands in the vicinity of the bog while
the surrounding uplands remained open and treeless. Spruce had been displaced
by the ash with climatic warming.

ZONE III. This double zone is dominated by tree taxa. Zone Ilia, dominated
by cool temperate species, contains a sharp decline in ash and increases in
alder, elm, and oak. Ilia also contains the last major occurrence of spruce
and fir; it is dated between 11,600 and 10,600 BP. In Zone 1 1 1 b the cool-
temperate taxa are replaced by warm-temperate trees. Ash, fir, spruce, larch,
alder decline further or disappear from the pollen record while elm, ironwood,
hickory, and oak increase to maximums. Zone 1 1 1 b dates from 10,600 to 8300 BP
and is interpreted as the culmination of the transition from tundra and boreal
woodland to oak dominated deciduous forest. By the top of Zone 1 1 lb, the
dominant vegetation in the area was oak-hickory forest. The climate in
central Illinois at this time was wetter than at present.

ZONE IV. At 8300 BP there was an abrupt increase in ragweed (Ambrosia) and
shortly, after grass, Chenopods, and the sunflower group (Tubuliflorae)
increased. The pollen of the deciduous trees declined at the same time.
Between 970 and 860 cm depth the percentage of NAP (non-arboreal pollen)
increases from 3% to 37%. The percentage increase in NAP is also apparent in
the influx values. This increase in herb and grass pollen is interpreted as
the first appearance of prairie in the Holocene on the broad upland of central
Illinois. Oak pollen continues to dominate the pollen record, however, as
small remnants of forest persisted along river and streams. Prairie produces
small amounts of pollen because most of its constituent species, with the
exception of grass and ragweed, are insect-pollinated. Because of the
disproportional ly large production of pollen by trees, small NAP increases are
more significant than overriding percentages of trees. The shift from forest
to grasslands in central Illinois 8300 years ago suggest that climatic
conditions were becoming increasingly drier.

There is little vegetation change in the Chatsworth Bog pollen record
after 8300 BP. Once the area became prairie is has remained that way to the
present.

BIBLIOGRAPHY

Acker, L. L., M. S. Hodges, G. T. Keller, and R. Rehner, 1980, Soil Survey of
Ogle County, Illinois: Soil Conservation Service, U.S. Department of
Agriculture, 242 p.

Anderson, R. C, 1967, Sand and gravel resources along the Rock River in
Illinois: Illinois State Geological Survey Circular 414, 17 p.

Anderson, R. C, 1968, Drainage evolution in the Rock Island area, western
Illinois, and eastern Iowa: University of Illinois Agriculture Special
Publication 14, Urbana -Champaign, p. 11-18

Anderson, R. C, Prairies in the prairie state: Transactions of the Illinois
State Academy of Science 63, p. 214-221.

Anderson, R. C, and J. M. Masters, 1985, Terraces of the Rock River valley in
southern and northern Illinois, in Illinoian and Wisconsinan
Stratigraphy and environments in northern Illinois: The Altonian
revised: Illinois State Geological Survey Guidebook 19, p. 21-34.

Baker, R. G., T. J. Frest, and R. S. Rhodes, 1984, Paleoecology of Quaternary
sediments at Conklin Quarry, in B. J. Bunker and G. R. Hallberg, eds . ,
Underburden-overburden. An Examination of Paleozoic and Quaternary
strata at the Conklin Quarry near Iowa City: Geological Society of Iowa
Guidebook, p. 70-81.

Baker, R. G., R. S. Rhodes, D. P. Schwert, A. C. Ashworth, T. J. Frest, G. R.
Hallberg, and J. A. Janssens, 1986, A full-glacial biota from
southeastern Iowa, USA: Journal of Quaternary Science, v. 1, p. 91-107.

Baker, R. G., A. E. Sullivan, G. R. Hallberg, D. G. Horton, K. Z. Carter, and
D. P. Schwert, 1986, Paleoecology of the Biggsville area, western
Illinois, during Farmdalian time (abstract) : American Quaternary
Association 9th Biennial Meeting, May 31-June 6, University of
Illinois at Urbana-Champaign.

Berg, R. C, J. P. Kempton, L. R. Follmer, and D. P. McKenna, 1985, Illinoian
and Wisconsinan stratigraphy and environments in northern Illinois: the
Altonian revised: Illinois State Geological Survey Guidebook 19,
177 p.

Chamberlin, T. C, 1986 (editorial): Journal of Geology, v. 4, p. 872-876.

Deere, D. V., and F. D. Patton, 1971, Slope stability in residual soils: 4th
Panamerican Conference on Soil Mechanics and Foundation Engineering, San
Juan, Puerto Rico, p. 87-170.

Follmer, L. R., 1978, The Sangamon Soil in its type area— a review, in W. C.
Mahaney, ed., Quaternary Soils: Geology Abstracts, Norwich, England, p.
125-165; Illinois State Geological Survey Reprint 1979-1.

Follmer, L. R., 1983, Sangamon and Wisconsinan pedogenesis in the midwestern
United States, in S. C. Porter, ed., The Late Pleistocene, v. 1 of H. E.
Wright, ed., Quaternary Environments of the United States: University of
Minnesota Press, Minneapolis, p. 138-144; Illinois State Geological
Survey Reprint 1984-A.

Follmer, L. R., 1984, Soil— an uncertain medium for waste disposal, in 7th
Annual Madison Waste Conference Proceedings: University of Wisconsin,
Madison, p. 2 96-311; Illinois State Geological Survey Reprint 1985-C.

Follmer, L. R., and J. P. Kempton, 1985, A review of the Esmond Till, in
Illinoian and Wisconsinan stratigraphy and environments in northern
Illinois: the Altonian rvised: Illinois State Geological Survey
Guidebook 19, p. 139-148.

Follmer, L. R., R. C. Berg, and L. L. Acker, 1978, Soil geomorphology of

northeastern Illinois: Soil Science Society of America and Geological
Society of America Joint Field Conference Guidebook, 82 p.

Follmer, L. R., J. P. Tandarich, and R. G. Darmody, 1985, The evolution of
pedologic and geologic profile concepts in the Midcontinent, USA:
American Society of Agronomy Abstracts, p. 190.

Follmer, L. R., E. D. McKay, J. A. Lineback, and D. L. Gross, 1979,

Wisconsinan, Sangamonian, and Illinoian Stratigraphy in Central
Illinois: Illinois State Geological Survey Guidebook 13, 139 p.

Frye, J. C, and H. B. Willman, 1960, Classification of the Wisconsinan Stage
in the Lake Michigan glacial lobe: Illinois State Geological Survey
Circular 285, 16 p.

Frye, J. C, and H. B. Willman, 1963, Loess stratigraphy, Wisconsinan
classification and accretion-gleys in central-western Illinois:
Midwestern Section Friends of the Pleistocene, 14th Annual Meeting:
Illinois State Geological Survey Guidebook 5, 37 p.

Frye, J. C, and H. B. Willman, 1965, Guidebook for Field Conference C— Upper
Mississippi Valley, C. B. Schultz and H.T.U. Smith, eds . , 7th Congress,
International Association of Quaternary Research (Illinois Section: R.
F. Black, and E. C. Reed, organizers) : Nebraska Academy of Science, p.
88-90.

Frye, J. C, H. B. Willman, and H. D. Glass, 1960, Gumbotil, accretion-gley,
and the weathering profile: Illinois State Geological Survey Circular
295, 39 p.

Frye, J. C, H. D. Glass, J. P. Kempton, and H. B. Willman, 1969, Glacial
tills of northwestern Illinois: Illinois State Geological Survey
Circular 437, 45 p.

Frye, J. C, P. R. Shaffer, H. B. Willman, and G. E. Ekblaw, 1960, Accretion
gley and the gumbotil dilemma: American Journal of Science, v. 258, n.
3, p. 185-190.

Frye, J. C., H. B. Willman, M. Rubin, and R. F. Black, 1968, Definition of
Wisconsinan stage: U.S. Geological Survey Bulletin 1274-E.

Frye, J. C., L. R. Follmer, H. B. Glass, J. M. Masters, and H. B. Willman,
1974, Earliest Wisconsinan sediments and soils: Illinois State
Geological Survey Circular 485, 12 p.

Grantham, D. R., 1980, Soil survey of Winnebago and Boone Counties, Illinois:
U. S. Department of Agriculture, Soil Conservation Service, 27 9 p.

Griffin, C. D., 1951, Pollen analysis of a peat deposit in Livingston County,
Illinois: Butler University Botanicl Studies 10, p. 90-99.

Hallberg, G. R., R. G. Baker, and T. Legg, 1980, A Mid-Wisconsinan pollen

diagram from Des Moines County, Iowa: Proceedings of the Iowa Academy of
Science 87, p. 41-44.

Johnson, W. H., L. R. Follmer, D. L. Gross, and A. M. Jacobs, 1972,

Pleistocene stratigraphy of east-central Illinois: Illinois State
Geological Survey Guidebook 9, 97 p.

Johnson, W. H., A. K. Hansel, B. J. Socha, L. R. Follmer, and J. M. Masters,
1985, Depositional environments and correlation problems of the Wedron
Formation (Wisconsinan), northeastern Illinois: Illinois Geological
Survey Guidebook 16, 91 p.

Kapp, R. 0., and A. M. Gooding, 1964, Pleistocene vegetational studies in the
Whitewater Basin, southeastern Indiana: Journal of Geology, v. 72, p.
307-326.

King, F. B., 197 9, Plant macrofossils from Athens North Quarry, in

Wisconsinan, Sangamonian, and Illinoian stratigraphy in central
Illinois: Illinois State Geological Survey Guidebook 13, p. 114-115.

King, J. E., 1979 Pollen analysis of some Farmdalian and Woodfordian deposits
in central Illinois, in Wisconsinan, Sangamonian, and Illinoian
stratigraphy in central Illinois: Illinois State Geological Survey
Guidebook 13, p. 109-113.

King, J. E., 1981, Late Quaternary vegetational history of Illinois:
Ecological Monographs 51, p. 43-52.

Leighton, M. M., 1923, The differentiation of the drift sheets in northwestern
Illinois: Journal of Geology, v. 31, n. 4, p. 265-281.

Leighton, M. M., 1926, A notable type Pleistocene section: the Farm Creek

exposure near Peoria, Illinois: Journal of Geology, v. 34, p. 167-174.

Leighton, M. M., 1931, The Peorian loess and the classification of the glacial
drift sheets of the Mississippi Valley: Journal of Geology, v. 39, p.
45-53.

Leighton, M. M., 1933, The naming of the subdivisions of the Wisconsinan
glacial age: Science, v. 77, n. 1989;, p. 168.

Leighton, M. M., 1960, The classif icaion of the Wisconsin glacial stage of
north central United States: Journal of Geology, v. 68, P. 529-552.

Leighton, M. M., 1965, The stratigraphic succession of Wisconsin loesses in
the Upper Mississippi River Valley: Journal of Geology, v. 37, p. 323-
345.

Leighton, M. M., and J. A. Brophy, 1961, Illinoian glaciation in Illinois:
Journal of Geology, v. 69, n. 1, p. 1-31.

Leighton, M. M., and J. A. Brophy, 1966, Farmdale glaciation in northern

Illinois and southern Wisconsin: Journal of Geology, v. 74, p. 478-499.

Leighton, M. M., and P. MacClintock, 1930, Weathered zones of the drift sheets
of Illinois: Journal of Geology, v. 38, p. 28-53.

Leighton, M. M., and P. MacClintock, 1962, The weathered mantle of glacial

tills beneath original surfaces in north-central United States: Journal
of Geology, v. 70, p. 267-293.

Leighton, M. M., and H. B. Willman, 1950, Loess formations of the Mississippi
Valley: Journal of Geology, v. 58, p. 599-623.

Leighton, M. M., and H. B. Willman, 1953, Basis of subdivisions of Wisconsin
glacial stage in northeastern Illinois: Guidebook, 4th Biennial State
Geologists Field Conference, pt . 1: Illinois State Geological Survey and
Indiana Geological Survey, p. 38-39.

Leonard, A. B. 1974, Chronology and molluscan paleontology of two post-

Woodfordian bogs in northeastern Illinois: Illinois State Geological
Survey Circular 487, 28 p.

Leverett, F., 1898a, The weathered zone (Sangamon) between the Iowan loess and
Illinoian till sheet: Journal of Geology, v. 6, p. 171-181.

Leverett, F. 1898b, The Peorian soil and weathered zone (Toronto Formation?) :
Journal of Geology, v. 6, p. 244-249.

Leverett, F., 1898c, The weathered zone (Yarmouth) between the Illinoian and
Kansan till sheets: Iowa Academy of Science Proceedings, v. 5, p. 81-86.

Leverett, F., 1899, The Illinois glacial lobe: U.S. Geological Survey
Monograph 38, 917 p.

Lindroth, C. H., 1961, The ground beetles of Canada and Alaska: Part 1, Opusc.
Entomol. Supplement XX.

Lindroth, C. H., 1966, The ground beetles of Canada and Alaska: Part 4, Opusc.
Entomol. Supplement XXIX.

Lineback, J. A., 1979, Quaternary deposits of Illinois: Illinois State
Geological Survey map, scale 1:500,000.

Lineback, J. A., D. L. Gross, and R. P. Meyer, 1974, Glacial tills under Lake
Michigan: Illinois State Geological Survey Environmental Geology Note
69, 48 p.

McKay, E. D., 1979, Wisconsinan loess stratigraphy of Illinois, in

Wisconsinan, Sangamonian, and Illinoian Stratigraphy in central
Illinois: Illinois State Geological Survey Guidebook 13, p. 95-108.

McKenna, D. P., 1984, Age of surficial tills in Boone and Winnebago Counties,
Illinois: a soil geomorphic analysis: M.S. thesis, Northern Illinois
University, 80 p.

McKenna, D. P., 1985, Geology and geomorphology of the Oak Crest Bog, in
Illinoian and Wisconsin stratigraphy and environments in northern
Illinois: the Altonian revised: Illinois State Geological Survey
Guidebook 19, p. 61-74.

Meyers, R. L., and J. E. King, 1985, Wisconsinan interstadial vegetation of
northern Illinois, in R. C, Berg, J. P. Kempton, L. R. Follmer, and D.
P. McKenna, eds . , Illinoian and Wisconsinan stratigraphy and
environments in northern Illinois: the Altonian revised: Illinois State
Geological Survey Guidebook 19, p. 75-86.

Morgan, A. v., and A. Morgan, 1979, The fossil Coleoptera of the Two Creeks
Forest Bed, Wisconsin: Quaternary Research 12, p. 226-240.

Morgan, A. V., and A. Morgan, 1980, Faunal assemblages and distributional
shifts of Coleoptera during the Late Pleistocene in Canada and the
northern United States: Canadian Entomologist 112, p. 226-240.

Morgan, A. V., and A. Morgan, 1980, Paleontological methods of reconstructing
paleoclimate with reference to interglacial and interstadial insect
faunas of southern Ontario, in W. C. Mahaney, ed., Quaternary
Paleoclimate: Geological Abstracts, U.K.

Mundt, S. R., and R. G. Baker, 1919, A Mid-Wisconsin pollen disgram from Black
Hawk County, Iowa: Proceedings of the Iowa Academy of Science 8 6, p. 32-
34.

Rohlf, F. J., and R. R. Sokal, 1969, Statistical tables: W. H. Freeman and
Company, San Francisco.

Rubin, M., and C. Alexander, 1960, U.S. Geological Survey radiocarbon
supplement, v. 2, p. 129-185.

Ruhe, R. V., 1969, Quaternary landscapes in Iowa: Iowa University Press,
Ames, Iowa, 255 p.

Ruhe, R. V., 1976, Stratigraphy of mid-continent loess, USA, in W. C. Mahaney,
ed., Quaternary Stratigraphy of North America: Dowden, Hutchinson, and
Ross, Stroudsburg, PA, p. 197-211.

Ruhe, R. V., w. P. Dietz, T. E. Fenton, and G. F. Hall, 1968, Iowan drift
problem, northeastern Iowa: Iowa Geological Survey Report of
Investigations 7, 40 p.

Sauer, C. O., 1916, Geography of the upper Illinois Valley and history of
development: Illinois State Geological Survey Bulletin 27, 208 p.

Schneider, A. F., and L. R. Follmer, 1983, A buried Sangamon Soil in

southeastern Wisconsin, in Late Pleistocene history of southeastern
Wisconsin: Geoscience Wisconsin, v. 7, p. 86-97.

Shaffer, P. R., 1956, Farmdale drift in northwestern Illinois: Illinois State
Geological Survey Report of Investigation 198, 25 p.

Soil Survey Staff, 1975, Soil taxonomy— A basic system of soil classification
for making and interpreting soil surveys: U.S. Department of
Agriculture, Soil Conservation Service, Agriculture Handbook 436, 754 p.

Sullivan, A. E., 1985, Middle and Late Wisconsinan floras of western Illinois
and north-central Iowa (abstract) : American Association of Stratigraphic
Palynologists Meeting, Programs with Abstracts.

Voss, J., 1937, Comparative study of bogs on Cary and Tazewell drift in
Illinois: Ecology 18, p. 119-135.

Wascher, H. L:., R. P. Humbert, and J. G. Cady, 1948, Loess in the southern

Mississippi Valley: Identification and distribution of the loess sheets:
Soil Science Society of American Proceedings, 1947, v. 12, p. 389-399.

Willman, H. B., and J. C. Frye, 1970, Pleistocene Stratigraphy of Illinois:
Illinois State Geological Survey Bulletin 94, 204 p.

Willman, H. B., and J. N. Payne, 1942, Geology and mineral resources of the
Marseilles, Ottawa, and Streator Quadrangles: Illinois State Geological
Survey Bulletin 66, p. 148-149, 307.

Willman, H. B., H. B. Glass, and J. C. Frye, 1966, Mineralogy of glacial tills
and their weathering profiles in Illinois: Part 2, Weathering profiles:
Illinois State Geological Survey Circular 400, 76 p.

Willman, H. B., A. B. Leonard, and J. C. Frye, 1971, Farmdalian lake deposits
and faunas in northern Illinois: Illinois Geological Survey Circular
467, 12 p.

Willman, H. B., and others, 1967, Geologic map of Illinois: Illinois State
Geological Survey map, scale 1:500,000.

Williams, N. E., J. A. Westgate, D. D. Williams, A. Morgan, and A. V. Morgan,
1981, Invertebrate fossils (Insecta: Trichoptera, Diptera, Coleoptera)
from the Pleistocene Scarborough Formation at Toronto, Ontario, and
their paleoenvironmental significance: Quaternary Research 16, p. 146-
166.

Worthen, A. H., 1870, Geology and paleontology: Geological Survey of Illinois,
v. IV, 508 p.

Worthen, A. H., 1873, Geology and paleontology, Geological Survey of Illinois,
v. V, 619 p.

APPENDIX 1. A Preliminary Note on Fossil Insect Faunas from Central Illinois

Alan V. Morgan, Quaternary Research Institute, Department of Earth Sciences,
University of Waterloo, Ontario

Anne Morgan, Department of Biology, University of Waterloo, Ontario

As part of a long-term paleoentomological project at the University of
Waterloo, samples have been obtained from a number of sites close to the limit
of Wisconsinan glaciation in Illinois, Indiana, Ohio, New York, and
Pennsylvania. Preliminary samples from Illinois were first collected in 1972
(Morgan, unpublished) and established the foundation for further sampling in
following years. This report provides comments on the insect faunas extracted
from the Gardena and Clinton sites. The processing methods follow those
outlined in Morgan and Morgan (1979).

Gardena Section

The site at the Gardena Section is well exposed on the banks of a tribu-
tary stream flowing into Farm Creek east of Peoria, Illinois (Follmer et al.,
1979). The section exposes a sequence of 2.13 m of Morton Loess resting on
Robein Silt and overlain by a gray, massive diamicton (the Delavan Till Member
of the Wedron Formation). The top 1 to 3 cm of the Morton is a thin, continu-
ous layer of compressed moss that is overlain by an 8- to 10-cm light gray
lacustrine clay.

Wood taken from the base of the Morton near stream level (ca_. 2.0 m below
the contact with the till) has provided an age of 25,370 + 310 RCYBP
(ISGS-531). The moss layer (10 to 12 cm below the till) was dated at 19,680 +
460 RCYBP (ISGS-532).

Samples for insect analyses were taken from two levels. In 1981, 28.1 kg
were extracted from 1.85-2.0 m below the till, with an additional 76 kg from
the same level in 1982. Also in 1981, 22.8 kg were taken from the moss and
lacustrine clay layer and supplemented by an additional 121.8 kg in 1982. A
consistent ecological picture has emerged that permits some general comments
about the paleoenvironments of the Peoria region prior to the advance of the
late Wisconsinan ice.

The lower part of the Morton Loess in the Gardena Section contains a
numerically rich but wery poorly preserved insect fauna with a restricted
number of taxa. The presence of water and muddy marginal substrates is indi-
cated by a number of dytiscid and hydrophilid species including Hydroporus and
Helophorus, the carabid Dyschirius, and staphylinid species such as Bledius
and Stenus. The presence of conifer trees and other plants is indicated by at
least two species of scolytids, Phloeotribus piceae and Scolytus piceae, along
with several cuculionid (weevil) species. Other groups represented in the
fauna include oribatid mites, ants (Formica sp.) and alder flies ( S i a 1 i s
sp.). This assemblage suggested boreal forest conditions, although without
more specific identifications it is difficult to reconstruct the exact
environmental regime.

The insect fauna recovered from the moss layer at the top of the Morton
Loess contrasts markedly with the fauna from the base. Although the fauna is

dominated by staphylinid (rove) bettles, it also contains some extremely
interesting carabid species. Foremost among these is the ground beetle
Diacheila polita, which was the first-found fossil in the southern mid-
continent in the Early Wisconsinan Scarborough Formation at Toronto. D.
pol ita has subsequently been discovered in other early Wisconsinan sites in
Ontario and Quebec (Morgan and Morgan, 1980; Williams et al., 1981). This
highly distinctive species occurs (in some number) in the Gardena section and
further east at the Clinton site. The modern distribution of D. polita is
confined to Alaska, Northwest Territories and the Yukon. Lindroth (1961)
describes D. polita as inhabiting peaty soil on the open tundra, although it
is known that this species ranges down to the northern edge of conifers
(Morgan and Morgan, 1981).

Several well-preserved specimens of Elaphrus lapponicus have been
found. All were coppery-green and were identified from disarticulated pronota
and elytra. E. lapponicus is an hydrophilous species that, according to
Lindroth (1961) inhabits cold water areas near springs, where the vegetation
mainly consists of mosses. He also reports that this species rarely ascends
above timber limit and is not a true inhabitant of the tundra.

Staphylinids from the same strati graphic level include Olophrum
rotundicolle, a species with a typical boreal distribution and Acidota
guadrata, also a boreal inhabitant. Additional staphylinid species include
Arpedium, Stenus, and at least one other Olophrum.

The somewhat limited fauna from the top of the Gardena Section does give
a simplistic environmental picture of an open ground area, treeless, but not a
true tundra in the sense of the modern arctic tundra. Temperatures probably
were warm enough for trees to grow, but either lack of sufficient moisture,
or, more likely, winds blowing across the open environment prevented forest
growth.

Clinton Section

The fauna at the top of the Morton Loess in the Gardena Section is
remarkably similar to an insect assemblage recovered from an equivalent
strati graphic section in excavations made for a nuclear power station at
Clinton, Illinois, approximately 50 miles southeast of Peoria. The Clinton
Section was sampled twice before the exposure was closed and a total 159 kg of
sediment was removed for analysis. The organic horizon consisted of a thin
(up to 5-cm) layer of compacted mosses overlain by an additional 5 to 10 cm of
light gray lacustrine silty clay beneath Wedron Formation till. The moss bed
has been dated at 20,670^280 RCYBP (ISGS-828). The Clinton fauna contains
Diacheila polita and Elaphrus lapponicus as two common carabids, as well as
Agonum exaratum. A. exaratum is described by Lindroth (1966) as the most
pronouncedly arctic North American species of Agonum, rarely occurring below
forest limit. It has been found on soft, marshy ground at the margin of pools
and ponds, commonly with carices and sometimes mosses. As in the case of the
fauna at the top of the Morton Loess at Gardena, staphylinids including Stenus
and Olophrum rotundicolle are fairly common. A hydrophilid beetle, Helophorus
sempervarians, occurs commonly in the Clinton site. This is also a typical
boreal species inhabiting the margins of permanent ponds or temporary water
bodies. Non-beetle insect remains recovered from Clinton include Diptera (fly

puparia and chironomids) , Trichoptera (caddisfl ies) , Hemiptera and Homoptera
(bugs) and Archnidae (oribatid mites).

The general environmental picture at Clinton appears to be similar to
that of the Peoria region at approximately 20,000 B.P. Both the top Gardena
and Clinton faunas lack scolytids, and this suggests (albeit with the dangers
of negative evidence well in mind) that trees were probably not present in the
depositional catchment area. The carabids, staphyl inids, and hydrophilids at
these sites indicate open-ground conditions, although their modern boreal
distribution suggests that the environment was probably marginally capable of
supporting trees. If trees were not growing at Garden or Clinton 20,000 years
ago, then they must surely have not been geographically far away--possibly at
the most, 10-20 km. On the basis of insect requirements, July temperatures at
maximum glaciation (20,000-18,000 B.P) should have been about 11° or 12°C,
with a mean annual temperature possibly as low as -7° to -9°C.

Acknowledgements

We thank Leon Follmer of the Illinois Geological Survey and Jim King of
the Illinois State Museum for drawing our attention to the Garden and Clinton
sections. We are grateful to Leon Follmer and W. Hilton Johnson (University
of Illinois at Urbana-Champaign) for re-sampling the Clinton site prior to its
closure.

APPENDIX 2.

Comparison of the Complete Soil Profile and a Weathering Profile in
Rock (from Follmer, 1984).

Soil profile
(Follmer et al., 1979)

Weathering profile
(Deere and Patton, 1971)

Horizon Description

Zone of organic matter and
resistant mineral accumula-
ion; porous*

Zone Description

IA Top soil; organic material;
zone of leaching and eluvia-
tion; may be porous*

Zone of eluviation; porous,
may be vesicular*

Zone of clay accumulation or
gl eying; blocky peds commonly
coated with clay or secondary IB
minerals; biological pores*

"Characteristically clay-
enriched with accumulations
of Fe, Al and Si; no relict
structures*

(BC) B3

Zone of strong mineral
alteration; oxidized or
gleyed; clay coatings or
(CB) CI** stains on peds or joint
blocks; common roots in
joints; occasionally
porous and massive

Zone of moderate mineral
alteration; oxidized or
gleyed; jointed; calcareous
(C) C2 or equivalent; clay or

secondary minerals in joints;
geologic fabric within
structural units

Relict rock structure
IC retained; <10% core stones;
>90% soil -like material

(CD)

(DC)

•*

Zone of slight mineral

alteration; variable; few 1 1 A

joints with stains or veins

of secondary minerals;

unaltered "core stones"

between joints I IB

Soil -like to rock-like;
10 to 90/o core stones,
highly variable

Rock-like; altered or
stained along joints

Unweathered, unaltered,
(D) C4 unoxidized, massive or

stratified geologic material

III Unweathered rock; no
stains along joints

*A1 though descriptions are different, general agreement exists to use definitions
of the Soil Survey Staff (1975) for the solum.
**Transitional horizon.

( Resignations proposed by Follmer et al . (1985) in a paper read at the ASA
meeting in Chicago.

Chicago

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