Newsletter
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Glacial Deposits of
Williamson
County
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ECS of the
Shawnee
National
Forest
Hydric Soil Monitoring
ISCA Minutes
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ISCA Elections
President-Elect
Mark Bramstedt
graduated from the University of
Montana
with a B.S. in Forest Soils. He began
his soil career with SCS in Knox
County
and also mapped on the Peoria
County
survey. He was the Soil Survey Party
Leader in Jasper County
and Edgar County. After mapping, Mark moved into the Area Soil
Scientist position in old Area 2.
Currently Mark is the Area Soil Scientist with NRCS in Area 3 stationed
in Watseka. Mark has been a member of
ISCA since 1978 and Certified with ISCA since 1982. Mark is also ARCPAC Certified and a
Registered Indiana Soil Scientist (pending).
Bruce Houghtby is
a graduate of the University of
Illinois
with a B.S. in Agronomy. He has worked
in Orange County
and Randolph County
in Indiana. In Illinois Bruce has mapped in Knox, Coles, Macoupin and White
Counties. Currently he is employed with John Raber and Associates Inc. in McHenry,
Illinois.
Bruce was ARCPAC Certified in 1980 and been a member of ISCA since 1988. He is also Certified
with ISCA.
Vice-President
Steve Elmer is a
graduate from the University of Wisconsin-Stevens Point, with a B.S. in
Resource Management/Soils Emphasis. He
began his soil career in Wisconsin mapping on three soil
survey projects. Steve then moved to
Connecticut
as a Soil Survey Party Leader. In 1977
he came to Illinois as a Party
leader and headed four Northwest Illinois Soil Survey Projects. Currently Steve is the MLRA Party Leader in
the Rock Falls
office. Steve is ISCA and ARCPAC
Certified.
Don Fehrenbacher
graduated from the University of
Illinois
with a B.S. in Forestry. He then
received his M.S. in Soils also from the University
of Illinois. He started his
SCS/NRCS career mapping in Iroquois
County
and then moved west as the Soil Survey Party Leader in
Ford
County. For a short time Don was the Party Leader in
White
County before accepting the Area
Soil Scientist position in Bourbonnais. Don is currently stationed in Plainfield
as the Watershed Team Leader. Don is a
Charter member of ISCA and is also ISCA Certified.
Secretary
Chris Cochran
received his B.S. in Forest Science from the University
of Illinois and began working with
SCS as a party member of the Kane
County
and Champaign County
soil surveys before serving as Area Soil Scientist in Macomb. In 1980, Chris headed west to Arizona
still working for SCS/NRCS. While in
Arizona
he also spent time mapping in North Dakota
and New Mexico. Chris continues to work for NRCS as the MLRA
party leader in Charleston. Chris is a Charter member of ISCA.
Tom D'Avello
graduated from Ohio State
University where he received his
B.S. in Agronomy. He began his career
with SCS in eastern Ohio in
1981. He has also mapped in Florida
and Montana. In 1988, he went back to school at Michigan
Tech and received is M.S. in Forest Soils.
After receiving his M.S., he went back to Ohio
where he was the survey leader in Ross
County. Tom has been the GIS specialist in Illinois
since 1990 working on projects such as Soilview,
SSURGO, bathymetric mapping, GPS and general GIS
applications.
ISCA Annual Meeting
The
ISCA Annual Meeting has been planned for March 29th,
2003. No details about the location or the time
have been established as of this date.
More information on the meeting will be forthcoming from Program
Chairman and or the Current President.
Nominations
for the bent auger award will be made at the annual meeting. Below we have a picture of a Humvee high centered, and four innocent people. A couple of ISCA members caught a ride back
to town and left these four helpless people stranded in a strip mine in
Randolph County. It was a very cold day in December 2001. Just remember sometimes when people leave to
go get help, they never come back. The names of Jerry Berning
and Sam Indorante were not used in this story in order to protect their
innocence.
Glacial Deposits of
Williamson County
Leon Follmer
ISGS
Glaciers are masses of
ice that can grow to immense size and cover an extensive area. All of Williamson County was once covered by a continental-size glacier during the next to the
last glacial stage 125,000 to 180,000 years ago, named for Illinois. Glaciers
disturb the ground as they pass over and create a large variety of deposits and
landform features. To
the careful observer it is relatively obvious that glaciers eroded and
deposited a mixture of bedrock materials in the process of a glaciation. The evidence is first noticed in the gravel and boulders
of the deposits that we call till, which is a relatively uniform mixture of
clay, silt, sand and gravel deposited by a glacier. This may seem straight forward but
sometimes we find parts of the glacial landscape that are not easily explained,
i.e., it is not clear how some of the glacial features and deposits were
formed. Some features are quite mysterious
on first observation because they do not seem to be compatible with the present
landscape. To deal with this we often
dismiss the odd relationships we can not explain.
A typical familiar
pattern on the Illinoian till plain of southern
Illinois is to find thick glacial deposits under level or
gently rolling landscapes. This conjures
up an image of the glacier carrying the materials or even pushing it along and
smearing it out as a more or less homogenous mixture. But when we find stratified glacial
deposits scattered around on bedrock controlled upland hills it may seem a bit
odd. In a re-examination of the
surficial geology of Williamson County, Illinois, a model has been developed to
explain the origin of stratified glacial deposits found in many places in the
Shawnee Hills and on the bedrock controlled upland hills to the north that have
been overridden by the Illinoian glacier.
The
odd observations. In many places of
Williamson County isolated nearly level areas are scattered throughout the bedrock
uplands. In places they join to produce
a stepped geomorphic surface. In some
views they appear like terraces or benches.
The underlying deposits have been examined in only a few places. In places normal till is present but in other
places the “odd” observations of stratified glacial deposits have been found or
no glacial drift at all. All of these
settings have a loess cover up to 8 feet thick.
The loess cover is a sequence of Peoria-Roxana-Loveland loesses more than 5 feet thick in most places and covers
the underlying materials that range from Pennsylvanian bedrock to a large
variety of glacial deposits. The glacial
deposits include till, stratified diamicton, sand and silt with some gravel and
clay. Diamicton is a mixture of fine-grained
sediments and pebbles. In all these
settings the soils have been mapped as upland types such as Ava,
Hosmer and related soils. The stratified deposits are commonly silty
but range from fine silt to coarse sand with lenses of loamy diamicton and clay. They underlie somewhat level areas, which are
terraces of a special kind. Where loess directly
overlies bedrock in level areas, they are presumably erosional
benches. Under soils in sloping areas,
the sediments vary from one type to another. In a few places
loess-covered stratified glacial deposits are on the highest parts of the local
landscape.
The idea for the model
comes from places where ice-walled glacial lakes have been studied, such as in North Dakota, Canada, and other parts of the world. During the melting phase of a stagnant
glacier, much of the meltwater runs off into glacial streams and away from the
area. A large
portion of the sediments that had been entrained in the glacier is carried away
but some of it remains in place forming normal till. In places some of the meltwater has
nowhere to go and collects in basins forming lakes on the glacier. Sediments that collect in the lakes promote
melting of the surrounding ice, which promotes the size of the lakes to
grow. As lakes grow, they can merge with
nearest neighbors to form larger lakes.
Eventually the lake bottom melts through the ice down to the
ground. At this point the lake becomes
surrounded by the remnants of the stagnant glacier, thus becoming an ice-walled
lake.
Sediments accumulate in
the ice-walled lakes until the glacier finally melts away. In some places the top of the lake sediment
is above the surrounding land and stands out like a flat-topped mesa. Where these features occur depends on how the
total glacial sediment load is distributed and the melting processes. In hilly bedrock
terrain the distribution of glacial sediments is highly irregular compared to a
typical ground moraine on a flat landscape where a diamicton layer can have a
uniform thickness over large distances. The nature of
the ground beneath the glacier seems to have little connection to where
ice-walled lakes occur. Thus the lakes
deposits can seem to occur anywhere.
There may be a few ice-wall lake remnants on the highest parts of some
hills in Williamson County, but none have been verified yet.
However, there seems to be evidence for several ice-walled lakes on
every topographic quadrangle in Williamson County.
The ice-wall lake model
also explains how a series of stepped surfaces on lake sediments can form. A lake at a high level could by chance drain
into an adjacent lower lake and eventually merge. Where a series of lakes merged in this way it
would produce a stepped geomorphic surface on the lake deposits. In a general sense, ice-walled lake sediments
are a special type of basin-fill deposits.
They have a facies (lateral) relationship with
normal till that is deposited directly from the glacier as well as with glacial
lacustrine deposits formed on the glacier or a stable substrate. In general the ice-walled basin deposits are
intermediate between what we would call normal till and normal lake
deposits. Also, it is reasonable to
expect normal till under stratified glacial basin deposits in this model.
The glacial basin model
solves another problem in the region.
Glacial Lake Muddy covered the northwest corner of Williamson County. It was a glacial slack water
lake that formed during the last glaciation [Late Wisconsinan,
14,000 to 25,000 years ago] and produced the Equality Formation, which is
largely stratified silty clay loam to clay.
It occurs only in the lowest parts of the Big Muddy River watershed and covers parts of five counties
north and west of Williamson
County. In this
regional lowland there are many little hills within the relatively flat
lowland. The cores of many of these
hills are presumable composed of glacial drift that has been called Illinoian till by many people. Some are bedrock highs or kames of Illinoian sand and gravel, and all are covered by variable
amounts of loess.
Where the drift in the
hills has been examined it commonly is a soft ablation type of till and
commonly contains lenses of fine sand.
The upper part of the drift is weathered by Sangamon soil formation.
All across this regional lowland, a loess-covered Sangamon Geosol has been found in a variety of parent materials,
particularly in fine sand. [Geosol: a paleosol catena defined
in stratigraphic terms.] At this point a big picture begins to emerge
-- The whole watershed of the modern Big Muddy River
system was a big basin formed during deglaciation. When the Illinoian
glacier stagnated, the melt water in this region was not able to flow away and
accumulated into a gigantic glacial lake.
This formed the lowland of the Big Muddy watershed. It would have been a temporary
lake of Late Illinoian age similar in character to the large glacial
lakes that formed on the Late Wisconsinan till plain
of northeastern Illinois. Eventually the late Illinoian lake in the Big Muddy lowland found an outlet to
the Mississippi River forming the modern course of the Big Muddy River through the Shawnee Hills. The lowland evolved into a Sangamonian wetland producing thick accretion gley profiles [cumulic
Aquolls].
Recent observations of
thick till in buried bedrock valleys of southwestern
Williamson County suggests that the pre-Illinoian Big Muddy River flowed southwards out of the county before the Illinoian glaciation. In this area the glacier totally
changed the drainage pattern. Following
the time of Sangamon soil formation [Sangamonian
Stage], the rivers of the Midwest during Early Wisconsinan
time went into an erosional phase and caused deep
incision of the main rivers and significant headward
erosion of first order streams into the upland areas. The Mississippi River
base level at the time was about 60 to 80 feet below the present level. A portion of the Big Muddy lowland was eroded
out and was later refilled with the Equality slack water deposits. The Late Wisconsinan
lake did not reach the heights of the Illinoian lake and its deposits completely covered up any
expression of the previous topography in the basin. There is some evidence for a middle Wisconsinan [Altonian] lake but
it did reach the level of the Late Wisconsinan
maximum and its deposits [lower Equality] are now deeply buried. The total Equality thickness is up to 50 feet in the
lowest parts of the Big Muddy basin.
When the Illinoian glacier advanced to its limit just south of
Williamson County, it filled former valleys with drift and "dehorned" the
bedrock hills and leveled them out somewhat.
Over the glaciated part of the Shawnee Hills the ice thickness and
amount drift in the ice would have been variable from place to place. When the glacier stagnated some of the water
and sediments would have collected in low spots forming lakes of various
sizes. The glacier was sufficiently
thick to cover all of Williamson
County which made it possible for ice-walled basins to
form anywhere where the local conditions were suitable, even on top of what
turns out to be the hill tops of the present topography. So far, coarse channel deposits of Illinoian meltwater streams have not been found, which
indicates a lack of an integrated drainage system in
Williamson County during the late Illinoian.
The border zones around
ice-walled basins would be unstable and generate mass wasting deposits that
flow into the basins as the ice melts.
This is probably the major producer of the stratified sandy silty
diamicton we see in many places. It is
the most likely explanation of how diamicton layers become interstratified with
bedded clay, silt, sand and gravel. [Note: Diamicton is a textural name
equivalent to pebbly loamy sediments. A
diamicton may or may not be a till]. The
soft somewhat stratified diamicton is often called ablation till because it is
assumed that it accumulated on the glacier as the glacier melted. It is generally not very compact and
described by civil engineers as normally consolidated.
Diamicton deposited
below a glacier, a good till, is usually compressed and dewatered by weight of
the glacier and is usually more uniform and
dense. It commonly shows evidence of
deformation. If a deposit is compressed
by a force greater than the normal overburden pressure, it is called over
consolidated by engineers. However, if
water is trapped in the diamicton it will not be compressed or over
consolidated. Diamicton deposited by a
glacier is till and rarely shows much stratification. Diamicton that is mobilized by some event
after it was released from a glacier is better called debris flow deposits or
stratified drift. In a broad sense this
creates three classes of diamicton: good
till, ablation till, and diamicton debris or debris flow deposits.
In the investigations so
far, the stratified Illinoian glacial sediments
appear to be scattered across the uplands of Williamson County and commonly occur under terrace-like landform features. They appear to be
related to the location of the present day drainage pattern. Also, they appear to be wide spread across
the level areas of the Illinoian till plain in
general. In
Williamson County the higher terrace features have no concordant relationships with their
nearest neighbor. The bigger ones that
are larger than a square mile in size usually show some stepped surface
features in cross section. At most places the slopes
are gradual and are interrupted by flat spots [A slopes on soil maps]. In a few places distinct changes in slope or
scarps [C slopes on soil maps] separate terrace levels. The Illinoian
sediments underlying terrace remnants are informally called Glasford
basin-fill deposits if they are stratified and contain diamicton, or they are
correlated with the Pearl Formation if they are dominated by stratified sand
and silt. If areas can be delineated
that are dominated by bedded silt and clay, they will be correlated with the Teneriffe Formation.
All have a mature Sangamon soil profile developed in them.
At lower elevations there are more occurrences of terrace
remnants that have concordant relationships, where surfaces on the landform
segments have about the same elevation.
The lowest level is the most widespread and consistent. These observations lead to a conclusion that
the ice-walled lakes that formed during the deglaciation
of the Illinoian glacier started out with no
pattern. With time the lakes either
dried up or coalesced. Surviving lakes
at the lower elevations merged to form a final big lake stage in the
Big
Muddy River basin. The big lake phase had a shore line that
ranged from about 400 to 420 feet in elevation.
At this time sediments of this lake are correlated with the Pearl
Formation because they appear to be dominated by fine sand. A full range of glaciofluvial-lacustrine
deposits is expected to occur in other places, but at this time we don’t know
their distribution. This lake is informally called
glacial lake
Herrin after the town which is
located on the south shore of this late Illinoian
lake. It is speculated that at the
highest contiguous lake level extended north to beyond Mt Vernon and covered
the region that is the present day lowland of the Big Muddy River
watershed.
Conclusions. The
interpretation of ice-walled, glacial basin features in
Williamson County raises other questions that are the focus of a continuing
investigation. Primary issues are how
many geological units can be differentiated on 1:24,000 scale geologic maps of
the county and how the geologic units should relate to the soils of
Williamson County. A report will be prepared after the 2003 field season. Work in this project is jointly supported by
the Illinois State Geological Survey and the Natural Resources Conservation
Service.
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WILLIAMSON COUNTY QUATERNARY MAPPING LEGEND
FOR 1:24,000 QUADRANGLES
1/23/03 draft
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SYMBOL*
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NAME
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DESCRIPTION
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c
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Cahokia
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Alluvium. Silt to clay rich, poorly stratified
sediments, weathered and leached in most places. Has a weakly developed soil profile in the
upper 5 feet. Underlain by Equality
clay or fine sand at most places.
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e
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Equality
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Lacustrine silt and clay,
interbedded, has a thin covering of alluvial or eolian deposits. Commonly laminated below the zone of
weathering and interbedded with some sand.
Weathered and leached to 10 feet.
Has a well developed soil profile in the upper part and is calcareous
in the lower part. Subdivided into 3
map units:
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e-1
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Low
Terrace
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Mostly clayey deposits on a
surface slightly above the flood plain ranging up to an elevation of about
380 feet. Covered by an indeterminant amount of alluvium (<0-5 feet) which is
masked by a well developed soil profile.
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e-2
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High
Terrace
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Silt and clay deposits on a
surface above e-1 that ranges up to an elevation of about 395 feet. Usually covered by 3 to 6 feet of eolian
silt or fine sand. Soils are well developed
and more oxidized than e-1 soils.
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e-s
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Sandy
Equality
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Sandy
facies of e-1 and e-2 in bar or natural levee
landforms. Loess and fine sand up to
10' thick in places overlying bedded clay, silt and
sand. Soils are well developed and
more oxidized that e-2 soils.
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pe
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Pearl
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Fine sand with a Sangamon Geosol in the upper 10 feet. On a terrace level above e-2 at an
elevation of about 400 feet near Herrin and rises to a level of about 440 to
the east and south. Underlies the
Equality north and west of Herrin.
Overlain by 5-10 feet of loess (Peoria,
Roxana and Loveland), which has a
well developed soil in the upper part.
Contains beds of sand and gravel where thick. Has a facies
relationship with Glasford basin fill (g-b) and Glasford till (g).
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g-b
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Glasford basin fill
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Stratified silt with lenses of
sand and loamy diamicton. Upper part modified by the
Sangamon Geosol and is overlain by 5-10 of loess (Peoria,
Roxana and Loveland), which has a
well developed soil in the upper part.
Appears as discontinuous terrace levels across the upland at
elevations from 420 up to 550 feet. Has a facies
relationship with Glasford till (g) at higher
elevations and Pearl (pe) at lower elevations.
Likely contains gravel at the base and overlies till where glacial
deposits are thick. Loess over eroded bedrock may be
common where depth to bedrock is shallow.
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g
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Glasford till
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Silty diamicton in most
places. Modified by the Sangamon Geosol in the upper part and covered by 5-10 feet of
loess (Peoria, Roxana and
Loveland),
which has a well developed soil in the upper part. Usually more dense and uniform than the diamicon in g-b.
Is the upland member of a facies with g-b
and pe. Overlies Pennsylvanian bedrock and is
discontinuous in places.
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B
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Bedrock
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Pensylvanian
sandstone, shale and limestone with less than 4 feet
of loess cover. Outcrops of bedrock
are common. Discontinuous patched of
glacial deposits are common. Surface
soils are well developed but variable.
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L
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Loess
over Bedrock
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Loess, 4-8 feet thick
overlying bedrock. Discontinous
patches of glacial deposits are common.
Area of strongly developed Grantsburg soils.
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ML
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Made
Land
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Disturbed land,
unclassified.
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SM
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Strip
Mine
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Surface coal mines that are
reclaimed to various degrees.
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*
Lower case letters are map symbols used by the ISGS. The prefex Q is
dropped for convenience. The capital
letters are symbols selected for this mapping project.
Ecological
Classification System of the Shawnee
National
Forest
Bryan Fitch
Soil Scientist
Shawnee
National
Forest
The
Shawnee
