S^A^o^^f
557
IL6of
1997-2
KARST REGIONS OF
Open
Fiio
Series
ILLINOIS
t
1997-2
l««
MAY
S.V. Panno, C.P. Weibel, and
illinois
W.
State Geological Survey
615
E.
Peabody Drive
Champaign,
Illinois
61820
Li
A
l-»>
1 5 1997
KARST REGIONS OF
Open
File
Series
ILLINOIS
1997-2
S.V. Panno, C.P. Weibel, and
W.
Li
y
Illinois
»^p>
«
State Geological Survey
MAY
615
E.
Peabody Drive
Champaign,
Illinois
61820
1 5 1997
KARST REGIONS OF
ILLINOIS
S.V. Panno, C.P. Weibel, and
W.
Li
ABSTRACT
Karst occurs
in Illinois
rocks. Approximately
approximately
35%
25%
where bedrock exposures and subcrops consist
of Illinois'
(equals
9%
bedrock
is
carbonate rock, and of that area,
in
southwest and southern
Mississippian limestones are predominant. Karst encountered
dominant landforms, included sinkhole
karst,
in Illinois,
was
the margins of the
Illinois
features are concentrated
north-central
southwest
occur
in
Illinois, (3)
Illinois,
and
northeastern
till
in detail.
is
either
exposed
at land surface or
(diamicton), loess, and other unlithified sediment around
Basin, and along the flanks of structures within the basin. Karstic
in five
regions:
the Lincoln
(5)
as classified by their
the focus of our efforts because these rocks are
susceptible to karst development. Carbonate bedrock
relatively thin glacial
where the
Only natural karst terrains are
land.
studied herein, and only the most karstified areas are described
of Illinois
Illinois
the
Illinois,
Hills of
Shawnee
and
in
(1)
the Driftless Area of northwest
the western
Hills of
southern
Illinois, (3)
Illinois.
A few
La Salle and Douglas Counties
Illinois, (2)
the Salem Plateau of
in
caves and sinkholes
carbonate rocks
associated with either the LaSalle Anticlinorium or the northeast flank of the
(Kankakee Arch).
The
cave karst, and pseudo-sinkhole and pseudo-
cave karst that resulted from human modifications to the
covered by
carbonate
of the state) includes the state's five karst regions.
highest degree of karstification occurs
The carbonate bedrock
of
Illinois
Basin
Digitized by the Internet Archive
in
2012 with funding from
University of
Illinois
Urbana-Champaign
http://archive.org/details/karstregionsofil19972pann
INTRODUCTION
Background
Carbonate rock comprises approximately
area underlain by carbonate rocks,
35%
25%
of the
bedrock surface
of that area (equals
9%
in Illinois.
of the state)
is
Of the
included
in
the five regions that contain evidence of numerous karstic features at the land surface. The
term "karst"
is
defined by Ford and Williams (1989) as "...terrain with distinctive hydrology
and landforms arising from
a
combination of high rock
secondary porosity." Features that typify karst
solubility
and well developed
terrain include closed depressions (sinkholes),
caves, large springs, fluted rock outcrops (Ford and Williams, 1989), blind valleys and
swallow holes (White, 1988).
Carbonate rocks generally have low primary porosity and permeability; however,
secondary porosity
(fractures) permits the rapid transport of large
volumes
of
water
into
through the rock. The movement of surface waters (rainwater and snowmelt), through
and into fractures
terrains.
soluble carbonate bedrock
Because of the microbial generation
carbonate rock,
bedding planes
minerals
in
in
infiltrating
in
soil,
responsible for the development of karst
carbon dioxide
water becomes acidic
in
the soils overlying
prior to entering fractures, joints
and
carbonate rocks. Small amounts of calcite and/or dolomite (the dominant
carbonate rock) dissolve
Calcite:
Dolomite:
until
of
is
and
in
accordance with the following simplified reactions:
CaC0 3 + FT ~ Ca 2+ + HC0 3 -
CaMg(C0 3
+2FP«*Ca 2+ + Mg + + 2HC0 3 2
)
2
the water approaches saturation with respect to the solubility of these mineral phases
(White, 1988). The slow dissolution of carbonate minerals over thousands to hundreds of
thousands of years gradually enlarges
through which water moves.
which groundwater flows
Some pathways become
in
and pathways along bedding planes
large conduits or caverns through
to points of discharge (e.g., springs).
conduits eventually can result
eventually results
joints, fractures,
in
Continued enlargement of the
the collapse of overlying rock and
fragmentation and
finally,
soil.
Surface erosion
destruction of the conduit system (White,
1988).
The
relatively large interconnected pores present in fissured or karstified
allow rapid
movement
of
water
into
constitute locally important aquifers
and through the rock bodies. These rock bodies often
in Illinois;
however, fissured and karst aquifers are very
susceptible to surface-derived contamination. Recharge to karst aquifers often
(analogous to water
movement
carbonate rock
to drainage tiles)
and carries with
it
is
rapid
materials (often
macroscopic) from the land surface that include human and animal wastes, pesticides, urban
runoff,
and other waste products associated with the human culture of
recharge to non-karst aquifers typically undergoes
a
a region. In contrast,
slow migration through materials
thick, clay-rich glacial diamicton) that generally provide sufficient time
(e.g.,
and environment
for
chemical, biological, and physical degradation and retardation of pollutants. Unfortunately,
residents
who draw groundwater from
karst aquifers for
domestic use
risk ingesting
contaminants. Rare and endangered species that inhabit underlying caves are also
from chemical and bacterial contamination
terrain
is
present
citing facilities
is
in Illinois is
important
such as waste disposal
in
groundwater.
when conducting
sites
addition,
knowing where karst
regional geological screening for
and low-level nuclear waste repositories. Thus,
important to identify the locations of karst terrain
and regulatory purposes.
In
at risk
in
it
the state for water-resource protection
Purpose
The purpose
of this investigation
the karst terrains of
karstification.
map
The
Illinois
Illinois
to prepare a state-wide
map and
maps
detailed
of
and to describe the geologic and hydrogeologic controls of
detailed karst
of the state of
was
maps presented
(Weibel and Panno,
in
herein
were prepared from
press) (Figure
a smaller-scale
1).
METHODOLOGY
Karst
Maps
Karst
minute
aerial
(1
maps were constructed
:24, 000) topographic
photographs
(1
:20, 000),
on the basis of landforms observed on 7.5-
for the state
maps and
stereo pairs of U.S. Department of Agriculture
bedrock lithology, cave locations, and sinkholes indicated on
Natural Resources Conservation Service (formerly the Soil Conservation Service) county
survey maps. Areas mapped as karst were
carbonate bedrock
is
most susceptible
A map
of the
caves of
confidential inventory of
Illinois
checked by the authors. As discussed above,
to dissolution, particularly
the land surface. The occurrence of caves
terrain.
field
in
found
an area
in
was used
where
is
it
occurs at or near
as an indicator of karst
carbonate rock was constructed using
313 caves (compiled by
J.E.
Gardner of the
History Survey from his work and from a data base prepared by the
The term "cave"
soil
Illinois
Illinois
a
State Natural
State Museum).
defined as "any natural cavity or series of cavities beneath the surface of
the earth. Such cavities are usually classified as caves only
entrance by humans" (Mohr and Poison, 1966).
A
literature
if
they are large enough to permit
search also
was conducted
karstic features observed within the state and neighboring states. Karst regions
for
were
delineated on the basis of the location of indicator sinkholes, caves, and carbonate rock,
without regard
for the thickness
and nature of Quaternary overburden. Because
all
carbonate
Jr.j
X
Carbonate
Bedrock
Non-carbonate
Bedrock
Sinkhole
Areas
Scale 1:3,000,000
_j
_i
i
i
i
i
i
i
i
i
i
i
Kilometer*
Figure
1.
Map
of the
Weibel and Panno,
in
bedrock geology of
press).
Illinois
showing sinkholes and caves (modified from
rock
shows some degree
the state
in
no area
is
of dissolution (usually along joints
described as "karst" unless
it
was
and bedding planes),
identified as having a karst aquifer with
associated karstic features.
Cross Sections
Cross sections of the areas containing carbonate bedrock and karstic features (Figure
were constructed
to
The cross sections
at the Geological
examine relationships between bedrock formations and
are schematic
and were based on the following:
Records Library of the
references describing the geology of the
and
3)
Illinois
in
karstification.
well records available
State Geological Survey (ISGS), 2) published
surficial
unpublished cross sections from the ISGS
cross sections are explained
1)
2)
sediment, bedrock surface and subsurface,
Map
Library.
Formation codes used
in
the
Figure 3.
DISCUSSION
The focus
of this investigation
is
on the carbonate bedrock of
Illinois
because these are
the rocks most susceptible to karstic development. These rocks are either exposed or
subcrop
at the
bedrock surface beneath
glacial deposits
around the margins of the
Illinois
Basin on the flanks of the Kankakee, Mississippi River, Pascola, and Wisconsin Arches, and
the Ozark
Dome, and,
east-central
Illinois
within the
Illinois
(Figure 2). Karstic features are concentrated
Driftless Area, the Lincoln Hills, the
Sinkholes and caves found
in
generally isolated, and occur
Kankakee Arch.
Basin, on the crest of the LaSalle Anticlinorium
in
north-central
Salem Plateau, and the Shawnee
Hills
Illinois,
in
the
(Figures 1, 2).
Kane, Kankakee, La Salle, and Douglas Counties are rare and
in
carbonate rocks associated with the LaSalle Anticlinorium and
Scale 1:3,000,000
"tSCOlA
Figure 2.
Map showing
of the Illinois Basin.
A *CH
locations of cross-sections, karst regions, and major structures
(in italics)
REGIONAL KARST MAPS
Caves
Predominantly
Noncarbonate Bedrock
Predominantly
Carbonate Bedrock
Sinkhole
Areas
REGIONAL MAPS AND CROSS-SECTIONS
Q-P = Quaternary, consisting mostly
of Pleistocene deposits
Penn = Pennsylvanian
Mcu =
Mel
=
Mississippian, upper Chesterian (includes Vienna, Menard, Clore, Kinkaid)
Mississippian, lower Chesterian (includes Renault, Ridenhower, Beech
Creek, Glen Dean)
Mvu =
Mississippian, upper Valmeyeran (includes St. Louis, Ste. Genevieve)
Mvm
Mississippian, middle Valmeyeran (includes Salem)
=
Mvl = Mississippian, lower Valmeyeran (includes Burlington, Keokuk)
Mk =
Mississippian, Kinderhookian
Du
= Devonian, Upper
Dm
= Devonian, Middle
Dl
S
(includes Grand Tower, Lingle)
= Devonian, Lower(includes
=
Silurian (includes Kankakee,
Ou
= Ordovician, Upper
Om
= Ordovician, upper Middle
Oma =
Bailey,
Backbone)
Sexton Creek, Hopkinton)
Kimmswick)
(includes Platteville, Galena,
Ordovician, lower Middle
01
= Ordovician, Lower
C
= Cambrian
(includes Shakopee)
Figure 3. Explanation for symbols, shadings, and abbreviations used
in
regional karst maps. Stratigraphic units are modified from Willman et
stratigraphic units
mentioned
in
cross sections and
al.
(1967). Relevant
the text are contained within parentheses.
In
the
Illinois
Basin, only Paleozoic-age rocks contain carbonate strata,
younger Mesozoic and Cenozoic rocks lack carbonate
strata.
Rock
include (from oldest to youngest) limestones and dolomites of the
whereas
units that are karstified
Lower and Middle
Ordovician and of the Silurian Alexandrian and Niagaran Series, limestone of the Lower and
Middle Devonian Series, limestones of the Mississippian Valmeyeran and Chesterian Series,
and the LaSalle Limestone of the Pennsylvanian Missourian Series (Figure
intensely karstified limestones occur within the Mississippian-age strata.
4).
The most
The regions that
contain numerous karstic features (particularly caves and sinkholes) are described
in detail
below. The geology and hydrogeology of each region are also discussed and formations that
have undergone karstic development are described. Formation codes, symbols, and shadings
used on the regional maps are explained
Shawnee
Figure 3.
Karst Region
Hills
Sinkholes and caves are abundant
The Shawnee
in
Hills
in
the karst of the
Shawnee
Hills of
southern
karst region (Figures 2, 5, 6, 7) includes Jackson, Union, Johnson, Pope,
Saline and Hardin Counties.
A few
sinkholes and caves are associated with the Lower
Devonian Bailey and Backbone Limestones and Middle Devonian Grand Tower and
Limestones
in
Illinois.
the west part of the
Shawnee
Hills.
Most sinkholes and caves occur
Lingle
in soil
overlying and within Mississippian Valmeyeran and Chesterian rocks (Figure 8A). Sinkholes
are
common
to
abundant
in
areas where bedrock
is
dominated by the Salem,
St. Louis, Ste.
Genevieve, Glen Dean, and Menard Limestones, and are found throughout most of the
Shawnee
of the
Hills.
Sinkholes also are
commonly associated with
Golconda Formation and the Kinkaid Limestone
features are relatively rare
in
the Renault Limestone,
in
the
Haney Limestone Member
the west part of the region. Karstic
Downeys
Bluff
Limestone Member of the
/
a
E
-CC
St. Louis
1,1,1
r;
/,
/.
S3
^7
fJ-i
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E
rTT
Salem
Cc?
C2
t,i,~
iiin
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i
LaSalle
Burlington
w-i-i-
IS£
Lingle
-J.-.H-4
Grand Tower
*— J.— A— l—A
Backbone
Bailey
st-.-w-.t
Racine
Kankakee/Sexton Creek/Hopkinton
^
.
»•
••
.
•
•
.
»
&
3n
/
Kinkaid
Galena/Kimmswick
'
?W
,
S
Platte ville
Clore
^rtrV
— s^f^-pJ*
Menard
'
-r
i
'
Shakopee
Vienna
Glen Dean
Haney
IXW-r
J
Beech Creek
xxx
rxx
X££.
^
Ridenhower
T-^trx
j
i
~rrr.
Downeys
Bluff
Renault
CX
Ste.
Genevieve
17-
Figure 4. Generalized stratigraphic
Carbonate units are shaded
to the right of the columns.
gray.
column of Paleozoic
Known
karstification
strata
in Illinois,
modified from
Bell et al.(1961).
zones are indicated by the stratigraphic names
North-Central
Salem Plateau
Scale 1:3,000,000
Shawnee
——
-i
i
i
i
i
i
Hills
i
Figure 5. Index of regional karst maps, outlined by boxes.
regions.
Dashed
lines indicate extent of karst
A
A'
Northeast
Southwest
Q-P-
200
200-1
-100 £
S 100-
1-0
A. Cross-section of the
B
Shawnee
Hills karst region,
modified from Weller and Ekblaw (1940) and Willman et
Northeast
Southwest
al.
(1967)
B'
200 -I
r-200
§ S
O)
>
Q
a
0)
(/>
(0
>
a
s 8
£ c
oj
co
ID
E 2
E
a)
100 -
L100
1
B.
Cross-section of the Salem
C
J*
Hills
Plateau karst region, modified from Weller and Weller (1939) and
West
Q-P
Q-P
Wllman
East
et
al.
C
-200
100-
-100
C. Cross-section of the south part of the Lincoln Hills karst region, modified from Baxter (1965, 1970), Reinertsen and
Treworgy (1991), Rubey (1952), Schultz (1993), Treworgy (1979), Whiting and Stevenson (1965) and Wilson and Odom
Figure 8. Cross-sections A-A', B-B', and
C-C
Ci
E
(1967)
200-
(1959).
r
Oj
Paint Creek Formation, Vienna Limestone, and the Clore Formation.
Vienna Limestone
is
too thin for the significant surface expression of karstic features. Within
the Clore Formation, sinkholes generally are found
which contains the thickest limestone
are
most commonly
Shale
Member where
of the
Shawnee
its
west
in
Hills area.
portion of the
A few
in
the Ford Station Limestone Member,
the formation. Sinkholes
is
in
the Kinkaid Limestone
Member, but can occur
the west part of the
carbonate content
which probably formed as
the
in
within the Goreville Limestone
Creek Limestone Member and,
In
most places the
In
higher.
Shawnee
The
within the
Hills,
Goreville
within the Negli
absent
is
in
Cave
Hill
the east part
sinkholes are associated with the Hardinsburg Sandstone
a result of dissolution of
Shawnee
the underlying Haney Limestone Member.
some sinkholes occur where
Hills,
thin
Pennsylvanian
Caseyville Sandstone forms the bedrock surface.
We
a result of dissolution of the underlying Goreville
Limestone Member of the Kinkaid
suggest that these sinkholes formed as
Limestone.
Groundwater
in
Shawnee
the counties of the
Hills
karst region
is
available
from sources
that include Silurian and Devonian carbonate rocks, Mississippian Valmeyeran limestones,
and Mississippian Chesterian limestones and sandstones. Solution-enlarged crevices of
Valmeyeran limestones, and
enhanced the permeability
faulting
and crevice development
of these rocks.
in
The carbonate rocks
the Chesterian rocks
of the
Shawnee
Hills
karst
region are used for rural, municipal and industrial water supplies (Pryor, 1956).
Salem Plateau Karst Region
The region adjacent
to the Mississippi River just south of East St. Louis
to as the "sinkhole plain" because
is
also part of the
it
is
often referred
contains a high density of sinkholes (Figures 5, 9, 10).
Salem Plateau Section
of the physiographic provinces of Leighton et
15
al.
It
Figure 9. Karst
Willman et
al.
map
for the north part of the
(1967).
Salem Plateau
karst region.
Geology modifed from
Figure 10. Karst
map
Willmanetal. (1967).
for the
south part of the Salem Plateau karst region. Geology modifed from
(1948). Approximately 10,000 sinkholes, numerous karst springs, and the largest caves
Illinois
are found
region (Panno, 1996).
in this
Randolph Counties consists
The bedrock geology
of St. Clair,
in
Monroe, and
and Pennsylvanian limestone, dolomite,
of Mississippian
sandstone, shale, claystone and coal (Figure 8B). The structural geology of the area
and close proximity to the Mississippi River are
(anticlines), relatively thin glacial drift,
responsible for the exposure of these rocks
typically less than
1
5 m, but
may exceed
1
in
5
these counties.
m
Drift
thickness
in this
area
is
and adjacent to stream valleys (Horberg,
in
1950).
Caves and sinkholes occur
in
Mississippian strata ranging from the Valmeyeran Salem
Limestone to the Chesterian Kinkaid Limestone. Many
probably
many
of the
caves occur
in
of the sinkholes (Weller,
the St. Louis Limestone. Solution features
Louis are primarily responsible for the widespread karst topography
region.
The trends
major structures
southeast
of long
caves
for the
The remnants
greater),
in
at
in this
outcrops and through fissures
cm
of these
in
diameter) that
initial
down
area formed as surface
in
near-surface bedrock.
cut over time to form large solution
conduits are visible
Monroe County. These caves
in
km
characteristically sinuous
in
in
in
Illinois
Caverns and
diameter
(5
of traversable passages).
"branchwork" type (per classification scheme
solution tributaries along bedding planes
parts of
are relatively large
and extensive (several have more than 5
typical of the
the west part of the
waters migrating along bedding planes eventually formed small
conduits (typically about 10
Foglepole Cave
the St.
this region are parallel or subparallel to the axial trend of
and Monroe Counties. Many caves
waters entered bedding planes
cavities.
in
the area. Anticlines, synclines and major cave systems trend northwest-
in
in St. Clair
Dominant routes
in
in
1939) and
of Palmer, 1991),
m
or
They
are
and form as
the limestone bedrock; thus, their passages are
plan view.
18
Sinkholes also are abundant
in
areas underlain by the Salem and Ste. Genevieve
Limestones and are often connected to underlying cave systems. Sinkholes are rarely
associated with the
Downeys
Bluff
Limestone Member of the Paint Creek Formation, Beech
Creek Limestone Members (and perhaps
in
the overlying Fraileys Shale
Member)
of the
Golconda Formation, and Vienna Limestone. The few sinkholes associated with the Cypress
Sandstone probably formed by dissolution and collapse of the underlying Ridenhower Member
of the Paint
Creek Formation.
Groundwater resources
in
these counties occur
the St. Louis Limestone and the overlying
in
the Valmeyeran strata that include
Aux Vases Sandstone.
Louis are sources of groundwater for domestic and rural supplies
region.
The Aux Vases Sandstone underlies
glacial drift. This
groundwater
The
region.
shallow groundwater supplies
aquifer and into the underlying
karstic
sandstone
thin glacial drift,
in this
in
part of this region, and
bedrock surface below thin
in this
Springs and wells
is
in
the St.
the west part of the karst
in
the east, forms the
also a reliable source of
however, does not offer much protection for
area. Wells drilled through the overlying Chesterian karst
Aux Vases Sandstone
zone and localized contamination
may
typically are not
cased through the
occur by this route (Panno et
al.,
1996).
Lincoln Hills Karst Region
Karstic features
in
the Lincoln
Hills
karst region (Figures 5, 11, 12) occur
Greene, Jersey, and Madison Counties
Pike, Calhoun,
in
in
Adams,
Middle Ordovician Kimmswick
Limestone, Silurian (Alexandrian Series) Sexton Creek Limestone, and Mississippian
(Valmeyeran Series) Burlington, Salem,
1
928; Rubey,
1
952) (Figure 8C,
lithologies of the
1
3A).
St. Louis,
Rubey
(1
and Ste. Genevieve Limestones (Lamar,
952) and Baxter
(1
965) described the
carbonate strata of the region. The Kimmswick Limestone dominantly
19
S
Mlas
1
1
1
1
1
1
1
1
1
1
1
>.
™
^B3
v^
8
Kllom«1ar«
1
\ «
1
1
1
P
R2W
Figure
11.
Willmanet
Karst
al.
map
(1967).
for the
south part of the Lincoln
Hills karst region.
Geology modifed from
;
Isabi
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consists of fine- to coarse-grained, massive limestone. The Sexton Creek Limestone ranges
from
a fine-grained
part.
The Burlington
Limestone
is
limestone
the north part of the area to a porous dolomite
in
and
lithologically similar
is
difficult to distinguish in
the south
The overlying Keokuk
a cherty, coarse-grained, crinoidal limestone.
is
in
many
places.
The Keokuk
probably contains karstic features, although this investigation has not verified such
occurrences. The Salem consists of a coarse-grained limestone that locally contains dolomite.
The overlying
St. Louis
Limestone
is
dominated by
fine- to very fine-grained, cherty
limestone, but also contains variable amounts of dolomite, conglomeratic limestone, and
arenaceous and
The
oolitic limestone.
medium-grained limestone that
Ste.
Genevieve Limestone consists of very
locally varies
from being argillaceous, to arenaceous^and to
oolitic.
MAY
Most
the
of the sinkholes
Kimmswick
region,
fine- to
in
in
the west part of the Lincoln
or St. Louis Limestones (Rubey, 1952).
3, 11).
Many
of the sinkholes
karst region occur in either'
The sinkholes
and near Alton, are associated primarily with the
Limestones (Figures
Hills
occur
in
St. Louis
in
Some
of these sinkholes, particularly in
thin layer of Pennsylvanian strata
(Rubey, 1952). Sinkholes
of
which contain trees
Sand and
Hills
in this
and Ste. Genevieve
relatively thick loess deposits that
region are typically shallow, bowl-shaped depressions,
or are filled with
Keokuk Limestones
drilled into
the
a
between the underlying limestone and the overlying loess
many
water and surrounded by trees.
gravel, dolomite, limestone, and
Wells also have been
in
southernmost Calhoun County, contain
sandstone aquifers are used
karst region for domestic water supplies. Wells and springs
Burlington and
wcV
the east part of the
overly the limestones and appear to have formed by stoping of the loess into voids
limestone.
1 5 1997
are the
in
in
the Lincoln
the Mississippian
main sources of domestic water from bedrock.
Devonian and Silurian rocks, but these are not as productive.
23
The Salem-St. Louis limestone
serve as a supply for
Jersey County
interval in
(Bergstrom and Zeizel,
rural wells
is
1
sufficiently thick
and creviced to
957).
Area Karst Region
Driftless
Near-surface and exposed carbonate bedrock
in
the Driftless Area of northwest
Illinois
(Jo Daviess and northwest Carroll Counties) are of Middle Ordovician or Silurian age (Figures
13B, 14). The Middle Ordovician
Group
Platteville
composed
is
of very fine-grained limestone
mottled with dolomite. The Galena Group overlies the Platteville Group and consists of
limestone and dolomite, except for
al.,
The
a basal
1975). Karstic features also occur
Silurian
(Willman,
1
is
in
shaley limestone and dolomite interval (Willman et
Silurian (Alexandrian
and Niagaran Series) bedrock.
divided into the Mosalem, Tete des Morts, Blanding, and Hopkinton Formations
973; Bunker
cherty dolomite (Heyl et
et
al.,
al.,
1
985). These rocks are
1959). Most,
if
not
all,
medium-
to coarse-grained, locally
of the sinkholes in this area occur
in
the
Niagaran Hopkinton Formation (Brian Witzke, Iowa Geological Survey, personal
communication).
Both caves and sinkholes are indicators of karst terrain
caves are the dominant feature
occur
in
in this
1
960). Bretz and Harris
dolomite, probably
in
strata
(1
),
in Illinois.
and
Webb
et
al. (1
961 described
)
a
cave
al.,
in Carroll
Most
of the
caves
1959; Brown and
County
in
Silurian
younger than the Hopkinton Formation. The caves are
predominantly solutionally-widened
961
the Driftless Area; however,
the Galena Group (Trowbridge and Shaw, 1916; Heyl et
Whitlow,
(1
region (Figures 5, 14)
in
joints,
according to descriptions by Bretz and Harris
994). Caves of this type are referred to as "network" caves
(Palmer, 1991), are fracture-controlled, and often follow solution features along near-vertical
fracture planes.
24
Figure 14. Karst
map
from Willman et
al.
for the Driftless
Area karst region of northwest
(1967) and Kolata and Buschbach (1976).
Illinois.
Geology modifed
Few
sinkholes
both Trowbridge and
common
in
in
in this
Shaw
Silurian rocks.
(1916) and Heyl et
We
al.
30
m
in
Ordovician Galena Group.
observed several sinkholes of
area.
The number
in
this
diameter and of smaller sizes
in
the Ordovician strata
1
982). The relationship between
soils
in
areas dominated by loess,
common
Glasford Formation. They are most
and within one to two kilometers
thick,
in this
most common adjacent
of a
in
silt
shown on our maps
maps by
indicates that
and diamicton of the Quaternary
areas where these materials are less than 6
stream valley.
In
m
the Driftless Area, sinkholes are
to the Mississippi River valley. Sinkholes
commonly occur
stream valleys because of the gradual lowering of the piezometric surface
table) near low-lying areas by surface erosion
towards
1959; Hallberg and
type and thickness (from stack unit
Berg and Kempton, 1988), and the locations of sinkholes
sinkholes mostly occur
al.,
the
in
of sinkholes associated with Ordovician rocks drastically increases
the northwest into Iowa where these strata are less dolomitic (Heyl et
Hoyer,
locally
the Silurian dolomite than
any sinkholes
did not study
photos. However,
(1959) noted that sinkholes are larger
al.
diameter) and more abundant
We
aerial
(1959) reported sinkholes to be
regolith underlain by Hopkinton dolomite. Heyl et
(averaging about
maps and
area are evident on topographic
(i.e.,
near
the water
and the associated collapse of formerly water-
saturated sediments (cover-collapse sinkholes) into solution-enlarged fissures. This
mechanism was proposed by Ford
(1
The limestones and dolomites
overlain by shale of the
northwest
Illinois,
joints, fractures,
where
it
is
and
964)
for sinkhole
of the Platteville
Maquoketa Group,
in
most
and solution
formation
the Mendip
Hills of Britain.
and Galena Groups, where they are not
are an important source of
of the northern third of the state.
cavities.
in
Groundwater also occurs
groundwater
in
Groundwater occurs
in
Silurian dolomite
in
on ridges
perched on underlying Maquoketa shale. This dolomite similarly contains crevices
26
and solution features that provide groundwater
Bergstrom,
1
for
farm and domestic supplies (Hackett and
956).
North-Central Karst Region
An
area that straddles the Rock River
in
Ogle and Lee Counties
comprises the North-Central karst region (Figures
central
Illinois
consist of the
5, 15).
Platteville
north-central
Carbonate bedrock units
Lower Ordovician Shakopee Dolomite
Group and the Middle Ordovician
in
Illinois
north-
in
of the Prairie du Chien
and Galena Groups (Figure 16A). Because of the
north-south trending Wisconsin Arch, these rocks are exposed along the tributaries of the
Rock River from near Rockford (Winnebago County)
al.,
1
967). The rocks are also exposed
Rockford, and
in
in
to near Dixon (Ogle County) (Willman et
road cuts and quarries on the south side of
road cuts north of Freeport (Stephenson County). Knappen (1926)
described the lithology of these strata near Dixon. The Shakopee Dolomite
is
first
a fine-grained,
porous, argillaceous dolomite which locally contains shale and sandstone. The Galena Group
consists of a porous, cherty, very fine-grained to very coarse-grained dolomite. The Platteville
Group consists
of a very fine- to coarse-grained, interbedded dolomite
locally contains argillaceous intervals.
of approximately
115m
(Foster,
The Galena-Platteville
interval
1926).
A few
in
in
the Byron-Dixon area
near-surface or exposed carbonate bedrock (Bretz, 1923; Knappen,
sinkholes also occur
in soils
overlying the St. Peter Sandstone, but
that these are due to dissolution of the underlying
the overlying sandstone and
where limestone
has an average thickness
956).
1
Sinkholes are the principle evidence for karstic development
and occur mostly
and limestone that
soil.
of the Platteville
Shakopee Dolomite and collapse
Knappen reported that over
Group
is
overlain by loess
27
we
75%
and
suggest
of both
of the sinkholes occur
silt,
and diamicton of the
Figure 15. Karst
map
(1967) and Kolata et
for the North-Central karst region.
al.
(1978).
Geology modifed from
Will
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Quaternary Glasford Formation. Comparison of the karst maps of this paper with stack-unit
maps developed by Berg and Kempton
areas where the bedrock
Quaternary cover
less
is
988) indicates that sinkholes commonly occur
(1
dominated by
is
than 6
m
Rock
valleys associated with the
thick,
River.
this stratigraphic
in
sequence, where the overlying
and are located within several kilometers of stream
The proximity
of sinkholes to the
stream valleys
may
be the result of reactivation of paleokarstic features. The gradual lowering of the piezometric
surface
(i.e.,
the water table) as stream valleys erode
of formerly water-saturated
fissures
may
downward and
the associated collapse
sediments (cover-collapse sinkholes) into solution-enlarged
also be a factor
in this
area.
There are no verified cave entrances
the North-Central karst region; however,
in
quarrying operations reportedly destroyed a cave
northeast of Dixon (Knappen, 1926).
We
in
observed
limestone of the Platteville Group
a sediment-filled
cave opening
the
in
Gregory-Anderson Co. quarry on the south edge of Rockford. At the northeastern edge of the
region, Bretz (1923) referred to an unverified cave reportedly located south of Rockford near
the Winnebago-Ogle county border. Bretz also reported several occurrences of open cavities
(probably solution features)
in
the limestone that
were encountered during the
drilling of
water wells.
Solution-enlarged fissures are
Freeport.
They range
in
common
width from 0.25
m
in
in
the Gregory-Anderson Co. quarry. Despite the
we
only
mapped
sinkholes
Groundwater
joints, fractures,
in
in
the road cuts and quarries near Rockford and
road cuts along Interstate 39 to 8
common
occurrence of fissures
m
wide
in this
in
region,
the Byron-Dixon area (Figure 15).
north-central
Illinois is
available
in
the Galena-Platteville dolomite where
and solution cavities are present and interconnected over a relatively large
areal extent. Mills et
al.
(1993) reported that groundwater flow
30
in
the Galena-Platteville
aquifer
was
and subhorizontal zones of solution,"
primarily through "...subvertical fractures
the latter of which are probably stratigraphic breaks. They noted that hydraulically connected
subhorizontal solution features have been identified that extend laterally for at least 1.2 km.
The
availability of
water from these strata
is
adequate
for domestic, farm, municipal,
and
use (Foster, 1956); however, water-producing zones are distributed irregularly
industrial
(vertically
and horizontally) due to the
and distribution of the cavities
irregular nature
(Csallany and Walton, 1963).
Other areas containing karstic features
Karstic features have been
five karst regions.
addition,
some
These areas
documented
are mostly
of the features occur
in
in
carbonate bedrock
covered with
unlithified
carbonate bedrock
in
in
areas outside of the
Quaternary deposits.
areas where the bedrock
In
is
overall predominantly noncarbonate.
Northeast
Illinois
The bedrock
area
is
of northeast
most covered with
karstic features
Illinois
regolith
in a relatively
contains a few, widely dispersed karstic features. This
and outcrops are few
large area (from
in
number and
size.
The paucity
of
Lake to Kankakee Counties) and definite
evidence of widespread extant karstification processes are the reason
for not referring to this
area as a karst region.
Silurian (Alexandrian and Niagaran Series) rocks
in this
area.
These rocks
are on the northeast flank of the
plunges to the southeast and separates the
al.,
1
comprise most of the bedrock surface
Illinois
axis of
which
Basin from the Michigan Basin (Visocky et
985). These rocks are typically buried under 30
31
Kankakee Arch, the
m
or
more
of clayey diamicton
and lake
sediments (Figure 16B).
1
area, the Alexandrian Series (lowermost Silurian)
973). The Wilhelmi Formation
sand and shale partings near
its
slightly argillaceous dolomite.
is
an argillaceous dolomite with coarse
base. The Elwood Formation
The Kankakee Formation
is
is
divided
silt,
fine
an abundantly cherty, pure to
a relatively pure dolomite that also
contains shale partings. The younger Niagaran Series (middle Silurian)
Joliet,
is
Elwood, and Kankakee Formations which are chiefly composed of dolomite
into the Wilhelmi,
(Willrman,
In this
divided into the
is
Sugar Run and Racine Formations. The lithology of these formations ranges from pure
dolomite to
argillaceous and cherty dolomite containing
silty,
occur locally
some
thin shale beds. Reefs
the Racine Formation (Willman, 1973). The upper surface of the Niagaran
in
Series dolomite
is
an erosional surface (Willman, et
al.,
1975) and
is
creviced
in
outcrop.
Otto (1963) and Buschbach and Heim (1972) interpreted the buried Silurian dolomite of
northeast
data.
of
The
as a karstic surface on the basis of seismic refraction, borehole, and outcrop
Illinois
latter
study covered over
2000 square
Cook County, east Du Page County, and
Heim described the bedrock as
southwest
"...a
part of northern Will County.
dissected surface with numerous
to east-west trending valleys that slope to the east,
Rare and typically small caves occur
is
kilometers of the greater Chicago area, most
exposed along stream
in
Buschbach and
hills,
and enclosed depressions."
Kane and Kankakee Counties where
valleys. Zeizel et
northeast-
Silurian dolomite
(1962) stated that "enlargement of
al.
joints,
fractures, and bedding planes by solution has taken place" typically at or near the bedrock
surface. Otto (1963) prepared a detailed
abundant
karstic features
Conversely,
in
map
had been exposed
of the
in a
bedrock surface near
deep excavation
for a
Joliet
power
where
plant site.
the younger Niagaran dolomite, Bloom (1978) described only minor karstic
features found along and interpreted to be controlled by joints and bedding planes.
During our
field
work,
we
found solutionally widened fractures and caves exposed
32
in
quarries, excavations, and a
few
natural bedrock exposures.
These caves and fractures
are
typically filled with very fine-grained material that renders these features ineffective as
conduits. However, exhumation and flushing of
materials could result
fill
in
the rejuvenation
of a conduit system. Solutionally-widened fractures, sinkholes, solution features
horizontal grooves), and caves
were observed
in
(i.e.,
Lehigh Quarry, Kankakee River State Park
(Kankakee County). Active sinkholes and sinking ephemeral streams occur near the
River
in Will
County. Sediment
Quarry describe by
(Bretz,
the buried bedrock surface
classification
scheme
Kankakee County
classified as
in
some
karstic features in the Racine Formation in the Lehigh
1940) contained early to middle Pennsylvanian spores. Much
in
northeast
may
Illinois
exhumed
karst.
The
such as those along Rock Creek
may have been exposed by
active sinkholes
of
be classified as paleokarst (per
of White, 1988). Karstic features
the Kankakee Formation
in
Illinois
in
Will
County may be
in
erosion and be
classified as sinkhole
karst.
The
Silurian dolomite aquifer in northeast Illinois
Upper Bedrock Aquigroup (which
the most productive aquifer of the
is
also includes the Ordovician Galena-Platteville interval and
the Ancell aquifer). Specific yields for this aquifer are dependent on the distribution and
intensity of crevicing, and the size of the fracture openings. Consequently, specific yields
from
this aquifer are
extremely variable (Visocky et
the Silurian dolomite aquifer
prevalent (Zeizel et
al.,
is
the upper 15
m
al.,
1
985). The most productive part of
where solution-enlarged fractures
are
1962).
Douglas County
A cave
entrance
in
an abandoned barrow
pit
and dissolution features
quarry are indicators of karst near the village of Tuscola
33
in
in
an active
Douglas County. During
excavation of
a
barrow
pit for
material to be used
interstate highway, a small cave
cave was
but
was
in
not
in
was encountered.
the construction of the adjacent
This
east of Tuscola and the
pit is just
the floor, which consisted of Devonian limestone. The cave
filled
relatively small
with sediment, suggesting that karstification processes are active.
nearby quarry, about
but appear to be
was
1
filled
.5
km
widened
east, solutionally
occur
joints
with sediment. These karstic features occur
Devonian limestone
in
in
an isolated
outcrop/subcrop of limestone, surrounded by predominantly noncarbonate bedrock,
axis of the LaSalle Anticlinorium. Further study
these karstic features and
if
a karst aquifer
is
In a
at the
required to determine additional details on
present.
is
La Salle County
Several sinkholes and a cave are indicators of karst
La Salle and Oglesby
in
La Salle County.
A few
in a
small area near the villages of
sinkholes occur
LaSalle Limestone southeast of Oglesby. The LaSalle Limestone
the otherwise noncarbonate dominated Pennsylvanian strata of
rarely
used as
the Late Pennsylvanian
in
is
This limestone
Illinois.
source for groundwater and only for domestic use
a
the thickest limestone
(R.
in
is
Brower, ISGS, personal
communication).
The cave occurs
in
the
of La Salle. In this area, the
Limestone, but
it
is
Shakopee
is
a
strata
is
about
1
.5
km
east
more widespread bedrock than the LaSalle
only locally utilized as a groundwater source.
water from sandstone
Shakopee
Lower Ordovician Shakopee Dolomite and
above and below
this dolomite.
Most deep wells obtain
Where
either the LaSalle or the
are used as aquifers, joints/fractures provide the porosity and they
solutionally enlarged.
34
may be
PSEUDO-KARSTIC FEATURES
Karst-like or pseudo-karstic features similar to sinkholes occur
collapse of abandoned underground mine tunnels have resulted
associated piping of
soil. Soil
piping
may
also take place
in
in pit
areas where the
subsidence and
where drainage
in
poorly
consolidated materials such as loess and sand intersects underground cavities and
progressively erodes materials along
pit
may
subsidence that
concomitant collapse
cavities
may
in
may form
As shallow
piping often form
true karstic areas.
and other subsidence
for the formation of sinkholes
(less
than 60 m) room and
pillar
water and
mines collapse,
of overlying poorly consolidated materials, and/or soil piping into these
sinkholes
in
overlying terrains (e.g., Bauer et
al.,
1993). The mines also
be responsible for groundwater and surface water contamination due to their efficiency
transporting surface-derived contaminants to groundwater and surface waters.
Underground mines
were extracted,
extracted, and
in
are located
is
in
Jo Daviess County, zinc and lead ores
Pope and Hardin Counties, where fluorspar was
in
responsible for
these areas are discussed
open space
Ordovician rocks
the predominantly noncarbonate Pennsylvanian rocks,
in
Soil piping
in
Mississippian rocks
extracted. Coal mining
of
in
soil
(Figure 17), that act as drains for infiltrating surface
groundwater, have been responsible
in Illinois.
flow path. Mine collapse and
be indistinguishable from sinkholes
Underground mines
phenomena
its
occurs as
(e.g.,
in
most
Treworgy
a result of
et
of the
al.
(1
mined out areas
where coal was
in Illinois.
989) and Damberger
et
al.
(1
The locations
984).
surface water draining rapidly through the
soil into
an
mine openings, fissures associated with mine-collapse). As the pressure
the infiltrating water increases
in
the
soil,
the
soil fails
and collapses
into the openings.
Eventually, cavities are formed at depth along the flow path as the soils collapse or stope
35
of
Mined-out
Areas
Scale 1:3,000,000
_i
i
i
i
i
i
i
i
i
i
i
Kllomslori
Figure 17.
Map showing
mined-out areas where psudo-karst features are
likely to
occur.
upward
into the overlying materials.
Continuous upward stoping of
the formation of a sinkhole at the surface
(e.g.,
soil
eventually results
in
White, 1988).
CONCLUSIONS
Approximately
approximately
9%
or
of the
in
Illinois is
carbonate rock, and
these regions, which are on the margins
In
and along structures within the basin, carbonate bedrock
subcrops beneath
are concentrated
bedrock surface of
includes the five karst regions.
of the Illinois Basin
exposed
25%
glacial diamicton, loess,
the Driftless Area
in
northwest
and other sediments. Karstic features
north-central
Illinois,
Hills of
the west part of the state, the Salem Plateau of southwest
Hills of
southern
Salle
Illinois.
A few caves and
either
is
sinkholes are found
Illinois,
Illinois,
northeast
in
the Lincoln
and the Shawnee
Illinois,
and La
and Douglas Counties, and are associated either with carbonate rocks along the LaSalle
Anticlinorium or the northeast flank of the
Illinois
Basin (Kankakee Arch).
ACKNOWLEDGEMENTS
This work
was funded through
with state funds from the
Illinois
a grant
from the
Illinois
State Geological Survey,
Groundwater Consortium, and
Illinois
Department
of Natural
Resources.
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Bauer, R.A., Trent, B.A. and DuMontelle, P.B., 1993. Mine subsidence
the homeowner.
Illinois
State Geological Survey Environmental Geology,
Baxter, J.W., 1965. Limestone resources of Madison County,
Survey Circular 390, 39
Bell,
A. H., M. 0. Oros, and
Illinois
J.
Facts for
in Illinois:
Illinois. Illinois
1
6
p.
State Geological
p.
Van Den
State Geological Survey
Berg,
Illinois
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961
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Petroleum Industry
Petroleum 75,
37
1
21
p.
in Illinois,
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960.
Bergstrom, R.E. and
Zeizel, A. J.,
1957. Groundwater geology
State Geological Survey Circular 232, 28
Illinois
A Systematic
Bloom, A.L., 1978. Geomorphology:
Prentice-Hall, Inc.,
New
510
Jersey,
western
in
Illinois,
p.
Analysis of Late Cenozoic Landforms.
p.
Bradbury, J.C., 1963. Limestone Resources of the Lower Kaskaskia Valley.
Geological Survey Circular 346, 22
Geological Survey Bulletin 43,
Bretz, J H.,
939. Geology
1
Survey
Bretz, J H.,
Bulletin 65,
1940. Solution
Geology,
Bretz, J H.,
1
v.
48,
1
8
Bretz, J H.,
cavities
Illinois
and Harris,
of the
S.E., Jr.,
and Whitlow, J.W.,
Chicago region, part
1
32
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II
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the Pleistocene.
Illinois
State
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1961. Caves of
to Illinois State Geological
1
J.,
1123A,
sites for flood
G.E.,
B. J.,
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Technical Information Series No. 13,
Buschbach, T.C. and Heim,
State Geological Survey
960. Geology of the Dubuque South Quadrangle, Iowa-
Ludvigson, G. A., and Witzke,
Structural and Stratigraphic
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p.
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Illinois.
1
1
p.
1-93.
985. The Plum River Fault Zone and the
of Eastern Iowa.
26
Iowa Geological Survey,
p.
1972. Preliminary geologic investigations of rock tunnel
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in
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Survey Environmental Geology Notes 52, 35
Illinois
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