Cahokia Alluvium Parkland Sand Equality Formation, Dolton Member Henry Formation Sand and gravel within Wedron Formation Sand and gravel within Winnebago Formation Pearl Formation (includes Hagarstown Member) Sand and gravel within Glasford Formation Mounds gravel and related units Cretaceous sediments, silts, sands, etc. Pennsylvanian rocks, mainly sandstones Mississippian rocks, mainly limestones, some sandstones Silurian and some Devonian rocks, mainly dolomite Ordovician and Cambrian rocks, mainly dolomite, some sandstone
The scale of these data is 1:250,000.
These data are appropriate for use in regional thematic analysis. The data are not appropriate as a geodetic, legal or engineering base. The datasets were not and are not intended as a substitute for surveyed locations, such as can be determined by a registered Public Land Surveyor. Although useful in a GIS, the data have no legal basis in the definition of boundaries or property lines.
In April 2004 the source coverage was transitioned to storage in an Oracle RDBMS using the ArcSDE geodatabase model. The result (this version) is designated edition 20040401.
The source coverage (edition 2.0) was entirely reconstructed, making the previous version (coverage edition 1.0) obsolete. This edition retains the edition 2.0 data.
Revisions to the original version (edition 1.0) to produce edition 2.0: (1) coverage was entirely reconstructed from updated STACK-ST stack-unit map coverage (2) items SHADE and SYMBOL are no longer included (3) items MS (map symbol) and STACK-UNIT from coverage STACK-ST were added (4) some polygons that were erroneously included in version 1.0 have been removed. Specifically, These were 10-20 polygons containing stack-unit layers identified as loamy and sandy diamictons within the Glasford Formation. These units, identified in coverage STACK-ST with the code "q" or "Q", are not considered potential aquifers and are not included in this coverage.
Any access to these data, Web sites, computer systems, electronic services, and electronic networks is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice.
Links to these are provided in the Cross References section.
It is important to realize that characteristics which identify formations as potential aquifers do not imply that a particular unit is indeed an aquifer. For example, although Cahokia alluvium contains coarse-grained sand and gravel deposits which could store or conduct groundwater, it is predominantly a silty deposit associated with periodic flooding. Similarly, there are certainly existing shallow aquifers associated with other geologic formations not identified on this map. Because these data are generalized over a large areal extent, the user needs a good working knowledge of the geologic formations used here in order to derive valid and useful interpretations. Descriptions of the stratigraphic classifications used in this data set can be found in Willman and Frye, 1970, Pleistocene Stratigraphy of Illinois, ISGS Bulletin 94. Also, several of these stratigraphic units have since been reclassified. The user should consult Hansel and Johnson, 1996, Wedron and Mason Groups: Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area, ISGS Bulletin 104.
ISGS information is the property of and copyrighted by the Board of Trustees of the University of Illinois with all rights reserved. University copyright policy is stated in the General Rules Concerning University Organization and Procedure, Article III, Section 4. A link is provided in the Cross References section.
Individuals or entities may make fair use of copyrighted ISGS material, such as reproducing a single figure or table, or using a brief text quotation, without obtaining formal permission, but in all cases the Illinois State Geological Survey must be credited as the source of the material. To reproduce ISGS information beyond the fair use standard, permission must be obtained from the ISGS Information Office, 615 East Peabody Drive, Champaign, Illinois 61820, 217-333-4747, isgs@isgs.illinois.edu. License fees and a license agreement may be required, depending on the proposed usage.
Any use of these data is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice. Links to these are provided in the Cross References section.
Map information is to be used at a scientifically and cartographically appropriate scale, that is, at a scale no greater than indicated on the map or as described in the documentation of the map or map data. Map information is not appropriate for, and is not to be used as, a geodetic, legal, or engineering base. Map information has no legal basis in the definition of boundaries or property lines and is not intended as a substitute for surveyed locations such as can be determined by a registered Public Land Surveyor.
The data do not replace the need for detailed site-specific studies.
It is important to realize that characteristics which identify formations as potential aquifers do not imply that a particular unit is indeed an aquifer. For example, although Cahokia alluvium contains coarse-grained sand and gravel deposits which could store or conduct groundwater, it is predominantly a silty deposit associated with periodic flooding. Similarly, there are certainly existing shallow aquifers associated with other geologic formations not identified on this map. Because these data are generalized over a large areal extent, the user needs a good working knowledge of the geologic formations used here in order to derive valid and useful interpretations. Descriptions of the stratigraphic classifications used in this data set can be found in Willman and Frye, 1970, Pleistocene Stratigraphy of Illinois, ISGS Bulletin 94. Also, several of these stratigraphic units have since been reclassified. The user should consult Hansel and Johnson, 1996, Wedron and Mason Groups: Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area, ISGS Bulletin 104.
The features were imported into the ISGS SDE enterprise database following steps outlined in ISGS procedure GISDB_0009.
Metadata updated.
CODE Identifies whether or not polygon is a potential aquifer as defined in this coverage. 0 - Not a potential aquifer 1 - Potential aquifer
STACK-UNIT This item is a 15 digit numeric code that indicates up to five geologic units present, their order of occurrence, and general thickness and depth. It is directly related to item MS in that MS is an alphanumeric designator that represents the same information as STACK-UNIT. STACK-UNIT consists of ten concatenated (redefined) items called (and in this order) UNIT1, QUAL1, UNIT2, QUAL2, UNIT3, QUAL3, UNIT4, QUAL4, UNIT5, QUAL5. UNITx (where x is 1, 2, 3, 4, or 5) is a two digit identifier for unit name (see the table below). QUALx is a single digit qualifier for each UNITx, giving thickness, depth and continuity information for the corresponding UNITx. For example, QUAL1 contains a code that gives descriptive information for UNIT1. UNIT1 is the uppermost unit, UNIT5 is the lowermost unit.
TABLE OF ITEM RELATIONSHIPS
UNITx MSx Corresponding Geologic Unit (MAP-SYMBOL)
(nonlithified and semilithified materials) 1 A a* Cahokia Alluvium 2 Y y* Peyton Colluvium 3 B b* Richland Loess 4 C c* Peoria and Roxana Loess 5 D d* Parkland Sand 6 E e* Grayslake Peat 7 F f* Equality Formation, Carmi Member 8 G g* Equality Formation, Dolton Member 9 H h* Henry Formation 10 I i* Wedron Formation, silty and clayey diamictons 11 J j* Wedron Formation, loamy and sandy diamictons 12 K Sand and gravel within Wedron Formation: 12 k* within 6 m (19.7 ft.) of surface 26 z* between 6-15 m (19.7-49.3 ft.) of surface 13 L l* Winnebago Formation, mainly sandy diamictons 14 M Sand and gravel within Winnebago Formation: 14 m* within 6 m (19.7 ft.) of surface 26 z* between 6-15 m (19.7-49.3 ft.) of surface 15 N n* Teneriffe Silt 16 O o* Pearl Formation (includes Hagarstown Member) 17 P p* Glasford Formation, silty and clayey diamictons 18 Q q* Glasford Formation, loamy and sandy diamictons 19 R Sand and gravel within Glasford Formation 19 r* within 6 m (19.7 ft.) of surface 26 z* between 6-15 m (19.7-49.3 ft.) of surface 22 U u* Wolf Creek Formation (mainly diamictons) 23 V v* Mounds gravel and related units 24 W w* Cretaceous sediments, silts, sands, etc. 25 X Surface mines/man-made land
(lithified materials) 41 1 1* Pennsylvanian rocks, mainly shales 42 2 2* Pennsylvanian rocks, mainly sandstones 43 3 3* Mississippian rocks, mainly shales 44 4 4* Mississippian rocks, mainly limestones, some sandstones 45 5 5* Silurian and some Devonian rocks, mainly dolomite 46 6 6* Ordovician rocks, mainly shale (Maquoketa Group) 47 7 7* Ordovician and Cambrian rocks, mainly dolomite, some sandstone
other 98 water body of water
QUALx 1 - Drift unit 6m thick, continuous throughout polygon area 2 - Drift unit 6m thick, locally less than 6m thick 3 - Drift unit < 6m thick, continuous throughout polygon area 4 - Drift unit < 6m thick, not continuous throughout polygon area
6 - Bedrock unit present between 6 and 15 meters below surface 7 - Bedrock unit not present continuously between 6 and 15 meters below surface; locally present at or just below 15 meters 8 - Bedrock unit present within 6 meters of surface 9 - Bedrock unit not present continuously above 6 meters below surface; but then is present between 6-15 meters
MS Item MS is the map symbol for each polygon. It is an alphanumeric character set that describes up to five geologic units present, their order occurrence, and general thickness and depth. Item MS is directly related to item STACK-UNIT in that STACK-UNIT is a strictly numeric designator that represents the same information as item MS. MS consists of five concatenated (redefined) items called MS1, MS2, MS3, MS4, MS5. Each redefined MSx(where x is 1, 2, 3, 4, 5) item represents a single geologic unit, MS1 being the uppermost and MS5 being the lowermost. Uppercase letters indicate nonlithified a semilithified units greater than 6m (19.7 ft.) thick. Lowercase letters accompanied by asterisk indicatenonlithified and semilithified units less than 6m (19.7 ft.) thick. Numbers unaccompanied by an asterisk indicatelithified units where the top occurs between depths of 6 to 15m (19.7-49.3 ft.) below ground surface. Numbers accompanied by an asterisk indicate lithified units where the top occurs between depths of 0 to 6m (0-19.7 ft.) below ground surface.
Some units are of varying thickness; this is represented by parentheses. An uppercase letter enclosed by parentheses indicates the unit is continuous throughout the polygon area but less than 6m thick in some areas. If the unit is the lowermost, it may not be present above the 15m depth, but generally lies at just below 15m. A lowercase letter (with asterisk) enclosed by parentheses indicates the unit is not continuous throughout the polygon area. If the unit is lowermost it may not be present above the 15m depth, but generally lies at or just below 15m. A number (without asterisk) enclosed by parentheses indicates the unit may not be present above the 15m depth, but generally lies at or just below 15m. A number (with asterisk) enclosed by parentheses indicates the unit may not be continuous in the polygon area within 6m of surface, but is present between depths of 6-15m over a portion of the polygon area.
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