Several major bedrock valleys are found across the state.
The greatest control for the present bedrock surface configuration was probably the preglacial surface configuration. Interpretations of bedrock topography have been modified since the 1950's. Horberg contoured his map with the philosophy that the bedrock surface map represented the preglacial topography modified by glacial erosion, which formed U-shaped valleys. The current map, showing narrow valley channels and bedrock knobs in wide channels, indicates complex preglacial and glacial erosion primarily from running water. The major valleys were formed before the minor valleys that appear as tributaries. Streams that formed during successive glaciations probably eroded to bedrock and produced the small tributary valleys to the main channels. The bedrock surface was less likely to be eroded as sediments accumulated during each successive glaciation.
Please refer to the metadata for the parent coverage, Buried Bedrock Surface of Illinois (GISDB_BEDGEO.IL_Bedrock_Topography_1994_Ln) for more information.
The data are not appropriate as a geodetic, legal or engineering base. The data set was not and is not intended as a substitute for surveyed locations, such as can be determined by a registered Public Land Surveyor. Although useful in a GIS as a reference base layer for maps, the data set has no legal basis in the definition of boundaries or property lines.
Recent updates to the data:
In March 2004 edition 1.0 of the data set was transitioned to storage in an Oracle RDBMS using the ArcSDE geodatabase model. The result (this version) is designated Edition 20040331.
Links to these are 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, email@example.com. License fees and a license agreement may be required, depending on the proposed usage.
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.
The source coverage was bedval.
The annotation feature class was imported into SDE from the source coverage using the method in an article entitled Converting Annotation from Coverage to Geodatabase Format (Colin Childs, ArcUser Magazine, October-December 2001, pp. 22-23) and the companion tutorial (referenced in the article.)
Prior to using the steps in the tutorial, a TAT coverage file had to be generated for the coverage. This was done in ArcInfo Workstation 7.2.1 with the following commands.
Arc: copyfeatures bedval anno bedval anno.anno Arc: build bedval annotation.anno
NAME - name of bedrock valley 1 - ancient Mississippi (Lower and Middle Illinois and Princeton) 2 - Mahomet (Teays) 3 - Kaskaskia 4 - Paw Paw and Rook 5 - Troy 6 - Pecatonica 7 - Onarga 8 - Little Wabash 9 - Embarras 10 - Skillet Fork 11 - Saline 12 - Big Muddy 13 - Macoupin 14 - Cache 200 - Carthage, Lower Spoon, Ticona, Danvers, Middletown, Pesotum, Danville 300 - Kempton and Chatsworth 400 - Kirkwood, Athens, Wyoming, plus four unnamed tributary channels (Pecatonica , Rook , Danville ) 999 - state boundary
Annotation features are included to display the bedrock valley name.
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Illinois Natural Resources Geospatial Data ClearinghouseGenerated by mp version 2.8.25 on Thu Apr 02 09:53:58 2009