North-Central Section - 43rd Annual Meeting (2-3 April 2009)
Paper No. 30-5
Presentation Time: 2:20 PM-2:40 PM

INTERPRETING SUBSURFACE GLACIGENIC SEQUENCES: AN EXAMPLE OF USING EXPOSED ICE-CONTACT SEDIMENTS AS A MODEL FOR MAPPING BURIED ICE-MARGIN DEPOSITS

THOMASON, Jason F., Illinois State Geological Survey, Institute of Natural Resource Sustainability, UIUC, 615 E. Peabody Dr, Champaign, IL 61820, thomason@isgs.uiuc.edu and BROWN, Steven E., Illinois State Geological Survey, 615 E. Peabody Dr, Champaign, IL 61820

Key challenges to better understanding buried depositional sequences are mapping and interpreting subsurface geologic data in areas where those data do not provide the detail or resolution of outcrops. Often, interpretation of subsurface data is dependent on the geologist's model of depositional environments. In northeast Illinois, we speculate that styles of deposition along some former ice-margins repeated during overall ice-margin retreat on a local scale for some glacial events. Therefore, in these situations, depositional models of sediment packages that we see at the land surface can be applied to buried sequences, where the subsurface data (such as water-well records) are not as clear as the geology displayed at the outcrop level. The “style” includes the environment of deposition in addition to the scale of individual sediment packages, beds, or units.

Rare exposures of coarse grained ice-contact deposits of the Lake Michigan Lobe are present in some quarries within the Fox River valley, about 30 kilometers west of the Lake Michigan shoreline. These include deltaic, fluvial, and collapsed deposits associated with the retreat of the ice margin during the Woodstock Phase (~16,000 C-14 ybp). East of these quarries, the deposits are buried by younger glacial sediments. Three-dimensional visualization of bulk subsurface data have allowed sediments associated with a buried former ice margin to be mapped while applying a depositional model analogous to the deltaic ice-contact deposits at land surface.

North-Central Section - 43rd Annual Meeting (2-3 April 2009)
General Information for this Meeting
Session No. 30
Sedimentology and Stratigraphy of Glacial Deposits II
Northern Illinois University Rockford: 101
1:00 PM-5:00 PM, Friday, 3 April 2009

Geological Society of America Abstracts with Programs, Vol 41, No. 4, p. 71

© Copyright 2009 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.