TITLE:
Modeling the Sediment Fill of the Upper Troy Pre-Glacial Bedrock Valley, McHenry County, Illinois, USA
AUTHORS:
Jodi Lau, Jason F. Thomason, David H. Malone, Eric W. Peterson
KEYWORDS:
Buried Bedrock Valley, Glasford Formation, Illinois, 3D Geologic Model, Quaternary
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.6,
June
21,
2016
ABSTRACT: The Troy
Bedrock Valley (TBV) and its tributary valleys are the principal pre-glacial
drainage in southern Wisconsin and northern Illinois, USA. This study focused
on the headwaters of a tributary that occurs in McHenry County, IL. Drilling,
geophysical surveys, and the analysis of existing geologic and water well data
were used to determine the lithologic and geometric characteristics of the
sediments that fill the paleovalley. A 3D geologic model of these sediments was
then developed in Petrel. More than
65 m of Quaternary sediments filled the paleovalley. The model domain covers
approximately 30 km2. The valley drains to the west and meanders, which is distinct from the
straight course of the overlying modern Kishwaukee River. The sediments that
filled the valley were subdivided into five units. These units include
Illinois-age Glasford Formation coarse-grained proglacial outwash and alluvial
deposits (GS2, GS1) and fine-grained lacustrine and diamicton deposits (G2 and
G1). The
Wisconsin-age Henry Formation sand and gravel cap the valley fill, and Cahokia
alluvium buries everything.