Transcript PowerPoint file - Illinois Valley Community College

Geologic History of
the Illinois Valley
Mike Phillips
Geology Professor
Illinois Valley Community College
Illinois Rocks



Igneous & Metamorphic: in the “Basement”
Sedimentary: bedrock
Unconsolidated material: on the surface
Rocks of northcentral Illinois
Exposures in the
upper Illinois
Valley:
 Ordovician


Silurian


Ottawa &
Starved Rock
Des Plaines R.
Pennsylvanian

remainder
Rocks of the central Illinois Valley

Ordovician (505 to 438 MYA)
Shakopee Dolostone: shallow marine
 St. Peter Sandstone: beach
 Galena-Platteville Dolostone: shallow marine


Silurian (438 to 417 MYA)


dolostone: shallow marine
Silurian-Mississippian (417 to 320 MYA)
No rocks exposed: eroded or not deposited
 LaSalle Anticline: fold

Rocks of the
central Illinois
Valley

Pennsylvanian
(320 to 286 MYA)
Carbondale
 Bond
 Modesto

Rocks of the central Illinois Valley

Pennsylvanian cyclothems

thin layers of varying type in repeated
sequences
coal
 sandstone
 limestone
 shale
 clay

varying coastal env.
 fluctuating sea level

Permian to
Quaternary
(286 to 1.8 MYA)
 erosion
Pleistocene
(1.8 MYA to
10,000 YA)

Unconsolidated
deposits
diamicton
 sand and gravel
 sand dunes (near
the river)
 loess
 laminated clay

The
ICE
AGE
10,000 YA to present
Thank You
Mike Phillips
Illinois Valley Community College
www.ivcc.edu/phillips
[email protected]
(815)224-0394
“The Geologic History of The Illinois Valley”
June 2006