geologic history of the illinois valley mike phillips geology professor illinois valley community...
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Geologic History Geologic History of the Illinois of the Illinois
ValleyValleyMike PhillipsMike Phillips
Geology ProfessorGeology ProfessorIllinois Valley Community Illinois Valley Community
CollegeCollege
Illinois RocksIllinois Rocks
Igneous & Metamorphic: in the Igneous & Metamorphic: in the “Basement”“Basement”
Sedimentary: bedrockSedimentary: bedrock Unconsolidated material: on the Unconsolidated material: on the
surfacesurface
Rocks of Rocks of north-north-central central IllinoisIllinoisExposures in Exposures in
the upper the upper Illinois Valley:Illinois Valley:
OrdovicianOrdovician Ottawa & Ottawa &
Starved RockStarved Rock SilurianSilurian
Des Plaines R.Des Plaines R. PennsylvanianPennsylvanian
remainderremainder
Rocks of the central Illinois Rocks of the central Illinois ValleyValley
Ordovician (505 to 438 MYA)Ordovician (505 to 438 MYA) Shakopee Dolostone: shallow marineShakopee Dolostone: shallow marine St. Peter Sandstone: beachSt. Peter Sandstone: beach Galena-Platteville Dolostone: shallow Galena-Platteville Dolostone: shallow
marinemarine Silurian (438 to 417 MYA)Silurian (438 to 417 MYA)
dolostone: shallow marinedolostone: shallow marine Silurian-Mississippian (417 to 320 Silurian-Mississippian (417 to 320
MYA)MYA) No rocks exposed: eroded or not depositedNo rocks exposed: eroded or not deposited LaSalle Anticline: foldLaSalle Anticline: fold
Rocks of Rocks of the central the central
Illinois Illinois ValleyValley
Pennsylvanian Pennsylvanian (320 to 286 (320 to 286 MYA)MYA) CarbondaleCarbondale BondBond ModestoModesto
Rocks of the central Illinois Rocks of the central Illinois ValleyValley
Pennsylvanian cyclothemsPennsylvanian cyclothems thin layers of varying type in thin layers of varying type in
repeated sequencesrepeated sequences coalcoal sandstonesandstone limestonelimestone shaleshale clayclay
varying coastal env.varying coastal env. fluctuating sea levelfluctuating sea level
Permian to Permian to QuaternaryQuaternary
(286 to 1.8 (286 to 1.8 MYA)MYA)
erosionerosion
PleistocenPleistocenee
(1.8 MYA (1.8 MYA toto
10,000 10,000 YA)YA) UnconsolidatUnconsolidat
ed depositsed deposits diamictondiamicton sand and sand and
gravelgravel sand dunes sand dunes
(near the (near the river)river)
loessloess laminated laminated
clayclay
TheTheICEICEAGEAGE
10,000 YA to present10,000 YA to present
Thank YouThank You
Mike PhillipsMike Phillips
Illinois Valley Community CollegeIllinois Valley Community College
www.ivcc.edu/phillipswww.ivcc.edu/phillips
[email protected][email protected]
(815)224-0394(815)224-0394
““The Geologic History of The Illinois Valley”The Geologic History of The Illinois Valley”
June 2006June 2006