Origin of
Solar System
(Earth)
The Big Bang
20
15
Nucleosynthesis
10
5
Billions of Years Before Present
PreCambrian
0
Mya
Geologic Time
570-505 Cambrian, Great Lakes covered shallow sea
505-438 Ordovician, Sandstone deposited, then limestone and dolomites
438-408 Silurian, erosion resistant coral reefs, dolomite formed by Mg substitution onto coral
408-360 Devonian shale, will be scraped away to form Lake Michigan
360-320 Mississippian limestone and shale, various rise and fall of sea -leads to Illinois Bow
320-286 Pennsylvanian - rise of land, tropical plants
286-245 Permian, Illinois above sea level
245-208 Triassic
204-144 Jurassic, Illinois remains dry, Dinosaurs
144-66
Cretaceous, Illinois shallow sea bed, more marine deposits
66-1.6
Tertiary (Paaleocene, Eocene, Oligocene, Miocene, Pliocene
1.6-300,000
Pre-Illinoian
300,000-125,000 Illinoian Glaciation
75,000-10,000
Wisconsin Glaciation, scrape Devonian shales to Silurian
Rocks, Creates lakes with high Ca/Mg content based on
Silurian rocks (Whiting events)
15,500
Kankakee Torrent: Lake Wauponsee rapidly lowered, in
northern Illinois, bedrock is within 15 inches of surface
in many places: creates high Mg soils in some places
wet soils in others. At Midewin, magnesium reaches 1.2%
typical values (0.003-0.6%)
Mississippian 360-320)
Pennsylvanian (320-286)
Distance long enough to
Affect temperature in winter,
Less so than in the summer
LO J
P
K
L
P
G
O J
K
The Kankakee Torrent
Catestrophic flooding 15,500 years ago
No flow of water to Atlantic through St. Lawrence
Flood scoured the land 160 ft about the present level of the
Illinois River
Starved Rock carved from the flood. Flood large enough to
carve down to bedrock (dolomite).
Sediments deposited along the Mississippi altered the course
of the Mississippi and Ohio Rivers
Natural Divisions sort of follow glacial
Deposits, but not entirely.
Soils sort of follow
Deposits but not entirely
Climate!!!
Geology Summary
1. Silurian Bedrock:
1. Mg and Ca content: prairies, lake chemistry
2. Sets boundaries of Great Lakes
3. Sets the drainage of Great Lakes (invasive species!)
4. Sets the current drainage of Chicago (history: Why Chicago?!)
5. Affects water table in parts of the Chicago area
6. Affects Deep Tunnel Project
2. Wisconsin glaciation
1. Gives us the Great Lakes
2. Great Lakes modulate the weather
3. Gives us the surface materials for soils
4. Sets the topography and drainage