Earth History GEOL 2110 The Cryptozoic (Precambrian) SuperEon Part 2: The Paleoproterozoic Era
Major Concepts After the formation of the Archean continental landmass (Kenoraland), Minnesota lay at a passive margin where sedimentary rocks accumulated including Snowball Earth tillites and the great Lake Superior banded iron formations. These sedimentary rocks were deformed ~1.85 Ga by the collision of volcanic arc terrane with Kenoraland, an event called the Penokean orogeny. This event sutured several Archean terrains together to form a larger continent called Laurentia. Laurentia continued grow in the Paleoproterozic by adding more terrains to the south at 1.7Ga (Yavapi orogen) and 1.6Ga (Mazatzal orogen).
Today’sLecture Kenoraland
Paleoproterozoic Rocks of Minnesota Sedimentary rock accumulated in the Animikie Sea then deformed in the Penokean Orogeny
Creating the Animikie Basin by Continental Rifting
Animikie Group Menominee Group Huronian Supergroup Archean Paleoproterozoic Sedimentary Rocks of the Lake Superior Region
Huronian Supergroup Sedimentary Rocks U-bearing Matinenda Fm Carbonates of the Espanola Fm Gowganda Fm Ramsey Lake Fm Bruce Fm TILLITES
Limestone Tillite Paul Hoffman
MESABI-TYPE IRON FORMATION Geologic Marker of a Major Evolutionary Event
STROMATOLITES (Fossilized Algal Mats) Evidence of Early Life
The 1.85 Ga Sudbury Impact The First Major Extinction Event ??
Paleoproterozoic Iron Ranges of the Lake Superior Region Ishpeming, MI Hibbing, MN
Rocheleau Pit Dunka Pit Peter Mitchell Pit
Progressive Deformation across the Penokean Orogen Eveleth – Flat-lying Biwabik Fe-Fm St. Cloud – Granite intrusions Jay Cooke Park – Deformed Thomson Fm
EvelethJay Cooke St. Cloud
Volcanic Arc Continental Shelf Suture –Niagara Fault
DENUDATION OF A MOUNTAIN BELT
Sioux Flambeau Baraboo Rib Mtn SIOUX QUARTZITE ~1.7 Ga Mature Sandstone Blue Mounds State Park Pipestone National Monument
More Paleoproterzoic Mountain-building Events Yavapai Orogeny: Ma Mazatzal Orogeny: Ma Holm et al., 2007
Summary of Paleoproterozoic Tectonic Events in the Upper Midwest Holm et al., 2007
PALEOPROTEROZOIC ACCRETED TERRANES Creation and Growth of LAURENTIA
Next Lecture The Final Chapter of the Precambrian The Meso- and NeoProterozoic