Geologic
Story
of
Minnesota
(as told by
its rocks)
Part II:
Paleoproterozoic
Rocks
Today’s
Lecture
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
Paleoproterozoic Sedimentary Rocks of the Lake Superior Region
Animikie Group
Menominee Group
Huronian Supergroup
Archean
Huronian Supergroup
Sedimentary Rocks
TILLITES
U-bearing Matinenda Fm
Ramsey Lake Fm
Carbonates of the Espanola Fm
Gowganda Fm
Bruce Fm
MESABI-TYPE IRON FORMATION
Geologic Marker of a Major
Evolutionary Event
STROMATOLITES
(Fossilized Algal Mats)
Evidence of Early Life
Hibbing, MN
Ishpeming, MI
Paleoproterozoic
Iron Ranges of the
Lake Superior Region
Rocheleau Pit
Dunka Pit
Peter Mitchell Pit
Progressive
Deformation
across the
Penokean Orogen
Jay Cooke Park – Deformed Thomson Fm
Eveleth – Flat-lying Biwabik Fe-Fm
St. Cloud – Granite intrusions
St. Cloud
Eveleth
Jay Cooke
Continental Shelf
Volcanic Arc
Suture –Niagara Fault
DENUDATION OF A MOUNTAIN BELT
SIOUX QUARTZITE
~1.7 Ga Mature Sandstone
Flambeau
Blue Mounds State Park
Rib Mtn
Baraboo
Sioux
Pipestone National Monument
More Paleoproterzoic
Mountain-building Events
Yavapai Orogeny: 1770-1730 Ma
Mazatzal Orogeny: 1650-1600 Ma
Holm et al., 2007
Summary of
Paleoproterozoic
Tectonic Events in the
Upper Midwest
Holm et al., 2007
PALEOPROTEROZOIC
MOUNTAIN-BUILDING
Creation and Growth of
LAURENTIA