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’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
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 ??
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
Eveleth – Flat-lying Biwabik Fe-Fm
Jay Cooke Park – Deformed Thomson Fm
St. Cloud – Granite intrusions
St. Cloud
Eveleth
Jay Cooke
Continental Shelf
Suture –Niagara Fault
Volcanic Arc
DENUDATION OF A MOUNTAIN BELT
SIOUX QUARTZITE
~1.7 Ga Mature Sandstone
Flambeau
Blue Mounds State Park
Rib Mtn
Sioux
Baraboo
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 ACCRETED TERRANES
Creation and Growth of LAURENTIA
Next Lecture
The Final Chapter of the Precambrian
The Meso- and NeoProterozoic