earth history geol 2110
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Earth History GEOL 2110. The Cryptozoic (Precambrian) SuperEon Part 2: The Paleoproterozoic Era. Major Concepts. - PowerPoint PPT PresentationTRANSCRIPT
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
MinnesotaSedimentary rock
accumulated in the Animikie Sea
then deformed in the Penokean Orogeny
Creating the Animikie Basinby Continental Rifting
Animikie Group
Menominee Group
Huronian Supergroup
Archean
Paleoproterozoic Sedimentary Rocks of the Lake Superior Region
Huronian SupergroupSedimentary
Rocks
U-bearing Matinenda Fm Carbonates of the Espanola Fm
Gowganda FmRamsey Lake Fm Bruce Fm
TILLITES
Limestone
Tillite
PaulHoffman
MESABI-TYPE IRON FORMATIONGeologic Marker of a Major Evolutionary Event
STROMATOLITES(Fossilized Algal Mats) Evidence of Early Life
Mesabi-type Iron FormationDepositional Environment (~ 2.0 Ga) - Organically mediated deposition
at the margin of the Animikie Basin
Occurrence - Minor structural disruption in northern Minnesota
Offshore Algal Reef
Si,Fe
ONearshore
Archean Crust
ANIMIKIE SEA(sand, silt, mud)(iron oxide, chert)(pelagic mud, turbidites)
Detrital sediment
Biwabik Fe-Fm.
Virginia Fm.
Pokegama Qtzt.
glacial till S N
~ 1 km
The 1.85 Ga Sudbury ImpactThe First Major Extinction Event ??
Paleoproterozoic Iron Ranges of the Lake Superior Region
Ishpeming, MI
Hibbing, MN
Hydrothermal Fluids
Taconite Ore
Natural Ore
Surficial Waters
Magnetite Hematite Goethite/Limonite
OXIDATIONLEACHING NATURAL ORENATURAL ORETACONITE ORETACONITE ORE
Fe3O4 Fe2O3 FeO•OHFe3O4 Fe2O3 FeO•OH
Rocheleau Pit
Dunka Pit Peter Mitchell Pit
Progressive Deformationacross the Penokean
Orogen
Eveleth – Flat-lying Biwabik Fe-Fm
St. Cloud – Granite intrusions
Jay Cooke Park – Deformed Thomson Fm
Eveleth Jay 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: 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 TERRANESCreation and Growth of LAURENTIA
Next Lecture
The Final Chapter of the PrecambrianThe Meso- and NeoProterozoic