1. Earth History GEOL 2110 The Cryptozoic (Precambrian) SuperEon Part 2: The Paleoproterozoic Era

2. 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).

3. Today’sLecture Kenoraland

4. Paleoproterozoic Rocks of Minnesota Sedimentary rock accumulated in the Animikie Sea then deformed in the Penokean Orogeny

5. Creating the Animikie Basin by Continental Rifting

6. Animikie Group Menominee Group Huronian Supergroup Archean Paleoproterozoic Sedimentary Rocks of the Lake Superior Region

7. Huronian Supergroup Sedimentary Rocks U-bearing Matinenda Fm Carbonates of the Espanola Fm Gowganda Fm Ramsey Lake Fm Bruce Fm TILLITES

8. Limestone Tillite Paul Hoffman

9. MESABI-TYPE IRON FORMATION Geologic Marker of a Major Evolutionary Event

10. STROMATOLITES (Fossilized Algal Mats) Evidence of Early Life

12. The 1.85 Ga Sudbury Impact The First Major Extinction Event ??

13. Paleoproterozoic Iron Ranges of the Lake Superior Region Ishpeming, MI Hibbing, MN

15. Rocheleau Pit Dunka Pit Peter Mitchell Pit

16. Progressive Deformation across the Penokean Orogen Eveleth – Flat-lying Biwabik Fe-Fm St. Cloud – Granite intrusions Jay Cooke Park – Deformed Thomson Fm

18. EvelethJay Cooke St. Cloud

19. Volcanic Arc Continental Shelf Suture –Niagara Fault

20. DENUDATION OF A MOUNTAIN BELT

21. Sioux Flambeau Baraboo Rib Mtn SIOUX QUARTZITE ~1.7 Ga Mature Sandstone Blue Mounds State Park Pipestone National Monument

22. More Paleoproterzoic Mountain-building Events Yavapai Orogeny: 1770-1730 Ma Mazatzal Orogeny: 1650-1600 Ma Holm et al., 2007

23. Summary of Paleoproterozoic Tectonic Events in the Upper Midwest Holm et al., 2007

24. PALEOPROTEROZOIC ACCRETED TERRANES Creation and Growth of LAURENTIA

25. Next Lecture The Final Chapter of the Precambrian The Meso- and NeoProterozoic