2. Tectonics in Wisconsin Presentation originally created by Dr. Dyanna Czeck, UW-Milwaukee (Slides #3, 4 and 5 are from NICE (Northern Interior Continental Evolution) Working group presentation at ILSG 2006

4. NICE, 2006

6. Aeromagnetic Map of Wisconsin Geon 18 Penokean amphibolite metamorph 1744 Ma amphibolite metamorphism Yavapai age terrane Geon 16 amphibolite metamorphism Granite-rhyolites invading Mazatzal age terrane NICE, 2006

7. Tectonic Events in Wisconsin Granite-greenstone terrane formation (approximately 2700-2500 Ma) Penokean Orogeny (~1900 Ma) Mazatzal Orogeny (~1600 Ma) Mid-Continent Rift (~1000 Ma) Terranes = mini continents Orogenies = mountain- building events Rifts = lithosphere pulls apart

8. tapestry.usgs.gov/ages/ precambrian.html Exposed Precambrian Rocks in the U. S. (anything older than 570 Ma)

9. Precambrian (Archean and Proterozoic) rocks are underlying much of North America! http://www.paccd.cc.ca.us/instadmn/physcidv/geol_dp/dndougla/home/DRDHOME.htm

10. The Amazing Archean (4.6-2.5 Ga): ircamera.as.arizona.edu/ MIRI/life.htm Painting by K. M. Towe of stromatolites 3.5 Ga

11. How to Make Continents: Earliest earth had one crust –Ultramafic composition (not much silica) Today: –Oceanic crust (mafic) –Continental crust (felsic) What makes continental crust so special? –Most felsic material (quartz rich) –Not dense, so doesn’t get subducted How to make continental crust ? nataliedee.corrupt.net/ index.php

12. Volcanic Processes that can form more felsic magma from ultramafic magma 1.Fractional crystallization http://www.usd.edu/esci/figures/158370.JPG

13. Fractional Crystallization http://www.usd.edu/esci/figures/157525.JPG Bushveld Complex, Australia

14. Volcanic Processes that can form more felsic magma from ultramafic magma 2. Partial Melting Bowen’s Reaction Series: minerals with low melting temperature melt first http://www.usd.edu/esci/figures/158371.JPG Low Melting Temp High Melting Temp

15. whyfiles.org/031volcano/ main2.html Partial Melting = incomplete melting of a more mafic rock. http://www.crazy4candy.com/images/uploads/snickersF.gif melt - felsic residue - more mafic

16. Earliest Microcontinents http://earth.usc.edu/~geol150/public_html/evolution/image s/prepaleozoic/earlytectonics.jpg Small Felsic Continents Big Mafic Ocean Crust Little sedimentary basins at continent’s edges Felsic continental crust slowly created by partial melting OR fractional crystallization.

17. Results in: 1.Deformation (reverse faults, folds, shear zones)! 2.metamorphic rocks! 3.big mountain chain! Traces of Continental Collisions:

18. Traces of Archean Mini Continental Collisions: Granite- Greenstone Terranes Special rock assemblages found in Archean areas

20. North American Superior Province Based on Card and Ciesielski, 1986 The best granite- greenstone terrane in the world!!!!

21. http://www.uwgb.edu/dutchs/geolwisc/geohist/wipcarch.htm

22. http://www.paccd.cc.ca.us/instadmn/physcidv/geol_dp/dndougla/home/DRDHOME.htm

23. http://www.uwgb.edu/dutchs/geolwisc/geohist/wipcpor.htm Penokean Orogeny Sutured two Archean Terranes and a Proterozoic Terrane

25. http://www.d.umn.edu/geology/main/thomson.html www.isk.canoe-kayak.org/reports2001/ report9_01.html Thomson Formation near Jay Cooke State Park and Thomson, MN

28. Tilted Layers of Baraboo Quartzite and Phyllite: Van Hise Rock

29. Magnetic Anomaly Map Midcontinent Gravity High

30. http://www.winona.msus.edu/geology/MRW/mrwimages/mid-continentrift.jpg 1000 Ma Mid Continent Rift

31. Continental Rifting Caused by a Mantle Plume

32. Magnetic Anomaly Map Midcontinent Gravity High

33. http://www.bwca.cc/activities/hiking/superiorhikingtrail.html http://www.mwpersons.com/Travels/Gooseberry-falls.html Lake Superior Shoreline: Minnesota BASALT: Gooseberry Falls RHYOLITE: Palisades Head

34. www.photochromecollection.com/ WI/53297.html Lake Superior Shoreline: Wisconsin SANDSTONE: Apostle Islands

35. http://pubs.usgs.gov/info/mwni_cu/ Lake Superior Basin

36. www.polkcountytourism.com/gallery2/ interstatepark.html Interstate Park: St. Croix Falls, WI & Taylors Falls, MN

37. http://www.paccd.cc.ca.us/instadmn/physcidv/geol_dp/dndougla/home/DRDHOME.htm

38. The Grenville Orogeny was a huge collision!!!!! Resulted in: 1.Deformation (reverse faults, folds, shear zones)! 2.metamorphic rocks! 3.big mountain chain! 4.Formed a supercontinent! Diagrams from Chuck Bailey instruct.uwo.ca/earth-sci/ 200a-001/200lab1.htm Grenville Gneiss Erosion level