GEO 103 Lecture 18: Proterozoic Formations
22 Mar 2017
School
Department
Course
Professor
Document Summary
Archean cratons sutured along deformation belts (orogens) by ~1. 8 gyr. Laurentia then grew along the southern margin by accretion. Wopmay orogen marks site of ocean basin opening (to west) and closing. Early proterozoic sandstone-carbonate shale assemblages widespread near great lakes. Huronian and correlated rocks reflect development of passive margin. 75% of north american in place at end of grenville. 2000 km long and up to > 10 km thick sequence of volcanoes and sediments. Or may be related to collision (similar to lake baikal) Middle - late proterozoic basins formed on western margin of craton. Proterozoic rocks also preserved in grand canyon sequence. These ocean crusts get preserved when they are rafted up to the surface from plate tectonics. Supercontinent may have existed at the end of archean. Continental scale glaciation not common in earth"s history. Dropstones - big fragments of rock are stuck inside of the sediment.
