Rock Specimens on the Lawn, Jasper Conglomerate, 1100 North University Building, 1100 N University Ave, University of Michigan, September 22, 2020

https://lsa.umich.edu/earth/about-us/about-our-building/rock-specimens-on-the-lawn.html

Jasper Conglomerate

'More correctly called the Lorraine quartzite, 2.3 Ga Huronian rocks of southern Ontario; found associated with the Gowganda tillite, and may in fact be the outwash associated with the Gowganda glaciers. These rocks are the oldest rocks in North America that evidence an early Ice Age. Amount of red chert (jasper) varies considerably as does as the grain size. Quartzitic conglomerates and coarse sandstones are common. The rock is from the Lorraine Fm., which is part of the Paleoproterozoic Huronian Group. This unusual rock crops out exclusively along a 10 km-long ridge about 25 km NE of Sault Ste. Marie, Ontario. The Lorrain overlies the famous Gowganda Fm., which contains debris flows, tillite and varved sediments with ice-rafted debris thought to represent early Proterozoic glaciation. The source of the red pebbles is probably BIF or related siliceous exhalative sediment in adjacent Archean greenstone belt (basement) to the north, although no one has worked that out.'