Collingwood Limestone (MIOc;0)

State	Michigan
Name	Collingwood Limestone
Geologic age	Late Ordovician
Original map label	Oc
Comments	Secondary unit description from USGGS Geologic Names lexicon (ref. MI016): Named the Collingwood formation for Collingwood, Ontario, CAN. Unit is a thin formation of layers of fine-grained rather pure blue limestone alternating with thick beds of soft brown shale. Thickness is not known but appears to be less than 50 feet. Fauna, which is well developed at Collingwood, differs from that of typical Utica in many respects. Overlies Trenton limestone and underlies darker shales containing typical Utica fauna. The Collingwood is of Ordovician age.
Primary rock type	limestone
Secondary rock type	black shale
Other rock types
Lithologic constituents	Major Sedimentary > Carbonate > Limestone (Bed) Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Map references	Reed, Robert C., and Daniels, Jennifer (compilers), 1987, Bedrock geology of northern Michigan: Geological Survey Division, Michigan Dept. of Natural Resources, scale= 1:500,000
Unit references	Reed, Robert C., and Daniels, Jennifer (compilers), 1987, Bedrock geology of northern Michigan: Geological Survey Division, Michigan Dept. of Natural Resources, scale= 1:500,000 USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Alger - Chippewa - Delta - Luce - Schoolcraft