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Lower Mississippian Sedimentation In Northwestern Montana, Forest E. Haines
Lower Mississippian Sedimentation In Northwestern Montana, Forest E. Haines
Doctoral Dissertations
"Thirty-three measured sections, nine with thin sections and insoluble residues, were studied to determine the depositional history of the Allan Mountain Limestone and the lower member of the Castle Reef Dolomite of the Madison Group in northwestern Montana.
The Allan Mountain base is a fossiliferous limestone, herein named the Brownback Gulch Member, which thickens and becomes cherty to the southwest where the section at Lone Butte resembles that of the Bridger Range Waulsortian-type reefs. A crinoidal lag deposit marks a dis- conformity at the top. In the overlying silty limestone member a thin black shale (Unit 1) grades into normal …