Paleography and Conodont Biostratigraphy of Devonian Carbonate Rocks of the Whitefish MacDonald Range, NW Montana and SE British Columbia

SEWARD, W. PATRICK, and JOHN H. BUSH, University of Idaho, Moscow, ID

Five remote Upper Devonian carbonate sections measured within the Rocky Mountain fold and thrust belt of the Whitefish Range, northwestern Montana and contiguous MacDonald Range, southeastern British Columbia are bounded unconformably at the base by Middle Cambrian carbonate rocks and unconformably at the top by the Devonian-Mississippian Exshaw Formation.

Conodont zonation provides an age of late Frasnian to middle Famennian. Standard pelagic conodont zones represented are Polygnathus asymmetricus, Ancyrognathus triangularis, Palmatolepis gigas, Pa. triangularis, Pa. crepida, P. rhomboidea, and lower Pa. marginifera zones. Strata are equivalent in age to the Jefferson and Three Forks formations in central Montana, the Jefferson Formation in east central Idaho, carbonate units of Limestone Hill in eastern Washington, the Devils Gate Limestone and Pilot Shale in eastern Nevada, and the Fairholme Group, Alexo, and Palliser formations in British Columbia. Devonian carbonate lithologies examined in this study are dominantly subtidal and intertidal lime mudstone, wackestone, and bindstone interpreted to have been deposited above storm wave b se on a wide carbonate platform, during the early, less dramatic movements of the Antler orogeny.

This research will provide a data point that will fill a significant void in Devonian paleogeographic information in the northern United States and Southern Canadian cordillera.

AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)