Lithostratigraphy and Conodont Biostratigraphy of a West Canyon Limestone Equivalent (Upper Mississippian-Middle Pennsylvanian) in Southeastern Idaho

Larry E. Davis, Gary D. Webster

Upper Mississippian to Lower-Middle Pennsylvanian limestones and calcareous sandstones, which overlie the Manning Canyon Formation, crop out in the Albion, Sublett, and Bannock Ranges and the Black Pine, Deep Creek, and Samaria Mountains, and have been assigned to various formations and groups. Five carbonate and two siliciclastic lithofacies are recognized: bioclastic packstones to grainstones; whole-fossil wackestones to muddy packstones; bioturbated, arenaceous mudstones to wackestones; oncolite packstones to grainstones; bryozoan framestones; calcareous quartz arenites to sublithic arenites; and calcareous shales. The lithologies are interpreted as being deposited on a barrier shoal carbonate ramp along the eastern margin of the Oquirrh basin and are time-equivalent t the West Canyon Limestone of northwestern Utah.

Six conodont biozones are recognized in this West Canyon Limestone equivalent in southeastern Idaho and in ascending order are the Rhachistognathus muricatus; R. primus/Declinognathodus noduliferus; R. minutus/Idiognathoides sinuatus; Idiognathodus sinuosis; Idiognathodus parvus; and Diplognathodus coloradoensis/Neognathodus atokaensis Biozones. The Morrowan conodont biozones, Neognathodus symmetricus and N. bassleri, are not recognized, although time-equivalent strata are probably present. The absence of these two biozones is considered to be due to environmental controls on the name-bearers. Based on present conodont zonation, the Mississippian/Pennsylvanian boundary can be recognized at Samaria Mountain, Idaho.

Upper Mississippian to Lower-Middle Pennsylvanian stratigraphic terminology is being redefined for these lithologies in southeastern Idaho.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.