CUR - The Council on Undergraduate Research

Provenance and Paleodepositional Environments of the Tyler and Kibbey Formations, Big Snowy Mountains, Central Montana

Sophie Black1, Saré Campbell1, Devon A. Orme1, David Bowen1, Richard Bottjer2 1Department of Earth Sciences Montana State University, Bozeman, MT 59715 2Coal Creek Resources, 1590 S Arbutus Pl, Lakewood, CO 80228

This research seeks to reconstruct the provenance (i.e. where sediment was derived from), paleodepositional environment, and paleogeography of Montana during the Carboniferous period (350-300 Ma) through the use of sedimentologic observations and U-Pb detrital zircon geochronology on samples from type localities within the Big Snowy trough located in central Montana. The samples being analyzed are from the Alaska Bench Limestone, a unit that represents a Tyler Formation equivalent in this region, and the Kibbey Sandstone. Following sampling, zircons were extracted through density and magnetic separations and hand-picked for U-Pb geochronology, which uses U-Pb decay ratios to develop an age for each zircon from the samples. The U-Pb decay ratios from the samples produce age spectra that will be compared to age spectra of potential source regions to determine the provenance of the analyzed samples. Preliminary results show detrital zircon ages that best match igneous source regions found along the east coast of North America, namely the Appalachian orogeny. This suggests the presence of a continental-scale sediment dispersal system across North America during the late Paleozoic. These and ongoing geochronologic data and sedimentologic observations will also be compared to similar data collected on samples from the Lombard Fault, a type locality in southwestern Montana for age equivalent rocks to determine the similarities and differences in provenance and paleogeography from central to southwestern Montana during this time. 

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