Timing and source of late cretaceous volcanism in southwest montanaproject period: 06 01 2024-05 31 2025THIS project will provide new constraints on an important transition period in montanas geologic…

This federal Cooperative Agreement award, funded by the U.S. Geological Survey (USGS) under the National Cooperative Geologic Mapping Program (CFDA 15.810), provides $163,668 to Montana State University to conduct geological mapping and analysis in southwestern Montana. The project aims to better define the onset and timing of Cretaceous volcanism in the region, including the Elkhorn Volcanics, through field mapping, geochronology, and geochemistry. Two graduate students will be guided by university faculty to remap the Crow Creek quadrangle and investigate stratigraphic unconformities related to the onset of volcanism. The resulting geological data and maps will be provided to the Montana Bureau of Mines and Geology to support their ongoing mineral resource assessment work under the Earth MRI program. The award period is from June 1, 2024 to May 31, 2025.

Timing and source of late cretaceous volcanism in southwest montanaproject period: 06 01 2024-05 31 2025THIS project will provide new constraints on an important transition period in montanas geologic history, with implications for our understanding of regional tectonic models. The recipient seeks to better define the onset of cretaceous volcanism in montana, where a significant volume of off-axis magma proposed to be transported by deep ramp structures. Lack of quality age dates and geochemical data for these cretaceous eruptive centers, including the most voluminous system, the elkhorn volcanics, significantly limits our ability to test magma source and melt models, transport mechanisms, and regional structures, with poorly constrained timing on most extrusive events. In addition, the onset of volcanism in the region is marked by widespread volcaniclastic layers of unclear ages and origins, sitting on top of a sandstone unconformity. In this study, PH.d. Student natali kragh and m.SC. Student BEL liscomb will be guided in mapping techniques by DRS. Madison myers and kyle eastman (montana bureau mines geology) during the summer of 2024. The M.S. Student will focus on remapping the crow creek quad, a 7.5 quadrangle that has yet to be mapped at a 24K scale but contains the full elkhorn volcanic suite (currently mapped as seven separate eruptive units). The second project will focus on mapping and age dating multiple stratigraphic volcaniclastic unconformity contacts to better inform when the onset of volcanism occurred in the region. Information from this mapping project will be provided to the montana bureau of mines and geology to be used in conjunction with their ongoing geologic mapping and geochemistry projects supported by the USGS earth-MRI program, which investigates the critical minerals potential of late cretaceous magmatism.