A thermochronological history of burial and exhumation at Kevin Dome, Northwest Montana including the origin of CO2 in Upper Devonian Duperow Formation and the Bakken Petroleum system at the Dome

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Montana State University - Bozeman, College of Letters & Science


Kevin Dome is a geologic structure and historic hydrocarbon producer in northwest Montana. This structure is also a known CO 2 reservoir, yet its development has not been constrained with thermochronological techniques and the origin of the natural (~ 283 x 109 m 3) CO 2, of the Upper Devonian Duperow Formation, is not well understood. This work seeks to create a temporal understanding of the burial and exhumation history of Kevin Dome including the hydrocarbon generation and CO 2 emplacement. I constrained the burial and exhumation history at Kevin Dome with low-temperature thermochronology, carbonate clumped isotope thermometry, and thermobarometric proxies. I also tested for microbial, thermogenic, and magmatic CO 2 source(s) as well as CH 4 and N 2 gas sources at the dome with major gas composition, stable and noble gas isotopic geochemistry methods. I found that Kevin Dome rocks were buried to oil and gas generation windows before exhumation during the Late Cretaceous-Paleocene (~65 - 72Ma) and the Oligocene-Miocene (~ 15 - 26Ma) at an average rate of ~ 0.27 mm/yr. My study supports an evolved forebulge-dome origination model for Kevin Dome that is driven by the Late Cretaceous-Paleocene emplacement of the Rocky Mountain overthrust in a Foreland Basin setting in northwestern Montana (and proximal Canada) and an Oligocene-Miocene erosional or epeirogenic event not previously recognized in northwest Montana. I estimated ~4 - 5 km more overburden erosion than was previously thought in the region and suggest that the Oligocene-Miocene exhumation terminated hydrocarbon generation at Kevin Dome. In terms of CO 2 origin, my data supports a magmatic origin for the Duperow CO 2, with emplacement during the Sweetgrass Hills igneous complex intrusion(~52 Ma). I also found that the CH4 and N2 gases at Kevin Dome were mainly thermogenic in origin. A CO 2 solubility model showed that ~98% of the CO 2 has been dissolved into the groundwater in the Bakken petroleum system's hydrocarbon-bearing reservoirs at Kevin Dome during migration. I present a novel approach of integrating modern t-T sensitive techniques, stratigraphy, thermal maturity data, and isotopic geochemistry to address the structural development of sedimentary basins/domes, hydrocarbon generation, and magmatic CO 2 emplacement and subsequent evolution.



Exhumation, Thermal History Modeling, Hydrocarbon Generation


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