Thermal History of the Mississippian-Pennsylvanian Boundary at Arrow Canyon, NV, USA: Insights from Carbonate Clumped Isotope and Fluid Inclusion Thermometry

Brock Shenton¹, Ethan L. Grossman¹, Benjamin H. Passey², Gregory A. Henkes², Stephen P. Becker³, and Robert J. Pottorf^3
1Department of Geology & Geophysics, Texas A&M University, College Station, TX, USA
²Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, Maryland, USA
³ExxonMobil Upstream Research Company, Houston, TX, USA
[email protected]

Constraining the temperature-time histories of sedimentary basins is useful in a range of geologic applications including tectonics and petroleum systems analysis. To enhance the accuracy of thermal history reconstructions it is important to test emerging techniques, such as clumped isotopes. The potential of carbonate clumped isotopes as a thermal history tool is suggested by elevated clumped isotope paleotemperatures in well-preserved fossils and from recent laboratory experiments showing that C-O bonds can undergo solid-state reordering during heating. While this phenomenon conceals primary paleoclimate information, it records burial temperatures useful for constraining basin thermal histories. Preliminary clumped isotope measurements of brachiopods, crinoids, diagenetic cements, and matrix material from within ~50 m of the Mississippian-Pennsylvanian boundary at Arrow Canyon yield paleotemperatures ranging from ~100-165 °C, which tend to cluster based on component type. New fluid inclusion microthermometry data indicate that strata were heated to at least 175-180 °C. The observation that all clumped isotope temperatures are lower than peak temperature estimates from fluid inclusion microthermometry suggests that clumped isotope compositions may have (1) reordered, but did not achieved thermal equilibrium with the burial environment, or (2) equilibrated at maximum burial temperature but now reflect ‘closure temperatures’ achieved during cooling. Perhaps more importantly, our clumped isotope data suggests that different components that experienced the same burial history can yield different clumped isotope temperatures. This conclusion highlights the importance of continued laboratory study of a range of carbonate components combined with applied studies spanning a range of different burial histories.

AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects