Differentiating early from later diagenesis in a Cretaceous sandstone and petroleum reservoir of the Cedar Mountain Formation, Utah

ABSTRACT Previously published anomalous whole-rock stable isotopic values from the Poison Strip Sandstone Member of Cretaceous Cedar Mountain Formation (CMF) eastern Utah are uncertain origins. This study investigated diagenetic history and processes responsible for these data. Accordingly, we integrated photomicroscopic techniques including polarized light microscopy, epifluorescence cathodoluminescence (CL) imaging, micromilling isotope samples, fluid-inclusion heating freezing measurements to this end. The key observations involved microscopic mapping calcite cement stratigraphy using CL imaging permit analysis isotopes cements that crystallized during early late diagenesis. zones sufficient submillimeter size mill out isolate microgram-sized samples enabled discrimination. Early have most positive δ18O (-10 -8.5‰ Vienna Pee Dee Belemnite [VPDB]) all components. pattern δ13C variation in indicates affinities with meteoric diagenesis previously documented literature on CFM. yield negative (-18 -16‰ VPDB). We interpret be anomalously low reported Member. Our discoveries bitumen late-stage pore fillings liquid petroleum fluid inclusions explain lower organic matter Δ13C unit. Comparatively carbonate originally derived analyses resulted high-temperature basinal (hydrothermal circulation and/or migration), rather than alternative interpretation related a paleoclimatic perturbation. results illustrative methods resolve long-standing geologic problem discriminating characterizing products vs. terrigenous clastic sedimentary strata.