ORGANIC CARBON CHEMOSTRATIGRAPHY AND X-RAY DIFFRACTION (XRD) MINERALOGY IN LACUSTRINE STRATA OF THE RUBY RANCH MEMBER WITHIN THE CEDAR MOUNTAIN FORMATION NEAR MOAB, UTAH
The “Lake Carpenter” site is a well exposed lacustrine sequence in the Ruby Ranch Member of the CMF near Moab, Utah was sampled from four trenches at 25 cm increments for geochemical analyses, specifically carbon isotope chemostratigraphy. In addition, XRD analyses improved the lithologic description. Results indicate silicate mineralogy consists of clays and quartz. Carbonate mineralogy fluctuates between calcite, high magnesium calcite, and dolomite. The presence of high Mg calcite and dolomite are consistent with previous interpretations of arid conditions represented by the Ruby Ranch Member.
The δ13C of sedimentary organic carbon ranges from a three point average of -28.8 ‰ (VPDB) to -23.4‰ (VPDB). Tentatively, these results appear to correlate with the carbon isotope excursions Ap10, Ap11, C9, Ap12, Ap13, Ap14, and Ap15 during the Late Aptian (C-isotope segments defined by Bralower et al., 1999 and Herrle et al., 2004). This is also supported by previous lithostratigraphic and chemostratigraphic work within the CMF that correlates with these Aptian segments.