ASSESSING ALTERATION OF EDIACARAN-CAMBRIAN CARBON ISOTOPE VALUES AT MOUNT DUNFEE, NV
At Mount Dunfee, strata recording the basal Cambrian negative carbon isotope excursion show negative covariation of δ44/40Ca with δ13C values, as well as positive covariation of Sr/Ca ratios with δ13C values and Mn/Ca ratios with δ44/40Ca values. Where δ44/40Ca values trend toward more negative values (-1.4‰) and correlate with high Sr/Ca ratios, we interpret neomorphism of primary aragonite under conditions that preserve primary geochemical signatures (sediment-buffered); such values are found in strata with δ13Ccarb values approaching 0‰. In contrast, where δ44/40Ca values trend towards -0.6‰ and correlate with low Sr/Ca ratios, we interpret resetting of the primary δ13Ccarb values by a diagenetic fluid rich in isotopically light carbon. Together these data suggest that the stratigraphic variability in the Esmeralda Member is a result of local differences in the preservation of sediment chemistries rather than global changes in seawater chemistry.