Biogeochemical significance of the Precambrian-Cambrian boundary carbon isotope anomaly; constraints from Oman

Abstract

Globally significant events of faunal turnover, tectonic reorganization, and biogeochemical change are now widely regarded to have closely coincided with the Precambrian. Cambrian boundary. Over the past decade, numerous studies have provided constraints on the age and duration of these events, the possible phylogenetic relationships between faunal assemblages, and the magnitude and significance of· contemporaneous shifts in the trace element composition and isotopic composition of C, O, S and Sr in the oceans. The Ara Group (Huqf Supergroup) of the South Oman Salt Basin (SOSB) presents an excellent succession with which to address this problem. At least six evaporite-carbonate sequences (A1 to A6) are observed in the SOSB. The carbonate rocks are tightly enclosed in a protective envelope of impermeable halite, and therefore these rocks have likely never exchanged isotopes with younger fluids.