A sequence stratigraphic approach to interpreting the δ13C record using an Early Cambrian carbonate platform

Abstract

The Early Cambrian Wilkawillina Platform displays a continuous platform to basin facies that enables physical time surfaces to be used to compare roughly synchronous δ13C values of carbonates to test their lateral variation in range. The two sections measured showed a progression from shallow water deposition of the Woodendinna Dolomite to deeper water deposition of the Oraparinna Shale in the basin while biostromes of Archaeocyatha developed on the shelf. Using a sequence stratigraphic approach, the sections were correlated using the time significant sequence boundaries shared between the two sections. Correlated by the sequence boundaries, stable isotopes (δ13C and δ18O) were then compared and found to be out of phase with each other. A chronostratigraphic diagram shows that carbonate deposition is not continuous over time and therefore, the δ13C record is episodic. This approach emphasises the punctuated nature of the record and the predominance of depositional hiatus in sections, while previous chemostratigraphic studies have assumed the δ13C record to be largely continuous through time when making correlations.