Diagenetic Overprinting by Salt Diapiric Fluids at the Beltana and Pinda Diapirs, South Australia: Implications for Paleoclimate Records, Carbon Storage, and Hydrocarbon Exploration

Salt structures and their related minibasins are associated with complex and dynamic fluid systems that can locally impact the cement characteristics of salt minibasin stratigraphy. The impacts of salt-related fluids have been investigated primarily in fracture vein fill, but are poorly constrained in the surrounding stratigraphy (i.e., host rock). This limits our understanding of how salt-related fluid systems diagenetically overprint minibasin stratigraphy through localized cement precipitation and at what spatial scale. The remarkably well-exposed Beltana and Pinda diapirs in South Australia offer an opportunity to explore salt-related fluid alteration in the mixed carbonate siliciclastic Wonoka Formation. Recorded in Wonoka stratigraphy is the most negative δ13C excursion in Earth history (the Shuram excursion), which has previously been shown to have consistent δ13C isotopic profiles across the Flinders Ranges. New sedimentologic, petrographic and geochemical (δ13C and δ18O) data from subsalt and suprasalt Wonoka stratigraphy at the Beltana and Pinda diapirs show increased isotopic variation in micritic dolomite cement the more proximal samples were taken to the diapir. Samples from along the salt–sediment contact indicate that isotopic variation is primarily concentrated within the subsalt stratigraphy. These results suggest that chemostratigraphic profiles for paleoclimate analysis and stratigraphic correlation should be collected >3 km from diapirs. This study can be used as an analogue to clarify reservoir quality adjacent to diapirs, which is useful for carbon storage and hydrocarbon exploration.