Chemostratigraphy in Miocene heterozoan carbonate settings: Applications, limitations and perspectives

The temporal variability of geochemical proxies can be used in time intervals characterized by global changes in marine chemistry to achieve improved stratigraphic correlation. The application of this approach in rocks lithified by cementation requires particular attention, as the original isotopic signature may have been modified by diagenetic processes and when bulk samples are used, could reflect facies-specific compositional changes as opposed to primary changes in the water column. This paper examines sedimentological and chemostratigraphic records from outcrops in the central Mediterranean and cores drilled on the Marion Plateau by the Ocean Drilling Program (ODP) Leg 194, where heterozoan carbonates accumulated during the Miocene. Specifically, the paper addresses how facies and preservation of original marine signatures differentially affect the quality of the dataset. The analysis indicates that, in general, heterozoan systems, relative to their tropical counterparts, show good preservation of marine signatures. Chemostratigraphy of Ters a viable low-resolution alternative for dating platform sediments considering the general lack of biostratigraphic markers in these settings. It is stressed. however, that care must be taken when interpreting these values, especially when the dataset is at a low resolution or when post-depositional dolomitization took place. Furthermore, chemostratigraphy in shallow-water environments cannot be done without detailed facies analysis, as facies changes may impact bulk-rock stable isotope values.