Westernmost Tethyan/proto-Atlantic neritic archives of Early Aptian environmental change
Mineralogy, Petrology and Geochemistry
Final Report Abstract
This pilot study received funding in order to test the potential of Barremian-Aptian marine sections for their use as palaeoceanographic reference sections in Central Mexico. Detailed fieldwork in the 600 meter long Barranco San Lucas section, chosen based on literature study and intense collaboration with Mexican colleagues, and very time consuming laboratory work have not yet led to conclusive results due to the difficult diagenetic overprint of bulk and component specific samples. Approaches applied included sedimentology, stratigraphy, biostratigraphy, carbon isotope chemostratigraphy (both DIC and organic carbon) as well as 87Sr/86Sr chemostratigraphy. The at present most important result is the finding of a Lithocodium aggregatum microencruster interval at what might be the uppermost Barremian and lowermost Aptian transition zone. This microencruster interval shares very important similarities with comparable facies of the western margin of the Proto-Atlantic in Portugal. As we still wait for the completion of the last 150 section meter (mainly the Zapotitlan Formation), a conclusive age assignment of this important interval by means of 13Corg chemostratigraphy is still lacking.
