Geochemistry on sediment core CRP-1 (Table 1)

This material complements the Eocene trhough Miocene strata that was cored previously at CIROS-1, 70 km to the south. The paleoclimatic records of CRP-1 and CIROS-1 have been examined by calculating the Chemical Index of Alteration (CIA) of Nesbitt & Young (1982), using new data for CRP-1 materials and the data of Rose & Pyne (1988) for CIROS-1 mudstones.

The CIA is calculated from the relative abundance of Al, K, Ca, and Na, and its magnitude increases as the effects of chemical weathering increase. However, changes in sediment provenance can also effect the CIA, and such changes appear to dominate some parts of the CRP-1 and CIROS-1 record.Relatively large (47-60) and variable CIA values in the lithologically defined „lower sequence“ at CIROS-1 record the influence of chemical weathering during the late Eocene, a result of relatively mild climates and glacial influence, but not glacial dominance.