Organic geochemistry parameters for understanding the Messinian salinity crisis

Expedition 401 recovered 2.6 km of core from seven boreholes at four sites (3 in the Atlantic, 1 in the Mediterranean), which form a critical record for assessing Mediterranean overflow associated with the Messinian salinity crisis. The specific scientific objectives are: 1. Assess variations in organic inputs and palaeoproductivity in the four sites over time, at a low resolution, from the Miocene (Tortonian and early Messinian) to the Pliocene (Zanclean). This objective includes study of black carbon generated as a by-product of wildfires, which will be traced using polycyclic aromatic hydrocarbons. 2. Assess variations in depositional environment at the four sites, and notably at Site U1611 assess whether the thinly bedded sediments from the time of the Messinian salinity crisis were deposited in a lake (and if so, was it fresh water, brackish, saline, or hypersaline; with or without temporary connections to the Atlantic Ocean), or an embayment of the Atlantic Ocean. 3. Assess thermal maturity, geothermal gradient, and extent of diagenetic alteration of the organic matter during burial at the four sites. In particular, track the diagenetic rearrangements of biomarkers, from functionalised hopanoid and steroids, to hopenes, sterenes and diasteranes, and then to hopanes, steranes and diasteranes. 4. Carry-out a high resolution organic geochemical study of the intervals selected for multi-proxy work by the whole science party, which will probably be 1 to 3 precessional cycles from each of the four sites.