oa Organic Geochemical Insights into Organic Matter Sources and Paleoenvironments Across the Messinian Salinity Crisis

Biomarkers detected include steranes and sterenes, hopanes and hopenes, acyclic isoprenoids, and a wide range of aromatic hydrocarbons. Abundant ßaa steranes, sterenes, ßa and ßß-hopanes, and hopenes indicate that the OM is immature and very well preserved. Steranes and sterenes reveal there was a shift in the OM input with the onset of the MSC. The pre-MSC sediments are characterized by a dominance of C29 steroids, with lesser contributions from C27 steroids, and low contents of C28 steroids, consistent with a significant input from higher plants that is also shown by n-alkane distributions. In the MSC sediments by contrast, there is an increase in the proportion of C27 steroids, consistent with a shift towards more marine zooplankton and algal contributions. Post-MSC, the sterane distribution indicates a mixed input from terrigenous OM, algae, and marine zooplankton. Very little oleanane in any of the samples suggests limited angiosperm input, and the presence of retene is consistent with the higher plant contribution being dominantly coniferous. Sediments were deposited under anoxic or euxinic (Pr/Ph <0.8) conditions in the pre-MSC, which became partly dysoxic environment in the late MSC and post-MSC interval.