Detecting missing beats in the Mediterranean climate rhythm from magnetic identification of oxidized sapropels (Ocean Drilling Program Leg 160)

Abstract

Eastern Mediterranean sapropels are organic-rich sediments whose formation is related to variations in the Earth's orbit. They are therefore important for reconstructing past climatic variations and for producing astronomically tuned geological timescales. Previous studies have suggested that the distinctive magnetic properties of sapropels, which result from non-steady-state diagenetic reactions related to degradation of organic matter, might be used for identifying sapropels that have escaped visual identification after being completely erased during post-depositional oxidation. We present a high-resolution multi-proxy magnetic, geochemical and paleontological data set from selected intervals of Ocean Drilling Program Sites 966 and 967. Our results demonstrate that magnetic properties can be unambiguously used for identifying oxidized sapropels, and also for determining whether suspected intervals actually correspond to oxidized sapropels, because they enable detection of the former presence of organic matter and of climatic and oceanographic conditions suitable for sapropel formation. Systematic application of high-resolution magnetic analyses to future coring efforts in the eastern Mediterranean should allow determination of the original distribution of sapropels through long sedimentary sequences, which will improve our knowledge of paleoceanographic and paleoclimatic conditions that led to their formation.