Evidence from nitrogen isotope ratios for enhanced productivity during formation of eastern Mediterranean sapropels

摘要: THE formation of horizons organic-rich sediment (sapropels) in the eastern Mediterranean during Holocene and Upper Pleistocene1 has been ascribed2 to enhanced preservation organic carbon bottom waters rendered anoxic by restriction deep-water renewal, either lowered sea level glacial maximum conditions3 or presence low-salinity surface derived from increased runoff2,4. A second possibility is that sapropels formed as a consequence higher settling fluxes matter caused primary production connected with runoff5,6. Here we report core close mouth Nile, have significantly lighter nitrogen isotope ratios (15N/<14N) than intercalated marl oozes. We adduce evidence these large differences cannot be variable mixtures marine terrestrial having different isotopic compositions, extent type post-depositional alteration. The are consistent, however, utilization dissolved nitrate sapropel formation, implying were ultimately high plankton production, which led floor.