Genesis and depositional environment of organic-rich sediments in the Neogene organic-rich sediments from the Aleksinac deposit (Serbia): Part B

To determine the characteristics of the palaeoenvironment that affected organic richness, the Neogene organic-rich sediments in the Upper layer of the Aleksinac deposit (Dubrava block, Serbia) were examined. The studied samples are presumed to be of andesitic to felsic origin, with evidence of volcanic activity. Sediment generation was influenced by hydro-thermal fluids, which promoted the productivity of aquatic organisms and led to organic enrichment. Clastic input brought trace and rare earth elements into the basin. Palaeoenvironmental indicators derived from concentrations of major, trace, and rare earth elements show good accordance with organic geochemical data obtained in previous detailed studies, indicating deposition of the sediments in an anoxic lacustrine environment of variable salinity under warm, arid, and semiarid/semihumid climatic conditions. Such settings favoured primary bioproductivity in the lake, whereas a stable, stratified water column with highly reducing bottom water enhanced organic matter preservation. The lowering of total organic carbon content was mainly controlled by more humid episodes that promoted clastic influx and decreased organic matter concentration, rather than by changes in anoxic redox conditions.