| Abstract: | The stable isotopic compositions of organic C and N and the organic carbon (OC) content of the Oman Margin (ODP Site 724) sediments, ranging from Pliocene to Early Pleistocene in age, are used to infer palaeoproductivity in the area. At the boundary between the Pliocene and the Pleistocene, the amount of organic matter preserved is low compared to other periods before and after this transition period. This low OC content is associated with depleted N and C isotope values. This may indicate low primary productivity as a result of a diminished supply of nutrients caused by weak coastal upwelling. Higher amounts of OC, in conjunction with enrichment in the isotopic compositions of both organic C and N before and after the Pliocene-Pleistocene transition period, are likely to be a consequence of an increase in primary productivity, which resulted from a higher nutrient supply. However, a higher amount of OC may have resulted from enhanced preservation. The enhanced preservation may have resulted from an intrusion of highly saline waters from the Res Sea and Persian Gulf and/or restricted circulation. |
