The stable isotopic compositions of organic C and N and the organic carbon (OC) content of the Oman Margin (ODP site 724) sedimenk, 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 dimtni&ed supply of nutrients caused by weak coastal upwelling. Higher amounk of OC, in conjuxtion with emkhment 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 Red Sea and Persian Gulf and/or restricted circulation. R&uunC -Les compositions des isotopes stables du carbone et de l'azote organtque ainsi que la concentration en carbone organique des sediments de la marge d'Oman (site ODP 724), d'&ge Pliocene a P&stoc&ne inf&eur, sont utili&es pour 6valuer la paleo-productivite de la region. A la limite Pliccene/Pleistocene, la quantit$ de mat&e organique pr&erv&e est faible compar& a d'autres p&odes juste ankrieures ou post&ieures, Les concentrations peu &v&s en carbone organique sont associees a des rapports isotopiques appauvris en carbone et azote. Cela pour&t indiquer une productivite prima&e basse resultant de la diminution de rapport d'&menk nutritifs cause par la kible remontee c&i&e. A l'inverse, les plus grandes quantiks de carbone organique et les valeurs plus elev-6es des rapports isotopiques du carbone et de l'azote avant et apr&s la transition Plio&ne/P&istoc&ne ont probablement une cause inverse. Neanmoins, de plus grandes quantites de carbone organique pourraient @lement We la cons6quence de l'intrusion d'eaux fortement salees provenant de la Mer Rouge et du Golfe persique et/au de circulation restreinte.