Abstract: This is a study of the sedimentary and facies conditions in the Neogene of the southern part of the Iskenderun basin. The continous downwarping of this basin during neogene times resulted in the accumulationof marine sediments of miocene age up to a thickness of 1300 meters ,andof continental sediments of probable pliocene age up to a thickness over1200 meters. It is possible that the deep neritic sediments of miocene age,towards the centre of the basin, in the form of blue marls / marly claystone hame constituted a source-rock for petroleum, whereas a part ofthe sandy banks in the shallow neritic facies towards the border of thebasin may have constituted a reasonably good reservoir - rock. So it seemspossible that there exists petroleum-accumulation in these sandy parts iffavorable structures can be discovered. The presence of petroleum in themiocene rocks is proven by the petroleum seepages near the village ofÇengen aind by the gas-seepages near Yanantaş. It is however probablethat these sandstones ,and sands wedge out too rapidly towards the centreof the basin, so that it will be impossible to find any sufficiently porousrocks in the parts of the basin where we might expect some favorablestructures although it is possible that the sandy beds in the upper partsof the miocene, wedge out somewhat farther from the basin-border thanthe lower miocene sandstones. It must be excluded to expect any accumulation in the reef-limestone of the Miocene, because those limestonesare only to be found on the border of the basin, where they constitute afringing eerf.