Structure and Sedimentary History of Southeastern Mediterranean Sea-Nile Cone Area

Abstract

A detailed seismic, magnetic, and sonobuoy study of the southeastern Mediterranean and Nile cone area shows the details of recent sedimentation and tectonic activity, and especially the effects of salt deformation due to movement of a late Miocene evaporite sequence. The continental rise in this area can be divided into two major subprovinces: the Nile cone and the Levant platform. The name Levant platform is applied to the rough topography extending northward from the Sinai that separates the essentially smooth Nile cone on the west from the Cyprus basin on the east. The previously reported suggestion of two offshore fans (the Rosetta and Damietta) off the present mouths of the Nile is not confirmed; rather, one major feature is present--the Nile cone. Both the Levant pl tform and Nile cone have considerable thicknesses of Nile-derived sediment, but the topographic irregularities of the Levant platform result from greater vertical and horizontal flow of evaporites than on the Nile cone. The movements of evaporites have resulted in large numbers of collapse structures and a 100 km-long salt ridge at the northern edge of the Levant platform. The offshore Miocene evaporites are acoustically detectable (reflector M) and have been mapped. They are perhaps correlative with a nearshore reflector (P) that underlies much of the Nile cone area. Reflector P is either a middle to late Miocene carbonate sequence that prograded eastward during the Messinian regression or an erosional surface cut into pre-Messinian strata. This reflector marks the top of a broad anticlinal structure off the Nile delta and Sinai Peninsula. The volume of post-Messinian sediment (essentially all is Nile derived) is about 387,000 cu km (assuming an average sediment velocity of 2 km/sec), or an average sediment thickness of 1.89 km for the area and an average sedimentation rate of 37 cm/1,000 years.