Nile Submarine Fan: Sedimentation, Deformation And Oil Potential

Abstract

ABSTRACT The Nile Submarine Fan is one of the largest in the world. Fan sedimentation probably began in the late Pliocene, burying Miocene carbonates and evaporites (Messinian). Salt flow due to sediment loading caused uplift of the fan's eaStern flank to form the salt dome-studded Levant platform. The fan's western flank - the Nile Cone - is deformed by minor folding, faulting, and slumping. The modern fan ends at the Mediterranean Ridge, but formerly extended further, as Nile-derived turbidites are found beneath the ridge. Tectonic and salt-flow deformation of the ridge occurs as a response to subduction of the African plate beneath the European plate. Piston cores about 10 m long show that carbonate sediment occurs west of the fan and on the Mediterranean Ridge. Channels on the Nile Cone contain thick, clean, well-sorted, coarse-medium sands. Thick sequences of thinly-bedded muddy turbidites occur between channels. On the Levant Platform are complex mixtures of thin turbidite sequences and carbonate muds, while young channel deposits are lacking. East of the platform in the Cyprus Basin are mainly grey hemipelagic muds. Thin sapropels (with up to 25% organic matter) are common in cores' from allover the area. The turbidites also contain substantial organic matter (up to 2%) mostly as plant fragments. Sapropels and turbidites form potential petroleum source beds over the entire fan; channel sands form potential petroleum reservoirs that may be most common on the Nile Cone. Up-dip migration of oil to stratigraphic traps in abandoned channels makes the middle and upper parts (apex) of the Nile Cone of interest as a potential petroleum reserve. Similar traps, as well a8 structural traps, may occur beneath the Levant Platform. INTRODUCTION In the opinion of many marine geologists today (cf. Emery, 1973) the continental rise, a thick wedge largely of terrigenous sediment at the foot of the continental slope, may contain vast new petroleum reserves. Much of the rise is built by overlapping submarine fans that grow at the ends of submarine canyons at the foot of the slope, by deposition, from turbidity currents, of sand in channels and mud on levees and between channels (Whitaker 1976). Fan growth, both lateral &vertical, is a key factor in shaping the continental rise in almost every ocean basin. Because their muds contain substantial organic matter (so are potential source beds), and their channel sands are potential reservoirs, fans deserve careful examination in the search for new hydrocarbon deposits beneath the sea (Wilde & others, 1977). In this paper we examine the geological development of one of the worlds largest deep-sea fans, the 70,000 km2 Nile Submarine Fan, that covers much of the floor of the eastern Mediterranean, off the coast of Egypt (fig. 1), and attempt to assess its potential as a locus for oil &gas deposits.