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Abstract

Three-dimensional seismic data from the continental margin offshore Israel (eastern Mediterranean) show several large-scale mounded structures interpreted to be clastic intrusions. The structures are confined to the Zanclean (early Pliocene) and lower Gelasian (late Pliocene) intervals and restricted to an area of 40 × 20 km (24 × 12 mi) along the Afiq submarine canyon, a former depositional fairway of Oligocene age. Most of the features are circular to oval in plan view, range from 0.5 to 2 km (0.3 to 1.2 mi) in diameter at their base, and are flanked by kilometer-scale depressions interpreted as regions of sediment depletion. In cross section, the mounds are as much as 400 m (1300 ft) in height and have flank dips of as much as 20–25°. The largest structures may reach as much as approximately 0.75 km3 (0.17 mi3) in volume and represent economic hydrocarbon reservoirs.

Well data and direct hydrocarbon indicators show that the mounds are predominantly composed of gas-saturated sandstones along their flanks and crests, whereas their center is heterolithic. Petrophysical interpretation indicates the presence of chaotic and remobilized sediments in the core of the structures. The relationships of the mounds to the overburden exhibit both depositional and deformational geometries (e.g., onlap, forced folding). The proposed model for their formation is hydraulic jacking up of the overburden by forceful vertical and lateral intrusion of clastic sediments during shallow burial. Several episodes of intrusion alternated with the deposition of fine-grained clastic sediment during the Zanclean and early Gelasian to create the complex structures presented in this chapter. The suggested model has implications for the understanding of the trapping mechanism and reservoir properties of the mounded structures and needs to be incorporated in exploration and production strategies.

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