When Two Salt Tectonics Systems Meet: Gliding Downslope the Levant Margin and Salt Out-Squeezing From Under the Nile Delta

摘要

At present, salt tectonics in the Levant Basin comprises extension along the continental slope and folding and thrusting in the deep basin. However, here we show that the shape, the age, and the amplitude of deformation in the extensional and contractional domains do not fit the paradigm of "updip extension and downdip contraction." Deep basin shortening is not parallel to continental margin extension; it is younger and stronger. We propose that while extension of the Levant continental slope is an expression of basinward gliding, the deep basin shortening belongs to the circum-Nile deformation belt (CNDB) propelled by out-squeezing of salt from under the Nile delta. However, despite the independent driving forces, the two deformation systems seem to affect each other. In the southern part of the basin where the two systems meet, the NW gliding of the continental slope is restrained by the NE motion of the CNDB and vice versa. Interestingly, the beginning of folding along the CNDB (similar to 2 Ma) coincides with the establishment of a continental shelf offshore Israel. We thus propose that these two apparently independent phenomena express maturity of the Nile delta that had reached a size and shape sufficient to trigger salt out-squeezing and to form a continuous continental shelf from the Nile to Israel. This continuity allowed shelf alongshore sediment transport that further propagated the Israeli shelf northward and westward.