Research paperSeismo-stratigraphic evidences for deep base level control on middle to late Pleistocene drift evolution and mass wasting along southern Levant continental slope (Eastern Mediterranean)

•Plastered drift progradation was controlled by “deep base level”.•“Deep base level” periodically ca. 150 m beneath sea level.•“Deep base level” is controlled by contour current.•Oversteepening caused mass wasting during turnaround from base level fall to rise.

Since early Pliocene, a counterclockwise surface gyre transported Nile derived silt and clay northeastwards along the Levant coast, where a basinward prograding plastered drift emerged. Based on high-resolution seismic reflection data we develop a middle to late Pleistocene sequence stratigraphic scheme for this plastered drift. For creating stacked sections of the seismic data we used the common reflection surface (CRS) stack technology which enhanced lateral reflection continuity and visibility of deep reflections. The shelf comprises stratigraphic sequences which show classical, systems tract like stacking patterns of sea level controlled sequences such as offlapping forced regression deposits or diachronous ravinement surfaces which formed during base level rise. On the slope, base level was periodically located well below the wave base and thus rather controlled by hydrodynamics, presumably by high-velocity contour currents. Hence, the term 'deep base level' is introduced. The deep base level controlled especially down and backstepping slope deposits. This example shows that care has to be taken when interpreting subsurface data containing typical systems tract like seismic sequences, since such geometries do not necessarily imply shallow water deposition of the sediments. A chronostratigraphic analysis based on the seismic stratigraphy indicates that base level fluctuations were related to eccentricity driven glacio-eustatic fluctuations. Periodic mass wasting, facilitated by foreset over-steepening and possibly triggered by salt tectonics or erosion by the contour current occurred during late base level fall or early base level rise.

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