SEDIMENTARY STRUCTURES AND SEDIMENT TRANSPORT ACROSS THE CONTINENTAL-SLOPE OF ISRAEL FROM PISTON CORE STUDIES

The continental terrace of Israel consists of Nile-derived sediments. They are classified into three major groups, according to their struct ures: (1) irregularly to wavy laminated, coarse-grained sediments (qua rtz and skeletal debris) of the flat outer shelf and upper bend of the slope (10-20% of the bulk) which are influenced by currents. These se diments are bioturbated to various degrees. Smectitic silty clays (80- 90%) form two structural groups: (2) laminated, turbiditic sediments w hich accumulate on the slope, particularly in the canyons of the north ern slope. Irregular, wavy, thickly laminated, coarse-grained sediment s of the upper slope and canyon heads merge downslope with parallel, t hinly laminated, fine-grained sediments. Toward the foot of the slope and on the adjacent deep-sea floor lamination becomes indistinct and t he sediment is visually homogeneous. (3) Slump-generated mud lumps of various size which accumulate on the lower slope and along the transpo rt axes of the canyons. These are the most visible evidence for large- scale slumping mass movement. Transportational and depositional proces ses are far more intensive over the steep northern continental slope o f Israel, and especially in its canyons than over the gentle southern slope. Very stiff overconsolidated sediments unconformably overlain by the ubiquitous recent silty-clayey sediment were cored on steep secti ons of the middle continental slope and along the canyon walls. Their preconsolidation stress values suggest that these sections were former ly overlain by more than 40 m of sediment and now are exposed by slump ing. The downsliding slabs usually disintegrated into small fragments although several huge fragments could be identified along the canyon a xes.