FLUID FLOW AND SOLUTE TRANSPORT ASSOCIATED WITH THE DEFORMATION OF A PULL-APART BASIN: THE SEA OF GALILEE, ISRAEL

Pull-apart basins along the axis of large continental transforms are subject to several forces causing groundwater migration, each producing a characteristic flow pattern. Several techniques were combined to quantify the magnitude of these forces and the discharge pattern of groundwater and solutes into the Sea of Galilee. This is the lowest freshwater lake on Earth, and is located within the deep Kinarot pull-apart basin in the northern part of the Dead Sea Transform. Multi-channel seismic reflection data in the Kinarot basin define two distinct zones beneath the lake: 1) a deep graben (> 7 km) that underlies most of the lake, bounded by steep north-south longitudinal strike-slip faults, but with no internal faults; and 2) shallow pre-rift units underlying the northwestern faulted part of the lake. In the late Pleistocene, during a short high-stand phase of former Lake Lisan, saline water percolated into the subsurface of the Kinarot Basin. Since recession of Lake Lisan and the instantaneous formation of the fresh-water Sea of Galilee, the previously intruded brine has been flushed backwards towards the lake. The spatial distribution of brines in the bottom sediments, delineated by a TDEM survey, follows the geological structure and indicates that, in the graben, shallow brine is entrapped in low permeability sediment and near the northwest margins the brine is deep. Calculations based on a one-dimensional solute transport model reveal that solute flux from the graben area is less than 3% of the total solute flux towards the lake (before artificial diversion). This indicates that diffuse brine upflow and compaction-driven flow are negligible in the solute balance of the lake. Active faulting in the area underlying the northwestern part of the lake results in extensive topography-driven flow of brackish water that discharges at fault intersections, both onshore and offshore.