More than a thousand sinkholes have developed along the western coast of the Dead Sea since the early 1980s, more than 75% of them since 1997, all occurring within a narrow strip 60 km long and <1 km wide. This highly dynamic sinkhole development has accelerated in recent years to a rate of ~150-200 sinkholes per year. The sinkholes cluster mostly over specifi c sites up to 1000 m long and 200 m wide, which spread parallel to the general direction of the fault system associated with the Dead Sea Transform. Research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an ~10,000-yr-old salt layer buried at a depth of 20-70 m below the surface. The salt dissolution by groundwater is evidenced by direct observations in test boreholes; these observations include large cavities within the salt layer and groundwater within the confi ned subaquifer beneath the salt layer that is undersaturated with respect to halite. Moreover, the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution (Na/Cl = 0.5-0.6 compared to Na/Cl = 0.25 in the Dead Sea brine). The groundwater heads below the salt layer have the potential for upward cross-layer fl ow, and the water is actually invading the salt layer, apparently along cracks and active faults. The abrupt appearance of the sinkholes, and their accelerated expansion thereafter, refl ects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water. The eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh-saline water interface. As a result the salt layer, which originally was saturated with Dead Sea water over its entire spread, is gradually being invaded by fresh groundwater at its western boundary, which mixes and displaces the original Dead Sea brine. Accordingly, the location of the western boundary of the salt layer, which dates back to the shrinkage of the former Lake Lisan and its transition to the current Dead Sea, constrains the sinkhole distribution to a narrow strip along the Dead Sea coast.The entire phenomenon can be described as a hydrological chain reaction; it starts by intensive extraction of fresh water upstream of the Dead Sea, continues with the eastward retreat of the lake shoreline, which in turn modifi es the groundwater regime, fi nally triggering the formation of sinkholes.

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Organic‐rich Upper Cretaceous sequences in Israel were deposited in an extensive, highly productive upwelling‐linked system which prevailed along the southern Tethys margin, and lasted for ∼19 m.y. (Santonian to late Maastrichtian). An understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in Israel, representing an outer (Shefela) and an inner (Zin) facies belt. The nature of the upwelling system, and its effect on the sedimentary record, is related to two basic environmental parameters, namely paleoproductivity intensity and oxygen levels at the bottom. The assessment of these parameters and their interrelationship has been performed through the development of paleontological (foraminiferal) criteria, which are independent of the organic matter content. Following the establishment of these criteria, it is concluded that the productivity reached its maximum intensity during the late Campanian, which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin. This distribution is expressed in varied lithology (organic‐rich carbonates, phosphorites, and siliceous rocks) at the core of upwelling and a uniform lithology (organic‐rich carbonates) at the margin of this system. The uniform lithology of the Maastrichtian in both basins, composed of organic‐rich carbonates, is ascribed to a gradual weakening of productivity. The bottom conditions in the inner belt during the late Campanian (the time of maximum surface productivity) were near anoxic, changing to more aerated (dysaerobic) conditions during the early Maastrichtian. In the outer belt a more aerated bottom (dysaerobic) prevailed throughout the late Campanian to late Maastrichtian. The elevated organic matter content in both basins reflects the overall environment of high productivity; its actual variations, however, seem to be unrelated to changes in surface productivity and bottom oxygen levels.

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