Haim Shulman

Fault and salt tectonics in the southern Dead Sea basin

Abstract The sedimentary fill of the southern Dead Sea basin contains large amounts of salt and halokinetic features. In this study, the relationship between these halokinetic features and major faults was investigated. The basis for the interpretation was seismic reflection profiles from the southern Dead Sea basin. The seismic profiles were used to construct a series of two-way time structural maps and two-way time isochore maps for the various reflectors and sedimentary sequences in the area; such maps are published for the first time in the Dead Sea basin. Electrical and geophysical logs from wells in the area were used to relate the mapped reflectors and sequences with geological units. The seismic profiles give evidence to the largest subsidence that had occurred during the late Pliocene and that the amount of subsidence was much larger in the deeper part of the basin than in the median block. This difference in subsidence is partly a result of salt withdrawal. There are two ways to explain the present day structures of the southern Dead Sea basin. Either (1) basement faulting took place before salt deposition or (2) basement faulting took place during or after salt deposition. In this research, a combination of the two is favored. In particular the influence of the movement on the longitudinal fault separating the deeper part of the basin from the median block (Sedom fault) on salt flow is outlined. The much larger offset on the Sedom Fault in the northern part of the area is thought to be the reason for salt piercing only in this part of the area. It is also suggested that the Sedom Fault has experienced strike–slip movements and not only vertical movements. A ridge, the Neot Hakikar Ridge, is shown to divide the southern basin into two sub-basins. The presence of this ridge and the salt tectonics triggered motion on a listric fault (Amazyahu Fault) in the early Pleistocene. The listric curvature of the Amazyahu Fault induced antithetic faulting recognized in the Pleistocene sediments. Earlier studies have suggested that the depocenter migrated to the north. The isochore maps, however, show that locally the depocenter shifted to the southeast. This shift is probably caused by the movement along the Amazyahu Fault and the withdrawal of salt. A much larger amount of salt than previously thought is identified and it is suggested that salt reaches as far south as the Iddan Fault.

Seismic reflection profiles across the southern Dead Sea basin

Abstract The main structural and stratigraphic elements that form the Southern Dead Sea basin (SDSB), which is part of the Dead Sea transform fault system, have been broadly delineated with various degrees of certainty by a number of researchers. The recent exchange of seismic data between Israel and Jordan enable us to fill in some of the dashed lines and eliminate some of the question marks that appear on the previously published geological cross-sections. Two east–west seismic time sections, one from each side of the international border that dissect the basin, have been selected, composed and interpreted. A remarkable correlation of the three major sedimentary sequences that form the basin-fill (Miocene clastics, Pliocene salt and Pleistocene–Holocene clastics and evaporites) has been established between the lines and, hence, across the entire width of the SDSB. The Miocene and Pliocene series are cut off in the east by the Ghor–Safi fault that is the equivalent of the western Sedom fault, thus, indicating that all three major structural steps, known to exist in the west: (1) rim block, (2) intermediate block and (3) deep block, occurs also in the east, and that the SDSB is indeed a full graben. The Ghor Safi fault is the northern extension of the major Arava strike-slip fault. The very thin Miocene (if at all) and lack of Pliocene salt in the eastern intermediate block, unlike the western one, suggests that the Ghor–Safi fault was initiated earlier then the Sedom fault. Salt is present over the entire width of the basin but does not exceed the 900 m that were penetrated by the Sedom Deep-1 borehole. The salt is conformable with the overlying thick Pleistocene and except for the Sedom diapir, no halokinesis phenomena have been recognized to be associated with both units.

Salinity sources of Kefar Uriya wells in the Judea Group aquifer of Israel. Part 1—conceptual hydrogeological model

Abstract In the Yarkon–Taninim groundwater basin, the karstic Judea Group aquifer contains groundwater of high quality. However, in the western wells of the Kefar Uriya area located in the foothills of the Judea Mountains, brackish groundwater was locally encountered. The salinity of this water is caused presumably by two end members designated as the ‘Hazerim’ and ‘Lakhish’ water types. The Hazerim type represents surface water percolating through a highly fractured thin chalky limestone formation overlying the Judea Group aquifer. The salinity of the water derives conjointly from several sources such as leachates from rendzina and grumosols, dissolution of caliche crusts which contain evaporites and of rock debris from the surrounding formations. This surface water percolates downwards into the aquifer through a funnel- or chimney-like mechanism. This local salinization mechanism supercedes another regional process caused by the Lakhish waters. These are essentially diluted brines originating from deep formations in the western parts of the Coastal Plain. The study results show that salinization is not caused by the thick chalky beds of the Senonian Mt Scopus Group overlying the Judea Group aquifer, as traditionally considered but prevalently by aqueous leachates from soils and rock debris. The conceptual qualitative hydrogeological model of the salinization as demonstrated in this study, is supported by a quantitative hydrological model presented in another paper in this volume.

Late Proterozoic – Paleozoic Geology of the Golan Heights and Its Relation to the Surrounding Arabian Platform

. Weissbrod, T., 2005. The Paleozoic in Israel and Environs, in J. K. Hall, V. A. Krasheninnikov, F. Hirsch, H. Benjamini, and A. Flexer, eds., Geological Framework of the Levant, 2: Jerusalem, p. 283-316. Weissbrod, T. and Sneh, A., 2002. Sedimentology and paleogeography of the late Precambrian early Cambrian arkosic and conglomeratic facies in the northern margins of the Arabo-Nubian Shield. Isr. Geol. Surv. Bull., 87. Wolfart, R., 1967. Geologie von Syrien und dem Lebanon, 326 p. Gebruder Borntrager, Berlin.

Structural styles along the Dead Sea Fault

The Dead Sea fault is a left-lateral transform plate boundary separating the Arabian Plate and the Sinai sub-plate. Motion along the fault is not pure strike-slip and the direction of the plate boundary changes several times resulting in areas of transtension and transpression. This is evident by the variable morphology and structure. The fault is divided into two sections which differ by a reversal in the large-scale asymmetry – the southern section from the Gulf of Elat to south of Lebanon (where the eastern side is usually higher than the western side) and a section continuing northward from Lebanon to the Taurus mountain range in Turkey (where the western side is mostly higher than the eastern one). Along strike variations in topography and structure subdivide the southern Dead Sea fault into five segments. From south to north, these are the Gulf of Elat, Arava, Dead Sea, the Sea of Galilee and the Hula Valley. Deep Asymmetric pull-apart basins, which tend to become shorter and younger in age northwards, formed between left-stepping fault segments of the Dead Sea fault. These basins can be found in topographically lower areas and are separated by structural saddles. Both extensional and compressional features can be found along many of the basins themselves, suggesting that the tectonic regime is more complex than suggested in the simple models.

Potential Use of New Geological Findings for Water Exploitation in the Lower Jordan Valley

The Lower Jordan River Valley is part of the Dead Sea Transform. From a geological point of view it comprises a plate boundary between the western African Plate and the southern Arabian Plate. From a political point of view the area acts as a ‘triple junction’ of three nations: Jordanian, Israeli and Palestinian.