Akiva Flexer

Relative Sea Level Changes During the Cretaceous in Israel

Detailed lithologic, microfaunal, and biometric investigations, using relative abundances, diversity indexes, and duration charts of ostracods and foraminifera, allowed the recognition of sea level changes during the Cretaceous of Israel. Three major transgressive-regressive sedimentation cycles occur on the northwest margins of the Arabian craton. These cycles are the Neocomian-Aptian, which is mostly terrigenous sediments; the Albian-Turonian, which is basin marls and platform carbonates; and the Senonian, which is uniform marly chalks. The cycles are separated by two major regional unconformities, the Aptian-Albian and Turonian-Coniacian boundaries. The sedimentary cycles are related to regional tectonic and volcanic events and eustatic changes. The paleodepth curve il ustrates the gradual sea level rise, reaching its maximum during the Late Cretaceous, with conspicuous advances during the late Aptian, late Albian-Cenomanian, early Turonian, early Santonian, and early Campanian. Major lowstands occur at the Aptian-Albian, Cenomanian-Turonian, Turonian-Coniacian, and Campanian-Maastrichtian boundaries. This model for Israel agrees well with other regional and global sea level fluctuations. Four anoxic events (black shales) accompanying transgressions correspond to the Cretaceous oceanic record. We hypothesize the presence of mature oil shales in the present-day eastern Mediterranean basin close to allochthonous reef blocks detached from the Cretaceous platform.

Late cretaceous paleogeography of northern Israel and its significance for the Levant geology

Abstract Senonian-Maastrichtian sediments in northern Israel are characterized by a thick sequence of homogeneous chalk containing profuse planktonic foraminiferids and coccolithophorids. The occurrence (or absence) of chert, bitumen, quartz grains, phosphate content, the variations of plankton-benthos ratio, the generic and family composition of Foraminifera and thickness variations indicate that the sediments were deposited on an outer shelf area in a very non-turbulent pelagic sea. This sea, part of the Tethys ocean which covered all the Levant during the Late Cretaceous, became epicontinental in the vicinity of the Arabo-Nubian Massif. Thickness of sediments is a function of submarine depressions, wedge-out occurring towards uplifted areas which by and large are also present-day structures, except for the western part of the area. Here, non-sedimentation or sediments of reduced thickness can be explained by deposition on a steep part of the continental shelf beyond the shelf break or by erosion due to submarine currents on the outer shelf. The depth of the sea changed with time. Santonian sediments were deposited in water of relatively great depth (several hundred metres) which decreased during the Early Campanian and attained a minimum in very Late Campanian time. During Early to Late Maastrichtian time subsidence recommenced. Three marine facies belts are differentiated in the Late Cretaceous chalks of the Levant countries. The data of these rocks in northern Israel (part of the extreme western belt having poorly-defined continental affinities) were utilized in the palaeogeographic analysis of the Levant region.

The senonian succession in israel—Lithostratigraphy, biostratigraphy and sea level changes

Senonian rocks in Israel consist predominantly of homogenous chalk containing abundant nanno- and micro-fauna as well as horizons rich in megafossils. A synthesis of all available faunal data for the Senonian of Israel and the Levant indicates a series of transgressions and regressions. The sea level fluctuations are compared to the known global sea level data for the Senonian. A good correspondence is established between Israel and the global pattern throughout the entire interval with the exception of the Maastrichtian.

Late Cretaceous-Early Tertiary Development of Depositional Basins in Samaria as a Reflection of Eastern Mediterranean Tectonic Evolution

The Mt. Scopus Group in Israel consists of chalk, chert, phosphorite, organic-rich carbonate (locally known as oil shale), and shale of Coniacian- Paleocene age. The rock sequence includes several rock units, including the En-Zeitim Formation (with the related Har-Zefat Member), Mishash Formation, and Biriya Formation. Within the study area, the thicknesses of these rock units vary considerably (100-600 m), reflecting the geometry of basins that formed after the end of the Turonian and evolved during the early-late Senonian. Following the opening of the South Atlantic ridge during the Late Cretaceous, the convergence between Afro-Arabia and Eurasia generated a regional compressive regime throughout the eastern Mediterranean region. This compression formed the Syrian arc fold system that is characterized by a general northeastern direction; however, preexisting northeast- and northwest-directed fold and fault patterns responded differently in various areas. Chains of depocenters aligned along the northwest-directed faults subsided during different time increments. The bituminous chalk of Mt. Scopus Group preserved in these depocenters is considered a genuine petroleum source rock with a total organic carbon content of 10-15 wt. %. The tectonic pattern and the three-dimensional distribution of the impermeable sediments of Mt. Scopus Group are also important for groundwater exploitation in the area.

The Nubian Sandstone aquifer in the central and northern Negev, Israel: delineation of the hydrogeological model under conditions of scarce data

Abstract The Cl − content of ground water in the central and northern Negev ranges between 250 mg 1 −1 in the Beer Sheva area and 1600 mg 1 −1 near the Egyptian border, where the water is also thermal with high concentrations of sulphates and iron. During the last few years, groundwater resources in the heavily populated Beer Sheva area have become endangered by a continuing process of salinization. In the course of the present work, it was found that, in the study area, ground water flows through a multiple aquifer system including the Jurassic-Lower Cretaceous Kurnub Group and the Upper Cretaceous Judea Group aquifers. Because of the absence of impermeable beds at the boundary between the two groups, brackish ground water flows from the Kurnub Group into the overlying Judea Group aquifer. Moreover, numerous faults discovered in the subsurface facilitate lateral inflow of Kurnub ground water into the Judea aquifer. By interpreting new lithostratigraphic data from the Kurnub Group and seismic surveys made in the study area, it is shown that the Kurnub aquifer extends far beyond the hitherto known boundaries and contains an additional estimated volume of 51 × 10 9 m 3 of paleowater. The limiting factors of its exploitability are groundwater depth and salinity. The rational exploitation of the Kurnub paleowater may prevent salinization of the overlying Judea Group aquifer.

The interaction of two major old water bodies and its implication for the exploitation of groundwater in the multiple aquifer system of the central and northern Negev, Israel

Abstract In the Beer Sheva region of the Negev desert, the only significant fresh groundwater is contained within the Judea Group carbonate aquifer. It is found that this aquifer holds two distinctly different old water bodies. One such groundwater body has evolved in equilibrium with the carbonate aquifer rocks after being recharged during the Holocene in the Hebron Mountains north of the study area. At present, modern recharge, as denoted by the tritium and radiocarbon contents, is very minor. A subtle ‘piston effect’ generated by contemporary replenishment is discussed in representative hydrographs in Beer Sheva wells. Another groundwater body identified in the Judea Group aquifer derives from the underlying Kurnub Group aquifer. The regional artesian Kurnub Group aquifer (Nubian Sandstone) contains an older and brackish groundwater body which has been recharged in Sinai during Pleistocene pluvials. Faulting in the Beer Sheva region facilitated hydrologic contact between the two aquifers. Exploitation of the Judea Group has released confining pressures and resulted in the intrusion of Kurnub Group water into the overlying Judea Group carbonate aquifer. This process is most significant in those wells drilled close to major faults where salinity increases with pumping. The intruding water originating from the Kurnub Group sandstone aquifer has not yet equilibrated chemically with the carbonate host. The low pH and high temperatures that have been encountered indicate continuing and very recent intrusion. In the Beer Sheva area, in the absence of direct significant modern recharge (as determined from tritium and 14 C values), all waters should be considered as paleowaters that are being mined. A complete revision of the hydrologic concept by which the multiple aquifer system can be exploited is required, to take into account the fact that the fresh Judea Group groundwater is actually an old (Holocene) water body intruded by brackish and older (Pleistocene) water along fault zones.

The sequence stratigraphy of Mesozoic successions in the Levant margin, southwestern Israel: A model for the evolution of southern Tethys margins

The Levant margin, in the subsurface of the eastern Mediterranean area, formed during the early Mesozoic following rifting and subsequent opening of the southern Tethys Ocean. This work describes the stratigraphic evolution of the shelf edge and slope for this margin in southwestern Israel and in the adjacent Mediterranean Sea. The study is based on the interpretation of 27 wells and 92 seismic reflection lines totaling 2000 km (1243 mi). Depositional sequences and sequence boundaries of the Jurassic and the Cretaceous age inferred from seismic reflection terminations, wireline-log stacking patterns, lithofacies, and biostratigraphic data. Six low-order and 22 high-order depositional cycles were identified. Their stratigraphic architecture reflects shifts of depocenters from the basin to its margin, controlled by eustasy and regional subsidence. Aggrading and backstepping of carbonate platforms in the Levant shelf is associated with relative rises in sea level. Progradation of siliciclastic and carbonate slopes toward the basin is related to relative drops in sea level. The stratigraphic framework of the Levant margin presented here is in accordance with recently published Mesozoic sequence stratigraphy of the Arabian platform, therefore, it may be used as a working model for reconstructing other rifted Tethyan margins in the region. This study further emphasizes the reservoir potential of Jurassic and Cretaceous deep-water lowstand wedges offshore Israel, where extensive exploration efforts are currently occurring.

Mid-turonian anoxic event in Israel — a multidisciplinary approach

Abstract Bituminous marls of the Daliyya Formation with up to 2% total organic carbon content, from the Galame quarry, Mount Carmel, northern Israel were studied. A great part of the organic matter is composed of exceptionally abundant dinoflagellate cysts. These sapropelic sediments were deposited in oxygen-depleted, quiet waters in a shelf basin. The massive encystment and good preservation of the cysts, chitinous test linings of foraminifers and the occurrence of pyrite also indicate reducing environments. Primary production was stimulated by upwelling of nutrient-rich oceanic waters, influx of fresh-water and derivates from the Mount Carmel volcanism. A middle Turonian age was determined on the basis of planktonic foraminifers ( Helvetoglobotruncana helvetica zone) and ostracodes ( Cythereis rawashensis kenaanensis zone). The anoxic event in the studied area post-dated the main phase of the global Late Cenomanian-Early Turonian anoxic event OAE-2, due to a pre-existing structural high in this region.

A comparison of the eastern and western sides of the Sea of Galilee and its implication on the tectonics of the northern Jordan rift Valley

Abstract The Sea of Galilee divides two Neogene basins which are characterized by largely continental clastic sequences and basalt flows. Stratigraphic differences between the two basins are discerned. A comparison of the stratigraphy of both sides of the Sea of Galilee does not support the postulated 107 km left-lateral movement. Although some small strike-slip faults might exist, most faults are of a gravity dip-slip type. A postulated ridge trending NNE, buried under the Sea of Galilee, might have had a stratigraphic influence on sediment distribution between the eastern and western sides.

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.