Environmental geology in Israel

Conclusion The environmental topics reviewed above and in the following articles represent only the tip of the iceberg. Nevertheless, they might shed some light on the existing environmental problems which must be resolved.     

Bulk motion of ultrarelativistic conical blazar jets

Allowing for the conical shape of ultrarelativistic blazar jets with opening angles of a few degrees on parsec-scales, we show that their bulk Lorentz factors and viewing angles can be much larger than the values usually inferred by combining their flux-variability and proper-motion measurements. This is in accord with our earlier finding that such ultrarelativistic (Lorentz factor,  Γ > 30  ) conical jets can reconcile the relatively slow apparent motions of Very Long Baseline Interferometry (VLBI) knots in TeV blazars with the extremely fast flows implied by their rapid γ-ray variability. This jet geometry also implies that de-projected jet opening angles will typically be significantly underestimated from VLBI measurements. In addition, de-projected jet lengths will be considerably overestimated if high Lorentz factors and significant opening angles are not taken into account.     

Quantized Ray Theory for Non-Zero Focal Depths

The relation between p-Δcurves for surface and deep focus sources is investigated in order to construct synthetic body wave seismograms for non-zero focal depths by the quantized ray theory algorithm. The transformation of a surface focus p-Δ curve into a deep focus p-Δ curve is denned in terms of that curve which corresponds to surface focus rays reflected from the depth at which the deep focus is located. By analogy with the geometry of the surface focus formulation, paths of integration to obtain absolute travel-time and velocity-depth curves can be denned in the p-Δ plane. Explicit inversion from deep focus data is possible only when the velocity-depth structure above the depth of focus is known. Through a comparison of short period quantized ray theory synthetic seismograms with similar Cagniard-de Hoop computations, it is shown that quantized ray theory can be used for accurate predictions of body wave amplitude behaviour corresponding to a wide range of focal depths.     

From mass‐wasting to slope stabilization – putting constrains on a tectonically induced transition in slope erosion mode: a case study in the Judea Hills,Israel

Calcrete‐coated remnants of landslide debris and alluvial deposits are exposed along the presently stable hillslopes of the Soreq drainage, Judea Hills, Israel. These remnants indicate that a transition from landslide‐dominated terrain to dissolution‐controlled hillslope erosion had occurred. This transition possibly occurred due to the significant decrease in tectonic uplift during the late Cenozoic. The study area is characterized by sub‐humid Mediterranean climate. The drainage hillslopes are typically mantled by thick calcrete crusts overlying Upper Cretaceous marine carbonate rocks. Using TT‐OSL dating of aeolian quartz grains incorporated in the calcrete which cements an ancient landslide deposit, we conclude that incision of ~100 m occurred from 1056 ± 262 to 688 ± 86 ka due to ~0·3° westward tilt of the region; such incision invoked high frequency of landslide activity in the drainage. The ages of a younger landslide remnant, alluvial terrace, and alluvial fan, all situated only a few meters above the present level of the active streambed, range between 688 ± 86 ka and 244 ± 25 ka and indicate that since 688 ± 86 the Soreq base level had stabilized and that landslide activity decreased significantly by the middle Pleistocene. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrogeology,water quality,and microbial assessment of a coastal alluvial aquifer in western Saudi Arabia: potential use of coastal wadi aquifers for desalination water supplies

Wadi alluvial aquifers located along coastal areas of the Middle East have been assumed to be suitable sources of feed water for seawater reverse osmosis facilities based on high productivity, connectedness to the sea for recharge, and the occurrence of seawater with chemistry similar to that in the adjacent Red Sea. An investigation of the intersection of Wadi Wasimi with the Red Sea in western Saudi Arabia has revealed that the associated predominantly unconfined alluvial aquifer divides into two sand-and-gravel aquifers at the coast, each with high productivity (transmissivity?=?42,000 m²/day). This aquifer system becomes confined near the coast and contains hypersaline water. The hydrogeology of Wadi Wasimi shows that two of the assumptions are incorrect in that the aquifer is not well connected to the sea because of confinement by very low hydraulic conductivity terrigenous and marine muds and the aquifer contains hypersaline water as a result of a hydraulic connection to a coastal sabkha. A supplemental study shows that the aquifer system contains a diverse microbial community composed of predominantly of Proteobacteria with accompanying high percentages of Gammaproteobacteria, Alphaproteobacteria and Deltaproteobacteria.     

Palaeoenvironments of the Continental Intercalaire fossil from the Late Cretaceous (Barremian-Albian) in North Africa: a case study of southern Tunisia

Through the Late Cretaceous, the southern shore of the Tethys Ocean migrated north and south over short distances. These vicissitudes are documented in the Continental Intercalaire, a long series of mainly non-marine sediments deposited in which dinosaur or other reptiles tracks and floral fossils are common across southern Tunisia (North Africa). A combined taxonomic, climatological, and palaentological studies provides independent lines of evidence for reconstruction of palaeoenvironments. The Bou Hedma/Boulouha and Sidi Aïch/Douiret Formations from southern Tunisia span the later part of the Late Cretaceous. During the Late Cretaceous the Tunisian territory was an archipelago, thus a particularly suitable area for a more detailed study. We investigated the area’s plant palaeo-biogeography, using fossil wood, with information from both a literature survey and investigation of new samples. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. The climate during the accumulation of Barremian-Albian deposits in this region is inferred to have been warm and humid.     

Effect of diagenesis on clay mineralogy and organic matter in the Tunisian southern subsurface

This study aims to follow the effect of the diagenetic transformations on the clayey fraction and the organic matter of the Tunisian southern sub-surface. 61 samples from oil well named NWA-1 were recuperated for series of analyses. This study follows a comparative approach between the mineralogical, geochemical and petrographic studies. To discuss results from a statistical viewpoint, the Principal Component Analysis (PCA) was applied in order to find out any correlation between different components. The associated minerals quartz, feldspar, calcite, pyrite, anhydrite, gypsum, dolomite and olivine are also detected. These associated minerals remove by-products by the illitization reaction. The Index of Crystallinity (IC) of illite shows that, except some anomalies, the studied samples are between the epizone and the anchizone. Downward, samples show the effect of diagenetic processes and weak signs of low-grade metamorphism. As regards to the organic matter, values of Tmax range between 333°C and 463°C. On the other hand, potential hydrocarbon compounds (S2) show low values compared to those of (S1); but they maintain a similar variability from 0.63 to 21.12. SEM observations and X-ray microanalyses supported the formation of authigenic micro-quartz. The PCA of clay minerals, chemical components, and the depth shows three different populations. Feldspar, chlorite and quartz make up a population positively correlated with the depth. The second population seems to be indifferent to depth variation; it is made up of two sub-populations: the population of illite, gypsum and anhydrite, which is obtained by a counter clock rotation of depth population; and the population of pyrite, kaolinite, olivine phyllosilicate, which is obtained by an anticlockwise rotation of depth population. Third, the population of smectite, calcite and dolomite is inversely proportional to the depth variation. On the other hand, the PCA of TOC, Tmax, HI, S1, S2 and the depth make up a homogenous statistical population following the depth evolution.     

Parity and disparity between two Chama oysters: the reproductive biology of the Indo-Pacific C. pacifica Broderip,invasive to the Mediterranean Sea; and C. savignyi Lamy,indigenous to the Red Sea

The Indo-Pacific oyster Chama pacifica Broderip, 1835 (Mollusca, Bivalvia, Chamidae) is rarely found in the Northern Red Sea reefs of Eilat (Gulf of Aqaba), where it is outnumbered by its indigenous congener, Chama savignyi Lamy, 1921. The influx of Eritrean biota from the Red Sea into the Mediterranean Sea via the Suez Canal has led to the formation of massive Chama oyster beds along the Eastern Mediterranean shore. However, unlike the Northern Red Sea, the Eastern Mediterranean Chama beds are dominated by C. pacifica oysters, whereas C. savignyi is absent from this region. In an attempt to understand this difference in their respective distribution, the reproductive biology of both species was compared. Histological analysis of the male and female gonads, monitored monthly from March 2009 to August 2010 in both regions, revealed a similar reproductive cycle, comprising six stages: onset of gametogenesis, advanced gametogenesis, ripe, ready to spawn, spent and sexual rest. Female gonads demonstrated an additional, seventh stage – restoration, coinciding with inferred spawning of ripe gametes. Both species were found to be dioecious spawners, with a single, annual, temperature-dependent inferred spawning period. Chama pacifica was found to reproduce efficiently in maximal Mediterranean seawater temperatures not experienced by the Northern Red Sea Chama populations. This study demonstrates the high invasive potential of an oyster species despite its rarity in its source region.     

Bar structure in an arid ephemeral stream

This study describes the structure of gravel bars in Nahal Zin, an ephemeral stream in the Negev desert. The internal structure of the bars was examined along trenches and in shallow pits. Gravel sheets and unit bars form during transporting flow events in the main channel, on intra-bar channels and near bar heads. Unit bars are dominated by the Go facies. Compound bars develop from accretion around, and modification of, unit bars. Compound bars are active under the current flow regime and the average depth of the fill layer is about 35 cm. The structure of compound bars is dominated by Gm (massive), containing large amounts of sand. The second most common facies is clast-supported, openwork, and well sorted sediments of the Go (pebbles) facies. Bar formation, and the development of the range of facies evident in the bars is controlled by sediment supply, particularly the high volumes of sand-sized sediment, the passage of gravel sheets and bedforms during floods, and the lateral and vertical instability of the channel. Repeated scour and fill events have produced a diverse arrangement of facies, with numerous erosional contacts between depositional units. Lateral and downstream shifts in the pattern of scour and fill due to flow and antecedent conditions shape the channel morphology and bar internal structure. Ephemeral river bars differ from those of humid and proglacial rivers in terms of the dominant facies present, the arrangement of the facies within the bars, and the sedimentary structures developed within the depositional units and on the bar surface.