MINERALOGY, GEOCHEMISTRY AND ORIGIN OF CRETACEOUS CHERT FROM WADI AL-WALA, CENTRAL JORDAN

This research is aimed at detailed investigation of the origin chert rocks in Wadi Al-Wala area in central Jordan. The chert in the area is of Upper Cretaceous in age and belongs to the widely distributed chert on the western margin of the Arabian Plate. Field characteristic structures of these cherts indicate that they occur in three forms: bedded, concretion and brecciated structure. Nine representative samples were selected for the present study. The mineralogical study shows that the chert is mainly consisted of microcrystalline quartz, calcite microcrystalline quartz, fossils and phosphatic microcrystalline quartz. The bedded chert are composed almost entirely of microcrystalline quartz and secreting organism. Geochemical investigation of Wadi Al-Wala chert shows that the content of trace elements is considerably variable, and most trace elements are low. This may indicate that the chert in the study area is resulted from the leaching of country rocks by hydrothermal solution and the evidence from submarine hydrothermal origin of silica forming this chert. This is further supported by the low MnO/Fe2O3t ratio, Cr/Zn and Ni/Zn ratios

Subsidence et effondrements le long du littoral jordanien de la mer Morte : apports de la gravimétrie et de l'interférométrie radar différentielle

The Dead Sea shore is affected by major subsidence and sinkholes hazards due to the decrease of the sea level. The frequency of resulting accidents increased during the last four decades. Those phenomena could be at the origin of the catastrophic destruction of a major salt evaporation pond on 22 March 2000. In this paper, we show the main results of eight years of research in gravimetry and radar interferometry devoted to identify potentially hazardous areas, at different scales along the Jordanian Dead Sea coast, from the metric scale (gravimetric approach) to the kilometric one (interferometric approach). (C) 2003 Academie des sciences. Publie par Editions scientifiques et medicales Elsevier SAS. Tons droits reserves