TECTONIC AND NON-TECTONIC MESO-STRUCTURES IN THE LISAN FORMATION AND EQUIVALENT RECENT SEDIMENTS OF THE JORDAN RIFT VALLEY-CHARACTERIZATION AND FORMATION MECHANISMS

Abstract

In this study, the structural elements portrayed in the recent sediments of the Dead Sea, which became exposed at its shores due to the drop in its level are described, and the mechanisms leading to their formation are elaborated. These structures include Plumes and density inversions, subaquatic gliding, seismites, undulations and wavy structures, flexures, and overpressure structures. The formation of these structures is found to be the result of different triggering factors such as Earthquakes, tectonic activity, instability of slopes, density inversion, pore fluids overpressure resulting from gas production by biochemical processes within the sediments (sulfur bacteria reduction of sulfates and oxidation of organic matter (petroleum residues)), submarine groundwater discharge, and volume changes associated with the transformation of gypsum to basinite and anhydrite, and the reversal of that transformation. Each of these triggering factors can produce more than one type of structure, depending on the prevailing composition of the sediments, its layering attitudes, grain-size distribution, porosities, and differential pressure situations within the sediment packages. The main finding of the study is the clarification of the role of gas production within the sediments as a result of sulfur bacteria activity and of the volume change processes associated with the transformation of gypsum to anhydrite and the reversal of that transformation in the formation of the mesostructures of the Dead Sea sediments.