The role of hydrogeological base level in the formation of sub-horizontal caves horizons, example from the Dead Sea Basin, Israel

Abstract

This paper deals with the hydrogeological relationship between base levels of saline lakes and the formation of sub-horizontal caves. The mechanism presented here suggests that many horizontal cave levels in carbonate sequences are created adjacent to the saline lakes shorelines because of the converging of the groundwater flow above the fresh-saline water interface. The main factors that control enhanced carbonate dissolution and cave formation are high groundwater flow velocities in the shallow phreatic zone during a relative long steady state of the water table. High groundwater flow velocities are evident close to the Dead Sea due to the convergent fast flows above the shallow interface adjacent to the shoreline. The same could prevail in the case of previous paleo-lakes that existed in the basin. The synergetic combination of the above preconditions for enhanced cave formation seems to be responsible for the formation of elevation-controlled alignment of paleo-near shore cave levels in the central and southern (Dead Sea) portion of the study area. These are found on the western fault escarpment and basin margin in different stratigraphic horizons of carbonate lithology. Many of the cave levels can be linked to late QuaternaryHolocene lake levels obtained from dated lake sediments within the basin. The most common cave's elevation was found to be around 200 m below sea level which was the elevation of the Lisan Lake during part of its history. On the other hand, the Hula Basin in the northern part of the Dead Sea Basin was not occupied by saline water bodies since its formation as a base level, and thus the above preconditions for enhanced cave formation did not prevail.Indeed, this is evident by the lack of horizontal cave levels on its western carbonate margins unlike the situation in the south.

Subsurface Seawater Intrusion, an Additional Factor Influencing the Limnological History of the Dead Sea Basin

“…Kafri and Arad (1979) reported this in the northern part of the DSB. It was also discussed by Kafri et al (2007) and Kafri and Yechieli (2010). The same configuration of continental endorheic base levels below sea level and not far from the sea, are known in other places in the world and there also they are claimed to be caused by SSI.…”

Allochthonous Groundwater Microorganisms Affect Coastal Seawater Microbial Abundance, Activity and Diversity

“…About five km east of the coastline, the carbonate Galilee Mountains (Judea Group) are elevated. The Quaternary permeable filling of the coastal aquifer is recharged mainly from the east, by precipitation on these carbonate mountains (Kafri & Kessler, 2001; Paldor et al., 2020). Two fresh SGD components have been shown in previous studies: one shallow along the shoreline (Weinstein et al., 2006) and another deeper on the continental shelf, via preferential flow paths from the Judea Group aquifer (Paldor et al., 2019, 2020).…”