Spatial and temporal reconstruction of the late Quaternary Dead Sea sedimentary facies from geophysical properties

Abstract

The sedimentary sequences that accumulated within various lakes that occupied the Dead Sea Basin since the Pliocene, contain a detailed record of the climate and tectonic history of the area. Until recently, most of the information about these paleo-lakes was derived from exposures along the marginal terraces of the current Dead Sea (lake), focusing mainly on the last Glacial Lake Lisan and the Holocene-modern Dead Sea. The International Continental Drilling Program (ICDP) recovered a series of cores in the northern Dead Sea Basin, both in the deep depocenter (300 m water depth) and in shallower waters near the current shore. Here, we present downhole logging measurements that were used to provide continuous records of petrophysical properties at depth and to reconstruct lithological profiles. The study highlights how logging data can overcome gaps in drilled-core recovery and be used to examine subsurface geology on a regional scale. Gamma ray, resistivity and velocity wire logs were examined to infer a log-derived lithofacies. The reconstructed profiles presented in this study constitute a first attempt to link deep central settings of the basin with marginal sedimentary sequences. Three main facies were identified in the boreholes including: (Bartov et al., 2002) Finely laminated sequences of mudstones interbedded with siltstones to sandstones; (Bartov et al., 2003) Medium to thick bedded mudstone to sandstone: and (Bartov et al., 2007) Evaporites (e.g. halite and gypsum with some intervals of detrital sediments). The formations that were previously defined along the marginal terraces of the Dead Sea: the Holocene Ze'elim Formation, the last Glacial Lisan Formation, the last interglacial Samra Formation and the early to mid-Pleistocene Amora Formation are identified in the boreholes. A spatial correlation is established providing the stratigraphic architecture of the sedimentary structure beneath the Dead Sea during the late Quaternary. This paper combines geophysical and lithological data and provides the base for subsequent studies on facies interpretation.