Application of geoelectric methods on paleoenvironments of the Qa'el-Jufr lake, southeastern Jordan Plateau

Abstract

Resistivity sounding measurements were conducted on the Qa'el-Jufr lake, southeastern Jordan Plateau, with the aim of mapping of Quaternary medium and establishing the role of palaeoclimate deposition. Data collected at 20 locations were interpreted with curve matching techniques and 1-D inversion program in order to obtain final earth models. The results of interpretation and calibration are used to construct litho-resistivity cross sections across the study area in light of the surface and subsurface geological information.The inspection of litho-resistivity cross sections reveals the presence of two main alluvial sequences. The upper sediments that attain resistivities ranging from 5 to 120Ωm and thickness ranging from 6 to 18m are a mixture of reworked aeolian and alluvial sediments. The resistivity of this unit generally decreases south and centralwards, indicating more homogeneous fine silty sand nature of the Pleistocene sediments. The lower stratigraphic unit is the shallow sand and gravel layer saturated with fresh water. This layer is characterized by its relatively high resistivity (60–400Ωm) and varying thickness (8–23m) in the northern and eastern sides and by its relatively low resistivity (20–90Ωm) and varying thickness (10–40m) in the southern side.Geoelectrical data analyses of Qa'el-Jufr basin provide an important record of Quaternary paleoenvironments for the Jordan Plateau and evidence of several significant changes in climate regime. Gravels, sands and clays characterizing the deepest sediments demonstrate significant lacustrine and high moisture phase. Then the sediments grade upwards to sands and silts that may represent a gradual drying of the lake and increased aeolian activity. These new records of the paleoenvironments provide an important context to the archaeological record of the Jordan Plateau during Quaternary. Several archaeological surveys demonstrate extensive human exploitation of lakes and springs of the major wadis along the western margin of the Rift Valley. However, very little is known about the human exploitation of the desert interior. Qa'el-Jufr sediments demonstrate significant lacustrine and high moisture phases sufficient for human exploitation of the eastern desert during the Pleistocene.