The structure of the Dead Sea basin

Abstract

The Dead Sea basin is located along the left-lateral transform boundary between the Arabian and Sinai plates. Its structure and history are known from surface geology, drilling, seismic reflection and other geophysical data. The basin comprises a large pull-apart, almost 150 km long and mostly 8–10 km wide, which is flanked by a few kilometres wide zones of normal faulting. The basin formed at about 15 Ma or earlier, close to the beginning of the transform motion, and it reached about half its present length before the end of the Miocene. A strong negative gravity anomaly records a thick sediment basin fill: > 5 km under half its length, reaching a maximum of ≥ 10 km. The fill includes a few km of salt (ca. 6-4 Ma) which forms several diapirs. At any one time large parts of the basin subsided simultaneously, but the site of fastest subsidence seems to have shifted northward. Sedimentation rates reached at least hundreds of metres per million years or more in the Miocene, and ≥ 1 km/Myr in later periods. The basin structure is dominated by longitudinal faults: intrabasinal faults which delimit the pull-apart and which are the extensions of the major strike-slip faults north and south of the basin, and normal faults which extend along the basin margins. The latter faults express a small component of extension across the basin, whereas the pull-apart resulted from the much larger lateral motion along the basin. In addition, transverse faults divide the pull-apart into several segments with somewhat different histories. The pull-apart grew by becoming longer parallel to the transform motion. At shallow levels this was probably achieved by normal slip on transverse listric faults while the fill between them was little deformed. The crust under the basin was stretched and thinned during basin lengthening, which caused its subsidence. Basin formation was accompanied by uplifting of its flanks by ≥ 1 km. Sparse igneous activity occurred along the basin and its flanks. Its presence suggests a thermal anomaly in the lower lithosphere beneath the basin and adjacent parts of the transform.