Salt Tectonics of the Lisan Diapir Revealed by Synthetic Aperture Radar Images

Abstract

1.1 General setting In the Oligocene, the Africa-Arabia plate broke up separating Arabia and Sinai as individual plate and sub-plate. Since then, the Arabian plate moves northward along the Jordan Dead Sea Transform (JDST) fault more rapidly than the Sinai sub-plate. This left-lateral strike slip movement (Figure 1) had displaced Early Miocene dykes across the fault zone up to 100 km (Quennell, 1958; Freund et al., 1970; Garfunkel et al., 1981) and had resulted in the development of rhomb-shaped grabens such as the Dead Sea pull-apart basin along the main fault (Figure 1, inset). The Dead Sea Basin is the largest pull-apart along the JDST fault. It is about 150 km x 15 km. Repeated structural subsidence resulted in the accumulation of sedimentary rocks as much as 10 km thick (Garfunkel and Ben Avraham, 1996). Inside the basin, two sets of faults, both oriented roughly N-S, can be recognized (Figure 1, inset). The first set is the extension of the northern and southern segments of the JDST fault, forming the pull-apart basin (Ben Avraham, 1997; Garfunkel, 1997). These faults are accommodating most of the horizontal motion of the JDST fault. The second set is constituted by the transverse faults, oriented NNW-SSE, that cross obliquely the basin at interval of 20-30 km. Between these faults, the basin infill is slightly back-tilted toward the south with no large deformations (Gardosh et al., 1997; Ben Avraham, 1997; Al Zoubi and ten Brink, 2001). Strong deformations are known only near the diapirs formed by the salt of the Sedom Formation (2 km thick). The Sedom formation formed from the late Miocene to the Pliocene (5.3 2.5 Ma). It is composed of 75% rocksalt which arrived via marine ingression from the Mediterranean and Red Seas. This flooding has ceased, however, with a rise of intrusive rock in the Araba and Jezreel valleys (Figure 1). The rocksalt is interbeded with anhydrite and gypsum, reddish dolomite, silt, sand and clay. Since the early Miocene, the center of sedimentary deposition existed where the Lisan area (Figure 1, inset) is currently located. During the Pliocene excessive accumulation of sediment caused a diapiric upward movement of accumulated lower-density sediment to begin, thus forming several salt