Reactivation of the Levant passive margin and the reshaping of the continental-oceanic transition during the Late Tertiary
|Category||Paleontology and Stratigraphy|
|Location||International Geological Congress,oslo 2008|
|Author||Gvirtzman, Zohar۱; Bar, Oded۱; Steinberg, Josh۱; Zilberman, Ezra۱; Feinstein, Shimon۲; Folkman, Yehoshua۱|
|Holding Date||11 October 2008|
During the Middle Eocene a large part of Arabia was covered by seawater. Shortly after this widespread transgression northwest Arabia emerged while the Levant basin accelerated its subsidence. Re-examination of the stratigraphic record in the continental margin of Israel indicates that the Levant passive margin was reactivated at that time. Subsidence rate increased after prolonged gradual decay; the shelf-slope facies transition zone was revived; faulting and magmatism resumed and the Judea Hills began to rise as a part of a regional inland uplift. Here we distinguish between two processes that reshaped the continental-oceanic transition at that time. The first phase of activity began in Late Eocene or Early Oligocene (~33 Ma) when three large structural steps with a total vertical displacement of 1.5-3km formed between the Arabian Plateau and the eastern Mediterranean. This was followed by erosional and incisional processes that flattened the inland region and formed deep canyons across the newly formed steps; and by depositional processes that started to fill the subsiding Levant basin. Interestingly, sedimentation over the past 30 Myr produced about one third of the total sedimentary thickness of the 250 Myr old Levant basin. The stress regime responsible for the vertical motions at the Late Eocene- Early Oligocene is not clear at this stage of our study. However, we do have evidence for a second phase of faulting in the Miocene, 10-20 Myr after renewal of tectonism. This phase includes some magmatism radiometrically dated to Late Miocene. One fault we documented runs along the Israeli coastal plain just east of the Jaffa basin parallel to one of the structural steps formed earlier. It is 70 km long with a vertical displacement of 200-400m. A second sub-normal EW fault with a vertical throw of up to 1000m is identified from the coastal plain offshore along 20km. During the Miocene this fault had separated the subsiding Jaffa basin from the rising Carmel block. Interestingly, both faults are traced below the Plio-Pleistocene section which is mostly undisturbed. We suggest that in conjunction with the Suez rifting, a left-lateral fault system was formed along the Levant continental margin connecting the northern tip of the Red Sea-Suez Rift to the northern tip of the Sirhan-Yizreel-Qishon Rift. This left-lateral fault system allowed Arabia to slip northward relative to the Mediterranean lithosphere for some time until plate motion jumped inland to the Dead Sea Transform. Then, both the Suez Rift and the Jaffa Basin were gradually abandoned and buried by Plio-Pleistocene sediments. Attributing a strike slip motion to a fault along the Levant margin is a new paradigm suggested here. It explains why the Suez Rift does not continue northward into the Mediterranean lithosphere and provides a mechanism for the subsidence of the Jaffa basin that was formed between two segments of the left-lateral margin-parallel fault.