Geosciences Dept. Seminar: Tectonic and Sedimentary Processes of the Northern Gulf of Aqaba-Elat

Abstract:

The Northern Gulf of Aqaba-Elat (NGAE) is the northeast extension of the Red Sea, located at the southernmost part of the Dead Sea Fault, at the transition zone between the deep en-echelon submarine basins of the Red Sea and the shallow subaerial basins of the Arava Valley (Israel and Jordan). The research aims to compile an earthquake record for the past ~40kyr, locate the on-land continuation of the recently dominant active fault segment (the Avrona Fault), and characterize the top sedimentary cover across the NGAE in order to check the effect of tectonics on the sedimentary column. Field data was collected from three major domains: paleoseismic trenching on-land, coring in the shallow shelf (up to 100 m water depth) and coring in the deep marine basin (up to 600 m water depth). Trench observations lead to locating the on-land continuation of the marine Avrona Fault and suggest it ruptured the surface in two historically known earthquakes (1068 AD and 1458 AD).

High resolution grain size analysis of marine cores demonstrate discrete anomalies of sediment reworking events. Radiocarbon age constraints of these anomalies yield a set of dated events coinciding in ages, which demonstrate independent validation for their tectonic/seismic origin. Thus, a late Pleistocene to Holocene earthquake record for the Northern Gulf of Aqaba-Elat is compiled, dating back to ~40 ka. These high resolution grain-size and radiocarbon age determinations were used to compile a 3.5-D (3.5 dimensional) sedimentary model of age-depth-grain size for the top 3-5 meters of the NGAE, which conforms to- and validates the tectonic structure detailed by previous authors. It reveals a correlation between sediment age, dominant grain size and active tectonics: fine-grain, old sediment (up to 40 ka in the west and 8 ka in the east) in the margins, and young coarse sediment (up to 2-4 ka) in the middle of the basin, where most of the active sediment transportation (and tectonic activity) take place. The dominant sedimentary activity follows the migration of the active tectonic fault segments from east to west between 40 ka to present. A spatial/temporal evolutionary model is presented for the sedimentary processes of the NGAE since 40 ka to present, which correlates to the tectonic processes, suggesting three phases of development: (a) Late Pleistocene 40 to 12 ka;
(b) Early to Mid-Holocene 12 to 5-4 ka; (c) Late Holocene 5-4 ka to present.

Seminar Organizer: Dr. Ravit Heled