Accelerated subsidence and sedimentation in the Levant Basin during the Late Tertiary and concurrent uplift of the Arabian platform: Tectonic versus counteracting sedimentary loading effects

摘要

Since the Middle Eocene, the northwest Arabian Platform has been emerging from the water and rising above sea level, whereas the adjacent Levant Basin has been subsiding and accumulating a thick sedimentary section. This study investigates these opposing vertical motions and the relative roles of tectonic-driven versus isostatic adjustment forces involved. Such a distinction is strongly dependent on a reliable estimation of the paleobathymetry, which in pelagic environments may vary substantially. We use two different methods to estimate the paleo-water-depth in the deep Levant Basin in the Tertiary time. Isostatic balancing calculations with the adjacent inland region are employed to estimate the paleo-water-depth in the deep Levant Basin in the Middle Eocene, just before the commencement of the Late Tertiary tectonic phase. For later periods, we use morpho-structural elements such as abrasion surfaces and incised canyons to build laterally changing topo-bathymetry profiles. Our results indicate that in the Mid-Eocene water depth in the deep Levant Basin was 2-3.5 km, which gradually decreased to 1.5 km today. Based on these results, our analysis shows that the enhanced subsidence of the Levant Basin reflects an isostatic response to sedimentary filling of a pre-existing deep-water basin with no involvement of a downward tectonic force. On the contrary, we suggest that the regional tectonic force was upward, counteracting a sedimentary loading effect. Further regional implication of this understanding is that the cause for uplifting and exposure of the N W Arabian Platform in the Late Tertiary extended far westward beyond the inland region.