The genesis and development of large-scale erosion surfaces – insights from the Sinai-Israel micro plate

The geomorphological process creating the birth and development of large-scale erosional surfaces remains somewhat unclear. In this regard, new insights on the process leading to the creation of such large-scale surfaces were revealed during intensive study on the morphotectonic evolution of the Sinai-Israel micro-plate.

A major erosion surface developed during the Oligocene – Early Miocene, (34-20 Ma) in the northern Red Sea and southern Levant as a result of the combined effects: the formation of an ~3000 km × 1500 km crustal dome above the Afar plume, affecting the northeastern sector of the Afro-Arabian continent, and widespread fluvial erosion that gradually truncated the northern edge of this dome. The truncation of the northward tilted Sinai-Israel plate exposed the Precambrian basement rocks at its southern tip, while a series of sandstone and carbonate units were exposed at its central and northern sector. The Syrian Arc anticlines, developed in the Late Cretaceous, were deeply truncated, exposing their Triassic – Jurassic section. During this event, a geological section, estimated to be 2000-500 m, was removed from the entire region. The Oligocene Regional Truncation Surface (RTS) developed by a continues fluvial and chemical erosion acting on a gentle uplifted region, on which the rate of tectonic uplift was smaller than the ability of the erosive agents to erode and transport the eroded products out of the region, deposited them in the eastern Mediterranean basin. These clastic sediments are holding large-scale gas reservoirs. The reconstruction of this erosive surface is important for detection of the tectonic activity that predates the plate separation of the Sinai-Israel plate and the development of the Dead Sea Transform, initiated in 18-16 Ma along a preexisting suture line. The development of the truncation surface was followed by the deposition of Early Miocene fluvial sediments, deposited within broad channels and valleys, gently incising the original Oligocene erosion surface.

General uplift, tectonic depressions and dome structures developed during the Middle Miocene to Early Pleistocene (16–1.5 Ma), locally deforming the general flat relief left by the previous erosional stage. This rapid tectonic activity promoted the breakup and evolution of the Sinai-Israel microplate generated the development of a deeply incised drainage system, bordered by large-scale cliff. This new erosive pattern is best demonstrated by the deeply incised valleys developed within the core of the Syrian Arc anticlines. The interaction between the anticlinal structure and the Oligocene truncation surface is dictating the configuration of the oval valleys, while their development as deeply incised valleys evolved during younger tectonic events in the Miocene. Another modification to the former flat landscape was caused during the 1.5-1 Ma tectonic event that uplifted and tilted the Negev region toward the Dead Sea Rift. At this stage, a new drainage system was developed, deeply incising the former flat surface. However, despite these modifications, the original Oligocene erosive surface is still dominating the present skyline in the entire Middle East. During most of the time, the landscape evolutionary processes were active under arid climates, contributing to good preservation of diverse geomorphological features.