AAPG Geoscience Technology Workshop

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The Evolution of the Oligocene Regional Truncation Surface and Miocene Drainage Systems That Transported Siliciclastics to the Eastern Mediterranean Basin

Abstract

A Regional Truncation Surface (RTS) has developed during the Oligocene in the northern Red Sea and the Levant regions as a result of a combined effect of two main features: 1. Formation of a ~ 3000×1500 km crustal doming occupying the northeastern sector of the Afro–Arabian continent above an asthenosphere plume migrating northward from Afar toward Armenia and the Caucasus; 2. Widespread rock exhumation and fluvial erosion that gradually truncated the northern edge of this elevated terrain, depositing the eroded clastics in the eastern Mediterranean basin. The RTS erosional surface separates two main stratigraphic divisions identified within the Cenozoic continental sequence of the southern Levant: 1. Early Oligocene lacustrine-fluvial continental conglomerates preserved in down faulted structures below the Oligocene RTS surface; and 2. Early Miocene to recent polymictic conglomerates and finer clastics, which include clasts of rock units derived from the entire stratigraphic sequence down to the Precambrian basement, deposited after the RTS development. The reconstruction of the RTS surface in a regional scale shed light on the morphotectonic stages of the Afro-Arabian breakup and the depositional history of the Levantine basin, indicating two principal phases: 1. An Oligocene slow crustal doming accompanied with reactivation of pre-existing faults and widespread exhumation and erosion. This process was active for circa 10 Ma (Early Oligocene – Early Miocene), facilitating the development of the RTS. At the late stage of this erosion cycle the Early Miocene fluvial-lacustrine Hazava Formation was deposited along the western segment of the Oligocene-Early Miocene drainage system connecting the northern part of the Arabian sub-plate with the Eastern Mediterranean basin. 2. Early Miocene main rifting phase of the Red Sea and the Suez Rift was followed by an uplift of its shoulders and incision of the drainage systems since the late Miocene. The Dead Sea Transform (DST) was initiated during the Late Early Miocene, and was emplaced along a pre-existing suture line in the lithosphere, probably initiated during past major deformation phases. This two stage model indicates the mutual genetic relationship between the Early Oligocene phase of tectonic development following the penetration of the Afar plume and the post Oligocene rifting and continental breakup of the Afro-Arabian continent. The long-lasting regional Early Oligocene to Early Miocene erosion phase (10-15 Ma) contributed a large volume of clastics transported to the Eastern Mediterranean basin, facilitated the development of siliciclastic reservoirs for hydrocarbons.