Stratigraphic evidence for shear in structural development of the Triassic Levant margin: New borehole data on the epicontinental to deep marine transition in Israel

Abstract

Triassic tectonic movements that include shear along a significant portion of the Levant margin, are evidenced from microfacies analysis of material recovered from the Asher-Atlit 1, Ga'ash-2, Meged-2, Devora-2 and Ramalla-1 onshore boreholes.Seismic studies showed that structural lineaments attributed to early Mesozoic extension underlie coastal and central Israel, trending NE-SW beneath southern Israel and sub-parallel to the then- extensional Palmyride basin of Syria. A more curved trend, approximately NNW–SSE, lies to the north beneath central Israel. Coast-parallel sedimentary domains formed above these lineaments, which constitute the newly formed passive margin of the Levant coast in the Triassic. The sedimentary history of these domains indicates that some were linked to each other, and others disconnected. The relative vertical movement between one domain and another is explained by activation of transpressional and trans-tensional shear movements on the underlying curved faults. These subordinate vertical movements also created the discontinuous barriers and small subsiding basins that separate the epicontinental sedimentary domain from the open Tethys, causing partial restriction necessary for the intermittent development of thick evaporites in the internal domains, alternating with a regionally suppressed carbonate system. This zone is here named the Onshore Levant Margin Shear Zone (OLMSZ).Shear was invoked theoretically in a number of models for the tectonic evolution of the eastern Mediterranean as part of a Neotethyan opening system. This paper provides rock-based evidence for such shear applicable to 20% of the eastern Levant margin in the Triassic.