Folding Evolution at the Levant Basin, an Example of the Interplay Between Pre-Existing Weakness Zones and Regional Tectonics

Abstract

Recent giant gas discoveries within deeply buried structural highs in the middle of the Levant basin have attracted the attention of the industrial and academic communities striving to understand the origin of these structures, their relations with the tectonic history of the basin, and their evolution through time. The location of the Levant basin, at the conjunction of two plate boundaries separating the African Plate from Eurasia in the north and from Arabia in the east, further questions the relationship between the deformation in the basin and the regional plate tectonic processes. In particular: what is the origin of the deeply buried structures in the basin? Are they related to the Early Mesozoic rifting or to the Late Mesozoic – Early Tertiary Africa-Eurasia convergent phase? How are the structures in the basin related to the closure of the Tethys Ocean, to the onshore Syrian Arc fold belt (~1000 km – long fold belt extending from northern Egypt through Israel to Syria), and to the Dead Sea transform? Here we focus on a series of Syrian Arc type folds deeply buried in the Levant basin 50–200 km away from the onshore Syrian Arc mountain ridge. Observation from onshore and shallow marine subsurface, which have partly experienced erosion or non-deposition, provided important but partial information regarding the origin, timing of activity and spatial evolution of the Syrian Arc. Trying to fill up missing information, we take advantage of the continuous stratigraphic record preserved offshore in order to document folding evolution in time and space. Using >27,000 km of 2D seismic lines we interpreted axial plain of 72 folds. Combining with previous interpretation of 9 horizons, a detailed analysis of thickness variation across each fold was carried out, distinguishing between onlapping patterns, syn-tectonic depositional pattern, and post deposition truncation patterns. Altogether our study maps orientations, amplitudes and lengths of folds and determines the history of folding in the basin, distinguishing between episodes of activity comprising generation of new folds and reactivation older ones, and episodes of quiescence. Our results demonstrate that the Syrian Arc fold belt extend north-westward to more than 200 km offshore Israel, folding begun during the Late Cretaceous (Santonian) and continued for more than 80 m.y. till the Early Pliocene. The various folding episodes included reactivation of folds and generation of new ones. Interestingly, fold’s axes orientation remained relatively constant (NE to NNE) for more than 80 m.y., regardless of the ~ 150 anticlockwise rotation of Africa with respect to Eurasia since the Late Cretaceous and the development of new active plate-boundaries along the Levant borders since the Oligocene. Larger scale observations suggest the Levant folds are a part of a wider compressional belt, extending from Morocco to Syria, along the northern margins of the African-Arabian plate. Based on this observation and on our detailed analysis, we suggest the main control on folding direction is inherited extensional structures formed along Africa’s margin during Tethys opening and continuously rotate with it. However, the surrounding tectonic processes, which had minor influence on folding direction, did affect folding intensity and its spatial distribution. Folding ceased in the NW part of the basin in the Oligocene, peaked in the entire basin during Early Miocene coeval with the Red Sea-Suez rifting and convergence of Arabia with Eurasia, and gradually decreased since the Late Miocene, concurrently with the major activity along the Dead Sea Transform.

AAPG Datapages/Search and Discovery Article #90341 ©2019 AAPG Geoscience Technology Workshop, Exploration and Development of Siliciclastic and Carbonate Reservoirs in the Eastern Mediterranean, Tel Aviv, Israel, February 26-27, 2019