AAPG Geoscience Technology Workshop

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New Data of the Geodynamic Evolution of the Eastern Mediterranean

Abstract

The eastern Mediterranean, in the Neo-Tethyan collision zone, consists mainly of the Mesozoic terrane belt and the adjoining oceanic crust complex of the northern part of the Sinai plate. The recent discovery of large hydrocarbon deposits has attracted considerable attention to this region. We examined structural stages (from the Triassic to the Neogene-Quaternary) in the following tectonic-geophysical zones: (1) regions of continental crust in the Nubian, Arabian and Sinai plates, (2) oceanic crust of the eastern Mediterranean, and (3) thinned continental crust of the Mesozoic terrane belt. Combined analysis of gravity, magnetic, paleomagnetic, thermal, tectonic, structural and paleogeographical data sheds light on the tectonic evolution of this region. The Kiama paleomagnetic hyperzone of inverse polarity discovered in the oceanic crust of the eastern Mediterranean suggests transport along transform faults from the eastern part of the Tethys Ocean. Probably, this oceanic crust terrane (Lower – Upper Permian) is the most ancient block of the oceanic crust recognized till present. The Kiama hyperzone zone is discordant to the strike of the terrane belt and the Aegean-Anatolian plate. Seismic data indicate that to the west of the Kiama zone, a tectonic flexure developed in sedimentary cover that may have generated a fault contact of the western side of the Kiama zone with the adjacent basaltic crust of normal polarity (probably dating to the Middle Cretaceous). An integrated analysis of geophysical, radiometric and petrological characteristics demonstrates that the Kiama paleomagnetic zone is bounded by younger ocean floor rocks. Analysis of the Moho discontinuity map developed for the eastern Mediterranean by use the seismo-gravity analysis indicates that the crustal thickness of the Kiama zone is thicker than adjacent areas. The easternmost Mediterranean is characterized by significant lithospheric thickness (up to 125 km) whereas in surrounding regions this value is about 100 km. This fact testifies the significant geodynamic activity during the closing of the Neotethys Ocean. The last derived thermal flow data indicate that over the Kiama hyperzone an extremely low value was registered – 15 mW/m2. The discrepancy between the terrane belt and the Nubian-Arabian foreland, oceanic crust, and terrane belt testify to the allochthonous nature of the eastern Mediterranean. Analysis of the satellite-derived gravity field pattern and airborne observed magnetic field and their transformations (spatial derivatives and entropy maps) combined with facies analysis indicate an intricate tectonic pattern. In particular, a clear isolation of the Sinai plate from the Arabian and Nubian plates is visibly traced. The derived maps are accompanied with the newly developed tectonic schemes. These data help gain a better understanding of the dynamics of hydrocarbon basins in the continental and shelf depressions, as well as the deep depressions of the eastern Mediterranean where gas deposits in zones of oceanic crust have only recently been exploited. The last revised paleomagnetic map constructed for the eastern Mediterranean region indicates that the tectonic evolution of the region needs to be reconsidered. The Mesozoic terrane belt and most of the oceanic crust of the eastern Mediterranean are allochthonous and were transferred along the series of transform faults from the east. The western terranes were transferred probably from the region to the northwest from the modern position of the Persian Gulf. The integrated tectono-geophysical and paleogeographical specifics of deep zonation call for a reevaluation of regional criteria for oil and gas exploration. For instance, the performed geophysical-geological analysis indicates that the eastern Mediterranean hydrocarbon deposits may be a continuation of the Red Sea hydrocarbon province.