Slice Tectonics in the Eastern Mediterranean Basin

Abstract

Two systems of counterclockwise-converging and northeastward-curving left-lateral shears, which belong to a global pattern of spiraling geosutures, have played a major role in shaping the Eastern Mediterranean. The first one, the Pelusium system, composed of the Dead Sea, Pelusium Line, and Qattara-Eratosthenes shears, is primarily responsible for the structure of the eastern Levantine Basin and the Levant. The other one, composed of the Pliny-Sirte and the Antalia shears, forms the divide between the western Levantine and Ionian basins. Several other geosutures, such as the Coastal Fault of Israel, are also found within the Pelusium system, but they are not necessarily shears. Depositional basins were formed along the axes of the lithospheric subslices that are bound by the main shears. The troughs of these basins systematically hug their eastern boundary shears, whereas their basinal fill moderately rises and thins toward the west; excessive sediment accumulation has taken place in these troughs since Paleozoic or even late Precambrian time. The Levantine Basin, with its 15-16 km thick sedimentary sequence, is therefore considered a relict of the Tethys Ocean, which is of an appreciably older age than hitherto considered. The emphasis given in this chapter to the longitudinal tectonic elements following the slice tectonic concept does not diminish the role of the Tethyan (east-west to west-northwest) fault system in shaping the Mediterranean Sea. The Tethyan faults belong to a ramp valley-like compressional system in which a south to north crustal-shortening process occurs. Some of the Tethyan faults have been left laterally shifted because of movements along northeast-trending geosutures. The systematic northward counterclockwise convergence movement of the subslices between the sinistral shears results in oblique collision. The compression resulting from this collision generates the famous northeast-trending folds of the Syrian Arc, which are predominantly asymmetric to the southeast. The lithospheric slice that is bounded by the South Atlas shear and the Pelusium system (N-I slice), includes among its other components the Eastern Mediterranean Basin. This slice is moving inward, into the eye of the global pattern of spiraling geosutures (the Alpine-Himalayan Belt), at a slower rate than the N-2 slice (which is limited by the South Atlas and the Bay of Biscay geosutures and which includes, among its other components, the Western Mediterranean). The fundamental geologic contrast between the Eastern and Western Mediterranean basins could be genetically related to the differences in the geometries and in the rates of movements that are suggested to exist between these two slices.