Tectonic evolution of the Eastern Mediterranean and its implications for the Messinian salinity crisis

Güneş, Pınar (2017) Tectonic evolution of the Eastern Mediterranean and its implications for the Messinian salinity crisis. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The interpretation of a comprehensive set of high-resolution multi-channel seismic reflection profiles, multibeam bathymetry data and the litho- and bio-stratigraphic information from exploration wells across the Antalya Basin and Florence Rise revealed important conclusions on the Miocene to Recent tectonic evolution and the Messinian Salinity Crisis depositional history of the eastern Mediterranean Basin. This study clearly demonstrated the presence of a 4-division Messinian evaporite stratigraphy in the eastern Mediterranean, similar to that observed in the western Mediterranean, suggesting the existence of a similar set of depositional processes across the Mediterranean during the Messinian Salinity Crisis. However, the stratigraphic and depositional similarities of the evaporites between the eastern and western basins do not necessitate synchroneity in their depositional histories. The fact that the only saline water source for the eastern Mediterranean is the Atlantic Ocean and that the Sicily sill creates a physical barrier between the eastern and western Mediterranean impose several critical conditions. A simple 2-D model is developed which satisfies these conditions. The model suggests that the eastern and western basin margins experienced a nearly synchronized gypsum deposition associated with the initial drawdown of the Mediterranean level, followed by the resedimentation in the deep basins of the terrigenous and early evaporite deposits as the drawdown intensified. The synchroneity of evaporite deposition across the eastern and western basins broke down as the Sicily Gateway became largely subaerial during a period when the Calabrian Arc area experienced uplift associated with slab break-off: the Sicily sill must have remained within a “goldilocks” zone to allow the right amount of saline water inflow into the eastern Mediterranean so that evaporites (massive halite) could be deposited. During this time, the sea level in western Mediterranean was at the breach-level of the Sicily sill, thus no evaporite deposition took place there. The model suggests that further restriction of the inflow occurred across the Betic and Rif gateways as these regions also largely became subaerial associated with the uplift of the Gibraltar Arc region caused again by the lithospheric slab break-off. However, similar to the Sicily Gateway, the Betic and Rif gateways must also have remained within the “goldilocks” zone to allow the right amount of saline water inflow into the western Mediterranean so that massive halite could be deposited. The re-opening of the Betic and Rif gateways reflooded the western Mediterranean first, then the eastern Mediterranean allowing the deposition of a mixed evaporite-siliciclastic unit, followed by the transgressive sediments with a distinctive brackish water Lago Mage fauna. The interpretation and mapping of the tightly-spaced high-resolution multichannel seismic reflection profiles clearly improved our understanding of the Late Miocene–Recent tectonic and kinematic evolution of the Antalya Basin and Florence Rise and it is relationship with Cyprus-Eratosthenes collision zone, along the plate boundary between the African Plate and the overriding Aegean- Anatolian Microplate. The pre-Messinian Miocene structural architecture of the Antalya Basin and its southwestern extension into the Florence Rise is characterized by a very prominent broadly northwest-southeast striking and largely southwest verging fold thrust belt, with occasional northeast verging back-thrusts. During the Messinian a number of prominent thrusts remained active; however, numerous thrusts whichwere active during the pre-Messinian Miocene became inactive. During the Pliocene–Quaternary the stain was partitioned into five broadly northwest-southeast trending morpho-tectonic domains, each delineated by a distinctive seafloor morphology: (a) a domain across the inner and western Antalya Basin is dominated by extensional faults, (b) a domain immediately south of the extensional faults, is characterized by contractional structures, (c) a halokinetic zone in southwestern Antalya Basin north of the foothills of the Anaxagoras Mountain is characterized by numerous positive flower structures beneath a corrugated seafloor, (d) a domain across the crestal portion of the Florence Rise is dominated by prominent inversion structures, and (e) a domain across the northeastern and southwestern margins of the Florence Rise characterized by positive flower structures.

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