AAPG Geoscience Technology Workshop

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Seismic Stratigraphy, Evolution and Regional Context of Carbonate Platforms on the Southern Margin of the Eratosthenes High, Eastern Mediterranean


3D seismic over the south-eastern margin of the Eratosthenes High in the Cyprus Exclusive Economic Zone, eastern Mediterranean Sea, has provided new insight into the origin and evolution of this prominent feature. The data show two significant and fundamentally different carbonate platforms overlying an extensional basement. Seismic stratigraphic interpretation, correlation, and comparison with regional geological analogues suggest that the older of these is of Jurassic to Cretaceous age and the younger one of later Cretaceous or Tertiary age. Together they build a succession up to c. 2200 m in thickness. Both platforms are overlain by blanketing intervals of parallel seismic facies, probably representing pelagic or hemipelagic deposits. The older Mesozoic carbonate platform exhibits a uniform, layered stratigraphy over the whole of the area, but thickens gently south-eastwards towards the steep, truncated edge of Eratosthenes in response to flexural subsidence. The younger platform, in contrast, developed an extremely complex stratigraphy comprising multiple high-frequency sequences, the geometries of which were controlled by a combination of small-scale relative sea-level variations, structural movement and substrate collapse at several scales. The younger platform forms a linear, partly-detached trend paralleling the south-eastern margin of the high for over 60 km. The outer margin of this platform became pinned to a structural break in slope, while the inner margin prograded for over 30 km towards the interior of the high with relatively little aggradation, infilling an interior basin up to 200 m deep created largely by platform growth. The older platform is truncated at the margin of the high and dissected by deep-seated faults. These transect the entire stratigraphy, possibly up to the early Messinian, and form complex corridors of subsidence in the shallower section. The resultant northwest-southeast orientated linear troughs formed synsedimentary growth structures into which the younger platform prograded. Collapse of underlying karst may have accentuated this process. Subsidence over these features also locally affects the present sea floor. Following protracted termination of the younger platform, Messinian evaporites were thrust up onto the margin of Eratosthenes, locally scouring the underlying stratigraphy. Depression of the margin of the high, with concomitant tilting of both platforms towards the southeast, appears to have been contemporaneous with arrival of Eratosthenes at the Cyprus subduction zone in the Plio-Pleistocene and overthrust of the Messinian evaporites. “Back-stripping” this event using either of the flat platform surfaces as a datum provides useful insight into the deeper structure and stratigraphy of the Eratosthenes High.