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Sediment Transfer and Play Concepts Associated with Large Infilled Valleys in the Southern Mediterranean as a result of the Interplay between Tectonic and Sea Level.

Andrea Moscariello, Carlo Nicolai, Arnoud Slootman, and Antonio Benvenuti

Large and deep valleys are known to occur in the Tertiary and Quaternary record of the marginal regions of the Mediterranean.

These features reaching depth of up to 570 m below present sea level and width up to 6 km, are interpreted to have an erosional origin associated with sea level low stands occurring during early Oligocene and then late Miocene. During the Late Miocene, in correspondence of the Messinian salinity crisis, many of the larger incisions are thought to have been generated and/or reactivated (e.g. Nile, Sahabi, Rhone, Afiq). In the Mediterranean region, similar elongated v-shaped features, developed as a result of movement associated with thrusts tectonic and subsequent vertical readjustments (e.g. horst and graben structures). In both cases these features have acted as important conduits of terrigenous sediments which have been accumulated in a offshore position in places developing up to thousands meters of sediments.

The morphological study of both transversal and longitudinal profiles, the study of sedimentary succession pre-dating the incision as well as the one infilling the valleys, the reconstruction of the tectonic evolution during the valley formation, can be used to predict the presence and the quality of reservoir rocks and possible hydrocarbon systems associated with related distal clastic sedimentary wedges.

In this study we describe, compare and contrast two examples of large deeply incised ‘valley’ systems developed in different geographical and tectonic settings.

The first example is the Sahabi valley a 200 km long incision, reaching 750 m depth below present sea level formed during the late Miocene in northern Libya. The second is a complex valley network developed in the westernmost offshore of Sicily, in the Egadi islands area.

Despite the very different genetic origin and tectonic evolution of these prominent geological features, in both case studies the sedimentary infills display very similar characteristics suggesting similar sedimentary processes and therefore accumulation of large amount of deposits in a downstream location.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013