Miocene Patch Reefs from a Mediterranean Marginal Terrigenous Setting in Southwest Turkey
Anthony B. Hayward, Alastair H. F. Robertson, Terence P. Scoffin, 1996. "Miocene Patch Reefs from a Mediterranean Marginal Terrigenous Setting in Southwest Turkey", Models for Carbonate Stratigraphy from Miocene Reef Complexes of Mediterranean Regions, Evan K. Franseen, Mateu Esteban, William C. Ward, Jean-Marie Rouchy
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Small patch reefs, up to 8 m high and 40-50 m across, occur locally within Early Miocene terrigenous clastic sediments in the Kasaba basin of Southwest Turkey. The patch reefs are located within a prograding fan delta-type succession, interpreted as part of a foreland basin, underlain by a collapsed Mesozoic carbonate platform. The Miocene foreland basin developed in response to southeasterly thrusting of a thick pile of allochthonous thrust sheets, the Lycian Nappes, representing Tethyan continental margin and oceanic units. Well preserved, undeformed patch reefs are present in the Upper Miocene Kasaba Formation; poorly preserved patch reefs also occur in the Lower Miocene Kemer Formation.
The patch reefs developed directly on gravel and coarse sand fans, without pioneer coral development. The primary framework builders (Favites, Tarbellastraea, Montastraea, Porites) progressively changed in morphology upwards from dish-shaped, tabular corals, to large branching colonies. The patch reefs are asymmetrical in plan view, with more extensively developed off-reef facies on the landward flanks, where reworked reef-derived talus interfingers with terrigenous sediment. The primary coral framework was encrusted by a secondary framework of coralline algae and encrusting foraminifera. The reefs were modified by a variety of boring and grazing organisms (e.g., bivalves, sponges, bryozoa), producing abundant sediment that accumulated in areas between individual coral colonies and as off-reef flanking facies.
The patch reefs are interpreted to have formed on the abandoned, submarine toes of coastal alluvial fans, following switching in sediment supply and/or change in relative sea level. In Southwest Turkey, wave and storm activity in the microtidal Mediterranean Sea was mainly onshore, reworking reef-derived material landwards. The patch reefs were later buried by alluvial fans, overthrust during final emplacement of the Lycian Nappes, then exhumed following uplift and erosion during Plio-Quaternary time.
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Miocene carbonates are intensively explored and locally exploited for hydrocarbons in parts of the Mediterranean regions. The outcrop models presented in this publication provide excellent analogs for the highly productive Miocene carbonates from Iran, Iraq and Gulf of Suez and for smaller reservoirs in other localities. Lessons learned in the outcrops of the Mediterranean regions are applicable as well to Miocene carbonate reservoirs. The Miocene outcrops in Mediterranean regions can serve as models for the relationships between carbonate reservoirs, pre-evaporitic basinal sediments, and overlying evaporites. Additionally, the Miocene carbonate rocks exposed in the Mediterranean regions serve as important analogs for ancient carbonate-rimmed basins with or without basinal evaporites.