Middle Miocene coral-oyster patch reefs crop out at Murchas, south of the city of Granada in southern Spain. They are irregularly shaped masses of coral-oyster boundstone, up to 18m wide and 3-4 m high, that developed on the outer part of a homoclinal ramp, seaward of some sand shoals, in a mixed carbonate-terrigenous enviroment. In these patch reefs, oysters and hermatypic corals are the main frame-builders, their association being entirely fortuitous. Heliastrea is the predominant coral. Porites, Tarbellastraea and the phaceloid coral Mussismilia are also important components. These corals show no clear pattern in their distribution and appear embedded in a silty (bioclastic) matrix. Oysters in the reef community belong to the species Hyotissa squarrosa. They grew vertically one upon another, anchored directly to coral skeletons or, more commonly, attached to other oysters. Hyotissa is irregularly distributed but in places accounts for up to 70% of the reef. Encrusting organisms are restricted to sediments between individual coral colonies or between reefs.
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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.