Late Miocene Reefs of the Alicante-Elche Basin, Southeast Spain
Francesc Calvet, Dolors Vallès, 1996. "Late Miocene Reefs of the Alicante-Elche Basin, Southeast Spain", 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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The Late Miocene Alicante-Elche Basin, located in southeastern Spain, is filled with marls and evaporites in the depocenters and with a variety of carbonate facies (including reefs) and proximal deposits in the shallower areas. The Late Miocene deposits are composed of five lithostratigraphic units, which from base to top are Tabarca Unit, Torremendo Marls Unit, Reef Complex Unit, Terminal Complex and Gypsum and Marly Unit.
The Reef Complex Unit presents two morphologies: fringing reefs and atoll-like reefs. The fringing reefs trend E-W, between Alicante and Elche, and contain a variety of coral taxa. An asymmetrical atoll-like reef forms the Santa Pola hill and is composed of Porites.
The Terminal Complex Unit is well exposed at Santa Pola. It is composed of two distinct lithological units described here as sub-units: a basal calcarenitic sub-unit (transgressi ve deposits) and a cyclic stromatolitic sub-unit. The cyclic sub-unit consists of four main outcropping metric-scale shallowing-upward cycles bounded by erosion surfaces. The stromatolites occur at the base of each cycle and are interpreted as subtidal deposits. They grade upward into different facies (oolites, Porites patch reefs and sandy deposits).
The Late Miocene Reef System (Reef Complex Unit and Terminal Complex Unit) in the Santa Pola hill exhibits pervasive nondestructive dolomitization. The dolomite occurs as microcrystalline to subhedral-euhedral (7-45 µm) replacement fabrics and euhedral to rounded-anhedral crystal (7-30 µm) cements. The heavy stable isotope values (δ18O = +3.3 to 4.7 ‰; δ13C = +0.9 to 2.5‰) of the dolomites suggest a hypersaline influx, which may be related to the late Messinian evaporite event.
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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.