Sedimentary dynamics and topographic controls on the tidal-dominated Zagra Strait, Early Tortonian, Betic Cordillera, Spain
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Puga Bernabeu, Ángel; Braga Alarcón, Juan Carlos; Aguirre Rodríguez, Julio; Martín Martín, José ManuelMateria
Betic Cordillera Tidal-dominated straits Mediterranean-Atlantic connections Very large cross-bedding Submarine dunes
Date
2023-03Referencia bibliográfica
Rossi, V. M., Longhitano, S., Olariu, C. and Chiocci, F. (eds) Straits and Seaways: Controls, Processes and Implications in Modern and Ancient Systems. Geological Society, London, Special Publications, 523, 427 - 451.
Abstract
The approximately 350 m-thick stratigraphic succession of the Zagra Strait records an important oceanographic phase of basin interconnection between the Atlantic Ocean (Guadalquivir Basin) and the Mediterranean Sea through the Betic Cordillera (southern Spain) during the early Tortonian. The Zagra Strait developed as a narrow structurally controlled marine corridor. The sedimentary dynamics of the Zagra Strait were interpreted from the sedimentological features observed in six sections at well-exposed outcrops. Large-scale (>10 m high) compound dunes and compound–dune complexes moved parallel to the strait margins under strong tidal currents generated by tidal amplification at the strait entrance and exit. Dune distribution can be divided into three sectors with different palaeocurrent migration, lithological and topographical characteristics. The northern and central sectors were separated by a deep depression (>75 m water depth) where tidal currents were weaker and dunes were not generated. The southern sector records a relative decrease in current strength compared with the northern and central sectors, and a significant increase in the bioclastic content in the sediment. Terrigenous content generally increases towards the strait margins, and reciprocally, carbonates towards its axis. The closure of the Zagra Strait resulted from tectonic uplift of that part of the Betic Cordillera before the late Tortonian.