PROGRADING COASTAL SEQUENCE OF WAVE-BUILT STRUCTURES OF MESSINIAN AGE, SORBAS, ALMERIA, SPAIN

A well-preserved and virtually non-burrowed coastal sequence of Messinian age is described from the Sorbas basin, southeastern Spain. The sequence was formed as an out-building coast under the dominant influence of waves. Four main units are distinguished (Figs. 4 and 19), from base to top: 1. (1) A muddy unit with storm layers (original water depth greater than normal wave base, here ca. 10 m). 2. (2) Lower shore face, characterized by wave-rippled sandstone and parallel-laminated sheet sandstone. 3. (3) The upper shore face and beach with mega-cross-bedded conglomeratic sandstones, swash lamination and beach-rock breccia. The original depth of the sheet sandstone is estimated to be less than 9 m and of the mega-cross-bedded sandstones, less than 6 m. The mega-cross-bedded unit often shows herringbone structures, very similar to those of tidal regimes but here generated by waves and comparable to the internal structures of lunate mega-ripples of Clifton et al. (1971). The Sorbas sequence points to high-energy conditions on this coast. 4. (4) Units 1 to 3 are overlain by a fourth unit consisting of shallow lagoonal sediments with bird's foot imprints and chenier-like barrier sandstones with associated washover fans. A special feature of the Sorbas sequence is the transition from small-scale wave ripples to plane bed to mega-ripples by increasing wave energy. This sequence is comparable to that described by Davidson-ArnottDavidson-Arnott and Greenwood (1976) from the east Canadian coast, and differs from the Oregon coast sequence, described by Clifton et al. (1971). © 1979.