STUDY OF BEDFORMS ON WESTERN MEDITERRANEAN CONTINENTAL SHELF

There lie many sand dunes, sand ribbons, sand ridges and sand sheets on the outer continental shelf and slope of the Gulf of Cadiz, Ebro Bay, Barcelona coast and the Gulf of Lion of western Mediterranean. The dune wavelength ranges from 150 to 760 m, whereas the height ranges from 0.1 to 5 m. The longest dune reaches 3 km, of which the highest is up to 20 m.The downstream slope dips to SW, and the height is H=0.934L^0.0063, which is lower than the Flemming slope, the global standard in 1978. About 10 to 30 m high from the seafloor, the sand ridge has its length ranging from 4 to 24 km and the width is from 1 to 2.3 km.The thickness of sand sheet is from 12 to 30 m and its formation is related to Deglacial paleoshoreline.
Regarding the Strait of Gibraltar with a depth of 350m in the center, the Mediterranean circulation generated by the exchange of the Atlantic low-salt water mass and the Mediterranean high-salt water mass is the main force for the development of the submarine sandy bed. The cross-shore ravines and the currents along them, which are widely distributed off the coast, have also plaed a role on its formation.
¹⁴C dating indicates that the large dunes and ridges were formed during the period of Deglaciation from 11ka to 13 ka BP, when surface wave tended to stabilize. Only during the period of storm wave, while the bottom flow velocity is relatively high, the modern oceanic current can drive the sediment to move and partially destroy the original sandy bedforms.