Évolution de la biodiversité et de la distribution paléobiogéographique des échinides sur les côtes atlantiques du Maroc du Tortonien à l'Actuel


fr Geodiversitas 30 (1) - Pages 211-232

Published on 28 March 2008

Evolution of the echinoid biodiversity on the Morocco Atlantic coast from the Tortonian to the Present-Day.

The bibliographic synthesis of the works devoid to the Mio-Pliocene and the Quaternary of the Atlantic coast of Morocco has been completed by new field investigations in Agadir and Safi areas. This work has allowed to identify three Tortonian echinoid species or sub-species (Cidaroid, Schizaster sp., Scutella striatula), a single one for the Messinian (Cidaroid), eight for the Pliocene (Cidaroid, Psammechinus miliaris, Clypeaster aegyptiacus, Rotuloidea fimbriata, R. fimbriata fonti, Echinocyamus pusillus ?, Echinolampas hoffmanni, Prospatangus sp.), five for the Pleistocene (Paracentrotus lividus, Clypeaster rangianus, Heliophora orbiculus orbiculus, H. orbiculus semisol, E. hoffmanni) and two for the Holocene (Echinus sp., P. lividus). On a biostratigraphical point of view, the Tortonian strata are characterized by S. striatula, the Pliocene ones by R. fimbriata and C. aegyptiacus and the Pleistocene deposits by H. orbiculus and C. rangianus. Messinian and Holocene strata are biostratigraphically badly characterized by echinoid markers. As far as the paleobiogeography is concerned, the spatial distribution of echinoids reveals a conspicuous provincialism which during the Pliocene opposed a Mediterranean province with Clypeaster altus-aegyptiacus, extending to the Atlantic coast via the sub-province of the south-Rifian strait, and a West-African Atlantic province with Rotuloidea fimbriata, limited to the North at the Casablanca area. The Mediterranean water vein which extends, in the Present-Day, in the Atlantic Ocean through Gibraltar does not show a significative inheritance of the uppermost Neogene South-Rifian water vein. Indeed, the Clypeaster and Echinolampas taxa abundant in these areas during Miocene and Pliocene have today totally disappeared from the northern coast of Morocco.

Keywords :

Tortonian, Messinian, Pliocene, Quaternary, Morocco, Atlantic ocean, echinoids, biogeography, biodiversity

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