Les indices climatiques du Pléistocène supérieur et de l’Holocène des formations quaternaires de la côte atlantique (Rabat-Témara, Maroc)

Abstract

The area of Rabat-Témara is known for a very important quaternary sedimentary archives, which are found in the form of marine and continental deposits preserved along the Atlantic coast and also, as sedimentary filling in the cavities shaped in the calcarenites coastal ridge. The last dates on these sediments show that this karst filling covers the upper Pleistocene and the Holocene. The excavation of the cave of El Hahroura 2 shows a fairly homogeneous filling over the 3m. This constancy at the filling indicate a more or less identical climate from the layer 11 to the layer 2, which is mainly arid, with slight variations expressing wet and fresh climatic pulsations. The upper part of El Harhoura, attributed to the recent Neolithic, agrees with a setting in an environment corresponding to a return to wet climatic conditions. The study of the environments of the prehistoric caves shows that at the time of the installation of the humans on the Atlantic coast, the quaternary landscape is similar to the present one. The formation of the most littoral ridge was made during the isotopic stage 5, with formation of dunes fixed by vegetation and cemented by a carbonate bond. This ridge, more or less parallel to the coast, formed under wet climatic conditions already described in the filling of caves, with nevertheless warm recurrences. The installation of this ridge will contribute to the closure of the pre-existing coastal plain and leads to the formation of an oulja, open to the sea in favor of the lagoons. This oulja will host high-level marine deposits characterized by a mixture of marine and continental fauna. The dates of the deposits of the oulja and the internal ridge, in progress, will enable us to determine the age of cave digging; they will also help to determine the climatic phases prior to the settlement of prehistoric men in the region of Rabat-Témara.