Une flore d'âge ougartien (seconde partie du quaternaire moyen) dans les monts d'ougarta (Sahara Nordoccidental)

The analysis of a series of samples carried out in the versicoloured conglomerates of the “Oued Farès” (Ougarta Mountains, western Sahara) gives the first conception of what the vegetation was like in this region throughout the Ougartian (second phase of the Middle Quaternary). Superimposing on the herbaceous layer which widely represents the desert-like xerophyte element, the arborescent flora bears the imprint of diverse influences: a typical Mediterranean influence (Quercus ilex, Quercus coccifera, Pinus halepensis, Cedrus cf. atlantica, Oleaceae, Anacardiaceae, Vitis, Argania); an influence undoubtedly of the mountainous zones of the eastern Mediterranean (Alnus, Ulmus, Carpinus betulus, Salicaceae), and finally a tropical influence (Acacia, cf. Sapindaceae). If one should attempt to characterize the three main episodes which the stratigraphy permits one to distinguish in these formations studied on the spot (Lower Ougartian, Middle Ougartian, Upper Ougartian), one can recognize from the Lower Ougartian a relatively dry period both preceded and followed by a more humid phase; during the Middle Ougartian the climatic conditions favourize the simultaneous blooming of Mediterranean species and those of the outer Sahel; the Upper Ougartians remains poorly characterized by a very limited number of pollen grains.