Dynamique de la rivière Poulvar et morphogenèse de la plaine de Tang-i Bulaghi (Fars, Iran) à l'Holocène. Premiers résultats

Résumé En

The geomorphologic study of a part of the Poulvar River basin (Fars, Iran) has brought to light a series of Holocene deposits. The main deposit is 17 m thick, consisting mainly of silty sediments deposited during the early and middle Holocene. These deposits are unusual in such a mountainous environment. The study shows that structural and climate factors could explain this sedimentation. On the one hand, it occurred during the relatively humid Holocene Climatic Optimum, which may have contributed to soil erosion. On the other hand, the plains of structural origin located downstream from the Poulvar basin would explain the high base level of the river, the low incline of the longitudinal profile and the tendency towards sedimentation. This major episode is followed by a long period of erosion with only two phases of sedimentation. Data are still lacking to explain this phenomenon, which probably had two major causes: the return of aridity at about 6000 BP and the Zagros uplift.