Sedimentology and geochemistry of lacustrine terraces of three Middle Atlas lakes: Paleohydrological changes for the last 2300 cal BP in Morocco (western Mediterranean region)

In the Moroccan Middle Atlas Mountains, three lakes were used to characterize climate variability in the late Holocene. The methodology is based on sedimentological, geochemical, and mineralogical analysis of lacustrine terraces. Lake Ifrah is a natural lake. Waters are calc-magnesian, relatively very alkaline and oxygenated. Lake Afourgagh is of karst origin, with maximum depth 1.5 m. Lake Iffer is a smaller lake, sub-circular and relatively deep. Its area is 3.5 ha. Its maximum depth is 6.5 m at the center of the lake.Seven terraces located in the borders of the lakes were sampled and studied. Seven radiocarbon dates were obtained on organic matter and shells. The time period concerned is between 2300 cal BP and 400 cal BP. The results show high lake levels at about 2300 cal BP related probably to the wetter Iberian – Roman period in northern Mediterranean. Lake Iffer was deeper by about 30 m from its current level. 1000 cal BP probably marks the beginning of the decline with a drop in lake level of 20 m, which is ongoing in connection with drier climate and the beginning of the medieval climate anomaly.