Recent Sediments of Lake Tamda (middle Atlas, Morocco): New Insights from Geochemical and Sedimentary Records

This work presents the sedimentological and geochemical analyses on a sedimentary sequence taken by coring from Lake Tamda, located in the Middle Atlas, Morocco. This study aims to determine the parameters controlling the sedimentary and environmental dynamics and, consequently, the climatic dynamics. Waters in the lac are calc-magnesian, relatively alkaline, and well-oxygenated. Water dilution materializes the climatic influence from the hot season (summer) to the cold season (winter). The sedimentological and geochemical studies of surface sediments provide information on detrital sedimentation dominated by the silty-clayey fraction resulting directly from the erosion of the watershed. At Tamda cores, the sedimentary record shows three lithostratigraphic units. They represent three distinct sedimentary and geochemical deposition phases, marking three stages of lake-level fluctuation. Going toward the lake's center, there is a decrease in coarse fractions and carbonates and an increase in fine particles, organic matter, and magnetic susceptibility. The reasonably high carbonate contents at the edges are related to detrital inputs. The low levels of organic matter are linked to the current lowering of the lake level, while the low sedimentation rate is connected to the decrease in terrigenous inputs by water flows. Recent sedimentation at Lake Tamda is influenced by Allochthonous production, including seasonal inputs from the watershed and sometimes wind sedimentation.