Human and climatic impact on late quaternary deposition in the sparta basin piedmont: Evidence from alluvial fan systems

The evolution of four alluvial fans in the Evrotas Valley, southern Greece, was examined using a combination of geomorphological and sedimentological techniques. Source material for the fans is derived largely from the Taygetos Mountains, and thus the fan deposits provide proxy evidence for erosion of upland landscapes. Stratigraphic sequences exposed in the fanhead trenches suggest a progressive change in depositional style down-fan. Within the St. Johns, North Anogia, and North Xilocambi fans, debris flow deposits are gradually replaced by gravel- dominated hyperconcentrated flow deposits and then fine-grained hyperconcentrated flow deposits. Within the Kalivia Sokas fan, gravel-dominated hyperconcentratedflowdepositsgive way to fine-grained hyperconcentrated flow deposits, and finally to fluvial gravels. Mineral magnetic studies combined with thermoluminescence dating suggest that sedimentation also occurred over a similar time scale. Deposition cycles during the late Pleistocene appear to be climatically driven, with proximal and medial fan segments developing during stadial phases of the Riss/Wu¨ rm and Wu¨ rm, respectively. Distal segments aggraded during the Ho- locene. During interstadial episodes of the late Pleistocene, fan entrenchment occurred. Ho- locene accretion is likely to be related to human activity and appears to be concentrated in the early/middle Helladic and the Hellenistic periods, when population levels, indicated by increased numbers of archaeological sites, were rising.