Base level changes, river avulsions and Holocene human settlement dynamics in the Caspian Sea area (middle Kura valley, South Caucasus)

Geomorphological, geochronological and geoarchaeological analysis focusing on six tributaries of the Kura River provide valuable data concerning sedimentation rhythmicity and Holocene human settlement distribution at a regional scale. Seven new radiocarbon dates from the upstream part of these hydrosystems complemented the existing radiocarbon dataset (n = 32) obtained downstream. These data seem to indicate that upstream hydrosystems also reacted to marine regressions by powerful riverbed incisions and to transgression phases by thick valley infillings from at least as early as the Upper Pleistocene. The retroactive morphogenic effects were also perceived in intra-mountainous areas far from the Caspian shoreline. The land use patterns of the Caucasian societies dwelling in the valley of the Kura hydrosystem were affected by temporary river avulsions resulting in silty fans over the high terraces during the Neolithic–Chalcolithic periods. These river avulsions seem to be governed by local climate and base level changes linked to fluctuations of the Caspian Sea level over time. This is spatially and diachronically evidenced in settlement distribution, with almost exclusive localization on perched silty fans and river runoff from the key period of Neolithic development in the region. These new data must be considered in future geoarchaeological analyses concerning the Caspian Sea Basin and will contribute to the enhancement of the relative Caspian Sea level curve for the past 40 ka.