Holocene Valley fills of Southern Turkey and Northwestern Syria: Recent geoarchaeological contributions

Holocene alluvial fills from catchments ranging from <1 to > 100,000km(2) ( the upper Euphrates) are described for part of S Anatolia and NW Syria. The sequences indicate that mid-Holocene landscapes were moderately stable and in several areas were drained by reliable, perennial channel flows. Althou gh the boundary between mid and late Holocene deposits (ca. 2000 BC) is rep resented by sedimentary discontinuities in several alluvial sequences, thes e transitions were not necessarily contemporaneous. In places, ploughwash d eposits infilled valleys where sediment delivery had exceeded channel how d uring the last 4000-5000 y. In the Balikh valley human withdrawal of water for irrigation has depleted flow, thereby weakening that river as a palaeoh ydrological indicator. The limited lacustrine sequences do not necessarily provide a reliable palaeoclimatic record because they may relate to increas ed flood frequency from the inflowing rivers, which may, in turn, result fr om a range of anthropogenic and natural factors. Late Holocene channel fill s indicate less perennial flow, higher flow variations, increased erosion, or accelerated aggradation. Such environments appear to have characterized the last 4000-5000 yr during which time the impact of human population on t he landscape increased and climatic desiccation, albeit at fluctuating leve ls, had probably become more pronounced. (C) 1999 Elsevier Science Ltd. All rights reserved.