HOLOCENE GEOMORPHIC EVOLUTION OF THE AKLIMAN RIVER VALLEY (SINOP, TURKEY)

The Akliman Valley is a coastal river valley on the Black Sea coast of Turkey. The valley is flanked by steep, bedrock walls which abruptly transition to a flat, alluvial valley bottom. The valley bottom is a deltaic coastal plain that has developed through the Holocene from sedimentation by the Karasu River. The goal of this study is to document the extent and chronology of geomorphic and paleoenvironmental change in the valley over the last ~5,000 years. Modern observations of the landscape were supplemented by 15 gouge auger cores taken at various points around the valley bottom. These sediment cores, with penetration up to 12 m depth in the valley floor, were logged stratigraphically in the field. The cores were subsampled at ~10 cm resolution for subsequent lab analyses to characterize the sediments, and determine their most probable environment of deposition. Preliminary results, including from seven AMS radiocarbon dates, allow for the reconstruction of the paleogeography in the valley. The valley floor stratigraphy records an overall regressive sedimentary sequence with a shallow marine embayment being succeeded by the modern, subaerial environment. Stratigraphy in the southeast part of the valley is primarily dominated by deposits from fluvial sedimentation. However, deposits interpreted to be from the former marine embayment were encountered at ~10 m depth in the stratigraphy there. These deposits, located about 2 km from the present coastline, are probably from around the middle Holocene according to AMS radiocarbon dates from other cores. As the coastline prograded, the marine embayment in the northwest part of the valley was overtaken by fluvial sedimentation from the Karasu River, and eventually transitioned to the subaerial environment as seen at present. Here, stratigraphy from the gouge auger work showed marine embayments deposits at just a few meters depth in the subsurface. This southeast to northwest shift in fluvial sedimentation concurs with observations about the direction of longshore transport at the coast, in particular, how the mouth of the Karasu River has been pushed towards the northwest due to longshore transport. This paleogeographic reconstruction provides an important environmental context for interpreting archaeological evidence.