The Early Pleistocene development of the Gediz River, Western Turkey: An uplift-driven, climate-controlled system?

Abstract

This paper reports the latest details from an on-going investigation of the Early Pleistocene buried river terrace sequence of the Gediz River ∼40 km upstream of the Alaşehir graben in the Kula volcanic province, Western Turkey. Using clast lithology to characterise sediment provenance, we demonstrate that the buried Early Pleistocene terrace sequence of the palaeo-Gediz is overlain by the deposits of two carbonate-rich, northerly-derived, tributary systems. The surface form of these carbonate-rich deposits suggests deposition on alluvial fans, an interpretation supported by limited palaeocurrent data and upwards-coarsening sequences, suggesting fan progradation. It is argued that the formation and preservation of the palaeo-Gediz terrace sequence is intimately related to fan deposition, fan head entrenchment and fan progradation. Terrace formation is the result of incision in the main Gediz valley, a response to long-term uplift, during periods of lower sediment supply. Under low sediment supply conditions inferred fan head entrenchment is associated with fan toe progradation. This progradation would have led to the burial of the newly formed terrace of the Gediz. Subsequent higher sediment supply conditions would have led to renewed fan deposition. The direct coupling of the fan system with the main Gediz River during these periods would also result in deposition within the trunk river. The primary control of sediment supply is considered here to reflect changing vegetation cover, a function of changing Quaternary climates. These inferred controls suggest that the Gediz Early Pleistocene terrace sequence is an uplift-driven, climate-controlled system.