Cosmogenic dating of fluvial terraces in the Sorbas Basin, SE Spain

Abstract

Long term fluvial incision spanning the Late Cenozoic is recorded in many fluvial systems around the world by terrace landform sequences. The incision manifests itself as inset sequences of river terraces which form terrace staircases. The timing of the onset of incision and the rate incision then proceeds at is poorly constrained due to the difficulties in dating river terraces. This study applies the technique of cosmogenic exposure dating to a fluvial staircase, for the first time, in the Sorbas Basin, SE Spain. Cosmogenic exposure dating allows the timing of abandonment of the fluvial terraces to be calculated therefore recording periods of incision. Cosmogenic exposure dating and the profile method offer a viable way to date Early and Middle Pleistocene terrace deposits. Combined exposure and burial age’s approaches using paired isotopes allow for insights into terrace aggradation and fluvial incision timing. The fluvial deposits in the Sorbas Basin record 1.0 Ma of incision by the Río Aguas. The timing of aggradation and incision in the Sorbas basin has been linked to both tectonics and climate cycles. Terrace aggradation took place in glacial and interglacial periods. The abandonment of terrace surfaces occurred both at warming transitions and in interglacial periods. New uplift rates calculated for the Pleistocene fluvial system suggest that tectonic activity in the Sorbas Basin has been episodic. The south margin and centre of the Sorbas Basin has uplifted at a faster rate than the northern margin impacting on the rates of incision taking place in the fluvial systems. Overall tectonic uplift has increased the fluvial system sensitivity to climatic variations.