Long term response to lava damming: landscape evolution of an upland catchment in Western Turkey

Abstract We investigated landscape evolution of the Geren catchment, a small upland tributary of the Gediz river in Western Turkey. This highly gullied catchment is not only responding to gradual incision of the Gediz, but it has also been aperiodically dammed by lava flows since the middle Pleistocene. Fieldwork and dating demonstrated that lava damming of the Gediz and Geren catchment occurred at least three and possibly five times between 310 ka and 3.0 ka. Middle Pleistocene (> 140 ka) aggradational limestone-capped ridges consist of fluvial gravels proximal to a limestone scar and fine down to fine layered sands and silts downstream. These fills can be correlated to the 310-175 ka period of repeated damming. Subsequent erosion and aggradation sequences indicate how the Geren catchment has responded to base level lowering by stepped incision, leaving terrace remnants at MIS 4, 2 and 1. Especially terraces of MIS 2 and 1 show significant aggradation of fine sands and silts. We conclude that response of such an upland catchment to gradual base level lowering, punctuated damming, and climate, is complex and spatially diverse and cannot be unravelled using fieldwork alone. Landscape evolution modelling will be pursued to better understand catchment response to these different driving factors.