Unravelling Late Pleistocene and Holocene landscape dynamics: The Upper Guadalentín Basin, SE Spain 9

Landscapes in SE Spain have developed in response to tectonics, climate fluctuations and, more recently, human activity. Fluvial and colluvial sediments such as river terraces and slope deposits found in the valleys reflect a complex interplay between landscape forming processes. Investigating these sediment archives, we reconstructed landscape evolution for the Upper Guadalentín Basin, SE Spain, placing recent erosion processes in a landscape evolution context. Palaeo-lake sediments dated between ~ 17 and ~ 13.8 ka evidence that a Late Glacial lake existed in the area, probably formed by a sudden blockage of the Guadalentín river. Differences in relative height above the floodplain and age between the river terraces of parts of the Guadalentín river indicate that they have not been in equilibrium in the Late Quaternary. Deposition of river terraces along the upstream part of the river is recorded at ~ 13 and ~ 9.5 ka, whereas no evidence of deposition is found for that period along the lower part of the river. There, episodes of sedimentation occur at ~ 7.5–5 ka, ~ 3.4, ~ 1.6, ~ 0.7 and ~ 0.4 ka. This discrepancy is explained by the palaeo-lake and its influence on erosion and sedimentation processes through base level changes. Combining these processes, we propose a schematic model of Late Pleistocene and Holocene landscape evolution. From the model we can conclude that i) the influence of the palaeo-lake on deposition and erosion processes both upstream and downstream is evident; and for the younger river terraces that ii) episodes of deposition seem to coincide in time, but iii) episodes of erosion in between terrace level aggradation do not coincide and neither do terrace level heights and iv) no evidence of deposition is found for the upstream part of the river. Correlation of erosion and sedimentation episodes with climate change and human impact is discussed. Although some correlations can be made, there is strong evidence that climate was not the main driver of landscape processes. We suggest that internal dynamics and local processes are more important drivers for landscape dynamics in the Upper Guadalentín Basin than external and regional factor