The influence of tectonics, sea-level fluctuations and river capture on the quaternary morphogenesis of the semi-arid Pulpi Basin (southeast Spain)

Abstract

The semi-arid Pulpi Basin is located within a 250 km long left-lateral shear zone between Alicante and Almería The Pulpi Basin itself is crossed by the N20E-striking Palomares Fault, active during the Neogene and Quaternary. In the Upper Pliocene a major epeirogenic uplift occurred which caused emergence of the basins. Simultaneously, a change from marine to terrestrial sedimentation started and the development of the present landscape began. The Quaternary relief development in the Pulpi Basin has been particularly influenced by tectonic disturbances and river captures, which have had contrasting effects on different parts of the basin. In the southern basin tectonically induced dissection of the oldest Quaternary glacis level was accompanied by the influence of the fluctuations in sea-level: both factors have caused continuing erosion. In the central Pulpi Basin Mid-Quaternary fluvial capture processes were important for the morphogenesis. Since the loss of the catchment areas in the neighbouring Huércal-Overa Basin the fluvial activity of the rivers in the western part has been limited. The transition from the distal end of the Mid-Quatemary glacis to the present valley floor takes place without a noticeable step; no younger fluvial terraces are missing. In the eastern part, the catchment area of the main river has hardly changed since its establishment during the Upper Pliocene. Besides the relics of the oldest glacis level no further glacis accumulation developed. During the Mid-Quaternary only a fluvial terrace was deposited.