Field mapping and GIS visualisation of quaternary river terrace landforms: An example from the rí o almanzora, SE Spain

Abstract

This paper presents the mapping results of a Quaternary river terrace staircase associated with the evolution of the Rí o Almanzora in SE Spain. Prior to map compilation a formal landform stratigraphy was constructed from remote sensing and field reconnaissance using standard allostratigraphic procedures as outlined by the North American Stratigraphic Commission. The stratigraphic framework comprised five allomembers of the Río Almanzora Alloformation corresponding to an inset sequence of river terrace levels that document > 150 m of Quaternary fluvial incision by the Rí o Almanzora. The terrace stratigraphy was mapped in the field using a hand held GPS to construct control points that tracked breaks and changes in slope associated with terrace stratigraphic boundaries. The field map and survey data were compiled in a GIS geodatabase and overlaid onto a DEM and geological map data for analysis and visualisation purposes. The stratigraphic and mapping procedure outlined here follows a standard methodology for investigations of Quaternary river terrace sequences, which have traditionally been mapped by geological surveys as undifferentiated Quaternary sediments. Ultimately, map compilation was undertaken in order to facilitate reconstruction of the Quaternary fluvial history of the Rí o Almanzora in order to identify the key environmental controlling mechanisms (tectonics, eustacy, climate change) for driving river terrace aggradation and incision patterns. The identification of five major river terrace landform levels and integration with luminescence age data suggests a climatic control on landform development with river aggradation occurring during glacial and transition periods between glacials and interglacials. River downcutting is attributed to base-level changes linked to a long term uplift trend and climate related sea-level fluctuations.