MULTIPLE CALCRETE PROFILES IN THE TABERNAS BASIN, SOUTHEAST SPAIN - THEIR ORIGINS AND GEOMORPHIC IMPLICATIONS

This paper describes a sequence of Pliocene(?) to Quaternary age calcr etes developed within alluvial fan and fluvial gravels in the Tabernas Basin, Almeria Province, southeast Spain. Calcrete profiles are descr ibed from sites adjacent to major tributaries of the Rambla de Taberna s. Six distinct calcrete units are identified within the basin. These have variable distributions but have developed in an identifiable evol utionary sequence. Two pairs of calcrete units are widely present acro ss the basin preserving two former land surfaces. Each of the former l and surfaces has been planated and subsequently buried by alluvial fan or fluvial gravels. A massive calcrete unit is present at the base of each gravel sequence, immediately in contact with the underlying bedr ock, with a less well developed calcrete unit situated at the top of t he gravel sequence. The lowest two calcrete units within the basin are more spatially restricted and are confined to the floors and flanks o f incised drainage lines. The geochemistry, macro- and micromorphologi cal properties and geomorphological positions of the calcrete units ar e outlined and, on the basis of this information, their mode of origin identified. Two main modes of calcrete genesis appear to be present: massive calcretes situated in direct contact with bedrock are suggeste d to have formed by groundwater processes, whilst calcretes situated a t the top of gravel sequences are likely to have developed by pedogeni c processes, Calcrete genesis is subsequently considered in the contex t of the reconstruction of the early phases of landscape development, and is suggested to have been controlled by phases of uplift and stabi lity within the Tabernas Basin. (C) 1998 John Wiley & Sons, Ltd.