Pediments and alluvial fans: genesis and relationships in the western piedmont of the Flinders Ranges, South Australia

Abstract

Pediments and alluvial fans coexist in the western piedmont of the Flinders Ranges. The major representatives of the two landforms are interpreted as members of an evolutionary sequence. Pediments are formed first and are due to planation by short streams debouching from the quartzite and limestone ranges of the western part of the upland. The streams simultaneously deposited spreads of coarse allochthonous detritus which protects and preserves these covered pediments. Most pediments are dissected, though distributary bar plains, some of which are construed as incipient covered pediments, are not. On the other hand, those streams which extend eastwards, beyond the zone of quartzitic and limestone ridges and into the mainly argillaceous terrains of the core of the upland, carry large volumes of mixed clay, sand, cobbles and boulders, and have deposited alluvial fans on leaving the uplands, either in the scarp foot or on leaving the confines of rock outcrops and debouching on to alluvial plains. Thus, whether pediments or alluvial fans are developed in the piedmont zone depends on the extent, and particularly the lithological character, of the catchments drained by particular streams. © 1998 Taylor & Francis Group, LLC.