PEDIMENTS AND ALLUVIAL FANS - GENESIS AND RELATIONSHIPS IN THE WESTERN PIEDMONT OF THE FLINDERS RANGES, SOUTH AUSTRALIA

Pediments and alluvial fans coexist in the western piedmont of the Fli nders Ranges. The major representatives of the two landforms are inter preted as members of an evolutionary sequence. Pediments are formed fi rst and are due to planation by short streams debouching from the quar tzite and limestone ranges of the western part. of the upland. The str eams 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 const rued as incipient covered pediments, are not. On the other hand, those streams which extend eastwards, beyond the zone of quartzitic and lim estone ridges and into the mainly argillaceous terrains of the core of the upland, carry large volumes of mixed clay, sand, cobbles and boul ders, and have deposited alluvial fans on leaving the uplands, either in the scarp foot or on leaving the confines of rock outcrops and debo uching on to alluvial plains. Thus, whether pediments or alluvial fans are developed in the piedmont zone depends on the extent, and particu larly the lithological character, of the catchments drained by particu lar streams.