Frank G. Ethridge, 1985. "Modern Alluvial Fans and Fan Deltas", Recognition of Fluvial Depositional Systems and their Resource Potential, Romeo M. Flores, Frank G. Ethridge, Andrew D. Miall, William E. Galloway, Thomas D. Fouch
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Alluvial fans constitute a distinct landform and depositional system characteristic of piedrrnt areas. Fisher and Brown (1972) describe alluvial fans as cone-shaped piles of sediment built where streams issue from a highland into an adjacent lowland. Fan deltas and clastic wedges are related features that belong under the same general heading of Fan Systems. Fan deltas are alluvial fans that build into a standing body of water (ocean, sea, lake, etc.). They generally have a distinct group of distal environments that owe their existance to this body of water. Proximal environments of fan deltas and alluvial fans are quite similar. Clastic wedges comprise a series of overlapping alluvial fan and/or fan delta deposits. The term clastic wedge has generally been applied to these thick sequences of coarse detrital units associated with fault block rrountains.
Bull (1962, 1963, 1964 and 1968) conducted extensive investigations of rrdern, arid and semi-arid region alluvial fans. These investigations are summarized in two later papers (Bull, 1972 and 1977). Morphologically arid-region alluvial fans are cone-shaped deposits that can be divided into three geornorphologic units: fan head (proximal fan), mid fan, and fan base (distal fan; Fig. 1C). Arid-region alluvial fans generally displays a concave longitudinal profile (Fig. 1C) and a convex transverse profile (Fig. 1B). Fan surfaces slope from less than 1m to about 40m/km. Individual fans have lengths of i to 6 km and areas of 1 sq km to 900 sq km (Fisher and Brown, 1972; Spearing, 1975) although coalescing fans can form laterally