Alluvial Fans and Their Deposits in Devonian Hornelen Basin, Norway: ABSTRACT

Abstract

Conglomerate alluvial-fan bodies are well exposed around the fault margins of Hornelen basin. Detailed mapping of the bodies and of their internal facies variation together with logging of laterally equivalent profiles allows reconstruction of fan processes, geometry, internal cyclicity, and relation to contemporaneous flood-basin deposits. Of particular interest is fan-to-fan variation through Hornelen basin's 25 km succession, as illustrated by six examples from the northern and southern margins. Some fan bodies, particularly with small radius ( 30 cm/km) are entirely dominated by debris flows. The latter are commonly poorly sorted and massive or inversely graded. The ratio of bed thickness to maximum particle size in debris flows is usually less than 3. Other fans, usually thinner bodies, with greater radius (<6 km) and less abrupt downfan grain-size gradients, contain a significant amount of fluvial (braided stream) or sheet-flood deposits, which are usually concentrated in the middle or lower fan reaches. End_of_Article - Last_Page 828------------