Abstract

The study of alluvial fan sequences, the most proximal components of the alluvial spectrum, can be one of the most profitable avenues of research in basin analysis because fans are particularly sensitive to external influences and have a relatively high preservation potential. Tectonism has long been invoked to explain many variations in fan sediments, and increasingly the presence and nature of fan sequences in the rock record is being used to denote proximity to active faults and to document movement on these faults.

There are, however, many difficulties involved with the interpretation of alluvial fan sequences, not the least of which is deciding whether the sediments are truly components of an alluvial fan or the products of a different depositional system such as an alluvial braidplain. Many of the problems arise from a lack of knowledge about the relative roles in fan construction of allocyclic processes such as climatic change and tectonic activity, and of autocyclic processes such as channel avulsion and fanhead entrenchment.

Whilst researching alluvial fan sediments in a variety of tectonic settings and ages, it has become increasingly clear to the authors that there are many inadequacies in our understanding of alluvial fans, and hence weaknesses in the conclusions drawn from these sediments. This prompted the one-day meeting organized to promote discussion of the problems of distinguishing tectonic from other influences on the evolution of modern and ancient fans. 110 industrial and academic geologists gathered at the University of Bristol on 17th October 1987 to hear 16

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