Active and relict alluvial fans on contact karst of the Vrhpoljska brda hills, Slovenia

Abstract

Several types of contact karst are found within the Slovenian karst, but the most common is the ponor type, which usually develops at boundaries between flysch and limestone. One of these types is in the area of Vrhpoljska brda. In this contact karst area two types of alluvial fans appear on carbonate bedrock. Members of the first type are ordinary alluvial fans with active alluvial processes where flysch derived sediment covered limestone surface in a distinct fan shape. The other type, described as relict alluvial fans, is fan-shaped features preserved in the carbonate bedrock. These essentially bedrock landforms developed as a result of the gradual removal of pre-existing alluvial fan cover and the concurrent but non-uniform chemical denudation of the underlying carbonate bedrock. Geomorphologic and morphometric description of alluvial fans and relict alluvial are provided in the article and mechanisms of relict alluvial fans formation and transformation are discussed.