Fluvial Geomorphology Suggests Recent Tectonic Activity Near the Northern Barrier Range, western New South Wales

Abstract

Large faults expressed at the ground surface often have clear effects on drainage networks. Smaller scale tectonic activity, or that which occurs beneath sedimentary cover, can have more subtle effects that arise from changes to down-valley slope. These include an increase meander sinuosity or the development of anabranching. Fowlers Creek arises in the northern Barrier Range (NSW) and its terminal floodout flows across the flat surface of the Bancannia Trough. In the floodout's proximal and medial reaches the channel is sinuous but generally without active meander development. Active meandering occurs in only in two reaches, and is associated with higher slopes and repeated avulsions, the most recent being during the 20thC. It is suggested that small-scale uplift may have occurred, increasing the down-valley slope and therefore promoting meander development and avulsion. More closely spaced topographic data is necessary to support this hypothesis, however Fowlers Creek is one of nine creeks flowing east from the Barrier Range which show planform irregularities several kilometres from the rangefront. This supports the possibility of a concealed tectonic feature, and suggests that it is large-scale and linear. Major structures (e.g. mines, waste dumps) may be built in sparsely monitored remote locations where earthquake hazard estimation can be difficult. In such places, maps of fluvial geomorphology can be useful indicators of neotectonic activity.