The geomorphic evolution of the Warrumbungle Volcanic Complex, New South Wales, Australia

Abstract

Geomorphic analysis of the mid-Miocene Warrumbungle volcanic complex in north-central New South Wales revealed a highly dissected multi-vent ovoid shield, 55 km long and averaging 32 km wide. The volcanics rest unconformably on a pre-volcanic medium-relief sandstone landscape of broad valleys and flat interfluves. The degree of dissection, a function of the exceptionally large proportion of easily erodible pyroclastic material erupted during the volcano's 3.7 million year active life, varies considerably between the distal and proximal zones of extrusion. The proximal zone is preserved only in a skeletal state and is dominated by less erodible domes, plugs, and dykes. By contrast, the distal zone presents a characteristically gently sloping shield landscape with terraces where flow units are exposed. Remarkably, and probably as a result of the large number of explosive eruptions that were a dominant feature of Warrumbungle activity, four previously unrecorded crater remnants were recognised, as well as other previously unrecognised features. The preferential preservation of their lithology is perhaps a result of the partial/complete burial of these features by coeval activity and the development of dual scale radial drainage networks, with exhumation only occurring when local sub-drainage had been captured.