Geomorphological evidence of neotectonic deformation in the Carnarvon Basin, Western Australia

Abstract

This study examines channel-scale morphodynamics of ephemeral streams in the onshore Carnarvon basin in arid west-central Western Australia. The rivers in this region have low gradients, the landscape has low relief, and the rates of climatically and tectonically driven geomorphic processes also are low. As a result, the rivers in the Carnarvon alluvial plain are highly sensitive to minor perturbations in base level, channel slope, and fluvial energy. We use channel planform adjustments, stream gradient changes, and floodplain profiles across multiple ephemeral streams within a variety of catchments and flow regimes to determine if tectonically driven land level changes are affecting channel form and fluvial processes. Growth of individual fold segments is shown to have altered stream and floodplain gradients and triggered repeated avulsions at structurally controlled nodes. Aligned perturbations in channel form across multiple channel-fold intersections provide systematic geomorphic evidence for the location and orientation of neotectonic structures in the region. These features occur as a belt of low relief anticlines in the Carnarvon alluvial plain.

Geomorphological evidence for late Quaternary tectonic deformation of the Cape Region, coastal west central Australia

“…The NWMS separates sedimentary rocks of the Westralia Superbasin from Proterozoic Pilbara and Kimberley cratons and adjacent orogenic terranes. The fault systems follow the extended margin of western Australia and include a zone of late Neogene to Recent folding and faulting referred to as the Western Australia Shear Zone (WASZ) (Whitney and Hengesh, 2013;Whitney et al, 2014;Whitney and Hengesh, 2015). The WASZ comprises both onshore and offshore recently reactivated structures along the formerly rifted margin including well documented folds within the Cape Region (e.g., Malcolm et al, 1991) (Fig.…”

“…Reverse reactivation has occurred along offshore structures such as the Barrow Island anticline, Rowley Shoals Ridge, and Scott Reef (e.g. Boutakoff, 1963;Keep et al, 2007), along the coastal anticlines of the Cape Range Malcolm et al, 1991), and folds within the Carnarvon alluvial plain (Whitney and Hengesh, 2015). Anticlines in the Carnarvon basin have formed as fault propagation folds above blind, oblique reverse faults (McWhae et al, 1956;Hocking, 1988;Hillis et al, 2008).…”

“…In addition, a number of researchers have documented evidence for Quaternary tectonic activity in the Cape Region (e.g., Condon et al, 1955Condon et al, , 1956Boutakoff, 1963;Hancock, 1969;Logan et al, 1970;Allen, 1972b;van de Graaff et al, 1976;Denman and van de Graaff, 1977;Veeh et al, 1979;Kendrick et al, 1991;Clark, 2010;Clark et al, 2012). Folding of late Quaternary sediments in the Cape Range and Carnarvon Basin (Whitney and Hengesh, 2015), the presence of fault scarps (Whitney and Hengesh, 2013), and the occurrence of several historical large magnitude earthquakes (McCue, 1990;Leonard, 2008) clearly indicate that although western Australia may have low rates of tectonic deformation, it is not stable. Neotectonic deformation of this region has been recognized for more than 75 years.…”

Paleoseismology of the Mount Narryer fault zone, Western Australia: A multistrand intraplate fault system

“…Where not affected by faults, channel belts are weakly incised, and the regional stream gradient is consistently 1:1200 (Jutson, 1950). The channel responses proximal to faults are similar to, and locally more evolved than, the ephemeral stream responses to grow ing folds in the Carnarvon Basin northwest of the Mount Narryer fault zone (Whitney and Hengesh, 2015a).…”

Factors Controlling the Development of Straight Valleys and Streams in the Kurdistan Region, North and Northeast of Iraq

“…11). Such aspects are considered as geomorphological evidence for location and orientation of neotectonic activity (Whitney and Hengesh, 2015).…”