Drainage patterns in southeast Queensland: the key to concealed geological structures?

Abstract

Southeast Queensland's geomorphology is characterised by northwest -southeast-trending trunk drainage channels and highlands that strongly correlate with the distribution of geological units and major faults. Other geomorphological trends strongly coincide with subsidiary faults and geological domains. Australia is presently under compressional stress. Seismicity over the past 130 years records 56 earthquakes of 42 magnitude indicating continuing small-scale earth movements in the Moreton region. Highlands in this region are dominated by Paleozoic to Triassic metamorphic and igneous rocks, and are generally 20 -80 km from the coastline. Coastal lowlands are largely dominated by Mesozoic sedimentary basins and a veneer of surficial sediments. The eastern coast of Australia represents a passive margin; crustal sag along this margin could be expected to produce relatively short, highenergy, eastward-flowing drainage systems. We performed a geomorphological analysis to characterise the drainage patterns in southeast Queensland and identify associations with geological features. Anomalous channel, valley and escarpment features were identified, which failed to match the anticipated drainage model and also lacked obvious geological control. Despite their proximity to the coast (base level), these features include areas where drainage channels flow consistently away from, or parallel to, the coastline. Although many channels do coincide with geological structures, the drainage anomalies cannot be directly related to known structural discontinuities. Anomalous drainage patterns are suggested to indicate previously unidentified structural features and in some cases relatively young tectonic control on the landscape. Recent seismicity data have also been analysed to assess spatial correlations between earthquakes and geomorphological features. Our results show that structure largely controls drainage patterns in this region, and we suggest that a presently unmapped and potentially active, deep-seated structure may exist parallel to the coast in the northern coastal region. We propose that this structure has been associated with uplift in the coastal region of southeast Queensland since mid-Cenozoic times.

Contemporary genetic structure reflects historical drainage isolation in an Australian snapping turtle,Elseya albagula

“…This region is noteworthy for its complex biogeography, reflecting multifarious processes of landform development in an otherwise geologically quiescent continent. Volcanism, uplift, escarpment retreat, and sea‐level fluctuations have produced complex drainage patterns that are not yet well understood (Jones, ; Hodgkinson, McLoughlin & Cox, ; Vasconcelos et al ., ). In recent years, genetic studies have provided evidence for historical drainage rearrangements, revealing unexpected patterns in the distribution and relatedness of genetic lineages across now‐isolated catchments (Hurwood & Hughes, ; Hughes et al ., ).…”

Late Cenozoic intraplate faulting in eastern Australia

“…3b) do not show evidence for Cenozoic activity. Faults shown in blue (e.g., WIFS, and several segments of the NPFS) do not cut Cenozoic volcanic rocks but have been inferred to have undergone Cenozoic movement based on geological and kinematic analyses, and geomorphological considerations (Cranfield et al, 1976;Hodgkinson et al, 2007;Babaahmadi and Rosenbaum, 2014). The distribution of earthquake epicenters along these major faults may also indicate recent faulting (Hodgkinson et al, 2006(Hodgkinson et al, , 2007.…”

Style and intensity of late Cenozoic deformation in the Nagoorin Basin (eastern Queensland, Australia) and implications for the pattern of strain in an intraplate setting

“…9) according to the catalogue of historically and instrumentally recorded intraplate earthquake epicentres since 1875 (Rynn et al 1987;McKavanagh et al 1993;McCue, 1996). A relatively high density of these earthquakes occurred along major fault zones, such as the WIFS and NPFS (Hodgkinson, McLoughlin & Cox, 2007;Fig. 9), raising the possibility that these faults, including the Boynedale Fault and associated thrusts, are neotectonic reactivated preexisting structures.…”