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Landscape evolution in the Finke (Larapinta) river transverse drainage, Central Mountain Ranges, Australia

Baker Victor R.

Studia Geomorphologica Carpatho-Balcanica

2021

Vol. 55

9--44

The cross-axial pattern of the Finke (Larapinta) River across the central ranges of Australia developed through a complex combination of processes including early planation; deep weathering (late Mesozoic/early Cainozoic); long-term stream impression; etchplanation; progressive aridity, leading to late (Pliocene and Quaternary) changes in fluvial flood regimen; all associated with regressive river erosion, stream capture, and/or epeirogenic movements. An early phase of etchplanation explains the development on easily weathered rocks of intramontane basins and strike valleys. Combined with stream impression, this process led to the superposing of the Finke and the Hugh Rivers across resistant rock units. The most unusual aspect of the Finke is a palimpsest, developed in the Krichauff Ranges, in which an ancient, relict gorge, is incised into a local planation surface (the Shoulder Surface), and preserved as paleomeander segments, in which the original quartzite gravel fill has been cemented with iron oxides and silica. The Shoulder Surface was subsequently more deeply incised by a later manifestation of the river to produce the meandering contemporary gorge that is intertwined with the relict one. The incision of the contemporary gorge occurred in association with the change in flood regimen, and involved either (1) prior aggradation of the incised paleomeandering stream to permit alluvial meandering across the Shoulder Surface and subsequent incision into it, or (2) headward recession of a knick point created where the Finke flowed from resistant sandstones into what are now the strike valleys of the James Ranges, from which weathered mantles had been removed by etchplanation processes.