Australia: The Land Where Time Began

A biography of the Australian continent 

Cooper Creek Fan - Late Quaternary and Fluvial Interactions

Crustal warping in the Cenozoic produced the Innamincka Dome and associated fan, that is of low gradient, in the Strzelecki Desert which has aided the formation of palaeochannels, source-bordering transverse dunes and linear dunes that are superimposed. The course of Cooper Creek was impeded by these dunes and they preserved evidence of climate change as well as the processes of interaction between the formation of linear and transverse dunes. There are extensive fluvial and aeolian sand bodies at Turra, Gidgealpa and sites nearby that have been dated to marine isotope stages (MIS) 8-3 and the Last Glacial Maximum (LGM) that are at present surrounded, or buried beneath, overbank mud. Large channels transporting large amounts of bedload that was deposited as sandy alluvium on the downstream dome slope, which now form transverse dunes from what the authors1 suggest were probably bars exposed seasonally in a palaeo-Cooper system, having subsequently been blown to the north.

The base of the dune complex is at least MIS 7, about 250 ka in age, having been dated by thermoluminescence (TL) and optically stimulated luminescence (OSL), though it has subsequently been reworked by wind, and additional sand has been blown from the river. There was a period of enhanced river flow and sand supply about 120-110 ka during which source-bordering dunes were formed, and short episodes of formation of source-bordering dunes that occurred at about 85-80 ka and about 68-53 ka. From 28-18 ka enhanced flows and dune sediment supply was associated with the LGM. In the early to mid-Holocene there was a period of pronounced river flow and dune activity, though there is no evidence of Cooper Creek supplying sand for dunes since the LGM. Transverse dunes, that are aligned roughly parallel to east-west trending palaeochannels, appear to largely form the oldest basal sand units, with linear dunes having formed from and over these, that yield basal ages that range from MIS5 or MIS4, though they continued reworking and accreting through to the Holocene.

One of the few detailed chronological studies of the interaction between transverse and linear dunes resulted from this study. According to the authors1 the results of the study indicate that there is apparently no evidence that long-distance sand transport has played a significant role in the formation of dunes at this location, the linear dunes showing no significant decline in age downwind. Thee authors1 suggesting linear dunes appear to have accreted vertically from the underlying transverse dunes. In this section of the Strzelecki Desert a wind-rift vertical model, with lengthwise extension playing only a minor role, is the dominant mode of formation of linear dunes, and since the LGM most of the dune sediment has been sourced from adjacent swales.

 

Sources & Further reading

  1. Cohen, T. J., G. C. Nanson, J. R. Larsen, B. G. Jones, D. M. Price, M. Coleman, and T. J. Pietsch. "Late Quaternary Aeolian and Fluvial Interactions on the Cooper Creek Fan and the Association between Linear and Source-Bordering Dunes, Strzelecki Desert, Australia." Quaternary Science Reviews 29, no. 34 (2// 2010): 455-71.
Author: M. H. Monroe
Email: admin@austhrutime.com
Last updated: 31/03/2013
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading