Long-term waterfall dynamics in monsoonal Australia based on cosmogenic Be-10

Extensive plateaus, arrays of escarpments and a variety of waterfalls are iconic to northern Australia. How old and stable are these features ? Tectonically, northern Australia has been quiescent during the Quaternary. Rainfall is highly seasonal and dominated by the summer monsoon. In this setting, regional landscape dynamics should be strongly afected by uctuations in monsoon and the associated uvial processes. Here, we examine timescales and processes of waterfall evolution in northern Australia. Situated in the Kimberley sandstone plateau, Durack Falls comprise a series of 1-3 m falls, while Bindoola Fall is a large 15 m fall. Surprise Creek, 100 km south of Darwin, has three 3-5 m waterfalls with deep plunge pools developed at the edge of a quartzite plateau. Over 30 samples were collected from bedrock straths up- and downstream of the waterfalls and on their headwall. Their 10Be exposure ages (assuming zero erosion) reveal contrasting results. While two waterfalls in the Kimberley show relatively young, variable ages (15-110 ka for Durack and 11-57 ka for Bindoola), Surprise Creek indicates old, but uniform ages (94-160 ka). Out-of-channel,undisturbed bedrock exhibits consistently high 10Be equivalent to steady-state erosion rates of 2-5 mm/ka, in agreement with typical bedrock erosion rates observed across Australia. Based on these data, we here present a model to evaluate process and rates of waterfalls formation, and discuss the controlling factors.

Keywords

Rain, Dynamics, Erosion, Australia, Streams, Data

Citation

Fujioka, T., May, J. H., Fink, D., Nanson, G., Jansen, J., & Codilean, A. (2014). Long-term waterfall dynamics in monsoonal Australia based on cosmogenic Be-10. Paper presented at the AMS-13 The Thirteenth International Conference on Accelerator Mass Spectrometry, 24-29 August 2014, Aix en Provence, France, (pp. 212). Retrieved from: https://core.ac.uk/download/pdf/24848438.pdf

URI

https://core.ac.uk/download/pdf/24848438.pdf http://apo.ansto.gov.au/dspace/handle/10238/6406

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