Hydrogeochemical processes in a monsoon dominated karst environment, NW Queensland
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Date
2012-08-05
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Australian Geosciences Council
Abstract
The Lawn Hill region, NW Queensland Australia, is host to perennial streams fed by springs from a large karstic aquifer with sub-modern (>50 y) groundwater, developed in Cambrian carbonate lithologies. NW Queensland is subject to semi-arid monsoon climates, and consequently the modern ground and surface waters and their interactions are greatly dependent on seasonal variability of rainfall. We have used a range of techniques to evaluate hydrogeochemical processes including geochemical analysis of host rocks, and a range of isotopic and chemical analyses of ground and surface waters. Samples were collected over multiple sampling campaigns, including during the wet season. Surface waters and groundwaters from carbonate terrains were found to be similarly Ca(Mg) HCO3 type waters as expected from interactions with the karst carbonates, which were found to be composed of primarily dolomite and minor chert. However, there are many indicators (14C, 3H and others) of a more complex system with different temporal scales. Surface waters, while showing dolomitic interactions, have compositions which suggest interaction with underlying silicic lithologies before forming springs. Also, variability in the strength and timing of the monsoon appears to have an effect on activation of different springs and groundwater flow. Additionally, there are groundwaters with much longer residence times (∼6000 a) and chemistries indicative of interaction with silicic and underlying Proterozoic sedimentary units.
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Keywords
Monsoons, Caves, Queensland, Australia, Ground water, Climates, Carbon 14, Lithology
Citation
van der Ley, M., Cendón, D., Graham. I., & Spencer, J. (2012). Hydrogeochemical processes in a monsoon dominated karst environment, NW Queensland. Paper presented to the 34th International Geological Congress 2012, "Unearthing our Past and Future - Resourcing Tomorrow", Brisbane, Australia, 5-10 August 2012, (pp. 1442).