Groundwater in southeast Australia: links to recharge variations and past climates

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International Association of Hydrogeologists
Palaeogroundwater from many locations around the world contains water stable isotope trends that are linked to climatic and therefore recharge variations through the last ~30 ka. Some examples are the variations observed in the Sahara-Sahel region where humidity sources can be differentiated (Edmunds et al. 2004) and or the markedly depleted values associated with glacial activity in many basins of northern part of Europe and America (Baidla et al. 2009). ln Australia with the lack of extensive glaciation, it is anticipated that water stable isotope trends do not show major variations through time. However, in the South East of Australia, particularly in the Sydney Basin (NSW) and also across the continent in the Perth Basin (WA), deuterium excess (d-excess) show high values with an average of 15%o (n=135) in the case of the Sydney Basin. The high values are not only found in modern precipitation and groundwater but also in groundwater with residence times exceeding 20 ka for the Sydney Basin. Water stable isotopes from several locations around the Sydney Basin are presented showing regional variations and localised changes due to orography. The chronological framework is determined from 14C DlC in the same groundwater samples. The dominant siliciclastic nature of most of the aquifers in the region minimises major 14C dilution and the combination of general hydrogeochemistry and 87Sr/86Sr results are used to constrain processes such as the dissolution of dispersed carbonates when estimating groundwater residence times. These records will be, where possible, compared to higher resolution records such as pollen, where parallelisms and differences will be discussed.
Ground water, Australia, Stable isotopes, Climates, Rain, New South Wales, Western Australia, Carbon 14
Cendón, D., Meredith, K., Hughes, C., Hollins, S., Currell, M. & Markowska, M. (2013). Groundwater in southeast Australia: links to recharge variations and past climates. Paper presented to IAH 2013 Perth Australia : "Solving the groundwater challenges of the 21st century", International Association of Hydrogeologists 40th International Conference, Perth, Western Australia, 15-20 September 2013. (pp. 206).