U/Th Dating of Cold Water Tufa Deposits from Kimberly Region of Australia

April 27th, 2013

Paleoclimate records from Indonesia and the West Pacific Warm Pool (WPWP) reveal that changes in global and regional climate have altered the intensity and location of Indonesian-Australian Summer Monsoon (IASM) precipitation over glacial/interglacial cycles (Magee & Miller, 2004; Griffiths et al., 2009; Mohtadi et al., 2011).

Understanding the magnitude and timing of monsoon variability in tropical Western Australia is less well constrained because paleoclimate proxies across the region are sparse and have been limited to alluvial sequences (Muller et al., 2008; Wyrwoll & Miller, 2001) and shallow marine sediments (Magee & Miller, 2004). Recent stalagmite records developed in the Kimberly region of Western Australia provide high resolution records of IASM variability over the past 40,000 years (R. Denniston, personal communication), but do not necessarily reflect all aspects of a changing hydrologic cycle.

In order to develop a more complete picture of changing precipitation conditions over this time interval, samples of groundwater carbonate (tufa) deposits formed in the Kimberly region were dated using U/Th mass spectrometry techniques.  These deposits track changes in climate by marking the timing of groundwater discharge, which is controlled primarily by the amount of precipitation that is allowed to infiltrate into groundwater reservoirs (Yan et al., 2012).

Samples taken from the top half meter of the tufa mound date back approximately 3,000 years, with a maximum age of 4,800 years.  This suggests that the entire mound could date back between 35,000 and 57,600 years, providing evidence for a larger study to be done.

Aaron Campbell, ’13
West Liberty, IA
Majors: Environmental Studies, Geology

Sponsor: Rhawn Denniston

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