Hydroclimate of the Last Glacial Maximum and deglaciation in southern Australia’s arid margin interpreted from speleothem records (23–15 ka)
Pauline C. Treble1,2, Andy Baker2, Linda K. Ayliffe3, Timothy C. Cohen4, John C. Hellstrom5, Michael K. Gagan3, Silvia Frisia6, Russell N. Drysdale7, Alan D. Griffiths1, and Andrea Borsato61Australian Nuclear Science and Technology Organisation, Lucas Heights 2234 NSW, Australia 2Connected Waters Initiative Research Centre, UNSW Australia, Kensington 2052 NSW, Australia 3Research School of Earth Sciences, Australian National University, Canberra ACT 0200, Australia 4School of Earth and Environmental Sciences , University of Wollongong, Wollongong NSW 2522, Australia 5School of Earth Sciences, University of Melbourne, Parkville VIC 3052, Australia 6School of Environmental and Life Science, University of Newcastle, Callaghan NSW 2308, Australia 7School of Geography, University of Melbourne, Parkville VIC 3052, Australia
Received: 19 Dec 2016 – Accepted for review: 20 Dec 2016 – Discussion started: 21 Dec 2016
Abstract. Terrestrial data spanning the Last Glacial Maximum (LGM) and deglaciation from the southern Australian region are sparse, and limited to discontinuous sedimentological and geomorphological records with relatively large chronological uncertainties. This dearth of records has prevented a critical assessment of the role of the Southern Hemisphere mid-latitude westerly winds on the region’s climate during this time period. In this study, two precisely-dated speleothem records for Mairs Cave, Flinders Ranges, are presented, providing a detailed terrestrial hydroclimatic record for the southern Australian drylands during 23–15 ka for the first time. Enhanced recharge to Mairs Cave is interpreted from the speleothem record by the activation of growth, physical flood layering and δ18O and δ13C minima. Periods of lowered recharge are indicated by isotopic enrichment, primarily affecting δ18O, argued to be driven by evaporation of shallow soil/epikarst water in this water-limited environment. A hydrological driver is supported by calcite fabric changes. The Mairs Cave record indicates that the Flinders Ranges were relatively wet during the LGM and early deglaciation, particularly over the interval 18.9–16 ka. This wetter phase ended abruptly with a shift to drier conditions at 15.8 ka. These findings are in agreement with the geomorphic archives for this region, as well as the timing of events in records from the broader Australasian region. The recharge phases identified in the Mairs Cave record are correlated with, but antiphase to, the position of the westerly winds interpreted from a marine core in the Great Australian Bight. The implication is that the mid-latitude westerlies are located further south during the period of enhanced recharge in the Mairs Cave record (18.9–16 ka), and conversely are located further north when greater aridity is interpreted in the speleothem record. A comparison with speleothem records from the northern Australasian region reveals that the availability of sub-tropical/tropical moisture is the most likely explanation driving enhanced recharge, with further amplification of recharge occurring during the early half of Heinrich Stadial 1, possibly influenced by a more southerly-displaced Intertropical Convergence Zone (ITCZ). A rapid transition to aridity at 15.8 ka is consistent with a retraction of this tropical moisture source.
Treble, P. C., Baker, A., Ayliffe, L. K., Cohen, T. C., Hellstrom, J. C., Gagan, M. K., Frisia, S., Drysdale, R. N., Griffiths, A. D., and Borsato, A.: Hydroclimate of the Last Glacial Maximum and deglaciation in southern Australia’s arid margin interpreted from speleothem records (23–15 ka), Clim. Past Discuss., doi:10.5194/cp-2016-135, in review, 2016.