Discovery of a palaeolake at the terminus of the Murray-Darling Basin: a Holocene record of southeastern Australia’s hydroclimate and implications for current palaeoclimate reconstructions

De Carli, E; Hubble, T; Penny, D; Petley, DN; Clarke, SL; Hamilton, RJ; Gadd, PS; Brand, HEA

Discovery of a palaeolake at the terminus of the Murray-Darling Basin: a Holocene record of southeastern Australia’s hydroclimate and implications for current palaeoclimate reconstructions

Date

2015-07-27

Authors

Publisher

International Union For Quaternary Research (INQUA)

Abstract

The 1.073 million km2 Murray-Darling River Basin (MDB) drains 14% of Australia’s landmass, incorporates Australia’s most economically important agricultural region, and presents one of Australia’s most important and contentious water security challenges. In this study we report the discovery of a hitherto unrecognised terminal palaeolake system ’Lake Mannum’ that developed during the middle to late Holocene, as evidenced by an extensive sequence of laminated muds. The deposit contains grey coloured laminae rich in Fe and smectite, and olive-black coloured laminae K and illite rich, representing high discharge events from both the Darling and Murray River catchments respectively, providing a high-resolution proxy record of MDB hydroclimatic variability during the Holocene. Given the strong influence of major oceanic-atmospheric synoptic circulation features (ENSO, IOS-SAM, IPO, IDO) over the river system, variability in MDB discharge and delivery of suspended sediment flux to the continental shelf have been used as proxy indicators for southeastern Australian palaeoclimate during the Holocene. The existence of a lake system at the terminus of the MDB suggests that discharge of terrigenous sediment to the Southern Ocean was strongly suppressed during this time, meaning that Holocene climate reconstructions for SE Australia which rely on the marine sediment record require re-evaluation.

Keywords

Quaternary period, Southern Oscillation, Australia, Lakes, Rivers, Paleoclimatology

Citation

De Carli, E., Hubble, T. C. T., Penny, D., Petley, D., Clarke, S., Hamilton, R., Gadd, P. S. & Brand, H. E. A. (2015). Discovery of a palaeolake at the terminus of the Murray-Darling Basin: a Holocene record of southeastern Australia’s hydroclimate and implications for current palaeoclimate reconstructions. Paper presented at the XIXth INQUA Congress: Quaternary Perspectives on Climate Change, Natural Hazards and Civilization, Nagoya, Japan, 26 July to 2 August 2015.