The nature of climate change during the last deglaciation, and consequent environmental response(s) is one of the most widely researched and vigorously debated aspects of Quaternary science. The nature and extent of short-lived "events" during this period have received considerable attention, with the best documented being the Younger Dryas (YD), a cold reversal from 13 to 11.2 CAL ky BP. Evidence for Younger Dryas events is most conclusive from high latitude Northern Hemisphere environments. Recent research has, however, attributed a variety of environmental changes to the YD in equatorial (eg: Roberts et al., 1993, Maslin and Burns, 2000) and southern Hemisphere environments (eg: Denton and Hendy, 1994), although a number of contrasting studies exist (eg: Bennett et al., 2000).
Sites in Australia, and the Southern Hemisphere generally, can significantly contribute to understanding the nature of environmental change in the transition from the last glacial maximum (LGM) to the Holocene. In particular, there is considerable debate about the extent to which cold reversals observed in Antarctic ice cores are synchronous with the YD in the Northern Hemisphere, with both cooling (Stein et al., 1998) and warming (Monnin et al., 2001) being proposed. As Broecker (2000) observes, documenting the timing of climate change in Southern Hemisphere sites informs our understanding about fundamental climate dynamics, such as the coupling of the ocean-atmosphere system.
There is a paucity of sites in mainland Australia with continuous sedimentation through this transition period. North West Crater, a nested scoria cone in the Tower Hill complex (western Victoria), is one site that has demonstrated relatively rapid and continuous deposition from the LGM to the Holocene (DíCosta et al. 1989) and is presently a focus of high resolution, multi-proxy study. Here we present preliminary diatom results from this study. Although diatoms are not preserved through the whole of the transition period, they indicate a highly variable moisture balance following the LGM.
References
Bennett, K.D., Haberle, S.G. and Lumley, S.H. (2000). The last glacial-Holocene transition in southern Chile. Science, 290, 325-328.
Broecker, W.S. (2000). Abrupt climate change: causal constraints provided by the palaeoclimate record. Earth Science Reviews, 51, 137-154.
Denton, G. and Hendy, C.H. (1994). Younger Dryas age advance of Franz Joseph Glacier in the Southern Alps of New Zealand. Science, 264, 1434-1437.
DíCosta, D.M., Edney, P., Kershaw, A.P., and De Deckker, P. (1989). Late Quaternary palaeoecology of Tower Hill, Victoria, Australia. Journal of Biogeography, 16, 461-482.
Maslin, M.A. and Burns, S.J. (2000). Reconstruction of Amazon Basin effective moisture over the past 14,000 years. Science, 290, 2285-2287.
Roberts, N., Taieb, M., Barker, P., Damnati, B, Icole, M and Williamson, D. (1993). Timing of the Younger Dryas in East Africa from lake-level changes. Nature, 366, 146-148.
Monnin, E., Indermühle, A, Dällenbach, A, Flückiger, J., Stauffer, B., Stockner, T., Raynaud, D. and Barnol, J-M. (2001). Atmospheric CO2 concentrations over the last glacial termination. Science, 291, 112-114.
Steig, E.J., Brook, E.J., White, J.W.C., Sucher, C.M., Bender, M.L., Lehman, S.J., Morse, D.L., Waddington, E.D. and Clow, G.D. (1998). Synchronous climate changes in Antarctica and the North Atlantic. Science, 282, 92-95.