FINE RESOLUTION PALEOCLIMATIC RECORDS FROM SEDIMENTARY BASINS What has been done? What can be done? What is the value?

Peter Kershaw, Krystyna Saunders, Donald Walker, Peter Gell With Cameron Barr, Tara Lewis, John Tibby, Chris Turney Late Holocene pollen sites from John Tibby via Peter Gell (data contributed by • Widespread distribution in landscape – Kershaw, mapped by Sophie bias to humid margins Bickford) • Provide prelude to (and significance for http://www.aqua.org.au/Archive/ OZPACS/Pollen_Insets.jpg study of) the last 2ka • Generally cover much of the last 2 ka – Predominantly proxy record of lake level – And so effective rainfall* • Audit ecosystem condition and responses to non climate drivers* • Generally lack annual resolution even if annually laminated* • Dating a problem in non-annually laminated sediments, as in Australia* • *Characteristics generally exclude sequences from high resolution ‘global’ climate reconstructions (e.g. Mann et al. 1998, 1999; Jones and Mann 2004) • Recent realisation of potential for lower- resolution data to capture variation on multicentennial timescales (Moberg et al. 2005) provides some scope for optimism Stoney Ck Basin

Lake Bolac

Pejark Lakes Gnotuk and Allambie Lake Marsh Bullenmeri Lake Condah Lake Keilambete Lake Fred South Swamp Surprise Lake Lake Purrumbete Wangoom Red Rock Tyrendarra Swamp Cartcarrong Colac Basin Cobricao Lake Lakes Swamp

Late-Pleistocene – Holocene records

Mid-Pleistocene – Holocene records

Early-Mid Pleistocene records Sedimentology

Ostracod chemistry

(Jones et al. 1998) c. 2ka Lake Keilambete late Holocene – original notes of Jim Bowler. Evidence 1. Grain size analysis as index of water depth. 2. Carbonate production – a proxy for warmer conditions 3. Trees preserved in growth position . World’s best rain gauge lake

600 -150 BP – significantly higher lake levels C1000 – 600 BP Phase of warmer conditions and slightly lower water levels

Rapid rise (to allow tree preservation). Dates from organic muds 1900 and 1810 BP

2000 BP. Trees indicate stable and low lake levels for at least 100 years

Lake falling since 1870 (30m) and still falling (9m). 11 m in 1966-7 when Bowler crawling across the lake bottom.. Conclusions

6. The lakes are still adjusting to the fall in P/E ratio around c. 1840 7. With current and predicted further drying, most lakes will dry up by the end of this century Lake Coragulac 1970

Lake Coragulac 2007 High resolution ‘lake’ projects

• ANU Fine resolution pollen and time series analysis (Walker, Singh, Green, Dolman) • UNSW, ARC (Dodson, Mooney) • Strategic Monash Research Fund (Kershaw, Reid, Tibby, Leahy, Fluin) • ANSTO project (Heijnis, Harle) • PAGES OzPacs (Gell, Gale, Denham) • Land and Water Australia Innovation project, Ballarat/ Monash/Adelaide/EPA (Gell, Kershaw, Tibby, Leahy) • Marie Currie IIF TASCLIM project University of Berne (Saunders, Grosjean) • PAGES Aus2ka (Turney, Gergis) Metadata for high resolution palynological records covering at least the European settlement period in Australia. Results of rates of environmental change analysis on selected characteristics of sediment cores from selected sites in southeastern Australia within the last 2000 years. Adapted from Dodson and Mooney (2002) Aust. J. Bot. 50, 455-464.

Lake Curlip Bondi Lake Cobrico Crater Club Lake Barraga Swamp Lake Keilambete

European period

550 Pre- European period 270 230 1000 360 900 1000 590

1500 1600 Chord Distance/yr 1800 2140 210Pb Urban c. 1930 AD

Exotics (grazing) c. 1870 AD Native weeds c. 1840 AD Pre- 14C 830 ka European

Pollen record of Bolin Bolin Billabong, Yarra River From Leahy et al. (2005) River Research and Applications 21: 131-149 c.1944 Last fire

c.1870

c.1840

Lake Surprise, Mt. Eccles, SW , frozen spade record – 0-107 cm Comparison of hydrological records from volcanic lakes on the Western Plains of Victoria (modified from Cameron Barr 2010 – this meeting)

Lake Keilambete

Drier

Wetter

Drier, warmer

Wetter

Wet Dry Lake Barrine chronostratigraphy (D. Walker, submitted, Palaeo3) Jim Neale

Duration of Detritus- poor laminae

Strongly detrital marker band 7

Stratigraphy marked by interannual turbulant Frozen detrital events caused by lake overturn during very cold winters on average every 4 years and extreme ‘detrital marker band’ events every 250-580 years within ‘cooler’ last 5000 years. TASCLIM project: Regional quantitative reconstruction of temperature and precipitation featuring application of chironomids (Rees et al. 2008, Palaeolimnology) and reflectance spectroscopy of total early diagenic chloropigmnents (von Gunten et al. 2009) to a variety of selected Tasmanian sites.

A quantitative high-resolution summer temperature reconstruction based on sedimentary pigments from Laguna Aculeo, central Chile, back to AD 850 Lucien von Gunten, Martin Grosjean, Bert Rein, Roberto Urrutia and Peter Appleby The Holocene 2009; 19; 873 Conclusions

• Lakes are widespread through humid eastern part of Australia • Some can provide a picture of general climate change through the last 2ka but, due to site and catchment human impact, few are likely to provide accurate or quantitative climate records. • Likely that sites will be sensitive to different climate features (few temperature sensitive). • Chronology is presently of major concern at almost all sites. • Encouraging development of new techniques