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

•  Widespread distribution in landscape – bias to humid margins

•  Provide prelude to (and significance for 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

Late Holocene pollen sites from John Tibby via Peter Gell (data contributed by Kershaw, mapped by Sophie Bickford) http://www.aqua.org.au/Archive/OZPACS/Pollen_Insets.jpg

Tower Hill

Stoney Ck Basin

Colac

Red Rock

Lake Bolac

Lake Purrumbete

Basin Lakes

Lakes Gnotuk and Bullenmeri

Cobricao Swamp

Lake Wangoom

Garvoc

Lake Keilambete

Lake Terang

Pejark Marsh

Early-Mid Pleistocene records

Mid-Pleistocene – Holocene records

Late-Pleistocene – Holocene records

Lake Surprise

Lake Condah Fred South Swamp

Tyrendarra Swamp

Allambie

Lake Cartcarrong

c. 2ka

Ostracod chemistry

Sedimentology

(Jones et al. 1998)

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

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

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

C1000 – 600 BP Phase of warmer conditions and slightly lower water levels

600 -150 BP – significantly higher lake levels

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

. World’s best rain gauge lake

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

360

270

1000

1500

Chord Distance/yr

550

900 230

590

2140

1000

1600

1800

European period

Pre- European period

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

Urban

Exotics (grazing)

Native weeds

Pre-European

c. 1840 AD 14C 830 ka

c. 1870 AD

c. 1930 AD

210Pb

c.1944

c.1840

Last fire

Lake Surprise, Mt. Eccles, SW Victoria, frozen spade record – 0-107 cm

c.1870

Comparison of hydrological records from volcanic lakes on the Western Plains of Victoria (modified from Cameron Barr 2010 – this meeting)

Wetter

Drier, warmer

Wetter

Drier

Lake Keilambete

Wet Dry

Jim Neale

Frozen

Lake Barrine chronostratigraphy (D. Walker, submitted, Palaeo3)

Duration of Detritus-poor laminae

Strongly detrital marker band 7

Stratigraphy marked by interannual turbulant 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.

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

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.

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