A Late Holocene record of environmental change from the east coast of New South Wales, Australia
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Date
2019-07-30
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International Union for Quaternary Research (INQUA)
Abstract
A multi-proxy palaeoenvironmental record from a lake (36° 5'37.33"S; 150° 7'26.02"E) on the east coast of Australia provides a record of coastal development and vegetation succession over the last 3,800 cal. yr BP. Lead-210 and 14C dating built a robust age-depth chronology for the 61cm long core. Pollen, charcoal and x-ray fluorescence analysis provide records of vegetation change, fire regimes and catchment dynamics during the late Holocene. This study finds that an open coastal environment dominated by Amaranthaceae and Eucalyptus was present between 3,800 and 3,000 cal. yr BP when sea level on the east coast of Australia was ~1.7-1.5m higher than present. Rainforest indicators including Cyathea, Pomaderris and Nothofagus suggest a mixed wet Sclerophyll community was present either regionally or locally. Low pollen concentration and relatively high counts of Fe, S and Ca suggest iron sulfides and shell hash accumulated in a shallow or periodically exposed basin. Microscopic charcoal counts varied between 4,000 and 3,500 cal. yr BP and may indicate an increase in regional fire events. From 3,000 cal. yr BP Casuarinaceae and Poaceae increased and aquatic types Typha and Cyperaceae first appeared in the record suggesting the falling sea level allowed a barrier dune to form and a brackish to freshwater wetland to develop. Between 3,000 and 2,000 cal. yr BP Sr and Ti counts varied significantly, suggesting terrestrial and marine sediments may have periodically washed over the barrier dune and accumulated in the wetland during a period when sea level was ~1.1m higher than present. Sclerophyll open forest dominated by Casuarinaceae expanded until 2,000 cal. yr BP and then remained constant until present. Local and regional fire indicators increased briefly at 2,000 cal. yr BP. The presence of European settlers in the region is clearly identified by the occurrence of Pinus and the significant increase in regional and local fire regimes from 1900 AD and 1920 AD respectively. This multi-proxy record from a coastal lake in eastern New South Wales identifies the impact of sea level change and coastal progradation on vegetation and fire regimes and investigates natural and anthropogenic driven environmental change during the late-Holocene.
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Keywords
Quaternary period, Environment, Climatic change, New South Wales, Australia, Lakes, Coastal regions, X-ray fluorescence analysis, Pollen
Citation
Mackenzie, L., Fletcher, M.-S., & Gadd, P. (2019). A Late Holocene record of environmental change from the east coast of New South Wales, Australia. Poster presented to the 20th INQUA Congress 25th - 31st July 2019, Dublin, Ireland. Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1614