Browsing by Author "Le Métayer, P"

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    Late quaternary environmental change at Lake McKenzie, in subtropical eastern Australia: evidence from sedimentary carbon, nitrogen and biomarkers
    (Past Global Changes, 2013-02-13) Atahan, P; Heijnis, H; Le Métayer, P; Grice, K; Taffs, K; Hembrow, SC; Dodson, JR
    Fraser Island is part of a large sand mass that extends along the subtropical coastline of south-eastern Queensland. The island is a World Heritage site, listed for its unique natural environment that includes numerous perched oligotrophic dune lakes and a diverse suite of coastal and subtropical vegetation communities. Here we present geochemical and microfossil information for a sediment core collected from Lake McKenzie, in the island’s centre. AMS 14C and 210Pb dating has been conducted and indicates a basal age of ca. 37,000 cal. BP. A hiatus in the sedimentary record is apparent at around 25 cm depth and spans the time period from ca. 18,280 to 13,990 cal yr BP. Elemental and stable isotope measurements of carbon and nitrogen in bulk organic matter, along with biomarker and compound specific carbon isotope analyses, show a clear shift in lake conditions appearing with the re-commencement of sediment accumulation following this hiatus. A marked decline in the abundance of microfossils of the green colonial algae Botryococcus, coincides with a distinct change in composition of Botryococcus derived lipids and a shift to more negative δ13C values of long chain odd n-alkane compounds. An increase in lake size around 13,990 cal yr BP is suggested by the recommencement of sediment accumulation at the site, and is presumably in response to increased effective precipitation. The lake McKenzie record provides a long-term perspective on changing environmental conditions in central Fraser Island.
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    Late quaternary environmental change at Lake McKenzie, Southeast Queensland: evidence from microfossils, biomarkers and stable isotope analysis
    (University of Western Australia, 2013-07-10) Atahan, P; Heijnis, H; Dodson, JR; Grice, K; Le Métayer, P; Taffs, K; Hembrow, SC; Woltering, M; Zawadzki, A
    Unravelling links between climate change and vegetation response during the Quaternary is a research priority, and needed if the climate-environment interactions of modern systems are to be fully understood. Using a sediment core from Lake McKenzie, Fraser Island, we reconstruct changes in the lake ecosystem and surrounding vegetation over the last ca. 36.9 cal kyr BP. Evidence is drawn from multiple sources, including pollen, micro-charcoal, biomarker and stable isotope (C and N) analyses, and is used to improve understanding about the timing and spatial scale of past changes that have occurred locally and in the southeast Queensland region. The glacial period of the record, from ca. 36.9-18.3 cal kyr BP, is characterised by lower lake water levels and increased abundance of, or closer proximity to, plants of the aquatic and littoral zone. High abundance of biomarkers and microfossils of the colonial green alga Botryococcus occur at this time and include high variation in individual botryococcene 13C values. A distinct period of dry or ephemeral conditions at the site is detected during deglaciation, causing a hiatus in the sedimentary record covering the time period from ca. 18.3-14.0 cal kyr BP. The recommencement of sediment accumulation around 14.0 cal kyr BP occurs with evidence of lower fire activity in the area and reduced abundance of terrestrial herbs in the surrounding sclerophyll vegetation. The Lake McKenzie record conforms to existing records from Fraser Island by containing evidence for a mid-Holocene dry period, spanning the time period from ca. 6.1-2.5 cal kyr BP. © The Authors
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    Pollen, biomarker and stable isotope evidence of late quaternary environmental change at Lake McKenzie, southeast Queensland
    (Springer, 2014-10-30) Atahan, P; Heijnis, H; Dodson, JR; Grice, K; Le Métayer, P; Taffs, K; Hembrow, SC; Woltering, M; Zawadzki, A
    Unravelling links between climate change and vegetation response during the Quaternary is important if the climate–environment interactions of modern systems are to be fully understood. Using a sediment core from Lake McKenzie, Fraser Island, we reconstruct changes in the lake ecosystem and surrounding vegetation over the last ca. 36.9 cal kyr. Evidence is drawn from multiple sources, including pollen, micro-charcoal, biomarker and stable isotope (C and N) analyses, and is used to gain a better understanding of the nature and timing of past ecological changes that have occurred at the site. The glacial period of the record, from ca. 36.9 to 18.3 cal kyr BP, is characterised by an increased abundance of plants of the aquatic and littoral zone, indicating lower lake water levels. High abundance of biomarkers and microfossils of the colonial green alga Botryococcus occurred at this time and included large variation in individual botryococcene δ13C values. A slowing or ceasing of sediment accumulation occurred during the time period from ca. 18.3 to 14.0 cal kyr BP. By around 14.0 cal kyr BP fire activity in the area was reduced, as was abundance of littoral plants and terrestrial herbs, suggesting wetter conditions from that time. The Lake McKenzie pollen record conforms to existing records from Fraser Island by containing evidence of a period of reduced effective precipitation that commenced in the mid-Holocene. © Springer Science+Business Media Dordrecht 2014