QA_Vol 24_No 1_July 2007 - Australasian Quaternary Association

Table 1: Revised 14 C Ages for Section 1.The revised ages were calibrated using the package from Fairbanks et al. (2005).The locations of the dating samples on the section are shown in Figure 3.Materials and MethodsBulk sediment samples were collected from Section 1.Several attempts to recover spores and pollen fromthese sediments proved unsuccessful. Thus, the datareported herein pertain only to the Ostracoda andMollusca, and the carbon and oxygen isotopic compositionof their respective carbonate valves and shells.At 360 cm above the base of the exposed section(Figures 2 and 3), a dark grey-brown palaeosol separatesthe vertical section into two units, namely, a laminatedclayey silt upper unit and a lower more massive andhomogenous silty clay unit. For the purposes of thepresent study, ten roughly even spaced (7–18 cm)samples were taken from the lower unit and fivesamples from the upper unit.Subsamples of 40 g were soaked in 3% hydrogenperoxide solution for up to 3 days to remove the labileorganic matter. When effervescence ceased, the residueswere washed over a 90μm sieve. The retainedsediments were oven dried at 60°C and set aside formicroscopic examination. Using standard micropalaeontologicalprocedures, fossil ostracods (single valves),rare charophyte oogonia and gastropods were extracted,identified and counted.Stable isotope analysis of selected, weighed andcleaned ostracod and mollusc tests was carried out inthe School of Earth Sciences, Wollongong University,under the direction of Professor Allan Chivas. Theresults are reported relative to the V-PDB standard andhave a precision of better than ±0.02‰ for both δ 13 Cand δ 18 O. (Chivas et al. 2002).Figure 3. Section 1 of late Pleistocene sediments at theSlippery Dip locality (composite section after Williams etal., 2001). Dates shown are calibrated 14 C AMS ages.21 | Quaternary AUSTRALASIA 24 (2)