e-mail — Patrick.Moss@arts.monash.edu.au

The ODP 820A and Lynch’s Crater pollen and charcoal records suggest that there has been significant environmental change in the humid tropics of northeastern Australia over the last 250,000 years. Both records reveal clear cyclical vegetation patterns for the region, with complex rainforest communities expanding during interglacial periods (oxygen isotope stages 7,5,3 and 1) and contracting during glacial and stadial periods (oxygen isotope stages 8,6,4 and 2). In addition, there have been expansions in araucarian-rich drier rainforest and/or sclerophyll communities during glacial periods. Spectral analysis conducted on both records suggests that orbital forcing, particularly eccentricity and obliquity, play a major role in controlling the abundances of these various community types within the humid tropics region. Superimposed on these cyclical alterations in vegetation is an abrupt alteration in vegetation and burning in both the ODP 820 and Lynch’s Crater records. There has been a marked increase in sclerophyll taxa and burning, as well as a sharp decline in the fire sensitive conifers (Araucariaceae and Dacrydium) within the region over the last 250,000 years. This alteration occurred in two stages, at 137,000 to 130,000 years BP, possibly caused by the onset or intensification of ENSO (El Nino/Southern Oscillation) conditions during a very dry period, and at 40,000 years BP, possibly due to the influence of human activity.