A period of rainfall up to 50% higher than now occurred in northern Queensland during 7000 - 3000 BP, followed by a time of relative aridity during 2800-1600 BP (1). The latter is deduced from the occurrence of ‘chenier plains’ near the coast, consisting of ridges of shells or sands separated widely by mudflats. They result from several processes, notably variations of river mouth flow, indicating wet-season rainfalls inland. Ridges were examined from six locations along the north Australian coast, and the dating of each ridge was found from the C14 content of the shells.
Parallel changes have been observed in central Australia during 2800-2200 BP, inferred from the onset of sand accumulation (which implies increasing aridity) in the Simpson desert, for instance (2).
(1) Lees, B. & A. Clements 1987. Climatic implications of chenier dates in Northern Australia. Radiocarbon 29, 311-7.
(2) Wasson, R.J. 1984. Late Quaternary paleo-environments in the desert dunefields of Australia. In Vogel 1984, 419-32.
(3) Vogel, J.C. (ed.) 1984. Late Cainozoic Paleoclimates of the Southern Hemisphere (Balkema).