Timing of the Last Glacial Maximum from observed sea-level minima

During the Last Glacial Maximum, ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today. But few direct estimates exist of the volume of the ice sheets, or the timing and rates of change during their advance and retreat(1,2). Here we analyse four distinct sediment facies in the shallow, tectonically stable Bonaparte Gulf, Australia-each of which is characteristic of a distinct range in sea level-to estimate the maximum volume of land-based ice during the last gla ciation and the timing of the initial melting phase. We use faunal assembla ges and preservation status of the sediments to distinguish open marine, sh allow marine, marginal marine and brackish conditions, and estimate the tim ing and the mass of the ice sheets using radiocarbon dating and glacio-hydr oisostatic modelling. Our results indicate that from at least 22,000 to 19, 000 (calendar) years before present, land-based ice volume was at its maxim um, exceeding today's grounded ice sheets by 52.5 x 10(6) km(3). A rapid de crease in ice volume by about 10% within a few hundred years terminated the Last Glacial Maximum at 19, 000 +/- 250 years.