Sand dune formation over the last 140 ka in the Roxby dunefield, arid northern South Australia

Geomorphic investigations and optical dating integrated in a largescale archaeological excavation program at Olympic Dam have provided a chronology for dune formation extending back to before the last interglacial. Indurated dune cores of different ages have been in existence for at least 140 ka. The present dunes began building at >55 ka and they had largely formed by 21 ka at the height of the LGM. Dune building declined 21-14 ka, then increased again, peaking at 13 ka. Stable dune surfaces formed 12-9 ka and there was little sand accumulation during the Holocene. Parts of the dunes are mantled with loose, laminated sand mobilised after European grazing commenced in the mid-1800s. Most of the archaeological material is exposed at the surface and is of late Holocene age. The dunes also contain layers of stone artefacts (post LGM through to the late Holocene in age) which mark contemporary stable to slightly eroded surfaces. The post LGM archaeological assemblages can be correlated with palaeoclimatic records from other sources and they reflect episodic occupation of this arid landscape during relatively wet periods when the dunes were stable.