Late Holocene mega-tsunamis in the Tasman Sea: an assessment of the coastal archaeological record of New South Wales

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Abstract

Bryant and others have interpreted geomorphological and archaeological evidence from south-central New South Wales (NSW) to infer repeated inundation of this coast by mega-tsunamis in late Holocene time. However, the stratigraphy of two well-dated archaeological sites (Pambula Lake, Bass Point) shows no evidence that these camps were abandoned, or that the marine component of the diet of local Aboriginal peoples changed at or about 500 or 1500 cal. BP, the time of the two most recent inferred mega-tsunamis. In addition, the mean probability distribution of the youngest calibrated radiocarbon ages from 52 archaeological sites on the south-central NSW coast (grouped in three tsunami-susceptibility classes on the basis of site elevation and distance from the shore) does not differ from random expectations, and shows no evidence that sites were permanently abandoned in the aftermath of these inferred events. The mean probability distributions of calibrated radiocarbon ages from 108 charcoal samples from these sites does not differ from random expectations, and offers little support for the inference that the sites were temporarily abandoned about 500 or 1500 cal. BP. Probability distributions based on 70 marine shell ages show strong century-scale cyclicity, but this is likely too regular to be a product of mega-tsunamis. Moreover, changes in shellfish exploitation patterns and adoption of new fishing technologies by Aboriginal people on this coast do not coincide with the times of inferred tsunamis. The archaeological evidence offers no support for the hypothesis that mega-tsunamis inundated this coastline in the late Holocene.