Australasian palaeotsunamis — Do Australia and New Zealand have a shared trans-Tasman prehistory?

Palaeotsunami databases are now available for both Australia and New Zealand. They indicate that there is a distinct disjunct between relatively small historic events and their larger prehistoric counterparts. Historically, several tsunamis have affected both the Australian and New Zealand coasts and it would therefore seem logical to assume that larger, prehistoric events would leave a recognisable geological signal. A review of the two datasets indicates up to five possible contemporaneous Holocene palaeotsunamis. A more critical examination of some of the underpinning research however, indicates that there are significant differences between the approaches adopted for establishing the chronology of individual events, and also in the nature and extent of the physical evidence used. We conclude that there are two key steps that need to be taken to ascertain whether or not these Holocene events are contemporaneous. First, a consistent methodology for the calibration of radiocarbon dates needs to be adopted across both datasets. Second, the physical characteristics used to define the Holocene palaeotsunamis listed in the Australian database need to be critically reviewed. Once completed a more constructive investigation of possible contemporaneous trans-Tasman or Australasian palaeotsunamis can be made that will help to shed light on the nature of the regional risk from tsunamis. Globally, similar precautions should be taken prior to attempting comparisons between any palaeotsunami databases.