Putting a spin on palaeotsunami deposits

Abstract

Palaeotsunami research is a relatively young discipline and while considerable progress has been made in identifying the evidence of past events there are still difficulties on occasion in differentiating between palaeotsunami and palaeostorm deposits. This has tended to focus debate on the similarities and differences between deposits laid down by the two differing processes at the expense of alternative hypotheses. Although coastal research in New Zealand a decade ago drew attention to high elevation coarse sediment deposits laid down by waterspouts, it was largely ignored by the research community. Re-analysis of a possible palaeotsunami deposit on a nearshore island in New Zealand, however, highlights the likelihood that this deposit, and perhaps many similar coastal ones, may have been laid down by waterspouts. In essence, the palaeotsunami-palaeostorm debate can no longer ignore waterspouts as an alternative hypothesis, but only time will tell how significant a contribution waterspouts have made to catastrophic coastal sedimentation.

Landscape archaeology—The value of context to archaeological interpretation: A case study from Waitore, New Zealand

“…In the context of possible alternatives, such as tornado and storm surge damage, it must be noted that recognisable tornado deposits are less structured than those reported at Waitore (Goff et al, 2016). Furthermore, typical heights for storm surge range up to 1.0 m around the coast of New Zealand, although most are usually less than 0.5 m (Bell et al, 2000).…”

The origins of marine and non-marine boulder deposits: a brief review

“…3). While these tend to be deposited in a broad swath across hillsides, multiple events over time can produce high elevation boulder fields (Goff et al 2016).…”

“…Dam collapse and the catastrophic draining of Lake Berryessa and Lake Oroville in northern California (White et al 2019) 3 Mechanisms capable of producing shore parallel boulder deposits Tsunamis, storms (including extreme marine inundation events), waterspouts, cliff retreat and catastrophic flooding below sea level all have the capability of producing extensive, commonly shore-parallel boulder deposits (Table 1), which may contain meso-boulders. These produce significant "replication" (Goff et al 2012(Goff et al ,2016 of continuous or discontinuous deposits along tens, if not hundreds, of kilometers of shoreline.…”

“…There has been considerable discussion about how tsunami and storm generated deposits, which can cover entire coastlines, can be distinguished (e.g., Nott 2003;Atwater et al 2012;Richmond et al 2011;Goff et al 2012;Spiske et al 2020, and references therein). The limited amount of research on waterspout deposits means that the potential nature and extent of these sediments is still poorly understood (Goff et al 2016). Cliff retreat is related to a specific geomorphology and should, therefore, be easily identifiable.…”

“…Boulders from a deposit 60-80 m above sea level. Boulders were sourced from the shore platform, with evidence of a wave cut notch visible on the right hand side of the boulder and gastropod borehole indicated in a AfterGoff et al (2016)…”