Tsunami or storm waves?: determining the origin of a spectacular field of wave emplaced boulders using numerical storm surge and wave models and hydrodynamic transport equations

Abstract

Well-imbricated large boulders of quartzite, greater than 100 tonnes weight, occur along the crest of an island, 8 m above modern sea-level, in the Gulf of Carpentaria, northern Australia. The imbrication, alignment of boulder A axes parallel and sub-parallel to shore, boulder lithology (Proterozoic quartzite), size grading of boulders along shore and transverse to shore and their topographic position along the crest of the island show that they were unequivocally deposited by waves. Revised hydrodynamic wave transport equations are used along with numerical storm surge and wave models to determine the type of wave responsible for deposition of these boulders. The maximum storm surge and storm generated waves attainable under the most severe intensity tropical cyclone (880 hPa) at this location are considered too small to have transported the boulders. Tsunami, despite this locations sheltered environment, maybe an alternative mechanism.