Abstract
-
Large-scale inundation events, such as storm and/or tsunami, represent a major coastal hazard with
the potential to damage property, infrastructure and resources, and cause loss of life. To advance
understanding of modern tsunami and their potential affects, we must recognise the signatures of
palaeotsunami. Many palaeotsunami deposits undergo alteration after deposition, resulting in loss of
some potential identification proxies used in the identification of such deposits. For example, in
swampy/peaty environments, the decomposition of organic matter produces acids. These, in turn,
dissolve carbonates out of the deposit, such as marine macro- and microfossils that could be used for
identification of a marine inundation. However, quartz grains are abundant in coastal inundation
deposits. When the quartz grains are transported via strong hydrodynamic processes, they undergo
surface abrasion, resulting in distinctive microtextural features.
In this study, cores were collected from several back-barrier estuaries and swamps along the eastern
coastline of Australia. These sites are often swampy or peaty, resulting in poor microfossils
preservation. Therefore quartz grains were used as a proxy for identifying extreme marine
inundations. The specific microtextural signatures for tsunami transported quartz grains observed in
these deposits were fresh surfaces and percussion marks. Also observed was the angularity and
dissolution of the surface of the quartz grains, and adhering microparticles. Within the suggested
tsunami deposits1,2, an increase in fresh surfaces and percussion marks were observed, with almost
complete resurfacing of some grains.