Cyclone-generated washover deposits and landforms of Western Australia – Sediment characteristics and chronology of geo-archives and palaeotempestological implications (DFG-funded, MA 5768/1-1)
Palaeotempestology, the study of prehistoric storms, uses sedimentary evidence to enlarge the temporal frame given by historical records and provides important information about past storm frequencies and magnitudes. In particular for the time period >400 years and for the Southern Hemisphere in general, prehistoric storm data is needed. Geomorphic and sedimentary archives store traces of tropical cyclones and tsunamis, as particular depositional landforms, deposits or erosional features. However, the identification of event deposits from the geological record and their interpretation is associated with a number of difficulties, including the spatial and temporal variability of geological archives, the application of different dating techniques, and the differentiation between tsunami and storm deposits, notably where modern deposits and/or historical reports on the event are absent. In this regard, increasing the data pool of TC and tsunami deposits by analysing modern analogues for which documentation of climatologic and geophysical parameters and/or geomorphic and sedimentary effects are available are key components to unravel the fossil record and the history of past events.
The NW coast of Western Australia (WA) is highly vulnerable to extreme wave events. On average 1-2 TCs impact the coast per year, and ten historically documented tsunami events impacted the W Australian coast since 1858. Within the framework of this DFG-funded research we investigate sedimentary archives along the coastline of the Pilbara, NW Australia, between Coral Bay and Onslow. By means of a broad range of methods, our study aims at implementing sedimentological and geomorphological baseline research on washover sediments and landforms in one of the most cyclone-affected areas worldwide, where comparable studies are rare. The investigated archives comprise back-barrier washover sheets and mud flats, washover fans as well as sandy beach ridges along extensive mud flats. Due to their distinct geomorphology and their unambiguous relation to marine inundation and sediment accumulation during extreme wave events, these findings are assumed to store important information on the impact of past storm events in NW Australia. Thereby, our study also aims at detecting and discriminating known historical and unknown prehistorical tsunami impacts which are assumed to be stored in the sedimentary record as well. The combined use of 14C and OSL dating techniques will allow for the establishment of reliable chronologies on both prehistorical and historical time scales. In general, the research will contribute to the understanding of the complexity and variability of extreme wave deposits. The potential of washover landforms and sediments in the research on frequency and magnitude of past storm events will be evaluated.