Revealing Sediment Transport Pathways and Geomorphic Change in Washover Fans by Combining Drone-Derived Digital Elevation Models and Single Grain Luminescence Data

Chronostratigraphic investigations on coastal sedimentary records such as washover fans or beach-ridge sequences may be used to reconstruct storm chronologies on centennial to millennial time scales. However, modern analogs are pivotal in interpreting depositional processes and reducing uncertainty in evaluating the complex chronostratigraphic architecture of these landforms. Such a modern analog was provided by category 3 tropical cyclone (TC) Olwyn in 2015, which caused a significant storm surge in the Exmouth Gulf (Western Australia). Pre- and post-TC Olwyn geomorphological surveys and high-resolution drone-derived topographical data of a large washover fan document a detailed history of erosion and deposition during the event. The modern analog deposits provided an excellent opportunity to evaluate the use of luminescence-based proxies (luminescence inventories) for tracing event-related sediment source environments and understanding transport processes. Sediments deposited during Olwyn show a systematic relationship between luminescence characteristics and washover fan position. Seaward and central washover sections are indicated by well-bleached deposits due to the beach as the dominant source and/or long transport distances. Lateral washover deposits are characterized by rather local source areas and short transport distances, resulting in higher remnant ages of 70-140 a. Our data show that the combination of sediment source environments and sediment transport length across the fan represents the main control in resetting the luminescence signal and enabling reliable depositional ages to be calculated. It documents the benefit of investigating luminescence inventories when establishing chronologies from complex sedimentary records, thereby demanding a careful consideration of local processes and source areas when interpreting sedimentary TC records.

Automated summary

Chronostratigraphic investigations on coastal sedimentary records using modern analogs, such as the impact of tropical cyclone Olwyn in 2015, provide insights into depositional processes and sources. Luminescence characteristics in sediments deposited during the event can help trace sediment source environments and understand transport processes, influencing the reliability of depositional ages in complex sedimentary records.