Organic-geochemical proxy for tracing recent and historical Tsunamis in time and space

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Japanese sedimentary archives preserve millenarian tsunami deposits beyond human records. Since the beginning of instrumental records alone, over 300 tsunamis – large and small– have been documented from local earthquakes. Further on, hundreds of these stone tablets erect along the Japanese coastline, some dating back to more than 1150 years ago in the wake of the 869 CE Jogan tsunami. For the investigation of historic-, but especially to identify paleo-tsunami deposits from the sedimentary record, organic compounds show great potential based on their preservation potential. Such organic geochemical markers have been proven a valuable tool to investigate modern tsunami deposits and to detect those deposits beyond the limit of visual recognition. But based on high preservation potentials and indicative compound groups with high source specificities organic markers contribute also significantly to historical and paleo-tsunami research. Consequently, the aim of this study is the establishment of appropriate and reliable natural organic indicators combined with standard parameters (grain size, XRF, micropaleontology, dating) in a multi-proxy approach to identify historic- and paleo-tsunamis in sedimentary archives in principal. More generally, through this study, we further aim to combine interdisciplinary fields of research areas (i.e., tsunami research, organic geochemistry, and sedimentological/micropaleontological approaches) with the intention to gain a more holistic insight into processes (e.g., transport, deposition, tsunami backwash distribution) that occur in the last 40% of the inundation, which remain today virtually unknown, as they lay beyond the limit of visibly recognizable sandy tsunami deposits.