Modern approaches in palaeotsunami research

The number of tsunami-related scientific publications increased within the last years due to numerous extensive and destructive tsunami events worldwide. The research on tsunami deposits is needed to improve hazard assessment in coastal areas worldwide. While the state of knowledge is rising, the discipline is still relatively young and there are presently a high number of unsolved questions and processes. In the field of palaeotsunami research new insights gained from the most recent events, such as sedimentary characteristics, morphologic features, as well as the recently used methods or so called proxy toolkit, are not yet widely tested on historical events. In this thesis I try to shed light on diverse problems by means of three case studies carried out in coastal regions of the western Peloponnese (Greece), the Sultanate of Oman and along the eastern Gulf of Cádiz (Spain). There are open questions as to how the clear identification of tsunami deposits can be carried out and how the preservation of historical event deposits varies in specific archives. Furthermore, the proxy toolkit on palaeotsunami deposits differs from recent deposit investigations. The deposit characteristics, the way of detecting and proving them, the several types of archives, the deposit preservation potential and the challenges of the proxy toolkit are all discussed. The first case study from Greece uses an approach to detect palaeotsunami deposits by different classical investigation methods, such as sedimentological, palaeontological and geochemical investigations, in different environments/archives. Sedimentary evidence includes the existence of rip-up clasts in multiple sandy fining upward sequences with an erosive base as well as a mixture of foraminifera species from different habitats. Radiocarbon dating proves a minimum of one tsunami landfall in the study area between AD 540 and minimum AD 1274. The second case study from Oman demonstrates the extensive use of ground penetrating radar (GPR) as well as its potential and limitations concerning tsunami deposit investigations. This investigation method is tested on an inferred tsunami deposit which was identified in previous studies by huge blocks and boulders, most probably transported by tsunami wave action along the coast close to Fins (Oman). The investigated GPR facies reveals wedging out structures, channels, scours and erosion mounds, as well as landward directed foresets. Sedimentary evidence by trenching and age calibration is also presented. The third case study carried out along the south-eastern Gulf of Cádiz shows an integrative multi-method approach on palaeotsunami deposits. In this study several classical and new investigation tools/techniques were tested and compared to the most recently discovered tsunami characteristics. Furthermore, new tsunami features were found within the sedimentary record of high-energy event deposits. In the presented study a combination of different dating techniques (radiocarbon and optically stimulated luminescence) was also tested to yield possible event ages of the palaeotsunami. Based on the conclusions achieved from the presented studies I try to answer some of the main questions which arose at the start of this research, regarding the incomplete state of knowledge on tsunami features and characteristics. This thesis also comprises a summary of event ages in the different study areas. The event ages yielded by different dating results are compared to the recent tsunami catalogue of each region, and recurrence intervals which are necessary for an improved hazard assessment are discussed