Organic Geochemical Proxies of Tsunami Deposits
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Organic geochemical proxies of tsunami deposits From the Faculty of Georesources and Materials Engineering of the RWTH Aachen University Submitted by Piero Bellanova, M.Sc. from (Werl) in respect of the academic degree of Doctor of Natural Sciences approved thesis Advisors: Univ.-Prof. Dr.rer. nat. Klaus Reicherter Univ.-Prof. Dr.rer. nat. Jan Schwarzbauer Date of the oral examination: 19.12.2019 This thesis is available in electronic format on the university library’s website An old temple stands on the shore That has seen much come and go Will it fall to the water’s tongue? Will its song no more be sung? But no! In endures the crashing gales And a hidden temple by its side The water unveils Revealed by the waves that ate The sand Even in destruction, you showed Something grand Tsunami! You thief of land Joydeb and Moyna Chitrakar (2019) – Tsunami Abstract Abstract Natural hazards have accompanied humanity throughout history, however, amongst these tsunamis have been the least understood events until relative recent times. Broadcasting itself on the global stage tsunamis got into the center of public and scientific attention after the contemporary devastating events of the 2004 Indian Ocean Tsunami and the 2011 Tohoku-oki Tsunami. Focused research, started in the late 1980s, found its peak in the aftermath of these prominent tsunamis. In the course of tsunami investigations few methods have merit the status as standard proxies in the tsunami identification toolkit. In their broad application in paleo-, historic and modern tsunami surveys, standard sedimentological and paleontological proxies have become almost indispensable assets. This undisputed position, however, is crumbling since the limitations on the (solely) analysis of sandy deposits by these methods potentially contributed to the underestimation of the hazard potential along the Japanese coastline prior to the 2011 Tohoku-oki tsunami. These limitations in line with inevitable analytical progression is a byproduct of every newly introduced study into tsunami research. The newest introduction marks the promising application of organic geochemistry for characterization of tsunamites. Organic geochemistry is commonly used in environmental studies, however, its entry in context with increased numbers of inorganic geochemical studies represents the beginning of a new chapter in tsunami research. This thesis evaluates the limits of standard proxies before assessing the application and limitations of organic geochemical markers, both biomarker and anthropogenic markers. At three field locations, Boca do Rio (Portugal), Kahana Valley (Hawaii) and Sendai Plain (Japan) with varying sedimentological and environmental settings affected by tsunamis of different magnitude and age, standard and organic geochemical proxies are tested and results contrasted. At Boca do Rio a multi-proxy study was conducted not only characterizing the AD 1755 Lisbon tsunami but also lead to the detection of a yet unknown tsunami deposit event, most likely dating to the mid or late 1st millennium AD. With standard sedimentological, micropaleontological and inorganic geochemical methods we were able to extend the Portuguese tsunami record. Inorganic geochemical proxies are already frequently used to detect marine inundation events, however, certain proxies (e.g., salts) are limited by their low preservation potential. The Hawaiian Islands experienced due to their location in the center of the Pacific Ocean, dozens of tsunamis over the past 200 years. Two complementary studies on the Islands have led to the identification of multiple anomalous sand beds of tsunami origin by standard sedimentological proxies and an organic geochemical characterization of aforementioned with the first successful application of anthropogenic markers. Compounds, such as polycyclic aromatic hydrocarbons, pesticides and organochlorides, were extracted from the sediments and analyzed using gas chromatography-mass spectrometry. Distinct changes in concentration between the tsunami sands and the surrounding background sediment helped in identification. While application in rural areas remains difficult, this I Abstract presenting the first successful application of organic proxies on tsunami deposits also shows the potential of geochemical markers. Succeeding the positive results of the first application we present a concluding proof-of-concept study for biomarkers and anthropogenic markers. At the Sendai Plain the 2011 Tohoku-oki tsunami inundated the coastal lowland up to 4.5 km inland, causing massive destruction while eroding and redistributing large amounts of soil and sediment. This led to the release and distribution of anthropogenic markers and biomarkers from different sources across the Sendai Plain creating a unique geochemical signature in the tsunami deposits. Their concentrations differed significantly from the pre- and post-tsunami background contamination levels, reflecting the remarkable environmental changes on the Sendai Plain due to the tsunami. In this proof-of-concept study prior research results by Richmond et al. (2012), Szczuciński et al (2012) and Shinozaki et al. (2015) have been positively reproduced by organic geochemical proxies, and even extended by presenting more specific sediment sources due to the high source specificity of the detected compounds. While the application of standard proxies is crucial, the extension of available tools on disposal for tsunami identification is of importance. Organic geochemistry, the newest entry into this toolkit presents great potential in providing additional information on hydrodynamic processes, sediment erosion, transport and deposition, potential (water-)pathways (e.g., marine source, evidence of backwash) associated with tsunamis. Especially as these parameters are site-specific, they can be well-captured by organic markers due to their high source-specificity and good preservation potential. By this doctoral thesis we demonstrate the indisputable usefulness of standard proxies for tsunami investigations and the capabilities of organic geochemical proxies. Latter are presented by utilization on different sedimentary archives to highlight their future potential to close existing knowledge gaps still unanswered by standard proxies. II Kurzfassung Kurzfassung Naturgefahren haben die Menschheit durch ihre Historie begleitet, unter diesen Risiken sind Tsunamis diejenigen Ereignisse, die bis vor relativ kurzer Zeit am wenigstens verstanden und untersucht worden sind. Übertragen mit globaler Präsenz haben sie, nach den zerstörerischen Ereignissen des 2004 Tsunamis im Indischen Ozean und des 2011 Tohoku-oki Tsunamis, öffentliches und wissenschaftliches Interesse geweckt. Gezielte Forschungen seit den späten 1980ern fanden ihren Höhepunkt nach diesen verheerenden Ereignissen. Im Verlauf der Tsunami-Forschungen haben nur wenige Methoden den Status eines Standard-Proxys im Instrument-Repertoire zur Identifizierung von Tsunami erlangt. Bei ihrer breiten Anwendung in paläo-, historischen und modernen Tsunami-Studien sind sedimentologische und paläontologische Standard-Proxys unverzichtbar geworden. Diese unumstrittene Position wird jedoch in Frage gestellt, da die Limitierungen ausgehend von der (ausschließlichen) Analyse von Sandablagerungen dieser Methoden möglicherweise zur Unterschätzung des Gefahrenpotenzials für die japanische Küste vor dem 2011 Tohoku-oki Tsunami beigetragen haben. Diese Einschränkungen zusammen mit dem unvermeidlichen Fortschritt in der Analytik sind mitunter Grund von neuartigen Studien in den Tsunami-Wissenschaften. Die letzte Neueinführung stellt die vielversprechende Anwendung der Organischen Geochemie zur Charakterisierung von Tsunamiten dar. In zahlreichen Umweltstudien wird die Organische Geochemie regelmäßig genutzt, jedoch stellt ihr Ersteinsatz im Kontext zur zunehmenden Anzahl an anorganisch geochemischen Studien den Beginn eines neuen Kapitels in der Tsunami-Forschung. Diese Promotionsarbeit verdeutlich zunächst die Grenzen der bisherigen Standard-Proxys, bevor eine Bewertung der Anwendbarkeit und Limitierung von organisch geochemischen Markern, sowohl Biomarker als auch anthropogene Marker, folgt. An drei Untersuchungsgebieten, Boca do Rio (Portugal), Kahana-Tal (Hawaii) und Sendai-Ebene (Japan) die sich allesamt durch unterschiedliche sedimentologische und ökologische Bedingungen auszeichnen, zudem von Tsunamis unterschiedlicher Magnitude und Alters betroffen waren, werden Standard- und organisch geochemische Proxys getestet und deren Ergebnisse gegenübergestellt. In Boca do Rio wurde eine Multi-Proxy-Studie durchgeführt, die nicht nur den 1755 Lissabon Tsunami charakterisiert, sondern auch zur Entdeckung eines bisher noch unbekannten, auf das mittlere bis späte 1. Jahrtausend n. Chr datierende. Tsunami-Ereignisses führte. Mit den standardisierten sedimentologischen, mikropaläontologischen und anorganischen geochemischen Methoden konnten wir somit den portugiesischen Tsunami-Katalog erweitern. Anorganische geochemische Marker werden bereits häufig zur Erkennung von marinen Überflutungsereignissen verwendet, jedoch sind bestimmte anorganische Vertreter wie Salze in der Identifizierung von Tsunamiten durch ihr geringes Erhaltungspotential eingeschränkt. Die Hawaiianischen Inseln erlebten aufgrund ihrer zentralen Lage im Pazifischen Ozean eine Vielzahl von Tsunamis in den letzten 200 Jahren. Zwei sich ergänzende Studien auf den Inseln haben durch eine III Kurzfassung standardisierte sedimentologische und organische geochemische