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 Charakterisierung, im Zuge der erstmaligen Anwendung von anthropogenen Markern, zur Identifizierung mehrerer anormaler Sandlagen tsunamigenen Ursprungs geführt. Stoffgruppen wie Polyzyklische Aromatische Kohlenwasserstoffe, Pestizide und Organochloride wurden aus den Sedimenten extrahiert und mittels Gaschromatographie-Massenspektrometrie qualitativ und quantitativ analysiert. Deutliche Konzentrationsänderungen zwischen den Tsunamilagen und dem umgebenden Hintergrundsedimenten halfen bei deren positiven Identifizierung. Während sich die Anwendung von anthropogenen Markern in ländlichen Gebieten weiterhin als schwierig erweist, zeigt die erstmalige erfolgreiche Anwendung von organischen Proxys an Tsunamiablagerungen das Potenzial geochemischer Marker. Nach den positiven Ergebnissen der Erstanwendung stellen wir eine Studie zum Konzeptnachweis für die Anwendbarkeit von Biomarkern und anthropogenen Markern vor. Die Überflutung der Sendai- Ebene durch den 2011 Tohoku-oki Tsunami (bis zu 4.5 km landeinwärts) hatte eine massive Zerstörung sowie die Erosion und Verteilung von großen Mengen an Sediment, Boden und Schadstoffen zur Folge. Dies führte auch zur Freisetzung und Verteilung von anthropogenen und Biomarkern aus verschiedensten Quellen in der Sendai-Ebene, wodurch sich eine individuelle geochemische Signatur in den Tsunamilagen bildete. Dessen Konzentration unterscheidet sich signifikant von den Werten der Hintergrundkontamination vor und nach dem Tsunami, was auf die drastischen Umweltveränderungen für die Sendai-Ebene während des Tsunami zurückzuführen ist. In dieser Studie zum Konzeptnachweis wurden frühere Forschungsergebnisse von Richmond et al. (2012), Szczuciński et al. (2012) und Shinozaki et al. (2015) mit organisch geochemischen Proxys positiv reproduziert und sogar erweitert, durch den Nachweis spezifischer Sedimentquellen basierend auf der hohen Quellspezifität der detektierten Verbindungen. In Gesamtbetrachtung ist die Anwendung von Standard-Proxys von entscheidender Bedeutung, jedoch ist die Erweiterung der verfügbaren Instrumente zur Identifizierung von Tsunamis von hoher Wichtigkeit. Die Organische Geochemie als neuster Zugang in dieses Repertoire, bietet großes Potenzial um zusätzliche Informationen zu hydrodynamischen Prozessen, Sedimenterosion, Transport und Ablagerung, sowie potenzieller (Wasser-)Wege (z.B. marine Quellen, Hinweise auf den Rückstrom) die mit Tsunami-Ereignissen in Verknüpfung stehen, zu erlangen. Da diese Parameter ortsspezifisch sind, können sie aufgrund ihrer hohen Quellenspezifität und ihres guten Erhaltungspotenzials von organischen Markern erfasst werden. Zusammenfassend präsentieren wir in dieser Promotionsarbeit den unbestreitbaren Nutzen von Standard-Proxys für die Tsunamiforschung, jedoch zeigen die Fähigkeiten der organischen Geochemie, durch die Anwendung an unterschiedlichen sedimentären Archiven, das Zukunftspotential vorhandene Wissenslücken zu schließen, die von Standard-Proxys bisher noch unbeantwortet blieben.

IV

Foreword and Acknowledgements

Foreword and Acknowledgements Firstly, I would like to thank my supervisors, Prof. Dr. Klaus Reicherter and Prof. Dr. Jan Schwarzbauer, for enabling me to work within their research groups. Even though I first contacted the wrong person, Prof. Dr. Reicherter gave me the opportunity to come to Aachen following my time at the USGS. From there everything progressed very quickly: a successful application to the Graduiertenförderung of the RWTH Aachen, a successful DFG proposal and countless field work deployments have flown by in the past 3 years. I especially want to thank both of my supervisors for many opportunities to attend conferences and for sending me across the world to gain field work experience, for example, taking me along and allowing me to help organize a successful research cruise with the RV METEOR (M152). I appreciate the chance to prove, develop and establish organic geochemistry as a new prosperous tool in tsunami research, which few have attempted as it is a difficult and underestimated topic. I am looking forward to working with you and to continue working under your supervision on many more projects to come!

Further I would like to thank Prof. Dr. Littke for providing the opportunity to work in the environmental laboratories at the Institute of Geology and Geochemistry of Petroleum and Coal under the supervision of Prof. Dr. Schwarzbauer. I would also like to thank Yvonne Esser, Annette Schneiderwind, Kerstin Windeck, Werner Kraus, Miriam Birx and Phillipp Pelzer and everyone else that helped me analyze samples in the lab. Without your support and commitment the studies presented in this doctoral thesis would not have been possible.

Pushing me onto the path of tsunami research in the first place, I would like to thank my colleagues and supervisors Vanessa Nentwig (WWU University Münster, Germany) and Dr. Michaela Spiske (Basel University, Switzerland). Further I would like to thank my former supervisor Prof. Dr. Heinrich Bahlburg (WWU University Münster, Germany) for giving me the opportunity to study tsunami deposits in Chile during my Bachelor’s and Master’s degrees, thus sparking my interest in natural hazard research.

I would like to thank Dr. Bruce Jaffe and Dr. Bruce Richmond (USGS), who hosted me during my research stay at the Pacific Coastal and Marine Science Center in Santa Cruz. Both helped me with samples, constructive comments on manuscripts and academic support before and during my doctoral thesis. I want to thank Dr. Bruce Jaffe and Prof. Dr. Witold Szczuciński (Adam Mickiewicz University, Poland) for supplying samples from the Sendai Plain leading to a submitted manuscript in Marine Geology. I want to thank especially Dr. Bruce Richmond for taking me along on field work in Hawaii not only once but twice and including me in his research project, resulting in two successful publications in a special issue of Sedimenology. I would like everyone from both research groups and beyond, who stood next to me during all the hours in the lab, drilled cores in Spain, Portugal, Hawaii, Japan or India, hand-shoveled ginormous trenches in the scorching sun, traveled to conferences or just worked with me in any of the several projects during

VII Foreword and Acknowledgements my doctoral studies. Thank you everyone for letting me learn from you, for your input, your academic discussions and experiences!

The peer-reviewed articles of this doctoral thesis benefited from the support, critical comments and suggestions of: Prof. Dr. Helmut Brückner (University Cologne, Germany) for his continuous support of the projects, critical comments improving manuscripts and being a great lab partner on the RV METEOR no matter if it is in the dark taking OSL samples or at daylight preparing cores for photography. - Prof. Dr. Yuichi Nishimura (Hokkaido University, Japan), for his great support organizing and organizing field work trips to Japan; sharing his far-reaching knowledge about Japanese tsunami deposits and being a wonderful cooperative partner and host in Japan. I am looking forward to coming back to Japan and continuing working with you on many projects. - Dr. Pedro Costa (Universidade de Lisboa, Portugal) for sharing his insight and experience with tsunami deposits and microtextural analyses, his support during field work, a great time on the RV Meteor even in the presence of containers, his constructive comments on joint publications, his work in organizing and hosting an amazing tsunami field symposium in Lisbon and his work as Editor for a Sedimentology special issue (2 publications of this doctoral thesis). I am looking forward to continuing working with you both offshore and onshore in the future. - Dr. Hannes Laermanns (University Cologne, Germany) for the great field work sessions in Portugal and the continuing joint studies and manuscript preparations to come. - Dr. Dominik Brill (University Cologne, Germany) for supporting with OSL dates throughout the projects. - Prof. Dr. Martin Melles (University Cologne, Germany) for giving us access to his laboratory facilities and supplying XRF scans. - Anonymous reviewers who improved the manuscripts with their critical commentary.

I would like to thank everyone helping me proofreading and improving this doctoral thesis. A special thank goes to Mike Frenken, Luisa Helm, Christopher Weismüller, Andew McIntyre and SeanPaul La Selle.

Alla fine vorrei ringraziare mio padre, Cosimo Bellanova! Finally, I want to thank my father Cosimo Bellanova, who not only supported me along my entire academic career, but reminded me constantly to finish my thesis and approach new goals in life.

This doctoral thesis would not have been possible without the financial support of: - RWTH Graduiertenförderung (PhD scholarship) - US Geological Survey, Coastal and Marine Geology Program - Deutsche Forschungsgemeinschaft (DFG); Project number 323318298 (RE1361/28-1) and 390538253 (RE1361-32-1, SCHW750-22).

VIII

Contents

Contents Abstract ...... I Kurzfassung ...... III Foreword and Acknowledgements ...... VII 1 Introduction ...... 1 1.1 Tsunami research – a brief history ...... 1 1.2 Main objectives ...... 3 1.3 Thesis outline ...... 5 2 Tsunami events and study areas ...... 6 2.1 AD 1755 Lisbon tsunami (Portugal) ...... 7 2.2 AD 1946 and AD 1957 Aleutian tsunamis (Hawaii) ...... 8 2.3 AD 2011 Tohoku-oki tsunami (Japan) ...... 9 3 State of the art ...... 10 3.1 Tsunami research – state of the art ...... 10 3.2 Development of organic-geochemical analysis for tsunami research ...... 14 4 The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal ...... 19 4.1 Introduction ...... 21 4.2 Research area ...... 22 4.3 Methods ...... 24 4.4 Results ...... 27 4.5 Discussion ...... 35 4.6 Conclusion ...... 41 4.7 Acknowledgements ...... 41 4.8 References ...... 42 5 Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands ...... 49 5.1 Introduction ...... 51 5.2 Sedimentary evidence of historical and prehistoric distant-source tsunamis in Hawai΄i ...... 53 5.3 Study Area ...... 54 5.4 Methods ...... 58 5.5 Results ...... 61 5.6 Discussion ...... 68 5.7 Conclusions ...... 72 5.8 Acknowledgements ...... 73 5.9 References ...... 73 5.10 Supplementary Material ...... 79

XI Contents

6 Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i ...... 85 6.1 Introduction ...... 87 6.2 Study Area ...... 87 6.3 Methods ...... 90 6.4 Results ...... 92 6.5 Discussion ...... 102 6.6 Conclusions ...... 106 6.7 Acknowledgements ...... 107 6.8 References ...... 107 6.9 Supplementary Material...... 112 7 Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan) ...... 119 7.1 Introduction ...... 121 7.2 Study Area ...... 122 7.3 Methods ...... 125 7.4 Results ...... 128 7.5 Discussion ...... 137 7.6 Conclusions ...... 140 7.7 Acknowledgements ...... 141 7.8 References ...... 141 8 Resume...... 147 8.1 Applicability and preservation potential of organic markers ...... 147 8.2 Identification potential and new insights ...... 150 9 Conclusion and outlook ...... 155 References ...... 159 Contribution in publications and additional publications ...... 189 Declaration ...... 195

XII List of Figures

List of Figures

Figure 2.1: Tsunami hazard world map. Red: high tsunami risk coasts; Orange: intermediate tsunami risk coast; Yellow: low tsunami risk coast; Gray: no tsunami risk. (A) Hawaii field site (Kahana Valley) – AD 1946 Aleutian tsunami and AD 1957 Alaska tsunami; (B) Algarve field site (Boca do Rio, Portugal) – AD 1755 Lisbon tsunami; (C) Japan field site (Sendai Plain) – 2011 Tohoku-oki tsunami.…..….…...……………...………..6 Figure 3.1: Summary of post-depositional processes and alterations of tsunami deposits (modified after Chagué-Goff et al., 2017) ..………...……………………………………….…...13 Figure 3.2: Conceptual model of erosion, transport, distribution and deposition of organic- geochemical compounds during tsunami run-up and backwash ………...……………14 Figure 4.1: Field site of Boca do Rio (Portugal). (A) Overview map with analysed drilling cores (yellow), additional cores (grey) and modern reference samples (blue). (B) Oblique aerial photograph of the front of the Boca do Rio valley with beach and overwash fan. (C) Oblique aerial photograph of the valley with locations of the drill sites.………….23 Figure 4.2: Images of the sediment cores BDR 19 (1) and BDR 6 (2), with close-up view of the extreme wave event layers of BDR 6 [(3), (4)] …………………………..……………27 Figure 4.3: Cross section of coast-parallel transect T1 with corings BDR 6, 7, and 8, as well as the recorded ground penetrating radar (GPR) sequence. (A) Facies interpretation from sediment cores and extrapolated cross section of transect T1. Processing (B) and interpretation (C) of GPR profile of transect T1. Numbers in (C) indicate different facies, black marked zone is characterized by notably strong reflectors.…..………….28 Figure 4.4: Cross section of coast-perpendicular transect T2 with corings BDR1, 7, 25, 19 and 27, as well as the recorded radar sequence between BDR 7 and 25. (A) Facies interpretation from sediment cores and extrapolated cross section of transect T2. Processing (B) and interpretation (C) of GPR profile of transect T2. Numbers in (C) indicate different facies.………………………………………………………..……..29 Figure 4.5: Facies interpretation, granulometry, geochemistry and 14C age estimates of the sediment cores BDR 19 (A) and BDR 6 (B) from the central part and the western margin of the floodplain, respectively.…..….…...………………….………….……………………31 Figure 4.6: Principal component analysis (PCA) of the XRF data of core BDR 6 including the two extreme wave event (EWE) layers E1 and E2.……...………………………….………32 Figure 4.7: Age/depth model of BDR 19 according to Blaauw and Christen (2011). For facies determination see legend in Fig. 4.5.…..….…...………………………..…….………32 Figure 4.8: Representative SEM images of foraminifera obtained from sediment cores BDR 6 and BDR 8 ………………………………………………………………………………...34

XIII List of Figures

Figure 5.1: Inset globe shows the location of the Hawaiian Islands and the Aleutian Islands, the source of some of the largest tsunamis that have historically impacted Hawai΄i. The Fox Islands occupy a ca 480 km long segment of the Aleutian Islands. The hillshade map shows bathymetry and topography of the Hawaiian Islands with the locations of sites (red dots) cored in the search for tsunami deposits. Larger text and arrows label the three primary sites: Anahola Valley on Kaua΄i, Kahana Valley on O΄ahu and Pololū Valley on Hawai΄i.………………………………………………………….…………52 Figure 5.2: Core locations and sand thicknesses in Anahola Valley, Kaua΄i. (A) Depositional environments and landforms in Anahola Valley. Core locations in the wetland on the north-west bank of Anahola Stream are marked by green numbered circles (vibracores) and white dots (gouge cores). (B) Thicknesses of sands A1 (green), A2 (yellow) and A3 (red) are represented by circle diameters. Sand A1 is only observed in a few cores in the north-east section of the wetland. Sand A2 is also confined to the north-east section of the wetland but thins inland and away from the riverbank. Sand A3 is observed in cores up to 650 m from the shoreline and gradually thins inland……………..……….55 Figure 5.3: Core locations and sand thicknesses in Kahana Valley, O΄ahu. (A) Depositional environments and landforms in Kahana Valley. Gouge and Russian core locations in the wetland in the south-east part of the valley are marked by white dots. (B) Thicknesses of sand K1 (red) are represented by circle diameters. Sand K1 thins inland between 238 m and 478 m from the shoreline………….….………………...………………………56 Figure 5.4: Core locations and sand thicknesses in Pololū Valley on Hawai΄i. (A) Depositional environments and landforms in Kahana Valley. Core locations in the wetland are marked by green numbered circles (vibracores). White dots represent gouge cores collected by Chagué-Goff et al. (2012b). (B) Thicknesses of sands P1 (green), P2 (yellow) and P3 (red) are represented by circle diameters. Sand P2 (a deposit from the 1946 tsunami) was found in all cores and thins landward. The 1957 deposit (sand P1) was only found in cores VC1 and PO2……………………………………...…………57 Figure 5.5: Photographs, computed tomographic (CT) images, lithology and ages of core stratigraphy hosting prehistoric tsunami deposits at the three primary sites. (A) Vibracore VC8 from Anahola Valley. Sands A1 and A2 are in the lower half of the upper segment. The lower segment shows sand A3. (B) Core RC-02b from Kahana Valley showing sand K1. (C) Vibracore VC1 from Pololū Valley, with sands P1 and P2 in the upper segment, and P3 in the lower segment.………………...... …………………...... 62

XIV List of Figures

Figure 5.6: Vertical variations in grainsize distributions of tsunami deposits in Anahola Valley compared with distributions for deposits at Stardust Bay, Aleutians and from the Sendai Plain, Japan. For each vertical subsample from each of the four cores, the weight percent from each phi bin is represented by the colormap and faint white lines. Suspension graded intervals are indicated by the white arrows. (A) Grain-size distributions of sands A1 and A2 from core RC1-BR at Anahola. (B) Grain-size distributions of sand A3 from Russian core RC6-BR at Anahola. (C) Grain-size distributions of a tsunami deposit dated at 660 to 560 cal yr BP at Stardust Bay, Aleutian Islands, Alaska (Witter et al., 2016). (D) Grain-size distributions of a deposit sampled from trench on the Sendai Plain, Japan, from the 2011 Tohoku-oki tsunami (Jaffe et al., 2012).……………………………………………………………………..…………63 Figure 5.7: Lithological column and 137C data compiled from seven adjacent Russian cores at Anahola near core VC7 (Fig. 5.2). Solid line on the right shows 137Cs activity measured at 1 cm intervals. The dashed vertical line indicates the threshold 137Cs activity (0.3 dpm g -1), above which the accumulation of 137Cs in the sediment is apparent, typically in 1954 in sediment around the world (Pennington et al., 1973). At Anahola, this interval is between sands A1 and A2 at 44 to 45 cm depth. The peak activity at 32 to 33 cm corresponds to the years 1963 and 1964, following the peak in atmospheric nuclear testing in 1962……………………………………………………………………..….64 Figure 5.8: ‘OxCal’ modelled ages of tsunami deposits at sites in the Aleutians and Hawai΄i. Probability density functions (bars underneath show 95% confidence intervals) for each modelled age are shown in red for sand A3 in Anahola Valley, sand K1 in Kahana Valley and sand P3 in Pololū Valley. Probability density functions for Aleutian tsunami deposits from Stardust Bay (sands S2 and S3) and Driftwood Bay (sands C1 and C2) are shown in shades of blue (Witter et al., 2016, 2018). The 95% confidence interval age range derived from precise Uh/Th coral dating of the Makauwahi Cave deposit is represented by the symmetrical distribution (95% confidence interval) (Butler et al., 2017). The tsunami deposits in the three Hawaiian valleys have ages that overlap the ages of deposits S3, C2 and C1 in the Aleutians. However, because the distributions are so broad it cannot be determined whether or not the Hawaiian deposits were deposited by a single tsunami or multiple tsunamis of different ages. The distribution for the Makauwahi Cave deposit barely overlaps with the youngest end of the distribution from the Pololū Valley, but not with the distributions for any other tsunami deposits in the Aleutians or elsewhere in Hawai΄i………………...…………………………………..65

XV List of Figures

Figure 6.1: Overview map of the sampling site Kahana Valley, O‘ahu, Hawai‘i. (A) Location of the Kahana Valley on O‘ahu. (B) Overview of the Kahana Valley (imagery by DigitalGlobe®, 2018). (C) Core locations in the Kahana Valley. (D) Transect across the coring locations (imagery by DigitalGlobe®, 2018)……...………………….……….89 Figure 6.2: Selected identified anthropogenic organic geochemical marker groups and the selected compounds used for further analysis in this study.…………………….………………94 Figure 6.3: Delta plots of analyzed polycyclic aromatic hydrocarbons (PAH). Concentrations of pre- tsunami deposits (green) and post-tsunami deposits (red) are plotted relative to the concentration of the tsunami deposit (red line = 100%) of each sample core.……...... 96 Figure 6.4: Polycyclic aromatic hydrocarbon (PAH) concentration profiles with depths and graphic sediment description of all cores.…..….…...…………………………………………98 Figure 6.5: Diagnostic ratios with fluoranthene and pyrene (Fl/(Fl + Py)) plotting on the x-axis of each graph and: (A) anthracene and phenanthrene (An/(An + Ph)); (B) benz[a]anthracene and chrysene (BaA/(BaA + Ch)); and (C) phenanthrene and anthracene (Ph/An) plotting on the y-axis, respectively………………….……………99 Figure 6.6: Bumetrizole concentration profile with depths and graphic sediment description of core 13.……...……………………………………………………………………….101 Figure 6.7: Map of areas in the Kahana Valley used by the US military and munition response sites (modified after US Army Corps of Engineers, 2016).…………………………….…..105 Figure 7.1: Study site overview. (A) location of Sendai on Honshu Island (Japan) and the epicenter of the 2011 Tohoku-oki tsunami. (B) detail of Sendai Airport field site showing the Sendai airport as well as urban, industrial and agricultural areas. Black dots are sampling locations for former studies (Goto et al., 2011; Chagué-Goff et al., 2012a, 2012c; Jaffe et al., 2012; Jagodziński et al., 2012; Pilarczyk et al., 2012; Richmond et al., 2012; Schneider et al., 2014; Szczuciński et al., 2012), while red dots are sampling locations for this study. The max. limit of tsunami inundation (orange dashed line) is shown according to the Association of Japanese Geographers (2011) report.………123 Figure 7.2: Specific anthropogenic markers, biomarkers, and compound groups analyzed in this study.…………….…..………...……………….……………………………………129 Figure 7.3: Overview of results of n-alkanes with (A) representative chromatograms (trench 2) showing the n-alkane distribution of mass (m/z)= 85; (B) marine, aquatic and terrestrial n-alkane concentrations of each sample; (C) results of the terrigenous:aquatic ratio (TAR); (D) the carbon preference index (CPI) and odd-even predominance (OEP)...131 Figure 7.4: Concentrations of the five analyzed biomarkers groups in trenches T2 and T3 for tsunami deposits (blue bars) and pre- and post-event sediments (green and red)……….……132

XVI List of Figures

Figure 7.5: Delta plots of analyzed anthropogenic markers. Concentrations of pre-tsunami sediments (green) and post-tsunami sediments (red) are plotted relative to the concentrations in the tsunami deposit (blue line =100%) of each trench. For trench 3 (T3) no post-tsunami sediment was present above the tsunami deposit…………...…135 Figure 7.6: Normalized anthropogenic marker concentrations in trenches T2 and T3 for tsunami deposits (blue bars) and pre- and post-event sediments (dark-gray bars). Whiskers encompass the range of concentrations detected while boxes show 1 σ standard deviations from the mean concentration. Note that y-axes are either linear or logarithmic.………………………………………………………………….………136 Figure 7.7: Conceptual model for distribution of anthropogenic chemical compounds in a pre- tsunami setting, during tsunami inundation and in a post-tsunami setting. With concentration differences of three indicative anthropogenic marker (dibenzyl – pesticide; pyrene – PAH; pentachloroaniline – halogenated compound) analyzed samples of each setting. Inundation limit marks the max. distance water reached, limit of tsunami recognition marks the max. distance deposits can be detected (for comparison see Chagué-Goff et al., 2012a). Model is not to scale..……………...….138 Figure 8.1: Conceptual model of erosion, transport, distribution and deposition of sediments and organic-geochemical compounds/ pollutants during tsunami inundation and backwash in rural environments (left – Kahana Valley) and urbanized environments (right – Sendai Plain)…………………………..…………………………………………….....148

XVII

List of Tables

List of Tables

Table 4.1: Foraminifera content of samples from sediment cores BDR 6 and 8. The following classes

and signatures were use: 0 = absent (−), 1–10 = very rare (+), 11–30 = rare (++), 31–50 =

frequent (+++), 51–100 = very frequent (++++), >100 = abundant (+++++). The Index of Oceanity was calculated after Gibson (1989): I = planktonic foraminifera / (planktonic + benthic foraminifera)……………………………………………………………………………….33 Table 4.2: Radiocarbon ages. The 14C measurements were carried out by the 14CHRONO Centre, Queen's University Belfast, Northern Ireland, UK. The age estimates are presented as conventional and calibrated ages. Calibration with Calib 7.1 (data set: Intcal13.14C; Stuiver and Reimer, 1993; Reimer et al., 2013).……...…………………………………………….35 Table 4.3: OSL ages for sediment core BDR 19. The measurements were carried out in the Cologne Luminescence Laboratory (CLL). Sampling was in 2017 CE. For age calculation the Minimum Age Model (MAM) was applied (Galbraith et al., 1999)……….……….……….35 Table 5.1: Notable historical tsunami events impacting the Hawaiian Islands*.……………..……….52 Table 5.2: Radiocarbon data and stratigraphic context for samples from cores bracketing the ages of sand layers A3 in Anahola Valley, Kaua΄i, K1 in Kahana Valley, O΄ahu and P3 in Pololū Valley, Hawai΄i.*…..….…...………………………………………………...………...... 60 Table 7.1: Overview of anthropogenic markers and biomarkers, the environments they are found, and the sources they can derive from (visually modified after Bellanova et al., 2020).…...…...124 Table 7.2: Total organic carbon (TOC) and total inorganic carbon (TIC) results from liquiTOC II analysis (visually modified after Bellanova et al., 2020). ………………….……………..128 Table 7.3: Biomarker marker results of the six analyzed compound groups and the calculated indicative ratios: terrigenous aquatic ratio (TAR), carbon preference index (CPI), odd-even- predominance (OEP) (visually modified after Bellanova et al., 2020).…….……………..130 Table 7.4: Anthropogenic geochemical marker results of the three analyzed compound groups polycyclic aromatic hydrocarbons, pesticides and halogenated compounds (visually modified after Bellanova et al., 2020)..……………………………………………...…….133

XIX

Introduction

1 Introduction

1.1 Tsunami research – a brief history In the past century the world has grown noticeably closer, manifested by an increase in the transfer of information and the exchange of knowledge. As a result, our knowledge on natural disasters with high societal impacts, but low frequencies of occurrence, that have previously been forgotten between generations, has increased as well. Tsunamis have become known as some of the greatest natural hazards and have caused devastating amounts of destruction, loss of lives, economic crises and long-term societal consequences. Although the phenomenon of tsunamis described long ago by Herodotus (479 BC), Plinius the Younger (AD 79) and Japanese records following the AD 648 Hakuho-Nankai tsunami (described in AD 720; Goff et al., 2016), it took until the AD 1755 Lisbon earthquake and tsunami before the first systematic research efforts were undertaken by Sebastião José de Carvalho e Melo, better known as Marquês de Pombal. His studies in the documentation of the effects by the earthquake and tsunami led to the birth of modern seismology and the Memórias Paroquiais de 1758. One of the first milestones in modern tsunami research was the documentation of the AD 1896 Meiji Great Sanriku Tsunami by the Council on Earthquake Disaster Prevention (CEDP), which mentioned for the first time that earthquakes are forerunning phenomena of tsunamis (Shuto and Fujima, 2009). This caused an academic debate about the mechanisms causing tsunamis until about 1910 when researchers understood that fault motions of earthquakes can cause tsunamis (Shuto and Fujima, 2009). In the Edo era (400 years ago) coastal forests were planted to protect rice fields mainly from strong sea winds unintentionally creating a first line of defense against tsunamis (Sugawara et al., 2012a). First implementation of official countermeasures followed three months after the 1933 Showa Great Sanriku Tsunami, with proposals such as: (I) relocation of houses to higher ground; (II) coastal dikes, seawalls and control forests; (III) buffer zones and evacuation routes (Shuto and Fujima, 2009). Two main events in the mid-20th century, the 1946 Aleutian tsunami and the 1960 Great Chilean tsunami, affected wide areas of the Pacific Ocean initiating the foundation of the Pacific Tsunami Warning Center on Hawaii. Few studies documented the destruction of these events (e.g., MacDonald, et al., 1947; Shepard et al., 1949) focused on the earthquakes causing them, rather than discussing tsunamis as a geological phenomenon itself. The first findings of sedimentological evidence, however, were not documented until Wright and Mella (1963) described a 1-2 cm thick sand deposit resulting from the 1960 Chilean tsunami (Dawson and Shi, 2000). A surge in scientific interest was initiated by two publications of Atwater (1987) and Dawson (1988), kicking off modern tsunami research. Atwater (1987) described evidence of prehistoric tsunami deposits along the coast of Washington. Dawson et al. (1988) described anomalous sand deposits in Scotland produced by the prehistoric Storegga tsunami. However, researchers of both studies were criticized for proposing a tsunami as generating mechanisms,

1 Introduction as common scientific opinion preferred more frequently occurring storms as the origin for these deposits (Dawson and Shi, 2000). In the 1990s, paleo-tsunami research continued to grow with a number of key publications (e.g., Minoura and Nakaya, 1991; Paskoff, 1991; Atwater, 1992). In early publications authors (e.g., Dawson, 1996; Bourgeois and Minoura, 1997) identified distinctive and typical characteristics of tsunami deposits, some of which were later refuted, as a greater number of studies on tsunami deposits began to show that tsunami deposits are often quite variable and are strongly associated with local settings and sediment sources. With this first rise of tsunami research multiple new proxies were developed such as microfossil investigations (e.g., Hemphill-Haley, 1996) and early forms of inorganic geochemical investigations (e.g., Minoura and Nakaya, 1991; Chagué-Goff et al., 2002) used to positively identify tsunami deposits. Global social and political attention towards tsunami hazards was first spurred on by the events of the 2004 Indian Ocean tsunami, with over 230,000 casualties. This was followed by a spike in tsunami research and the standardization of granulometric and microfossil methods (e.g., Dawson and Stewart, 2007; Morton et al., 2007; Kortekaas and Dawson, 2007; Mamo et al., 2009; Bourgeois, 2009; Peters and Jaffe, 2010, Chagué-Goff et al., 2011). As a reaction to the lack of knowledge about recurrence intervals of major tsunami threats the 2004 Indian Ocean Tsunami was a catalyzing event for another peak of paleo-tsunami studies (e.g., Scheffers et al., 2005; Rhodes et al., 2006; Dahanayake and Kulasena, 2008; Lario et al., 2011). The worldwide televised 2011 Tohoku-oki earthquake and tsunami drew great scientific attention and surprised the world given that Japan is considered by many as the best-prepared against tsunamis and the most experienced country in terms of mitigating and recovering from in natural hazards. The tsunami resulted in the highest economical damage ever recorded by a natural hazard event (Daniell et al., 2011). Subsequent surveys documented a record inundation distance of 4.85 km inland at the Sendai Plain (Chagué-Goff et al., 2012). Studies of this deposit challenged the notion that the dominant type of sediment being deposited by tsunamis is sand. On the Sendai plain, sandy deposits represented 60% (2.9 km) of the inundated area, while muddy deposits were detected up to 4.65 km (95%) inland (Chagué-Goff et al., 2012c). Many studies focused on various aspects of the tsunami deposit along a single transect near the Sendai Airport (e.g., Goto et al., 2011; Chagué-Goff et al., 2012c; Goto et al., 2012; Jaffe et al., 2012; Pilarczyk et al., 2012; Richmond et al., 2012; Sugawara and Goto, 2012a; Szczuciński et al., 2012; see also special issue of Sedimentary Geology in 2012, Vol. 282), making this the most thoroughly studied tsunami deposits to date. The devastating effects of the 2011 Tohoku-oki tsunami could have been mitigated with greater understanding of the geologic record of Japanese tsunamis. On the Sendai Plain, deposits of the AD 869 Jogan tsunami provided indication that tsunamis had reached up 3.3 km inland in previous events (1.1 km from the modern coastline; Sugawara et al., 2012a). A historical Japanese document (Nihon- Sandai-Jitsuroku), describes the occurrence and damage by the AD 869 Jogan tsunami as well. Extensive studies on the Jogan tsunami have been published (e.g., Minoura et al., 2001; Satake et al.,

2 Introduction

2008; Okamura, 2012; Chagué-Goff et al., 2012a; Namegaya and Satake, 2014), however, as the actual used standard proxies are too limited to give an overall picture of historic and paleo-tsunamis in the Sendai Plain (Sugawara et al., 2012b), this might have led to an underestimation of the hazard potential. Recent tsunami research has focused on the study of historic and paleo-tsunamis (e.g. Shinozaki et al., 2015; MacInnes et al., 2016; Inoue et al., 2017; Kempf et al., 2018; Goff et al., 2018; Dawson et al., 2019). Another slowly but consistently growing area of tsunami research are offshore studies, presenting a partial view into poorly understood offshore mechanisms of tsunamis and the deposition of tsunami backwash deposits, for example Smedile et al. (2019) studying offshore deposits in the Augusta Bay (Sicily, Italy), Goodman Tchernov et al. (2016) presenting offshore evidence for a yet undocumented tsunami in the northern Red Sea, and Reicherter et al. (2019) extending the Holocene tsunami record of the Algarve coast (Portugal) with evidences of offshore tsunamites in shelf deposits up to 110 m water depth. In the past thirty years, the study of tsunami deposits has made immense progress. Early studies were key to developing our ability to identify tsunami deposits, and ongoing research has further refined our knowledge. Each new study on modern tsunami deposits fills in knowledge gaps and may reveal new and improved methods (proxies) for examining (paleo-) tsunami deposits in the future.

1.2 Main objectives The positive identification of (paleo-) tsunamites in the sedimentary records of coastal areas is as crucial as the acquisition of knowledge about its characteristics and extent. Only with an extensive dataset the hazard potential, recurrence intervals and evacuation areas can confidently be estimated. Traditional and standardized methods, based on the visible recognition of tsunami sand layers, were sufficient tools in past studies, however, as observations of the 2011 Tohoku-oki tsunami demonstrated, data relying only on sand layers can lead to an underestimate of inundation distance and does not focus on the entirety of the deposit. This underestimation did lead to a destructive and deadly trust in the placed defense mechanisms. Since the 2004 Indian Ocean Tsunami, but especially the 2011 Tohoku-oki tsunami, an intensified focus of tsunami research in identification of paleo-tsunamis (e.g., Rhodes et al., 2006; Morton et al., 2007; Dahanayake and Kulasena, 2008; Chagué-Goff, 2010; Goff et al., 2011a; Lario et al., 2011; Shanmugam, 2012) and extending the available identification techniques (e.g., Chagué-Goff et al., 2011; Shinozaki et al., 2015; Szczuciński et al., 2016; Costa et al., 2012a; Bellanova et al., 2019) is to be recognized. The aim of this doctoral thesis is to develop and establish new methods for identifying and characterizing tsunami deposits that can be used in multi-proxy studies alongside to standard techniques. Therefore, the application of indicative organic substances on tsunamites has been developed by merging modern approaches from different research fields: (1) tsunami research; (2) biomarker application (organic

3 Introduction geochemistry) and (3) the use of anthropogenic markers (environmental geochemistry). These methods can be used to determine if it is possible to discriminate between marine and terrestrial material, sediment transportation during tsunami events, and the corresponding organic marker compounds that can be used to trace the impact of tsunamis on the terrestrial and marine environment. So far, the use of organic geochemistry in tsunami research has been rare, although the approach of using specific indicators to determine prehistoric, historic and recent processes and impacts (so-called biomarker and anthropogenic marker approach) is well established. This may be because organic markers are extremely sensitive and have a high source specificity. In detail this doctoral thesis will: I) Apply organic marker compounds for the identification of recent and historic tsunami events in sedimentary records alongside of sedimentary standard methods.

II) Provide a characterization of tsunamites based on specific organic marker compounds (anthropogenic markers and biomarkers).

III) Contrast organic geochemical results with sedimentary evidences and inorganic geochemical applications

IV) Evaluate the complementary application of biomarker and anthropogenic markers in their ability of identifying tsunami deposits and their contribution to the existing dataset.

V) Build up and establish the organic-geochemical tool for a wide range usage in tsunami research, assessment of spatial inundation distribution and quantitative estimation of recent, historic and prehistoric tsunami impacts.

VI) Identification of yet undiscovered tsunami deposits in the sedimentary record based on multi-proxy analyses.

These main objectives shall provide the database for the verification and validation of this dissertations main work hypothesis that:

Organic markers, both biomarkers and anthropogenic markers, provide a powerful supplementary approach to sedimentary standard techniques, improving the knowledge on tsunami deposits in the sedimentary records, essential for future mitigation efforts of tsunami hazards.

4 Introduction

1.3 Thesis outline After the presentation of this thesis’s main objectives, the study areas are introduced in chapter 2, followed by a state-of-the-art review of methodological applications in tsunami research and the development of organic-geochemical applications for tsunami research in chapter 3. Subsequent chapters 4 through 7, briefly described in the following, present individual studies of this thesis that are already peer-reviewed published, accepted or submitted to be published.

Chapter 4 – The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal A multi-proxy study on the AD 1755 tsunami deposits in Boca do Rio (Algarve, Portugal), detecting a new, yet unknown extreme wave event deposits (older than 985–1147 cal. CE) in the sedimentary record.

Chapter 5 – Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands Presenting sedimentary evidences supported by numerical modeling and radiocarbon ages, this study provides an expanding dataset on multiple far-distant tsunamis affecting the Hawaiian Islands.

Chapter 6 – Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i This study is the first of its kind introducing organic anthropogenic markers for the identification and characterization of a tsunami deposits, described by conventional methods in Chapter 5, in the Kahana Valles, O’ahu, Hawaii.

Chapter 7 – Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan) As a proof-of-concept study, this chapter presents organic-geochemical findings (biomarkers and anthropogenic markers) of the 2011 Tohoku-oki tsunami, discusses them and linking findings such as widespread soil erosion and redeposition with the existing datasets.

Results and individual discussion of chapters 4 through 7 are summarized and discussed in chapter 8, before concluded in chapter 9, offering an outlook for upcoming studies to be undertaken and further development of the presented organic-geochemical applications.

5 Tsunami events and study areas

2 Tsunami events and study areas Tsunamis can be attributed to be a worldwide phenomenon; however, intensities and frequencies of events vary drastically. Furthermore, do coastal areas near active plate margins likely experience more frequent, and depending on the tectonic setting, more severe tsunamis. On the contrary may coastal areas that are considered safe be affected by impacts of far field or trans-oceanic tsunamis.

Fig. 2.1 Tsunami hazard world map. Red: high tsunami risk coasts; Orange: intermediate tsunami risk coast; Yellow: low tsunami risk coast; Gray: no tsunami risk. (A) Hawaii field site (Kahana Valley) – AD 1946 Aleutian tsunami and AD 1957 Alaska tsunami; (B) Algarve field site (Boca do Rio, Portugal) – AD 1755 Lisbon tsunami; (C) Japan field site (Sendai Plain) – AD 2011 Tohoku-oki tsunami.

About half (52.9%; Bryant, 2005) of all ever-recorded tsunamis originated and affected the coastal areas in and around the Pacific Ocean. This can be linked with the frequent activity of the Pacific ‘Ring of Fire’, the chain of subduction zones confining the Pacific Ocean, arousing four of the five largest earthquakes (MW >9) since records began. While the long-indoctrinated belief that tsunamis result only from large scale subduction earthquakes is however in parts still true, the discovery of smaller-scaled events caused by subaquatic landslides, lake rockslides and iceberg calving, changed this scientific view over time. Since 1990 at least 14 tsunami events have been recorded (Bryant, 2014), both small and almost unnoticed, as well as large, devastating and worldwide recognized (e.g., 2004 Indian Ocean tsunami and 2011 Tohoku-oki tsunami). Amongst the preferred human settlements are low-lying coastal stretches, which in turn pose the highest risk of inundation by a tsunami or other flooding events. Located close to urban coastal centers are vulnerable ‘critical infrastructure’, such as industry, hospitals, transportation hubs (airports, harbors) and power supply facilities (oil, gas and nuclear power plants). This vulnerability was publicly realized during the nuclear meltdown of the Fukushima Daiichi nuclear powerplant in result of the 2011 Tohoku- oki earthquake and tsunami. With growing world population and a disproportional growth of coastal population – >50% of world’s population by 2030 (Constanza et al., 2008; Constanza et al., 2014) – the hazard potential is drastically increasing within the following decades. While the occurrence of extreme

6 Tsunami events and study areas events such as tsunamis is not increased by climate change, the consequent sea-level rise will have a noticeable intensifying effect in the events of a tsunami. Seeking greater understanding of tsunami mechanism, pursuing to improve coastal defense infrastructure, the only way lays in enhancing our accessible toolkit investigating tsunamis. As this thesis proofs the concept of organic geochemistry, in particular anthropogenic marker and biomarkers, a variety of parameters need to be tested. Therefore, a selection of very specific locations with the following properties is necessary: (1) well-studied vs. non-studied locations, to test the application on verified tsunami deposits and test the method on lesser explored events; (2) urban vs. non-urban locations, testing the different sensitivities of the method and detecting a broad spectrum of organic markers; (3) historic vs. recent tsunami event locations, testing the temporal limits of the method and evaluating of the preservation potential of organic markers; (4) far-field vs. near-field tsunami locations, testing the magnitude of which organic markers are affected by different scaled tsunami events and sources. According to these properties three main locations for this doctoral thesis have been selected and will be introduced in the following.

2.1 AD 1755 Lisbon tsunami (Portugal) The historic tsunami caused by the AD 1755 Lisbon earthquake affected the coastal lowlands of the Gulf of Cadiz (Spain and Portugal) amongst other regions in the Northern Atlantic. Numerous studies have been conducted investigating deposits of the AD 1755 tsunami (e.g., Hindson et al., 1996; Kortekaas and Dawson, 2007; Reicherter et al., 2010; Costa et al., 2011; Cuven et al., 2013; Costa et al., 2016; Feist et al., 2019) and establish a tsunami catalogue for the region (e.g., Baptista and Miranda, 2009; Lario et al., 2010; Reicherter et al., 2010; Lario et al., 2011). Of all known sites, Boca do Rio (Algarve, Portugal; Fig. 2.1B) can be assigned to be the best-studied field site. First tsunami-related publications referencing and studying the Boca do Rio valley were carried out by Dawson et al. (1995) and da Silva et al., (1996). While the source of the AD 1755 remains speculative and a matter of ongoing scientific debate, over the years detailed and comprehensive studies using a broad variety of methods and tools (e.g., Hindson et al., 1998; Hindson and Andrade, 1999; Oliveira et al., 2009; Cunha et al., 2010; Costa et al., 2012a; Feist et al., 2019) expanded the knowledge about the sediment remains from the AD 1755 tsunami in Boca do Rio. Not only is this field site of archaeological interest, because of the Roman village uncovered and partially eroded by coastal retreat, but as well the lack of knowledge about recurrence intervals of tsunami events along the coast of the Algarve shows the urgent need for more research. Thus, the Boca do Rio field site has been selected as a study area for this doctoral thesis showcasing the scope of standard sedimentological and micropaleontological tools in tsunami research, as presented in chapter 4 – The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal.

7 Tsunami events and study areas

2.2 AD 1946 and AD 1957 Aleutian tsunamis (Hawaii) The Aleutian Trench along the northern rim of the ‘Pacific Ring of Fire’ is one of the most active tectonic regions in the world (e.g., Witter et al., 2016), causing tsunami events of a high recurrence. These are not only affecting the coastal areas of Alaska and the Aleutian Islands themselves, but as far-field tsunamis travel across the Pacific Ocean, also enforce harm at regions without prior notice of the earthquake. The most prominent and frequently affected area of far-field tsunamis are the Hawaiian Islands, located in the center of the Pacific Ocean (Fig. 2.1A). The islands experienced, beside locally volcanic and landslide driven tsunamis (e.g., Moore et al., 1989; McMurtry et al., 2004), effects of all major tsunami events in the past century that occurred in the Pacific Ocean (i.a., AD 1946 Aleutian tsunami, AD 1957 Aleutian tsunami, AD 1960 Great Chile tsunami, AD 1967 Alaska tsunami, AD 2010 Maule tsunami, AD 2011 Tohoku-oki tsunami). As the mostly muddy and peaty river valleys of the Hawaiian Islands can be regarded to be excellent archives for tsunami deposits, and the islands experiencing frequent tsunami inundation (95 tsunamis in 185 years, La Selle et al., 2019a) it is hardly remarkable that they take a prominent place in tsunami research (e.g., Lander and Lockridge, 1989; Burney et al., 2001; Goff et al., 2006a; Chagué-Goff et al., 2012b; Chagué et al., 2018). The partially high frequency in which Hawaii was affected by tsunamis of the same direction (e.g. AD 1946, AD 1957 and AD 1964) makes a distinct assignment of deposits to an event difficult. However, a comprehensive Hawaiian tsunami catalogue allows a correlation with far-field tsunamis and may best represent the tsunami history of the Pacific Ocean. Besides extensive numerical modelling efforts (e.g., Liu et al., 1995; Titov, 1999; Satake et al., 2002; Butler et al., 2014; Arcos and LeVeque., 2015; Bai et al., 2018), numerous studies have been conducted across all islands focusing on different events (e.g., Moore et al., 1994; Moore, 2000; Satake et al., 2002; Fletcher et al., 2003; McMurty et al., 2004; Goff et al., 2006a; Cheung et al., 2013). For this doctoral thesis the main two field locations of the Anahola Bay (Kaua’i) and Kahana Valley (O’ahu) have been selected. Focusing on the presentation of sedimentological standard techniques and allocation of the discovered tsunami deposits the Hawaiian field sites are presented in chapter 5 – Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands. Because the Kahana Valley is relatively uninfluenced by anthropogenic modifications and pollution (with the exception of a World War II military base; Bellanova et al., 2019), it was additionally selected for an application test of organic geochemical analysis in remote areas, presented in chapter 6 – Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i.

8 Tsunami events and study areas

2.3 AD 2011Tohoku-oki tsunami (Japan) Japan is a prime example for awareness and preparedness against tsunami hazards. However, the 2011 Tohoku-oki tsunami shook the country to its core hitting it stronger than models suggested. The nuclear catastrophe of Fukushima Daiichi revealed that the tsunami hazard has been underestimated, despite numerous studies investigating historic and paleo-tsunamis along the coastal areas of Japan (e.g., Abe et al., 1990; Minoura and Nakaya, 1991; Minoura et al., 2001; Sugawara et al., 2012a,b). The Tohoku- oki tsunami is the latest tsunami in a long line of recorded events, such as the AD 869 Jogan tsunami, AD 1896 Meiji-Sanriku tsunami, AD 1933 Showa-Sanriku tsunami, AD 1993 Hokkaido-nansei-oki tsunami. To date, the 2011 Tohoku-oki tsunami may be the best-studied tsunami as multiple research teams studied the remaining deposits immediately after the event (e.g., Hayashi et al., 2011; Mori et al., 2011; Fujii et al., 2011; Fritz et al., 2012; see also special issue of Sedimentary Geology in 2012, Vol. 282), with the renowned Sendai airport transect being the site with the single most conducted studies (e.g. Goto et al., 2011; Chagué-Goff et al., 2012c; Goto et al., 2012; Jaffe et al., 2012; Pilarczyk et al., 2012; Richmond et al., 2012; Sugawara and Goto, 2012; Szczuciński et al., 2012). For the first time a direct sedimentary comparison between deposits of a recent tsunami were made with deposits from a known predecessor (e.g., Sugawara et al., 2013). Furthermore, new insights have been made about general mechanics and sediment transport at the Sendai plain (e.g., Chagué-Goff et al., 2012a; Richmond et al., 2012; Szczuciński et al., 2012). Of these, the most noteworthy might be the discovery by Chagué- Goff et al. (2012a) identifying the maximum inundation limit 1.95 km beyond the limit of sandy tsunami deposits and even 0.2 km further inland than muddy deposits. This is leading to the generally accepted assumption that models based on evidences of sandy deposit derived from paleo- or historic tsunami records might be underestimated. Thus, the Sendai plain was selected as a suitable study area for this doctoral thesis. Besides, the well- studied and recent origin of the 2011 Tohoku-oki deposits, the Sendai plain field site offers through industrial and agricultural influences a broad variety in detectable organic compounds, as shown in first biomarker analysis by Shinozaki et al. (2015). Therefore, chapter 7 – Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan) – presents a proof-of- concept study testing anthropogenic markers and biomarker for tsunami characterization while confirming soil erosion, transportation and resettling during the tsunami observed by Szczuciński et al. (2012).

9 State of the art

3 State of the art Tsunamis represent one of the deadliest and most difficult to predict natural hazards not only in the past but also today. Thus, new methods and tools investigating mechanisms and basic principles of past and recent tsunami events are of high intrest. Applied on long-term coastal sedimentary archives these methods may allow a precise future hazard evaluation. Methods used, even in multi-proxy approaches, are yet not capable of capturing the full extent of tsunami inundation, as most methods still rely onthe visual identification of sand deposits, and are thus limited. Consequently, the development and establishment of new, high-resolution methods is necessary for the investigation of the yet difficult to analyze ‘invisible’ tsunami deposits beyond the limit of visual recognition (e.g., Chagué-Goff et al., 2012a,b; Judd et al., 2017). In this chapter the current methodological state-of-the-art in tsunami research will be presented followed by this doctoral thesis’ aim to develop and establish organic geochemistry as a modern tool for tsunami investigations. As new geochemical analyses not only lead to a detailed picture of well-studied modern tsunami deposits, they may be effective tools to investigate historic and paleo-tsunami or lead to the identification of yet unknown ‘hidden’ tsunami deposits in the sedimentary record.

3.1 Tsunami research – state of the art Since the earliest studies on sedimentary properties of tsunami deposits (e.g., Atwater, 1987; Dawson et al., 1988), several standard identification tools for tsunami investigations were developed and successfully applied (e.g., Goff et al., 2012; Goto et al., 2014; Jagodzinski et al., 2012; Pilarczyk et al., 2014; Sugawara et al., 2015). Amongst all methods applied across tsunami related publications, sedimentological investigations are most common (Morton et al., 2007), representing a basic and required standard method applied in most modern studies. Of all standard methods applied visual description of sedimentary features in tsunami deposits are the most common and first to be applied during field observations. To date, numerous occurring sedimentary features have been described, such as sediment composition (e.g., Jaffe et al., 2003; Goff et al., 2006b; Morton et al., 2007) fining and thinning inland (e.g., Jaffe et al., 2003; Morton et al., 2007; Higman and Bourgeois, 2008; Jagodziski et al., 2009); layer thickness (Peters and Jaffe, 2010); grading and suspension grading (e.g., Gelfenbaum and Jaffe, 2003); rip up clasts (e.g., Shi et al., 1995; Gelfenbaum and Jaffe, 2003; Jaffe et al., 2003; Fritz et al., 2007; Morton et al., 2007; Goto et al., 2011; Richmond et al., 2012; Feist et al. 2019); mud caps (e.g., Morton et al., 2007; Sawai et al., 2009; Chagué-Goff et al., 2011; Goto et al., 2011; Abe et al., 2012; Richmond et al., 2012); truncated flame structures (e.g., Matsumoto et al., 2008); erosive structures (e.g., Morton et al., 2010; Reicherter et al., 2010; Goto et al., 2012; Bahlburg and Spiske, 2012); and countless more sedimentary features have been described. Subsequently to sedimentary features, the second-most common proxy for the characterization of potential tsunami deposits are grain size analyses. Classification of transported tsunami grain size can

10 State of the art range across the entire scale from boulders (e.g., Dawson and Shi, 2000; Mastronuzzi et al., 2007; Goto et al., 2007; Paris et al., 2010a; Goto et al., 2010; Costa et al., 2011; Hoffman et al., 2013) to mud and soil (e.g., Minoura et al., 1994; Dawson and Shi, 2000; Goff et al., 2010a; Abe et al., 2012; Chagué- Goff et al., 2012a; Szczuciński et al., 2012). However, no characteristic grain size distribution can be assigned to tsunami deposits as local deposits grain sizes and composition are a highly dependent function of sediment sources available in the pathway of the inundating waves (Peter and Jaffe, 2010). However, the most prominent studied tsunami deposits are mostly comprised of sandy grain sizes (i.a., 2004 Indian Ocean Tsunami – e.g., Moore et al., 2006; Paris et al., 2007; Morton et al., 2008; 2011 Tohoku-oki Tsunami – e.g., Goto et al., 2011; Pilarczyk et al., 2012; Richmond et al., 2012) as these are generally easiest to visually recognize by the contrast to surrounding finer sediments in inundated areas. Statistical grain size parameters, such as mean, median, mode, sorting, skewness and kurtosis, are most commonly described (e.g., Shi et al., 1995; Szczuciński, et al., 2005; Jaffe and Gelfenbaum, 2007; Morton et al., 2008; Peters and Jaffe, 2010; Nakamura et al., 2012) as features of the sediments source, transportation mode and depositional environment. Observations of heavy mineral accumulations in tsunami deposits are frequent (e.g., Jaffe et al., 2003; Jagodziński et al., 2009; Chagué-Goff et al., 2011; Jagodziński et al., 2012; Nakamura et al., 2012; Costa et al., 2015). Thus, the study of heavy mineral versus light mineral distribution (e.g., Nakamura et al., 2012; Nishimura, 2019) or on their separation- based studies were conducted (e.g., Costa et al., 2012a; Bellanova et al., 2016; Costa et al., 2018). Another by now standard and frequently used proxy are macro- and microfossil assemblages of species such as foraminifera (e.g., Kortekaas and Dawson, 2007; Mamo et al., 2009; Sugawara et al., 2009; Reicherter et al., 2010; Pilarczyk et al., 2012; Hadler et al., 2013; Feist et al., 2019), nannoliths (Paris et al., 2010b; Szczuciński et al., 2012), diatoms (Hemphill-Haley, 1995; Hemphill-Haley, 1996; Kokociński et al., 2009; Sawai et al., 2009; Szczuciński et al., 2012). Commonly, but not exclusively, chaotic mixtures of microfossils derived by different sources (marine, brackish and freshwater, soil) which were eroded during the tsunami have been described (e.g., Bahlburg and Weiss, 2007; Sawai et al., 2009; Srinivasalu et al., 2009; Szczuciński et al., 2012). The integrity of microfossils can provide further insight into the flow during inundation, as often fragmental microfossils of shell hash are described (e.g., Dawson and Smith, 2000; Dawson, 2007; Kokociński et al., 2009; Sawai et al., 2009) which were likely damaged by the turbulent transport mode of the tsunami. The inland transport separation of different sized and thicken shells was described by Sawai et al. (2009) refereeing to similar observations as sedimentary landward fining. For the establishment of temporal frameworks of tsunami deposit in the sedimentary record and the calculation of recurrences intervals, different dating techniques find applications most frequently in historic and paleo-tsunami research. Most tsunami-related studies achieve the temporal assignment of their designated tsunami layer by dating via 14C radiocarbon (e.g., Minoura et al., 2001; Kelsey et al., 2005; Reicherter and Becker-Heidmann, 2009; Sugawara et al., 2012a; Brill et al., 2012; Witter et al., 2016; La Selle et al., 2019a; Feist et al., 2019). Radiocarbon ages provide limited ages, as oftentimes

11 State of the art only sediments above and below the tsunami can be dated (Brill et al., 2012). Studied tsunami deposits are often comprised of sand, thus optical stimulated luminescence dating (OSL; Prescott and Robertson, 1997) is in recent years more frequently used to cross-check radiocarbon ages. OSL dating records the elapsed time since sedimentation occurred (Brill et al., 2012), possibly causing error from incomplete or already prior to the event bleached quartz grains or deposition during night, thus less or no reset happening (Brill et al., 2018). In historic tsunami research additional archaeological evidences can be used for dating and the establishment of a rough temporal framework (e.g., McFadgen and Goff, 2007; Bruins et al., 2008; Koster et al., 2011; Dey et al., 2014; Vött et al., 2014; Hoffmann et al., 2015). However, dating techniques are still afflicted with errors, such as the reservoir-effects, relocation and mixture of sediments, contamination by anthropogenic effects, roots, sediment or other intact plant material, which need to be considered during discussion of the acquired ages. While numerous sedimentary proxies are available for the identification of tsunami deposits in the sedimentary record, unequivocal proxies remain to be developed. Uncertainties in the distinction between high energy event deposits are often based on the small number of methods and proxies used in most studies (Chagué-Goff et al., 2012b). Stand-alone evidences are not adequate to prove or refute the origin of a tsunami deposit due to numerous limitations, restrictions, and likelihood of confusion. On the contrary, is the occurrence of one or more tsunami identification proxies in a potential tsunami deposit (e.g., microfossils, heavy mineral accumulations) or the lack of visible tsunami deposits (e.g., no nearshore sand source available; identically looking sediments derived from the source area), not necessarily enough evidence to refute the origin of hypothetical tsunami deposits (e.g., Goff et al., 2001, Dominey-Howes et al., 2006; Goff et al, 2010a; Chagué-Goff, 2010). Moreover, the insights of Chagué- Goff et al. (2012a) following the 2011 Tohoku-oki tsunami demonstrated how limited the previously applied and as a sufficient standard regarded methods and proxies actually are. The acknowledged predecessor to the 2011 Tohoku-oki tsunami, the AD 869 Jogan tsunami (e.g., Goto et al., 2011; Sawai et al., 2012; Shishikura, 2014; Chagué-Goff et al., 2017), has been studied only based on visibility recognizable sand units, which led to the underestimation of the hazard potential resulting in insufficient protection measures. Studies of tsunami sand deposits at the Sendai Plain showed, that they only represent 60% (2.9 km) of the total inundation (4.85 km) of the 2011 Tohoku-oki tsunami (Chagué-Goff et al., 2012a). Much progress has been made in development of less frequently applied geochemical proxies, with the capability to extend the knowledge into tsunami deposits and provide a more accurate evaluation of the tsunami magnitude (Chagué-Goff et al., 2017). As Chagué-Goff et al. (2017) state, it is ironic that there are early publications by Minoura et al. (1987) and Minoura and Nakaya (1991) regarding geochemical applications that highlight their potential but instead favored easy to apply and faster result yielding sedimentary-based methods that have been dominant since. Following the 2004 Indian Ocean tsunami, geochemical applications are more frequently used and some may be regarded as standard by now. The most prominent are inorganic major and trace element proxies acquired by X- ray fluorescence measurements (e.g., Minoura et al., 1994; Chagué-Goff et al., 2002; Goff et al., 2004;

12 State of the art

Chagué-Goff et al., 2012a; Feist et al., 2019). With Al, Si, P, S, K, Ca, Ti, Mn, Fe, Rb, Sr and Ba being the most tested elements, and especially deposits with increases in Fe, S, Ti, Sr, Ba, Na, Ca, Cl, I or Br may originate from a high-energy coastal event (Cuven et al., 2013). Despite their popularity, inorganic elemental analyses are limited: (1) element’s concentrations may depend on grain size distribution; (2) elemental concentrations vary depending on location, climate, geomorphology and environment; (3) post-depositional changes may vary inorganic element concentration (Cuven et al., 2013; Chagué-Goff et al., 2012a; 2017). Water-leachable ions are proven powerful but transient proxy (e.g., Minoura et al., 1991; Szczuciński et al. 2005; Chagué-Goff et al., 2012a; 2015; Yoshii et al., 2013). Ions such as Na+, K+, Ca2+, Mg2+, Cl-

2- or SO4 represent salt components transported inland with the inundating tsunami (e.g., Chagué-Goff et al., 2017). However, preservation of water-leachable ions is relatively low as they may leach out of the sediment rather fast depending on the climate (Chagué-Goff et al., 2017). Chagué-Goff et al., (2012a; 2014) reported for the Sendai Plain salinity reduction in the deposits from the 2011 Tohoku-oki tsunami, with concentrations remaining higher than in the background soil. Higher preservation can be observed when salts subsequently changes their chemical form becoming organically bound (e.g., Biester et al., 2004). Few other inorganic geochemical applications have been tested, such as heavy metals (e.g., Szczuciński et al., 2005, 2007; Ilayaraja et al.; 2012; Kawabe et al., 2012; Nakamura et al., 2016) or stable isotope ratios (e.g., Chagué-Goff et al., 2012a; Dahanayake et al., 2012; Pilarczyk et al., 2012; Ikehara et al., 2014; Shinozaki et al., 2016), but due to several limitations, none of the tested inorganic applications can be considered a standard application in multi-proxy approaches, except already accessible and effortless major and trace element analyses via XRF. The numerous limitations make inorganic proxies susceptible to post-depositional changes and thus only restrictively practicable for historic and paleo-tsunami studies, as concentrations may be altered or leached out of the sediment beyond analytical recognition.

Fig. 3.1 Summary of post-depositional processes and alterations of tsunami deposits (modified after Chagué-Goff et al., 2017). 13 State of the art

3.2 Development of organic-geochemical analysis for tsunami research Inorganic geochemical proxies used for tsunami identification proved their capabilities to buffer limitations of sedimentary proxies, mainly being limited to visually recognizable sand deposits that make up only a fraction of the inundated area. However, the preservation potential of the most promising inorganic proxies, such as major elements and water-leachable ions, is relatively poor or may be strongly altered over time. An alternative proxy with similar significance for identification but considerably higher preservation potential may be represented by organic markers. Tsunami deposits in the sedimentary record may be characterized by organic-geochemical proxies reflecting the erosion, transport and deposition of mixed marine and terrestrial matter (Figure 3.2). This is possible, since tsunamis erode and transport not only particulate matter from marine to terrestrial areas and vice versa through backwash processes, but also the associated organic material. Affiliated organic biomarkers (e.g., n-alkanes, steroids, fatty acids, terpenes) and anthropogenic markers (e.g., polycyclic aromatic hydrocarbons, pesticides, halogenated industrial compounds) may be eroded from highly source specific point sources, incorporated into tsunami deposits and possibly be detectable in indicative concentrations beyond the limit of visual tsunami deposit recognition. In addition, organic biomarkers and historic anthropogenic markers may provide a geochemical insight into historic and paleo-tsunami research based on their persistency and high preservation potential compared to inorganic proxies.

Fig. 3.2 Conceptual model of erosion, transport, distribution and deposition of organic-geochemical compounds during tsunami run-up and backwash.

14 State of the art

Organic geochemical proxies for tsunami-related studies have been tested infrequently and not yet to their full potential. Most early studies featuring the analysis of organic proxies are completely restricted to bulk parameters, namely the analysis of organic matter content via loss of ignition (e.g., Chagué-Goff et al., 2002; Goff et al., 2010b; Chagué-Goff et al., 2012b). Noteworthy is the first example of a differentiation between marine and terrestrial organic matter with organic-geochemical proxies by Fleck et al. (2002). Based on resin-derived organic compounds (tricyclic diterpenes), steranes, hopanes and pristane/phytane ratios a characterization of fluctuating environmental conditions (acidic and redox conditions, bioturbation) caused by varying contributions of terrestrial and marine sedimentary input has been described (Fleck et al., 2002). The authors do observe anomalies (e.g., in the n-alkane distribution or the dibenzothiophene/phenanthrene ratio) which may represent a storm or tsunami origin. The focus of this study was not in characterization of this single events deposit but on long-term transgressive and regressive cycles. One of the first promising approaches using organic markers extracted by various analytical techniques was the investigation of polycyclic aromatic hydrocarbon (PAH) concentrations by Tipmanee et al. (2012). With nearshore offshore samples of the 2004 Indian Ocean Tsunami they were able to detect a slight increase of total PAHs concentration (sum of 13 individual PAHs) which they attributed to terrestrial input by the tsunami backwash. However, their extraction and analytical have deficiencies, such as the limited analyzed sediment amount (only 5 g), the lack of normalization of different sediments, sampling by grab sampler, likely causing disturbances or contaminations, and most important of all: no evidence was provided that samples taken near-offshore are actually of tsunami origin. This is not supposed to undermine the promising first results of Tipmanee et al. (2012) but needs to be addressed by discussing their results and demonstrating the delicacy and susceptibility for contamination and errors of sampling for organic markers. In follow-up studies by Pongpiachan et al. (2013) and Pongpiachan (2014) PAH concentrations from the same location at Andaman Sea affected by the 2004 Indian Ocean Tsunami were reviewed. The concentration of 12 PAHs, most of them repetitive of Tipmanee et al. (2012), were analyzed and compared with results from offshore sediments from locations across the world in an attempt to evaluate the risk assessment (Pongpiachan et al., 2013). This study was unclearly structured and resulted in a few inaccurate evaluations, potentially harming the reputation of organic markers and especially polycyclic aromatic hydrocarbons as promising proxies for tsunami studies. This did not improve by the repetitive study of Pongpiachan (2014) comparing the nearshore Andaman Sea samples from previous studies (Tipmanee et al., 2012; Pongpiachan et al., 2013) with onshore samples from about 400 km far away Songkhla lake, which far-off and located on the eastern coast towards the Gulf of Thailand, which unaffected by the 2004 tsunami. Some issues but by far not all regarding the application of PAHs to potentially identify tsunami backwash deposits were briefly reviewed by Pongpiachan and Schwarzer (2013). Despite these initial studies, very few studies have used more detailed organic-geochemical analyses of specific compounds in tsunami research. A primary study by Alpar et al. (2012) used concentration

15 State of the art profiles of n-alkanes, fatty acids and steroids to investigate and identify historical tsunami along a coastal area in southwest Turkey. Based on comparison of relative contributions of marine and terrigenous biomarkers they were able to distinguish deposits originating from historic tsunamis from the background sediments. Another successful pilot study by Mathes-Schmidt et al. (2013) combined organic-geochemical proxies with micropaleontological findings from sediments of the Thracian Coast (Greece). Standard micropaleontological parameters have been compared with aliphatic biomarker ratios, such as TAR, pristane/phytane, providing sufficient evidence that biomarkers as tsunami proxies achieved encouraging agreement with sedimentological, geochemical and micropaleontological results (Mathes-Schmidt et al., 2013). Noteworthy is the primary inclusion of the non-extractable fraction to the chemical analyses, providing additional information. The first application of biomarkers on recent deposits of the 2011 Tohoku-oki tsunami were introduced by Shinozaki et al. (2015). Analysis of a broad variety of organic proxies and biomarkers enabled the differentiation of tsunami deposits from the background sediments at the Sendai Plain (Japan). Presence or absence of source specific (e.g., dinosterols) and less specific substances (e.g., n-alkanes) reflect the interpreted deposition scenarios of the 2011 Tohoku-oki tsunami. The authors point out that findings indicate a complex behavior of organic indicators depending on grain size and sediment composition properties, differing concentrations for sandy and muddy tsunami deposits. Nevertheless, Shinozaki et al. (2015) conclude a high potential for biomarkers as a powerful proxy in tsunami research. On the contrary, less successful applications of biomarkers by Ünlü et al. (2012) on lagoonal sediments and Shinozaki et al. (2016) on marine-sourced biomarkers reveal the remaining challenges of organic markers to reliably identify tsunami deposits in the sedimentary archives. In summary the potential of organic markers as a powerful proxy for studying tsunamis in the sedimentary archives has been proven by the successful application in the past (e.g., Alpar et al., 2012; Mathes-Schmidt et al., 2013; Shinozaki et al., 2015) and has been emphasized by a review of geochemical tools in tsunami research by Chagué-Goff et al. (2017). They classified organic- geochemical analyzed via gas-chromatography and mass-spectrometry as a new emerging approach (Chagué-Goff et al., 2017), but pointed only to marine-sourced biomarker as potential tsunami- indicating compounds. Biomarkers are yet on a path to be established and recognized by the community as a standard tool providing (possibly) more insight than other frequently used methods in tsunami research. Besides the limited approaches of heavy metal (Szczuciński et al., 2005; Nakamura et al., 2016) and the application of PAHs (Tipmanee et al., 2012), the usage of anthropogenic contaminants as indicators in layers originated from modern tsunami events has not been considered. The usage of compounds with a high source specificity (e.g. through point sources), in particular xenobiotics, have not been examined. Even though the high source specificity of anthropogenic marker compounds is well known from environmental studies and particularly in geochronological studies these specific pollutants pointed unambiguously to specific emission sources (Heim and Schwarzbauer 2013). Based on our hypothesis

16 State of the art

(Chapter 1.2 and Fig. 3.2) this doctoral thesis further develops organic markers by cross-referencing organic-marker results with results from standard methods for tsunami identification. The source specificity of selected compounds for distinguishing terrestrial from marine sources has not been approached before in tsunami research, contemplating e.g., by agriculture derived substances like pesticides as terrestrial indicators, or specific biomarkers – n-alkanes, fatty acids, steroids – pointing to a higher marine input.

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Publication - The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal

4 The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal

Lisa Feist1, Sebastian Frank2, Piero Bellanova1,3, Hannes Laermanns2, Christoph Cämmerer1, Margret Mathes-Schmidt1, Peter Biermanns1, Dominik Brill2, Pedro J.M. Costa4, Felix Teichner5, Helmut Brückner2, Jan Schwarzbauer3, Klaus Reicherter1

1 Neotectonics and Natural Hazards Group, RWTH Aachen University, Lochnerstrasse 4-20, 52056 Aachen, Germany 2 Institute of Geography, University of Cologne, Albertus-Magnus-Platz, 50923 Köln (Cologne), Germany 3 Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University Lochnerstrasse 4-20, 52056, Aachen, Germany 4 Instituto Dom Luiz, Departamento de Geologia, Faculdade de Ciências da Universidade de Lisboa, Edifício C6, Campo Grande, 1749-016 Lisboa, Portugal 5 Philipps-Universität Marburg, Fachbereich Geschichte und Kulturwissenschaften, Vorgeschichtliches Seminar, Biegenstrasse 11, 35037 Marburg, Germany

Abstract In 1755 CE, a strong earthquake followed by a transatlantic tsunami destroyed large coastal areas; it also left its sedimentary imprints in the Boca do Rio valley (western Algarve, Portugal). This tsunami layer is very well preserved and has been analysed in several studies. Deposits of preceding extreme wave events, however, have rarely been described for the entire Algarve coast. In this study, we present a multiproxy analysis of seven sediment cores from the Boca do Rio region, organized in two crossing transects, one parallel and the other perpendicular to the coastline. The geochronological framework has been established by combining radiocarbon and optically stimulated luminescence dating with sedimentological and geochemical analyses (XRF, C/N, magnetic susceptibility, granulometry, micropalaeontology), and covers the palaeogeographical evolution of that area for the last four millennia. As expected, the 1755 CE tsunami was easily identified at all coring sites, as a sandwiched stratum between fine-grained alluvium. This event layer presents several tsunami characteristics, such as erosive basal contact, rip-up clasts, a fining-upward sequence, and a mud cap. At one coring site, a second extreme wave event layer of marine origin was detected within floodplain deposits, due to its granulometric, XRF, magnetic susceptibility and micropalaeontological properties. It is stratigraphically located below the 1755 CE Lisbon tsunami layer and can be associatedwith another yet undocumented extreme wave event, most likely dating to the mid or late 1st millennium CE.

Keywords Holocene landscape evolution; coastal environment; AD 1755 Lisbon tsunami; storm deposits; extreme wave events This chapter is a slightly modified version of the article published in Sedimentary Geology (2019), V. 389, p. 147-160, DOI: 10.1016/j.sedgeo.2019.06.004

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Publication - The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal

4.1 Introduction The southern coastal zone of Portugal, the Algarve, is the country's most vulnerable area concerning natural hazards, especially extreme wave events. Even though Portugal has been affected by tsunamis relatively seldom, the Algarve, located along the Gulf of Cádiz, has been subjected to earthquake-related tsunamis in the past (Baptista and Miranda, 2009; Lario et al., 2011). Several extreme wave events affecting the Algarve coast are reported in historical records, such as at 63 BCE, 382 CE, 1722 CE, 1761 CE, 1755 CE, 1941 CE, 1969 CE and 1975 CE, even though the existence and magnitude of some events remain a matter of discussion (Andrade et al., 2016; Baptista and Miranda, 2009). The most devastating event took place on November 1st 1755 CE (Baptista and Miranda, 2009); in geoscientific terms it is regarded as the best described and analysed among these events (e.g., Baptista et al., 1998; Baptista and Miranda, 2009; Costa et al., 2012b, 2016; Dawson et al., 1995; Hindson et al., 1996; Hindson and Andrade, 1999; Quintela et al., 2016; Reicherter et al., 2010; Rodríguez-Vidal et al., 2011). While the 1755 CE tsunami affected shores all around the northern Atlantic, widespread damages were recorded in coastal regions of Portugal, Spain and Morocco, where the combined effects of the earthquake and tsunami caused many fatalities and severe destruction, especially in coastal settlements along the Gulf of Cádiz, Peniche, and the metropolitan area of Lisbon (Santos and Koshimura, 2015). Although the exact epicentre of the earthquake triggering the tsunami is still debated (e.g., Baptista et al., 1998; Gutscher, 2004; Lario et al., 2011; Mader, 2001; Zitellini et al., 2001), it is attributed to locations near the Azores-Gibraltar transform fault zone – a suggested subduction area, with numerous active faults close to the Gulf of Cádiz, where a relatively high hazard potential for earthquakes and tsunamis is assumed (Lario et al., 2011; Duarte et al., 2013). Furthermore, there is geological evidence for one or more extreme wave events affecting the Gulf of Cádiz during Roman times (ca. 250- 50 cal. BC; Lario et al., 2011) in several locations in Spain (e.g., Bay of Cádiz: Luque et al., 2002; Guadalquivir estuary: Rodríguez-Ramírez et al., 2016) as well as a historic tsunami description in 881 CE (e.g., Morales et al., 2008; Reicherter et al., 2010). Although most extreme wave event-related research at the Algarve coast has focused on the 1755 CE tsunami, geological evidence exists for other possible events, caused by storms or tsunamis. Storm deposits have been reported for coastal lowlands at Martinhal (Kortekaas and Dawson, 2007), and the barrier island system of Faro (Andrade et al., 2004). Quite a number of publications about the 1755 CE tsunami impact on the Boca do Rio field site exist (e.g., Costa et al., 2012b; Dawson et al., 1995; Font et al., 2013; Hindson et al., 1999; Vigliotti et al., 2019), while only a few studies focus on the evolution of the Boca do Rio valley (e.g., Allen, 2003). In terms of the sedimentary record of the 1755 CE tsunami event, these publications analysed the event deposit for its compositional and microfaunal characteristics. The deposit can clearly be distinguished from the under- and overlying fine-grained floodplain layers. As yet, no evidence for other extreme wave events able to breach the beach and dune barrier has been documented, however, extreme wave events have been reported in other sedimentary archives along the Gulf of Cádiz (e.g., Dawson et al.,

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1995; Kortekaas and Dawson, 2007; Lario et al., 2011; Reicherter et al., 2010; Röth et al., 2015). As for the inner Boca do Rio valley, the changing ecological characteristics of the Holocene wetland environment have been studied by Allen (2003). He stated that, during Roman times, the modern wetlands were an estuary, which changed to a low energy environment about 1200 years ago (Allen, 2003). In the case of Boca do Rio, Roman ruins of a garum production complex are located in immediate vicinity of the modern coastline. During early Imperial Times, garum, i.e., a special kind of fish sauce, was transported from the Algarve throughout the Roman Empire (Teichner and Pujol, 2008). A sudden hiatus in the production in the 3rd century CE has been detected at a regional scale both in Portugal and Spain, and tentatively associated with either a political or natural cause (Alonso et al., 2004, 2015; Campos et al., 2015). Considering the relative vulnerability of the region to extreme wave events (Röth et al., 2015), a sudden destruction of the coastal production sites by a tsunami or storm event seems possible; plus, archaeological and historical evidences of such an event have been described in Baelo Claudia (Bolonia, Spain; Alonso et al., 2004; Sillières, 2006). Therefore, a high-resolution multiproxy approach was carried out with the aim of detecting geologic footprints of other extreme wave events (besides 1755 CE), including Roman times. In addition, reconstruction of late Holocene palaeoenvironments of the Boca do Rio floodplain was attempted.

4.2 Research area Located at the southwestern Algarve, Portugal (Fig. 4.1), the study area is constituted of a formerly V- shaped, sediment-filled river valley, dissecting a coast with prominent cliffs. The N-S orientation of this floodplain valley corresponds to a fault line (Dawson et al., 1995); it is framed by predominately Jurassic and Cretaceous Almádena cliffs (Hindson et al., 1999). The floodplain extends up to 1 km inland, where it splits up into three sub-valleys (Hindson and Andrade, 1999), through which the rivers Budens, Vale de Boi and Vale de Barão merge in the Boca do Rio valley. Located slightly above the tidal range, the floodplain is not affected by tides, but is seasonally flooded by the streams, when the river mouth is blocked (Hindson et al., 1999). A sand and gravel-rich overwash fan situated behind the beach marks the current landward limit of storm surges (Hindson and Andrade, 1999) (Fig. 4.1). The floodplain is composed of mostly fine-grained Holocene sediments (silt, clay). Its present vegetation pattern is that of fallow land after having been used for agriculture and salt production. Currently the area is a protected nature reserve. A road and parking lot separate the western dune complex from the rest of the floodplain (Fig. 4.1). It is bordered by a steep terrain with an active cliff, the steep beach break with coarse gravel and boulder from the cliff, and partly occupied by Roman dune-covered ruins (Figs. 4.1A, B). In contrast, the eastern part is bordered by a gravelly and sandy river mouth, which depending on the river's water level influences the surrounding floodplain and beach. Due to the eastbound coastal current, the Budens mouth is deflected towards the east; it is, however, highly variable and seasonally even blocked which leads to the flooding of the entire plain.

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The coastal zone is formed by a pocket beach with up to boulder-sized clasts (Fig. 4.1A). It is located between the seasonally blocked river mouth and the dune complex along the western cliff close to the Roman ruins. The coring sites of this study were organized in two crossing profiles: one perpendicular to the coastline, in N-S direction and up to 850 m inland, and the other one parallel to the coastline, up to 375 m inland (see Fig. 4.1).

Fig. 4.1 Field site of Boca do Rio (Portugal). (A) Overview map with analysed drilling cores (yellow), additional cores (grey) and modern reference samples (blue). (B) Oblique aerial photograph of the front of the Boca do Rio valley with beach and overwash fan. (C) Oblique aerial photograph of the valley with locations of the drill sites.

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4.2.1 Archaeological background In antiquity, the physiographic situation with the far inland reaching estuary facilitated the evolution of an extensive surplus production-oriented fishing site (e.g., Teichner et al., 2019). Between the 1st and 5th centuries CE, fish sauces (garum) and salted fish products, important ingredients for Roman cooking, were produced at Boca do Rio. Next to the production vats which were arranged in long rows parallel to the hillside, its own harbour installations served to land the fish catch and load ships with garum- filled ceramic containers (amphorae). The success and profitability of this maritime economy is testified by residential buildings with valuable mosaic floors and corresponding (public) baths, all lined up along the seashore (Teichner, 2016; Teichner et al., 2019). Human activities, however, were constrained not only by long-term changes of the natural environment, such as siltation as well as coastal erosion (Teichner and Mañas Romero, 2018), but also by short-term high energy events. Information on the detailed chronology of sedimentation in this environment can be compared to previous geoarchaeological investigations on Cerro da Vila (Quarteira, Portugal; Teichner et al., 2014).

4.3 Methods 4.3.1 Sampling A total of 26 sediment cores were obtained with a percussion coring device (Cobra TT of Atlas Copco and a hydraulic lifting unit) and arranged in two transects: parallel (T1, Fig. 4.1) and perpendicular (T2, Fig. 4.1) to the present-day coastline. Drilling depth varied from 2 to 7 m due to local conditions. In this study, seven selected sediment cores were analysed (Fig. 4.1). Sediment cores BDR 1 and 27 were drilled with open auger heads (outer diameters: 9, 6, and 5 cm) and used for an on-site description, while sediment cores BDR 6, 7, 8, 19 and 25 were drilled with closed steel pipes (outer diameter: 6.3 cm, with opaque liners) for OSL sampling and geochemical analyses. Generally, two cores with an offset of 50 cm were drilled, in order to bridge sediment gaps. Additionally, 21 surface samples with a volume of approximately 1000 cm3 from the river, river banks, beach and dunes, as well as seven rock samples from the surrounding cliffs were taken as facies and environmental reference samples (i.e., present-day analogues).

In the field open cores were photographed, described for sediment texture, colour, and CaCO3 content (test with 10% HCl), and a preliminary stratigraphic classification was given. Sedimentary units of each core were sampled in at least 10-20 cm intervals for later grain size and microfossil analyses for a detailed palaeoenvironmental reconstruction. The closed sediment pipes were opened and analysed in the laboratories of the Cologne and RWTH Aachen universities.

4.3.2 Ground-penetrating radar images In this study, two ground-penetrating radargrams (GPR; stitched together form 12 out of the total 430 radargrams collected) are presented, which follow the coring transect (Fig. 4.1). Non-destructive GPR measurements between boreholes were carried out using the SIR 3000 instrument (Geophysical Survey

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Systems, Inc.; GSSI) with a 270 MHz antenna. This frequency allows high-resolution measurements in a depth range from ca. 0 to 3 m below surface. Each profile was measured with a permittivity (ε) of 6 and the data measurement based on Distance-Mode, which is performed with a calibrated survey wheel. Due to the dry soil conditions during measurements, a relatively low ε was chosen. GPR data were processed at RWTH Aachen University with ReflexW software version 7.0, including processes such as move-start-time, bandpass butterworth, and average-xy-filter.

4.3.3 Granulometry In preparation for granulometric and geochemical analyses, 115 samples were dried at 40 °C in a drying chamber for 48 h, sieved to ≪2 mm, and crushed smoothly with a mortar to disintegrate the aggregates.

For grain size measurements, the samples were pre-treated with hydrogen peroxide (H2O2, 15%) in order

to remove organic matter, and with sodiumpyrophosphate (Na4P2O7, 46 g/l) to avoid coagulation (Gee and Or, 2002). The grain-size measurements were performed with a Laser Diffraction Particle Size Analyzer (LS 13320 Beckmann CoulterTM). Each sample was measured three times in 116 channels from 0.4 to 2000 μm using the optical Fraunhofer model. Grain-size parameters are based on Folk and Ward (1957), and were subsequently calculated by using GRADISTAT software version 8 (Blott and Pye, 2001).

4.3.4 Geophysical and geochemical properties of the sediments To identify different layers and to trace the origin of the sediments as well as possible changes in the depositional conditions, X-ray fluorescence (XRF) scans were applied. By using an ITRAX core scanner each lengthwise-cut sediment core was scanned with a resolution of 2 mm after it had been smoothed (Croudace et al., 2006). For geochemical analysis, the elements Fe, Ti, Ca, N, S and Sr, as well as C/N, Fe/Mn and Ca/Fe ratios were chosen, as they represent markers for the differentiation between terrestrial and marine environments as well as deposition facies (Cuven et al., 2013; Davies et al., 2015). Principal Component Analysis (PCA) was applied for the standardized values of the laboratory results, calculating parameters with the PAST software (version 3.1.1; Hammer et al., 2001) for the XRF data exemplary of the closed sediment cores BDR 6 and BDR 19. Organic carbon (TOC), total carbon (TC), nitrogen (N) and the C/N ratio were calculated in order to distinctively identify and differentiate between extreme wave events and floodplain deposits, using the method described by Meyer and Teranes (2001). Samples were measured with a Vario EL Cube (Elementar Analysensysteme GmbH, Hanau, Germany). Before measurement the material was

homogenized and weighed out into tin boats for TC and N determination. CaCO3 was treated the same way and additionally dissolved inorganic carbon with 10% HCl before TOC was determined using the Vario EL Cube.

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Magnetic susceptibility (MagSus) properties were analysed using a Bartington MS2 Magnetic Susceptibility System with a MS2K Sensor. The MagSus characteristics were measured in 2 cm intervals on each lengthwise-cut sediment core with an accuracy of 1.0 in SI units.

4.3.5 Micropalaeontology As preparation for micropalaeontological analysis, three samples from BDR 6 and four samples from BDR 8 were wet sieved using a Retsch AS 200 sieve shaker with a pile of six sieves of 2000 μm, 1000 μm, 500 μm, 250 μm, 125 μm and 63 μm mesh size (sieves following DIN 4188). The micropalaeontological study was then conducted using a Zeiss Stemi 2000C microscope. Due to the sample size, only semi-quantitative analyses were carried out on 20 g of each sample. To describe the overall microfossil content and particularly study the foraminifera, all tests were counted and attributed to following classes: 0 = absent, 1–10 = very rare, 11–30 = rare, 31–50 = frequent, 51–100 = very frequent, ≫100 = abundant. Some representative specimens were photographed with a Zeiss supra 55 scanning electron microscope (SEM; Carl Zeiss Microscopy GmbH, Jena, Germany).

4.3.6 Dating techniques 4.3.6.1 Radiocarbon dating Altogether eight samples of plant remains and charcoal from the two closed sediment cores (BDR 6 and BDR 19; Fig. 4.2) were 14C-dated in the 14CHRONO Centre, Queen's University, Belfast, UK. All ages were calibrated using the Calib 7.1 software (calibration data set: Intcal13.14c; Stuiver and Reimer, 1993; Reimer et al., 2013).

4.3.6.2 OSL dating The closed opaque liner tubes of sediment core BDR 19 were opened under subdued red light in the Cologne Luminescence Laboratory, and four samples were taken for optically stimulated luminescence

(OSL) dating. The samples were sieved (100–250 μm), treated with HCl and H2O2 to remove carbonates

and organics, respectively, and with Na4O7P2 for dispersion. Subsequently, gravity separation was carried out using heavy liquid solutions (sodium polytungstate; ρ1 = 2.68 g/cm3, ρ2 = 2.62 g/cm3) in order to separate pure quartz extracts. The quartz was etched with hydrofluoric acid to remove the surface affected by alpha radiation (Wintle, 1997). Aliquots of 1 mm diameter or ca. 30 quartz grains each were prepared on steel discs and measured on an automated Risø TL/OSL DA 20 reader equipped with a 90Sr/90Y beta source delivering ~0.07 Gy/s, blue LEDs and U340 filter. The measurement was conducted following the SAR protocol of Murray and Wintle (2003), including a preheat at 220 °C (determined by means of a preheat-plateau test). Burial doses were calculated by using the Minimum Age Model (MAM), since incomplete signal resetting was indicated by the dose distribution (Galbraith et al., 1999). The annual dose rate derived from the decay of uranium, thorium and potassium in the

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sediments was determined by laboratory high-resolution γ-spectrometry and using the software DRAC (Durcan et al., 2015).

Fig. 4.2 Images of the sediment cores BDR 19 (1) and BDR 6 (2), with close-up view of the extreme wave event layers of BDR 6 [(3), (4)].

4.4 Results 4.4.1 Ground penetrating radar results Two radargram profiles were selected as representative for the transects addressed in this study. All radargrams have a small offset (≪1 m) from the individual coring sites. All processed radargrams show similarities in structure of their reflectors, layer thickness and the distinct differentiation of three units until the detection limit. The radargram representing transect T1 parallel to the coastline (WE), between coring sites BDR 6, 7 and 8, spans over 104 m across the valley. The three identified units in the processed radargrams are well visible and can be assigned to distinctive sedimentary facies, based on their properties (Fig. 4.3). Unit 1, the top layer with a thickness ranging between 70 and 80 cm, shows an overall parallel internal layering in its reflector pattern, with only little thickness variations. Unit 2 appears more irregular with reflectors creating a “zig-zag” pattern. Furthermore, the thickness of this

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layer shows a westward thinning. At coring location BDR 7, a broken and lost steel coring tube, which could not be recovered during field work, is causing strong reflectors (Fig. 4.3). A similar stratification as unit 1 can be identified in unit 3. However, the reflectors in unit 3 are closer and less bent. This layer ends at the resolution limit of 2.8 m with an overall thickness of 1.6 m. The radargram representing transect T2 perpendicular to the coastline (S-N), between coring sites BDR 7 and 25, spans over 104 m distance. Three individual units were identified (Fig. 4.4). Unit 1 with a thickness of 0.8 m exhibits numerous even, subparallel, slightly curved reflectors with a moderate continuity. In addition, there is an average amplitude as well as a small reflection range. Unit 2 shows an uneven structure with “zig- zag” pattern and variations in thickness ranging between 0.4 and 0.5 m. There are many chaotic and discontinuous reflectors contained in unit 2. Like the top layer, unit 3 indicates even and parallel internal layering with partially stronger radar reflections arising from dielectric contrasts than in unit 2. The reflection continuity is more continuous than the reflectors in the other two units. Due to these reflectors the alluvial units 1 and 3 are different from the event layer E1 (unit 2). At the resolution limit of 2.8 m depth ends the bottom layer with a detected thickness of 1.6 m.

Fig. 4.3 Cross section of coast-parallel transect T1 with corings BDR 6, 7, and 8, as well as the recorded ground penetrating radar (GPR) sequence. (A) Facies interpretation from sediment cores and extrapolated cross section of transect T1. Processing (B) and interpretation (C) of GPR profile of transect T1. Numbers in (C) indicate different facies, black marked zone is characterized by notably strong reflectors.

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Fig. 4.4 Cross section of coast-perpendicular transect T2 with corings BDR1, 7, 25, 19 and 27, as well as the recorded radar sequence between BDR 7 and 25. (A) Facies interpretation from sediment cores and extrapolated cross section of transect T2. Processing (B) and interpretation (C) of GPR profile of transect T2. Numbers in (C) indicate different facies.

4.4.2 Sample stratigraphy and geochemistry The sediment cores gained from the Boca do Rio floodplain reveal a similar pattern in their stratigraphy, although the thickness of the single layers and precise depositional succession slightly vary. The base of each sediment core is formed by a relatively well sorted medium sand (unit A) that is characterized by elevated Ca and Sr values, as well as Ca/Fe and C/N ratios (Figs. 4.5, 4.6). In most cases a sudden change divides the sand of unit A from the overlying fine-grained sediments with high Fe and Ti values (units D and B). Only in the case of BDR 19 there is a significant transitional layer (unit C). In every sediment core unit D forms the uppermost layer with a thickness between 0.84 m (BDR 1) and 3.05 m (BDR 27; Fig. 4.5). In all cores a poorly sorted, 8 to 37 cm thick layer of coarse sand is intercalated in unit D at depths between 0.7 and 1.32 m (unit E1; Figs. 4.5-4.7). A second comparable layer is only found in sediment core BDR 6 (unit E2; Figs. 4.5, 4.6). In the following, the sediment cores BDR 6 and 19 shall be presented in detail since they are representative for the palaeoenvironmental evolution of the Boca do Rio floodplain.

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4.4.2.1. Sediment core BDR 19 BDR 19 from the northern part of the valley comprises a stratigraphy of 4.47 m (Figs. 4.1, 4.2, 4.5). The lowermost sediment unit (A; 4.47-4.34 m b.s., metres below surface) consists of homogeneous dark grey medium sand with relatively high values of C and Ca/Fe. With sharp contact follows a grey silty clay (4.34-4.18 m b.s.). While Ca reaches the lowest values of the entire stratigraphy, the concentrations of TOC, Ti and Fe are high (unit B). Unit C (4.18-3.68 m b.s.) shows a granulometric shift from clay to sand. This is reflected in decreasing contents of Ti and Fe, aswell as a significant rise of Ca and the C/N ratio. This layer contains several macroremains of plants and angular lithoclasts (transitional unit C). The stratum at 3.68-2.40 m b.s., a homogeneous well sorted medium sand, is comparable with the lowermost section (unit A). The colour gradually shifts from yellowish grey to reddish grey. While Ti remains low, Ca as well as C/N and Ca/Fe rise to the highest values of the whole stratigraphy. Only the thin section at 2.72-2.60 m b.s. stands out with decreased Ca and higher Fe values. The uppermost unit D from 2.40 m b.s. to the top consists of rather poorly sorted clayey to sandy silt with continuously high values of Fe and low values of Ca and S. While TOC is significantly lower than in the sandy layers below, the share of Corg is slightly elevated (see Fig. 4.5). Embedded in unit D is the two-parted layer E1, which consists of a fining-upward coarse sand at 1.16-1.03 m b.s., and a transition layer at 1.03- 0.82 m b.s. (unit E1). The coarse sand stands out, not only due to the coarser mean grain size but also due to a rise in inorganic carbon, reduced values of organic carbon, and the occurrence of shell fragments.

4.4.2.2. Sediment core BDR 6 The bottom section (2.00-1.62 m b.s.) of the westernmost sediment core BDR 6 consists of relatively well sorted yellowish grey medium sand (~350 μm), which is rich in shell fragments (unit A; Figs. 4.2, 4.3, 4.5). This layer is characterised by generally high, slightly decreasing values of Ca, while Fe, magnetic susceptibility and TOC are on low levels. For a better distinction of the single facies, the principal components analysis (PCA)was applied for six parameters (PCs); it formed a spatial distribution explained by the first two components (PC 1: 58.9%, PC 2: 22.6%; Fig. 4.6). Subsequently PC 1 was plotted against depth (Fig. 4.5). Additional parameters were calculated for PC 3: 12.1%, PC 4: 5%, PC 5: 3.5% and PC 6: 0.1%. Although a certain overlap of the different facies must be admitted, a distinction of facies A (littoral), B (lagoonal) and D (alluvial), as well as the event layers (E1 and E2) is possible. From 1.62 to 1.26 m b.s. reddish brown clayey silt with mean grain size below 15 μm dominate. This section has to be divided in two different layers. While Ca remains very low, Fe and Ti start to rise around 1.40 m b.s., indicating a shift from unit B (1.62-1.40 m b.s.) to unit D (1.40- 1.26 m b.s.). In the silt layer from 1.19 m b.s. to the surface, Fe remains high (unit D). MagSus mirrors the Fe concentration. In comparison to the sand layer below, TIC decreases, while TOC stands out with high values that rise close to 2% towards the surface. Embedded in the clayey silts of unit D are two distinct layers of brownish medium sand with sharp boundaries: unit E2 at 1.26-1.19 m b.s. and unit E1 at 0.80-0.75 m b.s.. They were described in the field

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as potential extreme wave event deposits. Their mean grain size values reach ~100 μm and ~130 μm, respectively, and each one seems to have a fining upward sequence. While Ca remains relatively low, Fe and N drop significantly in comparison to the surrounding silts. The same holds true for magnetic susceptibility.

Fig. 4.5 Facies interpretation, granulometry, geochemistry and 14C age estimates of the sediment cores BDR 19 (A) and BDR 6 (B) from the central part and the western margin of the floodplain, respectively.

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Fig. 4.6 Principal component analysis (PCA) of the XRF data of core BDR 6 including the two extreme wave event (EWE) layers E1 and E2.

Fig. 4.7 Age/depth model of BDR 19 according to Blaauw and Christen (2011). For facies determination see legend in Fig. 4.5.

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4.4.3 Microfossil assemblage Shell fragments are abundant in all samples. Especially foraminifera, ostracoda, (juvenile) bivalvia, gastropoda, enchinoidea and bryozoa are present. The microfossil assemblage of unit A of BDR 6 is the least diverse. Enchinoidea and bryozoa fragments are abundant, followed by benthic foraminifera, whereas ostracoda and gastropoda are rare and planktonic foraminifera are very rare. In total 79 benthic and 2 planktonic foraminifera individuals were counted (see Table 4.1). Elphidium crispum, E. williamsoni, Ammonia beccarii and Globigerina sp. were identified. Approximately a third of the foraminifera were broken and some showed abraded tests. In unit E1 (BDR 6, BDR 8), enchinoidea fragments are abundant or very frequent, followed by benthic foraminifera and bryozoa fragments (both very frequent to rare). Ostracoda are found to be very frequent to rare in samples from BDR 8, but they are absent in samples from BDR 6. In total 30-103 individual foraminifera were counted in samples from unit E1 (see Table 4.1). The most common species is E. crispum, followed by A. beccarii, E. williamsoni and Haynesina germanica, while Quinqueloculina seminula and Globigerina sp. only appear sporadically (Fig. 4.8). In core BDR 8, the variation in species of foraminifera slightly increases with depth (from 4 to 6 species). In unit E1, especially the sample from BDR 6 and the uppermost sample from BDR 8 revealed that almost half of the individual foraminifera were broken. Unit E2 of BDR 6 presents a richer, in terms of species and numbers, microfossil content compared to unit E1. Foraminifera, both benthic and planktonic, enchinoidea fragments and bryozoa fragments are abundant, ostracoda are frequent, while fewer gastropoda and juvenile bivalvia were detected. In total, 1725 benthic and 228 planktonic foraminifera individuals were counted (see Table 4.1). Among them, A. beccarii and Globigerina sp. were the most common species, followed by H. germanica and E. crispum, as well as infrequent E. williamsoni and Bolivina sp. (Fig. 4.8). In unit E2 only a few foraminifera tests were broken but many of them were reworked and altered.

Table 4.1 Foraminifera content of samples from sediment cores BDR 6 and 8. The following classes and signatures were use: 0 = absent (−), 1–10= very rare (+), 11–30= rare (++), 31–50 =frequent (+++), 51–100=very frequent (++++), ≫100=abundant (+++++). The Index of Oceanity was calculated after Gibson (1989): I=planktonic foraminifera / (planktonic+ benthic foraminifera).

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Fig. 4.8 Representative SEM images of foraminifera obtained from sediment cores BDR 6 and BDR 8.

4.4.4 Radiocarbon and OSL ages Eight charcoal and wood fragments from the cores BDR 6 and 19 were 14C-dated; they roughly cover the time span between ~2000 cal. BCE and 1450 cal. CE. Four samples from sediment core BDR 19 were dated via optically stimulated luminescence (OSL); they indicate a comparable time range as the 14C ages. The calculated age estimates are shown in Tables 4.2 and 4.3.

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The calibrated 14C ages (2 σ) are noted in the figures of each profile, including the sample depths (Figs. 4.5, 4.7). The three 14C ages BDR 19/5, BDR 6/2 and BDR 6/3 are left out in the further discussion. While the first one, which is close to the limit of 14C dating, is definitely overestimated, we assume the dating of modern material such as roots for the ‘modern’ ages. Based on the ensemble of 14C and OSL age estimates, an age/depth model according to Blaauw and Christen (2011) was established for sediment core BDR 19 (Fig. 4.7).

Table 4.2 Radiocarbon ages. The 14C measurements were carried out by the 14CHRONO Centre, Queen's University Belfast, Northern Ireland, UK. The age estimates are presented as conventional and calibrated ages. Calibration with Calib 7.1 (data set: Intcal13.14C; Stuiver and Reimer, 1993; Reimer et al., 2013).

Table 4.3 OSL ages for sediment core BDR 19. The measurements were carried out in the Cologne Luminescence Laboratory (CLL). Sampling was in 2017 CE. For age calculation the Minimum Age Model (MAM) was applied (Galbraith et al., 1999).

4.5 Discussion 4.5.1 Interpretation of the stratigraphic units Based on granulometric, geochemical, and microfaunal results, six units, which represent different sedimentary environments of deposition, can be differentiated.

4.5.1.1 Unit A – sublittoral to littoral The well sorted medium sand of unit A suggests hydrodynamic conditions with relatively high sediment transport capacity. High values of Ca and low concentrations of Fe suggest a marine origin (Davies et al., 2015). Unit A closely resembles material of the present-day beach, as evidenced by the coarse shell fragments and the microfauna, especially E. crispum and E. williamsoni, which represent a shallow

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marine environment (Murray, 1991), while A. beccarii indicates a brackish subtidal-infralittoral, estuarine or lagoonal environment (Murray, 1991; Hofrichter et al., 2002). Additionally, the so-called Index of Oceanity (Table 4.1), calculated from the foraminifera assemblage (Gibson, 1989), attributes unit A to water depths of 0-5 m (Bellier et al., 2010).

4.5.1.2. Unit B – lagoonal The fine-grained sediments from unit B are evidence of a low energy environment. The grey colour and high Fe, Ti, S and Fe/Mn concentrations may indicate anoxic conditions (Aufgebauer et al., 2012; Cuven et al., 2013; Schmidt et al., 2008) which are characteristic of standing water bodies, e.g., in lagoons or ponded back barrier areas with limited connection to the open sea.

4.5.1.3. Unit C – transition layer This unit occurs only in the stratigraphy of sediment core BRD 19. It forms a transition layer that documents the gradual environmental shift from low energy to higher energy conditions, e.g., from a lagoonal or low energy estuary to a littoral/sublittoral environment. This is not only reflected in the granulometry, but also in the geochemistry, where a significant decrease in Fe, Ti and S is opposed to a remarkable rise in Ca.

4.5.1.4. Unit D – alluvial The sediments of unit D are silty to clayey with an average mean grain size below ~30 μm hinting at low-energy depositional processes and environments. The increased Fe and Ti contents and low concentrations of Ca indicate a terrigenous origin (Chagué-Goff et al., 2012a). Furthermore, the slightly increased TOC values suggest vegetation cover. Even though the granulometric parameters resemble closely those of unit B, the geochemical evidence allows for a clear separation between these two units, as demonstrated in BDR 6 where the sudden increase in Ti and Fe at 1.40 m b.s. indicates an abrupt shift from unit B to unit D. The terrigenous sediments of unit D accumulated during flooding events induced by fluvial slack waters or heavy rains on the low-lying areas of the valley plain (e.g., Hindson and Andrade, 1999). The slightly varying sand content within this unit reflects the fluctuating hydrodynamic conditions of the three rivulets dewatering into the Boca do Rio floodplain (Boggs, 2006; Fig. 4.1). Nearly the entire present- day valley floor is covered by this unit. This is also reflected by the top layer in the radargrams, horizon 1, which partially shows stronger radar reflections arising from dielectric contrasts than in horizon 2 (unit E1). Many of these reflectors are caused by changes in the water content (Dam, 2001; Heinz, 2001), since in unconsolidated sediments the water content is related to the grain size distribution. Alluvial deposits of unit D contain mainly fine-grained sediments with higher capillary forces leading to a higher in situ water content.

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4.5.1.5. Units E1 and E2 – extreme wave event layers The deposits of units E1 and E2 are generally attributed to extreme wave events based on their erosional basal contact, sharp grain-size increase (compared with the sandwiching strata), their micropalaeontological content and specific geochemical fingerprint (Figs. 4.2, 4.5). The chronological framework implies the association with two events: E1 represents the 1755 CE Lisbon tsunami, and E2 an as yet unknown predecessor event (Tables 4.2, 4.3, Fig. 4.7).

4.5.2. Unit E1 – 1755 CE tsunami Sediment unit E1 has already been described as an extreme wave event deposit (e.g., Costa et al., 2012b; Dawson et al., 1995; Font et al., 2013; Hindson et al., 1996; Hindson and Andrade, 1999). The sandy stratum exhibits a complex stratigraphy with several subunits. Larger grain sizes indicate a high-energy flow regime, in which suspended sediment transport was also possible. Several characteristics indicate a tsunami origin: erosive basal contact, rip-up clasts, distinctive subunits with varying grain size, fining- upward sequences (suspension grading; Fig. 4.2) and mud cap. At BDR 8 this layer is made up of four subunits, while other coring locations present less subunits. With GPR technique, event layer E1 could be clearly identified. The radar sequences match well with the obtained stratigraphy (see correlations in Figs. 4.3, 4.4). Unit 2 shows an internal zig-zag structure, which is much different from the radargrams of the sandwiching alluvial units (1 and 3) of unit D. The irregular structure of the reflectors is generated either by the subunits created by individual waves (run- up and backwash) during an extreme wave event, or by other internal structures, such as heavy mineral layers, shell layers or scattered clasts. Furthermore, according to the radargrams, the event layer E1 is present along the entire length of both transects. High concentrations of Ca and Sr indicate a marine origin, related to their strong chemical affinity in compounds as well as the positive correlation in sediments and marine bioclasts or shells (Chagué-Goff, 2010; Chagué-Goff et al., 2017). Low magnetic susceptibility corresponds with high amounts of calcium carbonate and quartz (Dearing, 1999). In addition, the marine origin is underlined by the faunal content (Table 4.1, Fig. 4.8). Shell fragments were abundant in unit E1 of all sediment cores. The foraminifera assemblage shows a typical mixture of littoral, shallow marine (E. crispum, E. williamsoni, Q. seminula), and brackish estuarine or lagoonal (A. beccarii, H. germanica) species (Armstrong and Brasier, 2005; Murray, 1991). As already detected by previous studies (e.g., Hindson et al., 1999), the foraminifera assemblage of unit E1 resembles the assemblage of unit A (sublittoral – littoral), while presenting a lower total number of individuals in unit E1 as compared to unit A in BDR 6. Furthermore, many macro- and microfossils were broken and reworked which indicates the high depositional energy during the extreme wave event and/or the origin from the beach. According to the Index of Oceanity (Gibson, 1989), water depths were 0-5 m (Bellier et al., 2010). This supports the assumption of the beach and the very nearshore as sediment

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sources and is in agreement with water depths derived from endolithic shells retrieved from boulders as documented by Hindson et al. (1996). The characteristics listed above and the classification of unit E1 as a tsunami deposit correspond to existing publications about the Boca do Rio sediment archive (e.g., Andrade et al., 1994; Dawson et al., 1995; Hindson et al., 1996; Hindson and Andrade, 1999). However, OSL dating of sediments in this study slightly predates the 1755 CE event (1673 CE ± 54 BDR 19; Fig. 4.5, 4.7). This may have been caused by incomplete bleaching of the OSL signal during tsunami transport (Brill et al., 2012), and by the in general dim luminescence signal of relatively young deposits (Madsen et al., 2005). Incomplete bleaching is very common for tsunami sediments due to only partial exposure to daylight. Similar remnant ages as observed in this study (i.e., ca. 80 years) have also been reported for recent tsunami layers of the 2004 Indian Ocean tsunami (Brill et al., 2012), as well as for the 1755 CE tsunami at the Scilly Isles, United Kingdom (Banerjee et al., 2001). However, agreement with the expected age is given when a 2 σ confidence interval – as used for reporting radiocarbon ages (instead of 1 σ, which is typically used to report OSL ages) – is applied. The coast-parallel profile (BDR 6 to 8; Fig. 4.3) presents a changing thickness of the deposit. Close to the river (BDR 8), the layer is thickest, while close to the dune (BDR 6) it is smallest. The reason is the inundating dynamics of the tsunami waves, which used the least dissipating path onshore along the river. While bottom roughness (due to plants, etc.) leads to earlier deposition along the western end of the valley and therefore a lesser inland inundation, the typically channelized backwash (e.g., Dawson and Stewart, 2007) possibly remobilizes sediments causing deposition and layer thickening towards the river at the eastern side. None of the analyzed reference samples exclusively qualifies as likely sediment source for the event unit E1. The comparison revealed that – regarding grain size characteristics and transport mechanisms – this unit mostly resembles reference samples from the beach close to the river mouth. This, together with the greatest thickness close to the river indicates that the tsunami waves easily travelled along the path of the river, while eroding sediment from the beach and river banks, and later depositing this load on the floodplain close to the river.

4.5.3. Unit E2 – an as yet unknown extreme wave event deposit E2 consists of a sand deposit sandwiched by low energy muds (Fig. 4.2). The magnitude of this event was lower than the 1755 CE tsunami (unit E1), as evidenced by the smaller range in deposited grain size and its occurrence at only one coring site. Typical extreme wave event characteristics – an irregular or erosive basal contact, abundant shell fragments, incorporated mud within sand-sized sediments – are visible in unit E2 (Fig. 4.2). The granulometric results definitely separate it from the over- and underlying floodplain alluvium (unit D). This is confirmed by the results of the magnetic susceptibility and XRF measurements. Relatively low magnetic susceptibility, corresponding to low Ti, Fe, Fe/Mn and PC 1 values, and slightly elevated Ca

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and Sr concentrations indicate a marine origin (Chagué-Goff, 2010; Chagué-Goff et al., 2017). Yet the geochemical fingerprint of the 1755 CE tsunami, definitely separates the two events (e.g., the XRF- based Ca, Si and Ti contents in Figs. 4.5, 4.6). The micropalaeontological content supports the hypothesis of unit E2 being related to an extreme wave event (Table 4.1, Fig. 4.8). The abundant occurrence of A. beccarii and H. germanica indicates a brackish subtidal-infralitoral, estuarine or lagoonal source (Murray, 1991; Hofrichter et al., 2002), while Globigerina sp. (abundant) and Bolivina sp. (very rare) imply a source from the outer shelf with greater water depths below the storm wave base (Armstrong and Brasier, 2005; Murray, 2006). The foraminifera assemblage of this unit is the only one of the analysed samples that hints to sediment sources slightly farther away from the shore: the Index of Oceanity suggests water depths of 50-60 m (Bellier et al., 2010; Table 4.1). The micropalaeontological content, in particular the foraminifera assemblage, is clearly different from unit E1, especially in terms of total number of individual foraminifera. The marine origin of unit E2 and the discussed high energy environmental indicators lead to the conclusion that unit E2 was deposited by an as yet not documented extreme wave event. Based on the radiocarbon age taken directly above this unit, it is older than 985–1147 cal. CE (Fig. 4.5, Table 4.2). Thus a first chronological approximation suggests a possible correlation with one of the North Atlantic Holocene storm periods (HSP IV 50-900 CE; Sorrel et al., 2012). Recognized North Atlantic Holocene storm periods correlate with late Holocene periods of global rapid climate change, influencing the strength and location of westerly winds. Furthermore, periods of increased storminess recorded in sediments from the Mediterranean Sea correspond to the proposed North Atlantic storm periods and the associated increased storminess to a southward displacement of storm tracks during cold periods of the Holocene (Sabatier et al., 2012). In the case of the Algarve coast, correlations of sediment archives with storminess periods have not yet been achieved; however, multiple storm-induced sediment deposits were documented in the Ria Formosa lagoon (Andrade et al., 2004) and at the Praia do Martinhal (Kortekaas and Dawson, 2007). More recent storm events and storminess periods (e.g., HSP V: 1300-1650 CE; Sorrel et al., 2012) are better understood due to written records and later also instrumental data (Alcoforado et al., 2012; Pfister et al., 2010). On the other hand, the micropalaeontological assemblage contains species living offshore and at deep water depths below storm wave base (Globigerina sp., Bolivina sp.), which complicates a definite statement on the origin of the deposit, such as storm or tsunami. It is, however, noteworthy that, while the Portuguese tsunami catalogue (Baptista and Miranda, 2009) lists no tsunami event suitable to the age estimate of sediment unit E2, there is historical evidence of a tsunami event at 881 CE (Morales et al., 2008; Reicherter et al., 2010) along the Spanish coast of the Gulf of Cádiz. Since the occurrence of the stratum is restricted to only one coring site (BDR 6), no statement on the lateral distribution and unit thickness can be made. The reason for this singularity might be a changed river path in the past. The Budens stream, currently running east of the floodplain, is likely to have migrated in the past, as indicated by former cut banks in the west of the present floodplain. It was either

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easier for the waves to inundate the former river path, depositing its sediment load around the BDR 6 site, or other deposits of this extreme wave event have since been eroded or have not yet been detected. Definitely, further investigations are needed.

4.5.4. Scenario of the palaeoenvironmental evolution of Boca do Rio Based on the identification of the different depositional units and the dating results (14C, OSL), the following scenario can be assumed for the Holocene evolution of the Boca do Rio valley. The lowermost and oldest cored sediment layers represent littoral conditions (unit A); they were detected in all of the sediment cores of the N-S cross section. Thus, the sea once transgressed far into the valley. In many parts of the world, the maximum inland transgression was reached about seven to six millennia ago, when rapid sea-level rise decelerated and reached close to its present position (Boski et al., 2002, 2008; Lambeck and Purcell, 2005; Zazo et al., 1994). Thereafter, the river deltas evolved and the marine embayments were gradually infilled with alluvial, colluvial and estuarine/ lagoonal deposits (units B, C and D; e.g., Brückner et al., 2010, 2017). In case of the Boca do Rio valley the siltation might have been a consequence of sandy beach barrier growth, as similar processes have been observed in the Gulf of Cádiz, both in the Guadiana (Ruiz et al., 2004) and in the Guadalquivir (Boski et al., 2002; Klein et al., 2016) estuaries. In the case of our study, the marine transgression facies was not encountered. But the obtained ages of the marine strata suggest marine conditions inside the valley at least until ~2130 ± 230 BCE (BDR 19; Table 4.3, Fig. 4.5). As the estuary continued to be filled in with fluvial sediments, the shoreline gradually prograded seawards to its present position. Parallel to this evolution, a lagoon-barrier complex evolved due to the eastbound longshore drift. This is well documented in BDR 6, 19 and 27, where the littoral sands are covered by fine-grained lagoonal deposits which indicate still water conditions as documented in the microfauna and geochemistry (unit B; Figs. 4.5, 4.8). Littoral conditions, likely caused by the beach barrier, prevailed at the valley mouth, as indicated in the sediment cores BDR 1 and 25. The barrier protected the landward parts of the valley from the high energy dynamics of the open sea. In the first part of the 2nd millennium BCE (Table 4.1), a gradual transition from lagoonal to littoral conditions occurred (unit C; Fig. 4.2), indicating a renewed ingression of the sea into the valley. Even though the beach did not reach its northern margin, littoral deposits can be observed at least as far north as the location of BDR 19 (Figs. 4.1, 4.5). In the central part of the Boca do Rio valley the littoral environment persisted until the 1st millennium CE when continued alluvial infill caused a forced coastline regression that shifted the shoreline to its present position. What makes the Boca do Rio area special is that the uppermost layer of the alluvial plain is interdigitated with at least one, at site BDR 6 even two sandy strata: the geological footprints of extreme wave events.

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4.6 Conclusion Based on seven representative sediment cores, the evolution of the Boca do Rio floodplain could be reconstructed for the later Holocene. The multi-proxy approach with a combination of sedimentological, geophysical, geochemical and microfaunal data enabled a classification of different depositional facies at least for the last ~4000 years, as shown by 14C and OSL age estimates. During this period, the Algarve, including the Boca do Rio valley, was subjected to considerable landscape changes. The postglacial – early Holocene sea-level rise caused a major transgression of the sea into the lower reaches of the Pleistocene valleys and created a marine embayment with a ria-type coast, at the bottom of which marine strata were accumulated. When the sea-level rise considerably decelerated, secondary coasts evolved with a beach barrier – lagoon or a barred estuarine complex. Alluvial and colluvial sediments gradually infilled the formerly marine embayment. After coastal occupation during Roman times, the shoreline shifted seawards in the 1st millennium CE. The lagoon and coastal lakes behind the beach barrier were gradually silted up and transformed into the present floodplain (Allen, 2003). The Algarve coast has been subjected to earthquake-induced tsunamis and recurring severe storms (e.g., Baptista and Miranda, 2009; Ferreira et al., 2008). In the case of Boca do Rio, the sedimentary record proves that the valley is exposed to a high hazard potential for extreme wave events. In this study, two extreme wave events were detected in sediment cores retrieved from the Boca do Rio floodplain. These high-energy events, named as units E1 and E2, interrupted the formation of a low energy mud-dominated floodplain environment (unit D). Unit E1, detected in all of the sediment cores, can be unequivocally attributed to the well-known 1755 CE Lisbon tsunami, while unit E2, detected only at coring site BDR 6, originates from an as yet undocumented extreme wave event. An association of unit E2 with either a tsunami or a storm event remains difficult, despite high-resolution geochemical data, sediment properties and the foraminifera assemblage. For a more definite classification more information, e.g., on its lateral distribution, is needed. So far, tsunami catalogues do not present a perfect chronological match with such an event, and as yet no other study has detected a similar deposit. Until now, a relation between this extreme wave event and the decline of the Roman garum production can neither be proved nor disproved.

4.7 Acknowledgements This study was supported financially by the German Research Foundation (DFG; grant nos. TE 580/8- 1, RE 1361/28-1, BR 877/36-1). Prof. João Pedro Bernades (University of Algarve) and Ricardo Soares (administration of Vila do Bispo) supported our field work in Boca do Rio. We thank the laboratory personnel of both RWTH Aachen and Cologne universities, especially Nicole Mantke for her help with XRF measurements and Dr. Guillaume Desbois for assistance with the SEM imagery. Prof. César Andrade (Instituto Dom Luiz and University of Lisbon) kindly shared his broad knowledge about the 1755 CE Lisbon tsunami in general and the Boca do Rio area in particular. Two anonymous reviewers are thanked for their valuable comments which helped improve the manuscript.

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Morales, J.A., Borrego, J., SanMiguel, E.G., López-González, N., and Carro, B., 2008. Sedimentary record of recent tsunamis in the Huelva Estuary (southwestern Spain). Quaternary Science Reviews 27, p. 734–746. Murray, A.S., and Wintle, A.G., 2003. The single aliquot regenerative dose protocol: potential for improvements in reliability. Radiation Measurements 37, p. 377–381. Murray, J.W., 1991. Ecology and Palaeoecology of Benthic Foraminifera. Longman, Harlow, Essex, p. 408. Murray, J.W., 2006. Ecology and Applications of Benthic Foraminifera. Cambridge University Press, New York, p. 426. Pfister, C., Garnier, E., Alcoforado, M.J., Wheeler, D., Luterbacher, J., Nunes, M.F., and Taborda, J.P., 2010. The meteorological framework and the cultural memory of three severe winter-storms in early eighteenth-century Europe. Climate Change 101, p. 281–310. Quintela, M., Costa, P.J., Fatela, F., Drago, T., Hoska, N., Andrade, C., and Freitas, M.C., 2016. The AD 1755 tsunami deposits onshore and offshore of Algarve (south Portugal): Sediment transport interpretations based on the study of Foraminifera assemblages. Quaternary International 408, p. 123–138. Reicherter, K., Vonberg, D., Koster, B., Fernández-Steeger, T., Grützner, C., and Mathes-Schmidt, M., 2010. The sedimentary inventory of tsunamis along the southern Gulf of Cádiz (southwestern Spain). Zeitschrift für Geomorphologie 54, p. 147-173. Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Bronk Ramsey, C., Buck, C.E., Cheng, H., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T.J., Hogg, A.G., Hughen, K.A., Kaiser, K.F., Kromer, B., Manning, S.W., Niu, M., Reimer, R.W., Richards, D.A., Scott, E.M., Southon, J.R., Turney, C., and van der Plicht, J., 2013. InterCal13 and Marine 13 radiocarbon age calibration curves 0-50,000 years cal. BP. Radiocarbon 55, p. 1869–1887. Rodríguez-Ramírez, A., Villarías-Robles, J.R.J., Pérez-Asensio, J.N., Santos, A., Morales, J.A., Celestino-Pérez, S., León, A., and Santos-Arévalo, F.J., 2016. Geomorphological record of extreme wave events during Roman times in the Guadalquivir estuary (Gulf of Cadiz, SW Spain): an archaeological and paleogeographical approach. Geomorphology 261, p. 103–118. Rodríguez-Vidal, J., Cáceres, L.M., Abad, M., Ruiz, F., González-Regalado, M.L., Finlayson, C., Finlayson, G., Fa, D., Rodríguez-Llanes, J.M., and Bailey, G., 2011. The recorded evidence of AD 1755 Atlantic tsunami on the Gibraltar coast. Journal of Iberian Geology 37, p. 177–193. Röth, J., Mathes-Schmidt,M., García Jímenez, I., Rojas Bichardo, F.J., Grützner, C., Silva, P.G., and Reicherter, K., 2015. The Baelo Claudia tsunami hypothesis – results from a multimethod sediment analysis of Late Roman deposits (Gibraltar Strait, Southern Spain). Miscellanea INGV 27, p. 418– 423 (Conference Poster).

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Ruiz, F., Rodríguez-Ramírez, A., Cáceres, L.M., Rodríguez Vidal, J., Carretero, M.I., Clemente, L., Muñoz, J.M., Yañez, C., and Abad, M., 2004. Late Holocene evolution of the southwestern Doñana National Park (Guadalquivir Estuary, SW Spain): a multivariate approach. Palaeogeography, Palaeoclimatology Palaeoecology 204, p. 47–64. Sabatier, P., Dezileau, L., Colin, C., Briqueu, L., Bouchette, F., Martinez, P., Siani, G., Raynal, O., and von Grafenstein, U., 2012. 7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events. Quaternary Research 77, p. 1–11. Santos, A., and Koshimura, S., 2015. The historical review of the 1755 Lisbon Tsunami. Journal of Geodesy and Geomatics Engineering 1, p. 38–52. Schmidt, R., Roth, M., Tessadri, R., and Weckstrom, K., 2008. Disentangling late-Holocene climate and land use impacts on an Austrian alpine lake using seasonal temperature anomalies, ice-cover, sedimentology, and pollen tracers. Journal of Paleolimnology 40, p. 453–469. Sillières, P., 2006. Investigaciones arqueológicas en Baelo: Balance, interpretación y perspectivas. In: Sánchez de las Heras, C. (Eds.), Actas I Jornadas Internacionales de Baelo Claudia: Balance y perspectivas (1966–2004). Seville, p. 37–60. Sorrel, P., Debret, M., Billeaud, I., Jaccard, S.L., McManus, J.F., and Tessier, B., 2012. Persistent non- solar forcing of Holocene storm dynamics in coastal sedimentary archives. Nature Geosciences 5, p. 892–896. Stuiver, M., and Reimer, P., 1993. Extended 14C data base and revised Calib 3.0 14C age calibration program. Radiocarbon 35, p. 215–230. Teichner, F., 2016. A multi-disciplinary approach to the maritime economy and palaeoenvironment of southern Roman Lusitania. In: Vaz Pinto, I., Roberto de Almeida, R., Martin, A. (Eds.), Lusitanian Amphorae. Production and Distribution. Archaeopress Publishing Ltd, Oxford, p. 241–255. Teichner, F., and Mañas Romero, I., 2018. The mosaics from Abicada and Boca do Rio (Portugal) – a new perspective thirty years later. Journal of Mosaic Research 11, p. 257–271. Teichner, F., and Pujol, L.P., 2008. Roman amphora trade across the Straits of Gibraltar: an ancient ‘anti-economic practice’? Oxford Journal of Archaeology 27, p. 303–314. Teichner, F., Mäusbacher, R., Daut, G., Höfer, D., Schneider, H., and Trog, C., 2014. Investigações geo- arqueológicas para a reconstitução da evolução do litoral algarvio durante o Holoceno – recente (7000-1000 BP). Revista Portugues de Arqueologia 17, p. 141–158 (in Portuguese with English abstract). Teichner, F., Brückner, H., Reicherter, K., Paul, K., and Hermann, F., in review. Geoarchäologische Forschungen zur römischen Fischsaucenproduktion in Lusitanien. Proceedings of XIX ICCA AIAC Cologne/Bonn 2018. Vigliotti, L., Andrade, C., Freitas, M.C., Capotondi, L., Gallerani, A., and Bellucci, L., 2019. Paleomagnetic, rock magnetic and geochemical study of the 1755 tsunami deposit at Boca do Rio (Algarve, Portugal). Palaeogeography, Palaeoclimatology, Palaeoecology 514, p. 550–566.

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Wintle, A.G., 1997. Luminescence dating: laboratory procedures and protocols. Radiation Measurements 27, p. 769–817. Zazo, C., Goy, J.L., Somoza, L., Dabrio, C.J., Belluomini, G., Improta, J., Lario, J., Bardají, T., and Silva, P.G., 1994. Holocene sequence of sea-level fluctuations in relation to climatic trends in the Atlantic–Mediterranean linkage coast. Journal of Coastal Research 10, p. 933–945. Zitellini, N., Mendes, L.A., Cordoba, D., Danobeitia, J., Nicolich, R., Pellis, G., Ribeiro, A., Sartori, R., Torelli, L., Bartolome, R., Bortoluzzi, G., Calafato, A., Carrilho, F., Casoni, L., Chierici, F., Corela, C., Correggiari, A., Della Vedova, B., Gracia, E., Jornet, P., Landuzzi, M., Ligi, M., Magagnoli, A., Marozzi, G., Matias, L., Penitenti, D., Rodriguez, P., Rovere, M., Terrinha, P., Vigliotti, L., Zahinos Ruiz, A., 2001. Source of 1755 Lisbon earthquake and tsunami investigated. Eos, Transactions, American Geophysical Union 82, p. 285–296.

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5 Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands

SeanPaul La Selle1, Bruce Richmond1, Bruce Jaffe1, Alan Nelson2, Frances Griswold3, Beth Arcos4, Catherine Chagué5, James Bishop6, Piero Bellanova7, Haunani Kane8, Brent Lunghino9, Guy Gelfenbaum1

1 Pacific Coastal and Marine Science Center, U.S. Geological Survey, 2885 Mission St, Santa Cruz, California, 95060 USA 2 Geologic Hazards Science Center, U.S. Geological Survey, 1711 Illinois St, Golden, Colorado, 80401 USA 3 Department of Geosciences, University of Massachusetts, Amherst, Massachusetts, 01003 USA 4 Wood, 180 Grand Avenue, Suite 1100, Oakland, California, 94612 USA 5 School of Biological, Earth and Environmental Sciences, University of New South Wales Sydney, Sydney, Australia 6 Central Coast Regional Water Quality Control Board, 895 Aerovista Place, San Luis Obispo, California 93401 7 Institute of Neotectonics and Natural Hazards, RWTH Aachen University, Aachen, Germany 8 School of Ocean and Earth Science and Technology, University of Hawai΄i at Manoa, Hawai΄i, 96822 USA 9 EnerNOC, Boston, Massachusetts, 02210 USA

Abstract Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska– Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low-lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north-eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon-based age models date sand beds from three sites to ca 700 to 500 cal yr BP, which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian

Islands. Keywords Aleutians, deposit, distant source, extreme events, Hawai΄i, palaeotsunami. This chapter is a slightly modified version of the article published in Sedimentology (2019) DOI: 10.1111/sed.12623

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5.1 Introduction Tsunamis pose a significant hazard in the Hawaiian coastal zone (Richmond et al., 2001; Wood et al., 2007). According to Dudley and Lee (1998), the Hawaiian Islands have experienced 95 tsunamis over 185 years (1813 to 1998 CE), an average of one every two years, with a damaging tsunami occurring on average every five years. Tsunamis affecting the Hawaiian Islands can be locally generated or originate from distant sources throughout the Pacific Ocean basin (Fig. 5.1). Locally generated events are especially hazardous because of the limited warning time and potential large runup and extensive inundation. Rare catastrophic tsunamis are believed to have been locally generated in the Hawaiian Islands when huge volumes of material slid into the sea via flank failure collapse creating large inland runups up to several hundred metres above sea level (Moore et al., 1989; McMurtry et al., 2004). Recent earthquake-generated submarine landslides caused significant local tsunamis that produced identifiable tsunami deposits along the island of Hawai΄i in 1868 and 1975 (Goff et al., 2006a; Richmond et al., 2011a). Distant-source tsunamis that impact Hawaiian shores hours after they are generated can be destructive and deadly. Significant historical tsunamis (Table 5.1) include distant-source events from the Aleutians (1946 and 1957), Kamchatka (1923 and 1952), Chile (1960), Alaska (1964) and Japan (2011). Of these, the 1946 tsunami was the largest in most locations (Lander and Lockridge, 1989) and the deadliest (159 casualties) natural disaster of the last century in the Hawaiian Islands. The last tsunami with recorded runup greater than 10 m was in 1960. Historic tsunamis impacting the Hawaiian Islands are well-documented while the record of prehistoric tsunamis has not been well-established. The development of the geological record of prehistoric tsunamis would improve understanding of the frequency and size of past tsunamis impacting Hawai΄i. Because of the islands’ location in the north-central Pacific Ocean an improved documented tsunami history could add clarity to the frequency and range of past events in the Pacific and so improve coastal hazard assessment throughout the Pacific Ocean basin. This study presents research in the Hawaiian Islands that extends the record of distance source tsunamis. Thirteen coastal wetlands were cored, searching for geological evidence of large tsunamis generated by great (>Mw 8.5) subduction zone earthquakes around the Pacific Rim. Stratigraphic, sedimentary and 14C age evidence from three sites on Kaua΄i, O΄ahu and Hawai΄i suggest that a large tsunami struck the Hawaiian Islands sometime between 1250 and 1450 CE, which overlaps with the ages of tsunami deposits in the eastern Aleutians (Witter et al., 2018). Historic tsunami deposits at two of the three sites, determined by 137Cs dating to be from the 1946 and 1957 CE tsunamis, also share an eastern Aleutian source.

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Fig. 5.1 Inset globe shows the location of the Hawaiian Islands and the Aleutian Islands, the source of some of the largest tsunamis that have historically impacted Hawai΄i. The Fox Islands occupy a ca 480 km long segment of the Aleutian Islands. The hillshade map shows bathymetry and topography of the Hawaiian Islands with the locations of sites (red dots) cored in the search for tsunami deposits. Larger text and arrows label the three primary sites: Anahola Valley on Kaua΄i, Kahana Valley on O΄ahu and Pololū Valley on Hawai΄i.

Table 5.1 Notable historical tsunami events impacting the Hawaiian Islands*.

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5.2 Sedimentary evidence of historical and prehistoric distant-source tsunamis in Hawai΄i Documentation of deposits due to inundation by distant-source tsunamis in the Hawaiian Islands is sparse, especially for prehistoric events. However, in the last 150 years, the Hawaiian Islands have been struck by several distant-source tsunamis that deposited marine sand and other debris onshore (Table 5.1). Most notable were the 1946 and 1957 Aleutian tsunamis, and the 1960 Chile tsunami. Anecdotes and aerial photographs of damage due the 1946 tsunami at Kahuku Point, O΄ahu, show extensive sand deposits and tsunami related scour (Keating, 2008), but these deposits have not been preserved, most likely due to both aeolian reworking and anthropogenic activity. At the south-east corner of O΄ahu at Queen’s Beach, a road was damaged by the 1946 tsunami and photographs show coarse coral rubble mantling the road. Coarse clasts and gravel deposits are still present at Queen’s Beach from the 1946 tsunami and other more recent events (1952 Kamchatka, 1957 Aleutians and 1960 Chile) according to Keating et al. (2004). Shepard et al. (1949) observed coral rubble and sand deposited inland in northern Kaua΄i by the 1946 tsunami. These authors reported observations of sand 1.2 m (4 ft) thick on the highway at Haʻena (northern Kaua΄i), thinner beds of sand covering roads in other places on Kaua΄i, O΄ahu and Maui, as well as taro patches covered in sand in Waipi΄o Valley, Hawai΄i. Pololū Valley (Fig. 5.1), on the north- east coast of Hawai΄i, was inundated by the 1946 and 1957 Aleutian tsunamis, with maximum runup heights of approximately 17 m and 10 m above mean sea level, respectively (Lander and Lockridge, 1989). Chagué-Goff et al. (2012b) identified basaltic sand deposits within the upper half-metre of sediments in the valley, and used sedimentological, stratigraphic, geochemical, diatom, pollen, 210Pb and 137Cs data to attribute these sand beds to inundation from these events. The 1946 tsunami deposit was traced 250 to 350 m inland, thinned landward from 30 to 2.5 cm, and comprised multiple fining upward sequences in several cores. The 1957 tsunami deposit was only observed in one of five cores, with a 1 to 2 cm thick basaltic sand bed overlying the 1946 deposit. Chagué et al. (2018) identified marine sands most likely deposited by the 1946 Aleutian and 1960 Chilean tsunamis in peat and soil at Shinmachi, Hilo. The Makauwahi Sinkhole on the south-east coast of Kaua΄i may contain evidence of inundation by a prehistoric tsunami with a distant source, possibly in the eastern Aleutian Islands (Burney et al., 2001). The sinkhole, which is a remnant of a collapsed aeolianite cave complex, contains a bed of angular boulders, cobbles, gravel, marine sand and coral fragments that suggest that much of the sediment was washed into the sinkhole. Butler et al. (2014) inferred that a tsunami had overtopped the sinkhole wall at its lowest point (7.2 m above sea level). Numerical tsunami modelling by these authors demonstrated that a Mw ca 9.25 earthquake centred in the eastern Aleutians would have been required to generate a tsunami large enough to overtop the sinkhole rim and create the deposit. Based on 14C ages for kukui nuts and bottle gourds from the sinkhole deposit of 1430 to 1665 CE (520 to 285 cal yr BP) (Burney et al., 2001), Butler et al. (2014) proposed that the deposit was similar in age to a tsunami deposit on

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Sedanka Island in the Fox Islands of the eastern Aleutians, dated at 1290 to 1390 CE (660 to 560 cal yr BP) (Witter et al., 2016). More recently, 230Th – 238U ages on detrital coral in the sinkhole deposit narrowed its age to 1551 to 1593 CE (399 to 357 cal yr BP) (Butler et al., 2017). Fox Island stratigraphy contains evidence of nine large tsunamis from approximately the past 2000 years (Witter et al., 2018), at least some of which are likely to have been triggered by an Aleutian subduction-zone megathrust rupture. Because the new precise coral age does not overlap with the ages of presently dated tsunami deposits in the eastern Aleutians (Witter et al., 2018), an Aleutian source for the Makauwahi Sinkhole deposit is unlikely.

Numerical modelling of tsunamis generated by large (Mw 9.3), trench-breaking megathrust earthquakes in the Aleutians predict runups of 10 to 40 m along the north shores of Kaua΄i and O΄ahu (Bai et al., 2018). Because the 1946 and 1957 tsunamis deposited marine sand preserved in coastal wetlands in Kaua΄i and Hawai΄i, similarly sized or larger prehistoric Aleutian megathrust earthquakes could trigger tsunamis capable of leaving behind similar or more extensive deposits. Presented below are the results of the current study’s search for prehistoric tsunami deposits on three Hawaiian Islands, which uncovered evidence of only one or two prehistoric events in the past 750 years.

5.3 Study Area One of the challenges of this research was to find locations where prehistoric tsunami deposits are likely to be preserved. Studies of tsunami deposits around the world have typically been situated in low-lying coastal wetlands, beach-ridge plains and lakes (Nanayama et al., 2003; Pinegina et al., 2003; Kelsey et al., 2005) due to the preservation potential of these environments and ease of differentiating sand-rich tsunami or storm deposits from background sediment such as peat and mud. Many coastal wetlands and beach-ridge plains in the Hawaiian Islands have been utilized for taro and rice farming making it difficult to avoid sites undisturbed by humans. Slow sea-level fall over the past few thousands of years is another impediment to preserving tsunami deposits in Hawai΄i. An emerged intertidal bench at Kapapa Island on O΄ahu and a regressive marine contact in Hanalei coastal plain suggest that mean sea level was higher 5000 to 2000 cal yr BP than it is today (Grossman and Fletcher, 1998). This mid to late-Holocene highstand reached a maximum of about 2 m above present sea level around 3500 years ago. Subsequent regression led to development of strand plains in former embayments on Kaua΄i and O΄ahu (Calhoun and Fletcher, 1996). The island of Hawai΄i has experienced subsidence due to localized flexure of the oceanic lithosphere in addition to global eustatic sea-level rise (Ludwig et al., 1991; Fletcher et al., 2011), resulting in sediment backfilling of valleys (Chagué-Goff et al., 2012b). Due to the highstand and subsequent progradation or infilling, the record of tsunami deposits preserved in wetland peat and mud is limited to the past few thousand years. Reconnaissance of 13 sites on Hawai΄i, Maui, O΄ahu and Kaua΄i islands in 2015 revealed three sites (Anahola, Kahana and Pololū) with historical and prehistoric tsunami deposits along the north-eastern shores of Kaua΄i, O΄ahu and Hawai΄i, respectively (Fig. 5.1). Historical tsunami runups in the Hawaiian

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Islands show that the largest runups, on the north and north-east facing shores, are from tsunamis originating in the Aleutians (Lander and Lockridge, 1989). This study’s approach was to core in wetlands fronted by sandy ocean beaches with the assumption that flooding by a tsunami would deposit an identifiable sand bed within wetland mud and peat.

5.3.1 Anahola Valley, Kaua΄i Anahola Valley is a ca 1 km wide valley fronted by a mostly detrital, carbonate-rich, 100 m wide, sandy beach (Fig. 5.2). Anahola Stream, which drains the Namahana and Kalalea mountains, has its mouth at the north end of the beach. Anahola Bay faces east and is backed by an estuary lined with wetlands that extend 1.2 km inland along the left bank of Anahola Stream (Cheng and Wolff, 2012). The right bank of the stream consists of sand dunes that extend up to 0.3 km inland [Department of Hawaiian Homelands (DHHL), 2015]. Anahola Valley was traditionally farmed for taro and more recently for sugar (DHHL, 2010). In the wetlands an artificially elevated area on which structures have historically been built rises ca 1 m above the marsh and bisects the marsh into eastern and western sections. Anahola Bay has been impacted by five historical tsunamis. The 1946 tsunami was the largest: the waves were up to 4 to 5 m high to the north of Anahola and 8.5 m high along the cliffs to the south (Shepard et al., 1949). Several houses suffered damage in Anahola during the event. Runups in the area for the 1957, 1960, 1964 and 2011 tsunamis were 4.9 m, 1.8 m, 1.0 m and 2.4 m, respectively (Loomis, 1976; Lander and Lockridge, 1989; State of Hawai΄i, 2002; Miller and Roeber, 2014).

Fig. 5.2 Core locations and sand thicknesses in Anahola Valley, Kaua΄i. (A) Depositional environments and landforms in Anahola Valley. Core locations in the wetland on the north-west bank of Anahola Stream are marked by green numbered circles (vibracores) and white dots (gouge cores). (B) Thicknesses of sands A1 (green), A2 (yellow) and A3 (red) are represented by circle diameters. Sand A1 is only observed in a few cores in the north-east section of the wetland. Sand A2 is also confined to the north-east section of the wetland but thins inland and away from the riverbank. Sand A3 is observed in cores up to 650 m from the shoreline and gradually thins inland.

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5.3.2 Kahana Valley, O΄ahu The wetland study area in Kahana Valley, which is on the north-east-facing shore of O΄ahu, is part of the Ahupua΄a O Kahana State Park (Fig. 5.3). The wetland is separated from the Pacific Ocean and an 80 m wide beach consisting of carbonate sand, by a 3 m high coastal berm currently vegetated by Casuarina (ironwood) trees. The modern marsh, which covers an area up to 1.3 km inland and 0.5 km wide, is bisected by Kahana Stream and divided into two sections by the stream and bordering strip of swamp vegetation (Fig. 5.3). Marsh vegetation begins approximately 0.3 km inland from the beach. The shoreline is currently accreting at rates of up to 0.7 ± 0.3 m year -1 (Fletcher et al., 2011). The valley has been used by both Native Hawaiian and post-contact peoples for agriculture (Beggerly, 1990). An organic geochemical study of the sediments below 50 cm depth in the wetland indicated low overall concentrations of anthropogenic markers and pollutants (Bellanova et al., 2019). An environmental reconstruction of Kahana Valley by Beggerly (1990) suggested that Kahana Valley was a marine embayment from the end of the Pleistocene through the mid-Holocene sea-level highstand. Beginning in the mid to late Holocene the estuary transitioned into a lagoon, followed by a marsh that formed 1000 to 2000 years ago. Historical tsunamis had moderate runups in Kahana Valley (1946 = 2.1 m; 1952 = 2.0 m; 1960 = 2.5 m) (Shepard et al., 1949; Lander and Lockridge, 1989; State of Hawai΄i, 2002). The 1946 tsunami only inundated about 100 m into the grove of palm trees (1.6 m above sea level) located on the south side of the highway at the head of the valley. Higher runups up to 2.8 m occurred along the valley walls in Kahana Bay (Shepard et al., 1949). However, a

Mw 9.25 or larger eastern Aleutian earthquake, as proposed by Butler et al. (2014), would presumably result in much larger runups that would be capable of inundating far into the valley interior.

Fig. 5.3 Core locations and sand thicknesses in Kahana Valley, O΄ahu (A) Depositional environments and landforms in Kahana Valley. Gouge and Russian core locations in the wetland in the south- east part of the valley are marked by white dots. (B) Thicknesses of sand K1 (red) are represented by circle diameters. Sand K1 thins inland between 238 m and 478 m from the shoreline.

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5.3.3. Pololū Valley, Hawai΄i Pololū Valley (Fig. 5.1), on the north-east coast of Hawai΄i, is carved into basalts of Kohala Volcano (McDougall and Swanson, 1972), from which most of its beach and dune sediment are derived. As a result, the beach and dune sand here consist mostly of basaltic sand with trace amounts of carbonate, unlike the primarily carbonate-rich sand at Anahola and Kahana. A coastal marsh extends approximately 600 m inland and is bisected by the wide channel of Pololū Stream (Fig. 5.4). The mouth of the stream is constricted by a 30 m high sand dune and a seasonal beach berm and is typically only open to the ocean during periods of high stream flow. Pololū has been settled since the 13th Century and was subsequently abandoned by 1926 (Chagué-Goff et al., 2012b) following utilization of the valley for rice cultivation. The 1946, 1957 and 1960 tsunamis are well-documented in Pololū Valley, with maximum runup heights of 17 m, 10 m and 3 m above mean sea level, respectively.

Fig. 5.4 Core locations and sand thicknesses in Pololū Valley on Hawai΄i. (A) Depositional environments and landforms in Kahana Valley. Core locations in the wetland are marked by green numbered circles (vibracores). White dots represent gouge cores collected by Chagué-Goff et al. (2012b). (B) Thicknesses of sands P1 (green), P2 (yellow) and P3 (red) are represented by circle diameters. Sand P2 (a deposit from the 1946 tsunami) was found in all cores and thins landward. The 1957 deposit (sand P1) was only found in cores VC1 and PO2.

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5.4 Methods Stratigraphy at each site was documented in the field with gouge cores (1 m long sections, 30 mm and 60 mm diameters), Russian cores (0.5 m long sections, 60 mm in diameter) and surface samples. Vibracores (up to 4.42 m long, 76 mm in diameter) were collected from Anahola and Pololū valleys. Core locations were selected to constrain sand deposit extent and geometry based on historical tsunami inundation. All sample locations were determined using a handheld GPS unit (horizontal errors ca ± 4 m). Gouge and Russian cores were described and photographed in the field. Gouge cores were logged by describing stratigraphy in detail or by noting only the thickness and depth of clean sand beds. At vibracore sites, adjacent gouge cores were collected as a guide to correcting contact depths for the amount of vibracore sediment compaction. Compaction during vibracoring ranged from 24 to 55% and was related to mud and/or peat content. Much of the data described below [core locations, core photographs, computed tomographic (CT) scans, descriptions, grain size data, radiocarbon results, and sand depths and thicknesses] have been published in an accompanying US Geological Survey Data Release (La Selle et al., 2019b).

5.4.1 Computed tomographic scans Vibracores from Anahola and Pololū valleys, and a series of seven overlapping Russian cores at one site from Kahana Valley, were scanned for structure using X-ray computed tomographic (CT) density measurements made at the College of Veterinary Medicine at Oregon State University with a Aquilion 64-slice at 120 peak kV and 200 mA, with a pitch of 0.5 sec (100 mA-sec) (Canon Medical Systems Corporation, Otawara, Japan). Image slices were generated every 2 mm across the core, with a voxel resolution of 500 µm in the downcore and across-core directions. The raw DICOM images were processed using Horos software (horosproject.com) to apply a normalized colormap of -200 to 2200 Hounsfield Units to each image (Hounsfield, 1973; Reilly et al., 2017).

5.4.2 Grain size Grain-size analyses of three sand beds from Anahola Valley were performed at the US Geological Survey Pacific Coastal and Marine Science Center. Each sand bed was subsampled at 0.2 to 0.5 cm intervals. These samples were wet-sieved through 2.0 mm and 0.063 mm sieves and separated as gravel (>2.0 mm), sand (0.063 to 2.0 mm) and mud (<0.063 mm). The gravel fraction was analyzed by sieving. The sand fraction was run through a long (2 m) settling tube. Measured settling velocities were converted to sizes of equivalent quartz spheres in ¼-phi size intervals. The mud fraction was analyzed using a Beckman Coulter LS 13-320 laser diffraction particle size analyser (Beckman Coulter Inc., Brea, CA, USA) at ¼-phi size intervals. Statistical parameters of the grain-size distribution (for example, mean grain size, Φ 10, Φ 90, median, mode, standard deviation, kurtosis and skewness) of the samples are calculated using the graphic methods of Folk and Ward (1957) using pcSDSZ and GradiStat software

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(Blott and Pye, 2001). Grain-size distributions were plotted vertically in order to identify suspension grading, a distinctive type of normal grading that is identifiable where the entire grain-size distribution shifts to finer sizes upward in a deposit. Suspension grading is found in deposits formed in high-energy flows, such as tsunamis and turbidity currents (Jaffe et al., 2012).

5.4.3 Cesium dating Cesium-137 (137Cs) analyses of the upper half metre of peat in Anahola was conducted to determine if the uppermost two sand beds were likely to have been deposited by the 1946 and 1957 Aleutian tsunamis. Matching samples 1 cm thick from the upper 50 cm of sediment were combined from seven adjacent Russian cores near VC07 to collect enough sample material for analysis. Powdered samples were sealed in vials and 137Cs activity was measured using a high purity germanium (HPGe) well detector (Princeton Gamma Tech Instruments Inc., Princeton, NJ, USA) at the Pacific Coastal and Marine Science Center in Santa Cruz, CA, USA, following methods outlined in Appleby (2002).

5.4.4 Radiocarbon dating The age of potential prehistoric tsunami deposits was investigated using accelerator mass spectrometer (AMS) 14C ages on seeds, shells and plant fragments; bulk organic-rich sediment and shells sampled from the sediment above, below and within selected sand beds in order to bracket the time of deposition (Table 5.2; Appendix 5.S1). All radiocarbon ages were determined at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility in Woods Hole, MA, USA. After sieving selected sediment intervals on a 180 µm mesh, small macrofossils, many identified to genus level, were selected for dating under a microscope (5 to 259), rinsed with deionized water, dried for 24 h at 50 °C and weighed (Table 5.2) (Kemp et al., 2013). Bulk sediment samples were rinsed with deionized water, and the majority of rootlets were removed with tweezers before drying the sediment sample for 24 h at 50 °C. The AMS ages were calibrated with OxCal (version 4.3; https://c14.arch.ox.ac.uk/oxcal/) using the IntCal13 calibration curve (Reimer et al., 2013). The OxCal stratigraphic ordering software (methods of Ramsey, 2008, 2009) was used with the 14C ages to develop age models for the times when sand beds were deposited (models similar to those described by Nelson et al., 2014; Table 5.1; Appendix 5.S2). The accuracy of the models, however, depends on the interpretation of the context of each separate 14C sample (Ramsey, 2008), as well as consideration of the sedimentation processes that produced the wetland sequences containing sand beds (discussed for each dated core below). The ages on samples of bulk sediment were particularly difficult to evaluate: decayed, fine-grained carbon that was not fully removed by acid pretreatment could have been older than its host sediment. Four of eight bulk sediment ages are older than seed ages from the same levels in the cores (Table 5.2); but two bulk sediment ages are younger than seed ages from the same levels, probably because much younger, now decayed, roots grew into the sediment from above. Although the type of macrofossil dated and the likely stratigraphic context of each sample was taken into account, age

59 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands models that consider the depth of each sample in sequence (Witter et al., 2018) are inappropriate because many of this study’s samples are clearly reworked, and because sedimentation rates within these coastal sequences may vary by orders of magnitude. Instead, ages were grouped in a simple sequence model into phases above and below potential prehistoric tsunami deposits at each site to calculate probability distribution functions for the times of tsunami deposition (Ramsey, 2009). Grouping all but the most obviously reworked seed ages into the unordered phases required fewer assumptions about the degree of reworking and the extent to which ages were maximum or minimum limiting ages than would be the case if only the most limiting maximum and minimum ages at each site had been used.

Table 5.2 Radiocarbon data and stratigraphic context for samples from cores bracketing the ages of sand layers A3 in Anahola Valley, Kaua΄i, K1 in Kahana Valley, O΄ahu and P3 in Pololū Valley, Hawai΄i.*

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Table 5.2 (Continued) Radiocarbon data and stratigraphic context for samples from cores bracketing the ages of sand layers A3 in Anahola Valley, Kaua΄i, K1 in Kahana Valley, O΄ahu and P3 in Pololū Valley, Hawai΄i.*

5.5 Results 5.5.1 Anahola Valley, Kaua΄i Cores from the marsh along Anahola Stream contained up to three carbonate sand beds within interbedded peat, mud and silt. At Anahola, eight vibracores and ca 130 gouge and Russian cores were taken in the floodplain north of the stream between 280 m and 680 m inland from the shoreline (Fig. 5.2A). Most cores met refusal within a coarse carbonate sand bed that may have been deposited during a higher sea level in the late Holocene. Vibracores bottomed out between 2.8 m and 4.2 m depth within a dense carbonate sand bed overlain by a poorly sorted, muddy carbonate sand bed with shell fragments. The contact between these beds is sharp (<3 mm) in five of eight vibracores. However, the depth and mud content of these basal sand beds vary widely from core to core, with the upper depth of these beds ranging from 58 cm in VC1 to 250 cm in VC3. In cores where the tops of the basal sand beds are shallow, they are overlain by muddy peat units. Where the contact is deeper, the basal sand beds are overlain by sandy mud. A seed extracted from a peaty bed within the basal carbonate sand beds in VC4a returned an age of 2045 to 1924 cal yr BP (95 BCE to 26 CE; Appendix 5.S1). This age is consistent with the time of strand plain formation in Hanalei, Kaua΄i, from 2160 to 1940 cal yr BP (Calhoun and Fletcher, 1996) and the initiation of coastal plain development in ΄Upolu, Samoa from 2103 to 1899 cal yr BP (Kane et al., 2017). The marsh sediments above the basal carbonate sands are characterized by peat interbedded with mud and silt beds with up to three anomalous sand beds. Of the two shallow carbonate sand beds in the north- east part of the marsh, the thinner (A1) is from 1 to 3 cm thick and only observed as a clean sand bed in

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VC8, which is ca 300 m from the shoreline, and six gouge cores (Fig. 5.2B; Appendix 5.S3). The thicker of the two sands (A2) is up to 10 cm thick and is observed in four vibracores and 31 gouge cores throughout the north-east marsh, typically between 20 cm and 50 cm depth (Fig. 5.2B; Appendix 5.S3). Both sand units A1 and A2 are easily identified by their light tan colour and the sharp (<3 mm) upper and lower contacts with bounding mud or peat. In several cores (VC6 through to VC8), the lower contact appears to be erosional, with infilling of microtopography visible in core photographs and CT images (Fig. 5.5A). Where both A1 and A2 are observed, they are separated by 3 to 12 cm of muddy peat. Sand A2 is generally thicker in cores closest to the river mouth, and thinner towards the area of artificial fill (Fig. 5.2B). In VC8, the CT image shows roots penetrating through the entire unit, which is from 22 to 28 cm depth (Fig. 5.5A). Both sands A1 and A2 consist of poorly sorted, very fine to fine sand (Fig. 5.6A), based on grain-size analyses from Russian core RC1-BR (Fig. 5.2A). Vertical grain-size distributions are overall, fairly uniform in sand A2, but exhibit suspension graded intervals at 26.2 to 26.8 cm in A1 and 33.2 to 33.6 cm in A2 (Fig. 5.6A).

Fig. 5.5 Photographs, computed tomographic (CT) images, lithology and ages of core stratigraphy hosting prehistoric tsunami deposits at the three primary sites. (A) Vibracore VC8 from Anahola Valley. Sands A1 and A2 are in the lower half of the upper segment. The lower segment shows sand A3. (B) Core RC-02b from Kahana Valley showing sand K1. (C) Vibracore VC1 from Pololū Valley, with sands P1 and P2 in the upper segment, and P3 in the lower segment.

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Fig. 5.6 Vertical variations in grainsize distributions of tsunami deposits in Anahola Valley compared with distributions for deposits at Stardust Bay, Aleutians and from the Sendai Plain, Japan. For each vertical subsample from each of the four cores, the weight percent from each phi bin is represented by the colormap and faint white lines. Suspension graded intervals are indicated by the white arrows. (A) Grain-size distributions of sands A1 and A2 from core RC1-BR at Anahola. (B) Grain-size distributions of sand A3 from Russian core RC6-BR at Anahola. (C) Grain-size distributions of a tsunami deposit dated at 660 to 560 cal yr BP at Stardust Bay, Aleutian Islands, Alaska (Witter et al., 2016). (D) Grain-size distributions of a deposit sampled from trench on the Sendai Plain, Japan, from the 2011 Tohoku-oki tsunami (Jaffe et al., 2012).

In the Anahola cores selected for 137Cs analyses, sand A1 and sand A2 are at depths of 36.5 to 37.5 cm and 49.5 to 50 cm, respectively. Due to the 50 cm length of the Russian cores used for sampling, the bottom of sand A2 was cut off and was not included in the 137Cs samples; in a nearby gouge core, Sand A2 is 5 cm thick. Cesium-137 activity in the upper 50 cm of sediment peaks at 32 to 33 cm depth (Fig. 5.7), indicating that this sediment was deposited about 1963-1964, following the peak in nuclear testing that occurred in 1962 prior to the Nuclear Test Ban Treaty (Carter and Moghissi, 1977). Atmospheric nuclear testing started near the end of World War II (Pennington et al., 1973), but the onset of 137Cs detectable in sediment began in 1954. In Anahola this is marked where the 137Cs activity curve consistently exceeds 0.3 dpm g -1 above 45 cm depth (Fig. 5.7). A deeper carbonate sand bed (sand A3) within a sandy, muddy peat is found in six vibracores and 41 gouge cores between 63 cm and 180 cm depth, including most sites in the south-west marsh. Sand A3 thickness varies between cores and is thickest (25 cm) in VC8 in the north-east marsh, and thinner (3 cm) at the most landward site, VC5, 650 m from the shoreline (Fig. 5.2B; La Selle et al., 2019b). Freshwater snail shells of the species Tryonia porrecta (Mighels, 1845; Cowie et al., 1995) in sandy mud just above sand A3 aids correlation among cores despite large variations in the depth, thickness, colour and sedimentary structures observed in the deposit. These shells occur only in the 1 to 10 cm of sandy mud above sand A3. The shells break very easily, but most are intact. In core VC8, sand A3 has very sharp (1 mm) upper and lower contacts. The upper 5 cm appear to be slightly bioturbated based on roots visible in the CT image and the tan colour of the sand, similar to the lower modern sand bed (sand A2). The lower 20 cm of sand A3 consists of whitish carbonate sand, with weak planar laminations visible in the CT image (Fig. 5.5A). The sand bed consists of very fine to medium sand, with a bulk D50 of 2.6 phi (fine sand).

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Like sands A1 and A2, vertical grain-size distributions of sand A3 from core RC6-BR (Fig. 5.6B) exhibit suspension-graded intervals (99.5 to 101.0 cm and 105.5 to 107.0 cm). With the exception of the suspension-graded interval, the upper 10 cm of the deposit appears massive. Normal grading is observed between 107.0 cm and 109.5 cm, indicated by the gradual upward decrease in the medium to coarse fractions of the distributions (Fig. 5.6B). This normally graded interval is capped by the suspension- graded interval at 105.5 to 107.0 cm, which contains a shift of the entire distribution from mostly fine sand to mostly very fine sand. The bottom-most 3 cm of the deposit exhibit a weakly inverse-graded interval.

Fig. 5.7 Lithological column and 137C data compiled from seven adjacent Russian cores at Anahola near core VC7 (Fig. 5.2). Solid line on the right shows 137Cs activity measured at 1 cm intervals. The dashed vertical line indicates the threshold 137Cs activity (0.3 dpm g -1), above which the accumulation of 137Cs in the sediment is apparent, typically in 1954 in sediment around the world (Pennington et al., 1973). At Anahola, this interval is between sands A1 and A2 at 44 to 45 cm depth. The peak activity at 32 to 33 cm corresponds to the years 1963 and 1964, following the peak in atmospheric nuclear testing in 1962.

In VC4a, ca 600 m from the shoreline, sand A3 is a bed of clean fine sand with gastropod shells in mud above it. In this core, sand A3 caps a sequence of poorly sorted and coarse basal carbonate sand and lacks a clear lower contact. In VC2, 475 m from the shoreline, sand A3 consists of 6 cm of muddy, bioturbated, carbonate sand overlying 3 cm of clean, fine to medium carbonate sand. In this core, sand A3 is overlain by brown mud with Tryonia porrecta shells from 81.5 to 95.0 cm depth. On top of the mud is a 1 cm thick fine to medium carbonate sand with undulating, but sharp, upper and lower contacts. Tryonia porrecta shells were not observed above this sand, and this is the only core in which a clean carbonate sand was observed between sands A2 and A3.

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Organic material from six cores was radiocarbon dated to determine the age of sand A3 (Table 5.2). The most commonly dated macrofossils were Schoenoplectus sp. (bulrush) seeds found above, below and within the sand bed. Schoenoplectus seeds in the muddy sand with gastropods overlying sand A3 returned ages ranging from 530 ± 15 to 835 ± 15 14C yr BP, demonstrating that the seeds are decay resistant enough to be reworked over centuries following deposition. Because it is inferred in this study that the seeds may be reworked, but cannot be significantly younger than their host sediment, the youngest Schoenoplectus seed (530 ± 15 14C yr BP) from 0 to 2 cm above sand A3 is considered as a minimum limiting age for the post-tsunami sediments. The youngest Schoenoplectus seed found within sand A3 returned an age of 785 ± 20 14C yr BP, which is a maximum limiting age for deposition of the sand. Based primarily on these minimum and maximum limiting Schoenoplectus seed ages, the OxCal sequence model in this study dates deposition of sand A3 at Anahola to 704 to 535 cal yr BP (1246 to 1415 CE) at the 95% confidence level (Fig. 5.8; Table 5.2). Bulk sediment, wood, grass and Tryonia shells above, within and below sand A3 were also dated, but the resulting ages were too wide ranging and inconsistent to be used in the OxCal model (Table 5.2). A bulk sediment age from just below sand A3 returned an age of 505 ± 20 14C yr BP, but CT scans and photographs suggest that much younger roots may have penetrated into sand A3 and the peat below it. Tryonia porrecta shells returned ages that were typically hundreds of years older than Schoenoplectus seeds from the same intervals (Table 5.2), perhaps because these gastropods metabolized older carbon from carbonate sediment or seawater in the substrate (Dye, 1994; Pigati et al., 2010).

Fig. 5.8 ‘OxCal’ modelled ages of tsunami deposits at sites in the Aleutians and Hawai΄i. Probability density functions (bars underneath show 95% confidence intervals) for each modelled age are shown in red for sand A3 in Anahola Valley, sand K1 in Kahana Valley and sand P3 in Pololū Valley. Probability density functions for Aleutian tsunami deposits from Stardust Bay (sands S2 and S3) and Driftwood Bay (sands C1 and C2) are shown in shades of blue (Witter et al., 2016, 2018). The 95% confidence interval age range derived from precise Uh/Th coral dating of the Makauwahi Cave deposit is represented by the symmetrical distribution (95% confidence interval) (Butler et al., 2017). The tsunami deposits in the three Hawaiian valleys have ages that overlap the ages of deposits S3, C2 and C1 in the Aleutians. However, because the distributions are so broad it cannot be determined whether or not the Hawaiian deposits were deposited by a single tsunami or multiple tsunamis of different ages. The distribution for the Makauwahi Cave deposit barely overlaps with the youngest end of the distribution from the Pololū Valley, but not with the distributions for any other tsunami deposits in the Aleutians or elsewhere in Hawai΄i. 65 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands

5.5.2 Kahana Valley, O΄ahu The stratigraphy and sedimentology of Kahana Valley was investigated in 30 gouge and Russian cores, primarily along a shore-normal transect on the east side of the valley 240 to 880 m from the shoreline (Fig. 5.3). A landward thinning, carbonate sand bed (sand K1) was traced in cores between 238 m and 478 m from the shoreline in the freshwater marsh on the south-east side of Kahana Stream. Closest to the shoreline, sand K1 is thick (31 to 37 cm in cores gc13 and gc14; Fig. 5.3) and composed mostly of fine to medium sand. Although variable in thickness, the sand bed gradually thins to 1 cm at its inland limit (core gc05-FG). Sand K1 is overlain by sandy mud with Tryonia porrecta shells (Fig. 5.5B), the same species found above sand A3 in Anahola, in half of the cores containing sand K1 (6 of 12). A CT image of Russian core RC-02b shows that sand K1 is bioturbated, with upper and lower contacts ca 3 mm thick, and that its lower half consists of carbonate sand that is cleaner than in its upper half. The upper 50 cm of sediment in all 30 cores along the transect consist of compact alluvial silt, resulting from rice and sugarcane cultivation, flooding from Kahana Stream, and mass wasting of sediment from deforested slopes (Beggerly, 1990). This silt bed was difficult to core through and was typically not described in detail. Below the silt is ca 0.5 to 1.0 m of silty peat grading down into dark, organic rich, muddy peat. Sand K1 overlies peat interbedded with muddy, poorly sorted, volcanic sand. Cores typically met refusal around 2 m depth in coarse sand. In the ten cores where it was recovered, this sand bed consisted mostly of sub-rounded volcanic grains with scattered shell fragments of probable freshwater gastropods or bivalves. At 680 to 880 m from the shoreline along the transect, cores bottomed out in the lower of two volcanic sand beds without carbonate grains. This study attempted to determine the age of sand K1 by radiocarbon dating Schoenoplectus sp. (bulrush) seeds and bulk sediment (Table 5.2). Because the source of the carbon in the bulk sediment samples is uncertain, the bulk sediment ages are not used in the age model. Two Schoenoplectus seeds from just above sand K1 returned maximum ages (645 ± 20 14C yr BP and 600 ± 15 14C yr BP) that are interpreted as having been reworked from sediment below sand K1. Two other much younger seed ages from above sand K1 may also be reworked (470 ± 20 14C yr BP and 375 ± 15 14C yr BP), but because they are so much younger than the other seed ages, it is inferred that they are much closer minimum ages for the time of deposition of sand K1. The bulk sediment age from the same level in the core is about the same age (380 ± 15 14C yr BP; Table 5.2), but is difficult to evaluate. Because of uncertainties in the degree of reworking of the dated seeds, for the age model in this study the conservative interpretation that the youngest of the two seed ages is a minimum limiting age and the oldest seed age is a maximum limiting age for sand K1 can be made. With these assumptions this study’s OxCal sequence model gives a probability distribution range (with 95% confidence) for the time of deposition of sand K1 in Kahana Valley of 605 to 490 cal yr BP (1345 to 1460 CE).

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5.5.3 Pololū Valley, Hawai΄i In Pololū Valley, the nearshore, beach and dune sources of sediment are primarily basaltic sand, which can be difficult to distinguish from the fluvial sand sources towards the back of the marsh. Modern sand beds from the 1946 (sand P2) and 1957 (sand P1) Aleutian tsunamis have been mapped by Chagué-Goff et al. (2012b). A third, deeper sand bed (sand P3) in vibracore VC1 shares some characteristics with sands P1 and P2. Although five vibracores were collected, only two (VC1 and VC2) were deep enough to penetrate through the 1946 and 1957 tsunami deposits and well into prehistoric sediments (Figs. 5.4 and 5.5). The site of vibracore VC1 is ca 250 m from the shoreline near an overturned World War II-era landing craft. Core PO1 of Chagué-Goff et al. (2012b) (Fig. 5.4), which contained a 30 cm thick sand deposited by the 1946 tsunami, is within 10 m of VC1. The upper 0.5 m of VC1 consists mostly of dark brown peat, but at 15 cm depth a 3 mm thick bed of peat contains a trace amount of silt and very fine sand. This sand bed (sand P1) may correlate with the 1 to 2 cm thick 1957 tsunami deposit in core PO2 (Chagué-Goff et al., 2012b), the only other location where the 1957 tsunami sand bed has been found in the Pololū Valley. Sand P2, interpreted by Chagué-Goff et al. (2012b) to be the 1946 tsunami deposit, extends from 19.5 to 42.0 cm depth in VC1 (Fig. 5.5C). Here, sand P2 consists of dark grey, basaltic, very fine to fine sand with very sharp (<3 mm) upper and lower contacts, and a carbonate shell fragment in the lower 6 cm. The CT image (Fig. 5.5C) shows that the lower 15 cm of the core is weakly laminated, similar to sand A3 in the Anahola Valley. A lighter brown, peaty silt, which extends from 55.0 to 121.5 cm depth, abruptly changes to a sequence of silty peat and silt from 121.5 to 170.0 cm. Sand P3 is a rapidly landward-thinning sand bed that was confidently identified in four cores along the west bank of stream, 230 to 260 m from the shoreline. In VC1, sand P3, at 121 to 124 cm depth, consists of very fine to medium sand that is discontinuous across the core (Fig. 5.5C). The CT image shows that the overlying strata and the upper contact of sand P3 are angled 40˚ from horizontal. From 170 cm to ca 400 cm depth in core VC1 is a distinct facies of alternating tan silt and silty peat beds (La Selle et al., 2019b), which helps correlate overlying sand beds from two nearby gouge cores. In the seaward core (gc202), sand P3 is 24 cm thick (158 to 182 cm depth), and consists of a muddy, basaltic, medium to coarse sand. sand P3 in the inland core (gc201) is 1.5 cm thick (106.0 to 107.5 cm depth), and consists of basaltic very fine to medium sand with a sharp lower contact and a 3 mm long fragment of decomposed wood in the upper 5 mm of the sand bed. The deeper, tan silt and peat facies was observed up to 300 m inland but lacked overlying sand beds (except for sand P2 in the upper parts of some cores) beyond 260 m from the shoreline. Further inland, sand P3 was not identified, although sand P2 was found in the vibracores. Core VC2, 475 m from the shoreline at the southern end of the marsh, generally has a higher silt content than VC1 (La Selle et al.,2019b). Sand P2 in core VC2, from 54 to 64 cm depth, is an oxidized, orange and grey, fine sand with a sharp lower contact and decayed organic debris concentrated in its upper 5 mm. Gouge cores near vibracores VC3, VC4 and VC5, and on the landward side of the dune, contained

67 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands one to two muddy, poorly sorted, basaltic sand beds of varying thickness (5 to 37 cm) in peat below sand P2. Sediment above and below sand P3 in VC1 was sampled extensively for radiocarbon dating. Dated materials consisted of Brachiaria sp. (California grass) seeds, Schoenoplectus sp. (bulrush) seeds, unidentified round seeds and bulk sediment. All but one of seven seed samples returned ages with errors > ± 45 14C years, likely due to sample sizes <1 mg (Table 5.2). Because the source of the carbon in the bulk sediment samples is so uncertain, the bulk sediment ages were not used in the age model for this study. Of four ages on Brachiaria seeds above sand P3, two are old (740 ± 130 14C yr BP and 825 ± 110 14C yr BP) and so probably reworked. As at Anahola, the other two (285 ± 100 14C yr BP and 375 ± 90 14C yr BP) are much younger and so are likely minimum ages. However, the age difference between these two pairs of seed ages is ca 700 to 200 years, and their errors are very large (compared with other seed-age errors in Table 5.1), and so the accuracy and stratigraphic context of the ages is much more uncertain than for the seed ages at other sites. Below sand P3, an age on seeds from 12 cm below the sand bed is 730 ± 110 14C yr BP, a second on seeds from just beneath the sand bed (0 to 0.5 cm) is younger (625 ± 45 14C yr BP), and a third seed age is much younger (445 ± 65 14C yr BP). Because the seed ages span such a broad interval of time and have such large errors it is difficult to determine which most reliably date the sand bed. For this reason, all six ages within 4 cm of sand P3 were used in the OxCal sequence model to roughly constrain its age. Although the model results highlight the significant inconsistency in these ages, it yields a 95% confidence age for sand P3 of 630 to 534 cal yr BP (1320 to 1416 CE), which overlaps considerably with the age of sand K1 from the Kahana Valley (605 to 490 cal yr BP) and the age of sand A3 from the Anahola Valley (704 to 535 cal yr BP). Near the bottom of core VC1 (384.5 to 385.5 cm) dating of bulk sediment returned a calibrated age of 1713 to 1617 cal yr BP (237 to 333 CE; Appendix 5.S1).

5.6 Discussion 5.6.1 Tsunami origin of deposits The sedimentology, distribution, vertical grainsize trends and thickness of the sand beds in Anahola, Kahana and Pololū valleys are consistent with marine inundation and suggest deposition from high velocity flows, such as a tsunami. Sand beds A1, A2, A3 and K1 consist mostly of marine carbonate sand containing rounded coral and shell fragments. Their distinctive carbonate mineralogy and grain size, when compared qualitatively to the composition of the mud and peaty deposits typically deposited in the marshes further inland, indicate that the beach and nearshore environments were sediment sources for the sand beds mapped at Anahola and Kahana. Vertical grain-size trends in sands A1, A2 and A3 at Anahola exhibit characteristics typically observed in tsunami deposits. The presence of suspension graded intervals within the sand beds (Fig. 5.6A and B) suggest that during each depositional event, several waves inundated the marsh and that flow velocities were high enough to carry sand grains in suspension, which settled out of suspension as the

68 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands flow decelerated. In sand A3, the pattern of an inverse graded interval at the base of the deposit, overlain by a normal graded interval and then a massive section is also observed in prehistoric tsunami deposits in the Aleutians (Witter et al., 2016; Fig. 5.6C) as well as in deposits from the 2011 Tohoku-oki tsunami in Japan (Jaffe et al., 2012; Fig. 5.6D). Suspension graded intervals are also observed in the 1957, 1946 and prehistoric sand beds at Anahola, as well as the Aleutian prehistoric tsunami and Japan 2011 tsunami deposits. All sands (A1, A2, A3, K1, P1, P2 and P3) exhibit sharp (<3 mm) upper and lower contacts in most cores, which is a characteristic of deposits formed in high velocity flows. In Anahola and Kahana valleys, sands A2, A3 and K1 gradually thin landward, another characteristic commonly observed in tsunami deposits (Morton et al., 2007). In Pololū Valley, sand beds of marine and terrestrial sources are difficult to distinguish based on mineralogy because the beach, dune and nearshore environments are characterized primarily by black basaltic sand. However, Chagué- Goff et al. (2012b) reported high concentrations of marine diatoms, brackish diatoms and low numbers of redeposited pollen grains in the 1946 and 1957 tsunami deposits, suggesting that these sand beds were sourced from the beach and nearshore. Sands P1 and P2 share several similarities with the 1946 and 1957 deposits identified by Chagué-Goff et al. (2012b). Both sand beds are at approximately the same depth, are of the same thickness, and consist of clean, basaltic, very fine to medium sand, which strongly suggest that they were deposited by the 1957 and 1946 tsunamis, respectively. Because sand P3 is the only other well-sorted, basaltic, very fine to medium sand in cores VC1, gc201 and gc202, it is inferred that it is, most likely, a prehistoric tsunami deposit. Additional multiproxy analyses, such as those used by Chagué- Goff et al. (2012b), might confirm a tsunami origin for sand P3. The presence of muddy peat with concentrations of Tryonia porrecta shells in the few centimetres above sand A3 in Anahola and sand K1 in Kahana may indicate a sudden environmental change in both valleys following tsunami inundation. Relatively high concentrations of Tryonia shells were also observed just above the 1551 to 1593 CE deposit in the Makauwahi Sinkhole (Burney et al., 2001). In the Hawaiian Islands, Tryonia porrecta frequents wetlands and ancient fishponds and taro fields (Christensen, 2018), but whether it is an endemic species to Hawai΄i, or if it was introduced during human settlement, is unknown. Although Tryonia porrecta is identified as a freshwater gastropod, studies of Tryonia porrecta in San Francisco Bay (USA) show its tolerance of brackish conditions (Kitting, 2015), and this species has adapted to an entirely benthic life cycle in hot springs throughout south-western North American deserts (Hershler et al., 2005). The lack of Tryonia shells observed below sands A3 and K1 suggests that they were not abundant in the marsh prior to tsunami inundation. Therefore, it is plausible that the Tryonia shells just above the sands could represent an allochthonous assemblage that was transported by a tsunami from stream channels, lagoons, fishponds and (or) taro fields into marsh environments that Tryonia then colonized. In some cores, such as VC6 at Anahola, the mud and sandy mud beds above sand A3 that contain Tryonia shells are up to 45 cm thick suggesting that this species was living in some sections of the marshes for a significant amount of time following a tsunami.

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Although storm overwash as a source of the sand beds in Anahola, Kahana and Pololū valleys cannot completely be ruled out, observations of limited overwash sand deposition from two 20th Century hurricanes that have hit Kaua΄i (Category 1 Iwa in 1982 and Category 4 Iniki in 1992) support the interpretation that the sand beds in all three valleys were most likely deposited by tsunamis, because tsunamis deposit sand beds further inland than storms. The 1 to 5 mm thick laminae that are visible in the CT images of the lower parts of sands P2 and A3 in several cores are more typical of coastal storm deposits than tsunamis (Morton et al., 2007), and the erosional lower contacts and inland thinning of the deposits are features of both tsunami and storm deposits. In a field survey following the 1992 Iniki hurricane on the island of Kaua΄i, Fletcher et al. (1995), mapped marine sand overwash with excursion distances of ca 20 to 250 m inland and elevations in the range of 4 to 9 m above mean lower low water. Debris lines used to measure inland excursion were composed mostly of vegetation or debris from man- made structures. Debris fields contained boulders derived from adjacent seawalls and deposits of beach and dune sand, although the inland limit of sediments was not noted. Localized areas on the west coast of Kaua΄i had sand sheets up to 10 cm thick that extended a few tens of metres inland. However, sands A2 and A3 in Anahola were found up to 380 m and 650 m inland, respectively. sand K1 in Kahana was traced between 240 to 480 m inland. In Pololū Valley, sand P2 was traced about 500 m inland and, although sand P1 was only observed in core VC1, it is 280 m from the shoreline. Kennedy et al. (2012) modelled 643 synthetic hurricane scenarios for the southern coasts of O΄ahu and Kaua΄i and concluded that none of the scenarios led to storm surges >3 m high. Flooding from large rain storms is also capable of depositing silt, sand and fine gravel in all three valleys. At Kahana and Anahola, the marine carbonate sand in sand A3 rules out a fluvial source, but the source of basaltic sand in sand P3 at Pololū is more difficult to determine. Large floods tend to deposit muddy silt beds like those in the upper 50 cm of cores in the Anahola and Kahana valleys. Since 1914, at least 13 major rain storms have caused flooding of Anahola Stream (Fletcher et al., 2002), most notably in 1956, 1965, 1968 and 1991. Intense rainfall in April 2018 also caused major flooding. The muddy silts deposited during these events are visible in CT images in the Anahola vibracores (Fig. 5.5A). In Kahana Valley, fluvial sand beds consisting of volcanic grains were found 680 to 880 m inland. In Pololū Valley, well-sorted, basaltic, fine sand below sand P3 was not observed in VC1 and VC2, suggesting that flood deposits in the lower reaches of the valley do not typically consist of basaltic sand, and that silt is usually deposited during large rain storms. Where Pololū Stream enters the wetland, a small alluvial fan consisting of angular basalt pebbles and coarse black sand suggests that silt is transported well beyond the fan further towards the shoreline. In all three valleys, the position of the shoreline, geometry of stream channels, and extent of wetlands 500 to 700 years ago is not well-known. However, based on the mud and peat below sands A3, K1 and P3 in most cores, each valley hosted extensive wetlands at about this time. In Anahola Valley, sand A3 caps shallow basal carbonate sand in three cores, which may indicate that wetlands were less aerially extensive than today, and that marsh sediment was primarily accumulating in swales during prehistoric

70 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands tsunami inundation. Cores on the east side of Kahana Valley lack a basal carbonate sand bed, but a core on the west side of Kahana Valley encountered an impenetrable, coarse, carbonate sand at about 1 m depth. The coarse carbonate sand is consistent with core descriptions from Beggerly (1990), who suggested that this bed represents a prograding coastal sand bar that had extended ca 550 m from the modern shoreline ca 1300 cal yr BP. Perhaps the basal carbonate sand underlies the east side of Kahana Valley as well but is below the reach of the hand operated gouge corers used in this study. Subsidence of the island of Hawai΄i at a rate of about 2.6 mm year -1 (Moore and Clague, 1992) from loading by active volcanoes and eustatic sea-level rise has led to sediment backfilling of Pololū Valley (Vitousek et al., 2010), which consists of marsh and fluvial sediments down to depths of at least 4 m. The bulk sediment age from the bottom of core VC1 (1713 to 1617 cal yr BP) suggests that the marsh has been accreting for at least the past 1700 years at an average rate of roughly 2 mm year -1.

5.6.2 Timing of events Sand sheets in Anahola, Kahana and Pololū valleys record at least three different tsunamis over the past 700 years. At Anahola and Pololū, the upper two sands beds were deposited by the 1946 and 1957 Aleutian tsunamis. A deeper sand bed at all three sites is consistent with deposition by one or two tsunamis between 750 and 500 cal yr BP. Based on 137Cs activity in the upper 50 to 70 cm of sediment at Anahola, the two carbonate sand beds were deposited during inundation by the 1946 and 1957 Aleutian tsunamis. The carbonate sand bed in muddy peat from 36.5 to 38 cm depth is attributed to the 1957 tsunami given its position about 4 cm below the peak in 137Cs (reached between 1963 and 1964). Because runup near Anahola from the 1957 tsunami was higher (4.9 m) than for the 1960 tsunami (1.8 m), it is assumed that this sand bed was deposited by the 1957 event. The lower carbonate sand in these cores is about 5 cm below the depth marking the onset of nuclear testing (1954), and therefore was probably deposited by the 1946 Aleutian tsunami. For the prehistoric tsunami deposits, the 95% confidence intervals on the modelled ages at the three sites overlap the ages of tsunami deposits found on multiple Aleutian Islands between 660 and 560 cal yr BP (1290 to 1390 CE) (Witter et al., 2016, 2018) (Fig. 5.8). In addition to the contemporaneous tsunami deposit ages, it is suggested that the eastern Aleutians are the most likely source because the Aleutian subduction zone is known to possess the highest tsunami threat to Hawai΄i due to its geometry and propensity for large tsunamigenic earthquakes (Bai et al., 2018), and because the shorelines fronting Anahola, Kahana and Pololū valleys all face the eastern Aleutians. The geological records of prehistoric earthquakes and tsunamis on Simeonof, Chirikof and Sitkinak islands, 400 km, 650 km and 775 km east of the Fox Islands, respectively, do not contain events that clearly overlap in age with the Hawaiian prehistoric deposits (Briggs et al., 2014; Witter et al., 2014; Nelson et al., 2015). Other potential tsunami source areas with prehistoric evidence of tsunami deposits that may overlap an age range of 750 to 500 cal yr BP include subduction zones such as the Kuril-Kamchatka (Nanayama et al., 2003; Pinegina

71 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands et al., 2003; Bourgeois et al., 2006), Peru-Chile (Atwater et al., 2013; Kempf et al., 2017) and Cascadia (Priest et al., 2017). These non-Aleutian sources for the prehistoric tsunami deposits observed in Anahola, Kahana, and Pololū cannot be fully discounted without running tsunami models and further dating of deposits to better constrain age models. Although their 95% confidence ranges overlap by almost a century, the estimated age of the deposit at Anahola may be older (704 to 535 cal yr BP; 1246 to 1415 CE) than the deposits at Kahana (605 to 490 cal yr BP; 1345 to 1460 CE) and Pololū (630 to 534 cal yr BP; 1320 to 1416 CE). Therefore, the deposits at all three sites may have been deposited by a single far-field tsunami with an Aleutian source. Although more unlikely, it is also possible that the oldest sand bed at Anahola was deposited by an older tsunami, possibly sourced in the western Aleutians, Kamchatka, or even by a submarine landslide, perhaps triggered by a local earthquake. An expanded effort to date suitable material in cores containing prehistoric tsunami deposits at these and other sites could reduce the uncertainty in these broad age distributions. The age of the deposit in Makauwahi Cave (399 to 357 cal yr BP; 1551 to 1593 CE) (Butler et al., 2017) is younger than the ages of sands A3, K1 and P3. The only sand bed observed that could have overlapped in age with the Makauwahi deposit is at 81 cm in core VC2 in Anahola. It is possible this sand bed is a tsunami deposit younger than sand A3, but it could not be found in any other core at Anahola and matches no comparable deposits at Kahana or Pololū. Given the degree of preservation of deposits from the 1946 and 1957 Aleutian tsunamis at Anahola and Pololū, and the presence of prehistoric tsunami deposits at all three sites, it is very unlikely that deposits from a tsunami generated by a Mw 9+ earthquake in the eastern Aleutians in the past half-millennium would not be present in these wetlands.

5.7 Conclusions Previously unidentified prehistoric tsunami deposits on three separate Hawaiian Islands in the Anahola, Kahana and Pololū valleys exhibit sedimentological and stratigraphic characteristics common to tsunami deposits around the world, such as normal and suspension grading, inland-thinning sand beds and sharp lower contacts. Based on these characteristics and broad, overlapping age distributions for their times of deposition, it is inferred that these deposits record one, or possibly two, distant-source tsunamis. Deposits of the 1946 and 1957 tsunamis at Anahola (determined through Cesium-137 dating) were also identified, and in Pololū Valley the previously studied 1946 deposit was traced up to 500 m inland. Although the prehistoric tsunami deposits in Anahola Valley (704 to 535 cal yr BP; 1246 to 1415 CE) may be up to a century older than the deposits in Kahana Valley (605 to 490 cal yr BP; 1345 to 1460 CE) and Pololū Valley (630 to 534 cal yr BP; 1320 to 1416 CE), the broad, modelled age ranges for these events overlap with the ages of prehistoric tsunami deposits in the eastern Aleutians, suggesting a common earthquake source. Alternatively, the deposit in Anahola Valley could record an older event, possibly from a source further west in the Aleutians that only affected Kaua΄i. Future dating of more delicate, less reworkable macrofossils could demonstrate that the Anahola, Kahana and Pololū deposits

72 Publication - Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands are the same age as older or younger tsunami deposits dated in the eastern Aleutians and Kaua΄i. The prehistoric tsunami deposits in Anahola, Kahana and Pololū valleys are at least 90 years older (with 95% confidence) than the deposit in Makauwahi Cave, the only other known locality in the Hawaiian Islands with a prehistoric tsunami deposit from the last 750 years.

5.8 Acknowledgements This study was funded by the US Geological Survey, Coastal and Marine Geology Program. Nelson is supported by the US Geological Survey, Earthquake Hazards Program. The authors would like to thank: Chip Fletcher, Rhett Butler, James Goff and Carl Christensen for sharing their knowledge of the local area and assisting in the field. Maziet Cheseby, Alexandra Hangsterfer, Carl Christensen and Angela Tan for acquiring core scans, identifying gastropods, and performing grain size analyses. Erna Kamibayashi and Kaipo Duncan (Department of Hawaiian Homelands), Renee Kamisugi (Ahupua΄a O Kahana State Park), Bill Shontell (Kohala Preserve Conservation Trust, LLC), and Dave and Lida Burney (Makauwahi Cave Reserve) for providing access to field areas and for sharing their substantial knowledge. Shellie Habel, Daisuke Sugawara, Randy LeVeque and Chase Fletcher for their assistance collecting cores. The Pacific Tsunami Museum and Seth Judge for helping us manage and transport vibracoring equipment on Hawai΄i. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. Lastly, we would like to thank Rob Witter, Dave Tappin and an anonymous reviewer for providing invaluable comments that substantially improved the paper.

5.9 References Appleby, P.G., 2002. Chronostratigraphic techniques in recent sediments. In: Last, W.M. and Smol, J.P. (Eds.), Tracking Environmental Change Using Lake Sediments. Springer Dordrecht, p. 171–203. Atwater, B.F., Cisternas, M., Yulianto, E., Prendergast, A.L., Jankaew, K., Eipert, A.A., Warnakulasuriya, I., Fernando, S., Tejakusuma, I., Schiappacasse, I. and Sawai, Y., 2013. The 1960 tsunami on beach-ridge plains near Maullín, Chile: Landward descent, renewed breaches, aggraded fans, multiple predecessors. Andean Geology 40, p. 393–418.

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Kemp, A.C., Nelson, A.R. and Horton, B.P., 2013. Radiocarbon dating of plant macrofossils from tidal- marsh sediment. Treatise on Geomorphology. Methods in Geomorphology 14, p. 370–388. Kempf, P., Moernaut, J., Van Daele, M., Vandoorne, W., Pino, M., Urrutia, R. and De Batist, M., 2017. Coastal lake sediments reveal 5500 years of tsunami history in south central Chile. Quaternary Science Reviews 161, p. 99–116. Kennedy, A.B., Westerink, J.J., Smith, J.M., Hope, M.E., Hartman, M., Taflanidis, A.A. and Cheung, K., 2012. Tropical cyclone inundation potential on the Hawaiian Islands of Oahu and Kauai. Ocean Modelling 52–53, p. 54–68. Kitting, C.L., 2015. Persistence of habitats and populations of small, native Tryonia (Hydrobiidae) snails in brackish marshes around San Francisco Bay, California, after severe drought. American Malacological Bulletin 33, p. 325–330. Lander, J.F. and Lockridge, P.A., 1989. United States Tsunamis (Including United States Possessions): 1690-1988. National Oceanic and Atmospheric Administration, National Geophysical Data Center, Boulder, Colorado, Publication 41-2, p. 265. La Selle, S.M., Richmond, B.M., Griswold, F.R., Lunghino, B.D., Jaffe, B.E., Kane, H.H., Bellanova, P., Arcos, M.E., Nelson, A.R., Chagué., C., Bishop, J.M. and Gelfenbaum, G., 2019b. Core logs, scans, photographs, grain size, and radiocarbon data from coastal wetlands on the Hawaiian Islands of Kauai, Oahu, and Hawaii. U.S. Geological Survey data release, https://doi.org/10.5066/p9x4stjm Loomis, H.G., 1976. Tsunami wave runup heights in Hawaii. Hawaii Institute of Geophysics 76-5, p. 95. Ludwig, K.R., Szabo, B.J., Moore, J.G. and Simmons, K.R., 1991. Crustal subsidence rate off Hawaii determined from 234U/238U ages of drowned coral reefs. Geology 19, p. 171–174. MacDonald, G. A., Shepard, F. P., and Cox, D. C., 1947. The Tsunami of April 1, 1946 in the Hawaiian Islands. Pacific Science 1, p. 21–37. McDougall, I. and Swanson, D.A., 1972. Potassium-argon ages of lavas from the Hawi and Pololu volcanic series, Kohala Volcano, Hawaii. Geological Society of American Bulletin. 83, p. 3731– 3738. McMurtry, G.M., Watts, P., Fryer, G.J., Smith, J.R. and Imamura, F., 2004. Giant landslides, mega- tsunamis, and paleo-sea level in the Hawaiian Islands. Marine Geology 203, p. 219-233. Mighels, J.W., 1845. Descriptions of shells from the Sandwich Islands and other localities. In: Proceedings of the Boston Society of Natural History 2, p. 18–25. Miller, J. and Roeber, V., 2014. Final Report Tsunami Observer Program and the Tsunami of March 11, 2011. Environmental Center, University of Hawaii, Honolulu, Hawai΄i, p. 19. Moore, J.G., Clague, D.A., Holcomb, R.T., Lipman, P.W., Normark, W.R. and Torresan, M.E., 1989. Prodigious submarine landslides on the Hawaiian Ridge. Journal of Geophysical Research: Solid Earth 94, p. 17465-17484. Moore, J.G. and Clague, D.A., 1992. Volcano growth and evolution of the island of Hawaii. GSA Bulletin 104, p. 1471–1484.

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Morton, R.A., Gelfenbaum, G., and Jaffe, B.E., 2007. Physical criteria for distinguishing sandy tsunami and storm deposits using modern examples. Sedimentary Geology 200, p. 184-207. Nanayama, F., Satake, K., Furukawa, R., Shimokawa, K., Atwater, B.F., Shigeno, K. and Yamaki, S., 2003. Unusually large earthquakes inferred from tsunami deposits along the Kuril trench. Nature 424, p. 660-663. Nelson, A.R., Personius, S.F., Sherrod, B.L., Kelsey, H.M., Johnson, S.Y., Bradley, L.A. and Wells, R.E., 2014. Diverse rupture modes for surface-deforming upper plate earthquakes in the southern Puget Lowland of Washington State. Geosphere 10, p. 769–796. Nelson, A.R., Briggs, R.W., Dura, T., Engelhart, S.E., Gelfenbaum, G., Bradley, L.-A., Forman, S.L., Vane, C.H. and Kelley, K.A., 2015. Tsunami recurrence in the eastern Alaska-Aleutian arc: a stratigraphic record from Chirikof Island, Alaska. Geosphere 11, p. 47–65. Pennington, W., Tutin, T.G., Cambray, R.S. and Fisher, E.M., 1973. Observations on lake sediments using fallout 137Cs as a tracer. Nature 242, p. 324. Pigati, J.S., Rech, J.A. and Nekola, J.C., 2010. Radiocarbon dating of small terrestrial gastropod shells in North America. Quaternary Geochronology 5, p. 519–532. Pinegina, T.K., Bourgeois, J., Bazanova, L.I., Melekestsev, I.V. and Braitseva, O.A., 2003. A millennial-scale record of Holocene tsunamis on the Kronotskiy Bay coast, Kamchatka, Russia. Quaternary Research 59, p. 36–47. Priest, G.R., Witter, R.C., Zhang, Y.J., Goldfinger, C., Wang, K. and Allan, J.C., 2017. New constraints on coseismic slip during southern Cascadia subduction zone earthquakes over the past 4600 years implied by tsunami deposits and marine turbidites. Natural Hazards 88, p. 285–313. Ramsey, B.C., 2008. Deposition models for chronological records. Quaternary Science Reviews 27, p. 42–60. Ramsey, B.C., 2009. Bayesian analysis of radiocarbon dates. Radiocarbon 51, p. 337–360. Reilly, B.T., Stoner, J.S. and Wiest, J., 2017. Sed CT: MATLABTM tools for standardized and quantitative processing of sediment core computed tomography (CT) data collected using a medical CT scanner. Geochemistry, Geophysics, Geosystems 18, p. 3231–3240. Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Ramsey, B.C., Buck, C.E., Cheng, H., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T.J., Hogg, A.G., Hughen, K.A., Kaiser, K.F., Kromer, B., Manning, S.W., Niu, M., Reimer, R.W., Richards, D.A., Scott, E.M., Southon, J.R., Turney, C., and van der Plicht, J., 2013. InterCal13 and Marine 13 radiocarbon age calibration curves 0-50,000 years cal. BP. Radiocarbon 55, p. 1869– 1887. Richmond, B.M., Fletcher, C.H., Grossman, E.E. and Gibbs, A.E., 2001. Islands at risk: coastal hazard assessment and mapping in the Hawaiian Islands. Environmental Geosciences 8, p. 21–37.

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Richmond, B.M., Watt, S., Buckley, M., Jaffe, B.E., Gelfenbaum, G. and Morton, R.A., 2011a. Recent storm and tsunami coarse-clast deposit characteristics, southeast Hawai΄i. Marine Geology 283, p. 79–89. Shepard F.P., MacDonald, G.A., and Cox, D.C., 1949. The tsunami of April 1, 1946. Bulletin of the Scripps Institution of Oceanography 5, p. 391–528. State of Hawaii, 2002. Field Guide for Measuring Tsunami Runups and Inundations. State of Hawaii Department of Defense, Civil Defense Division, Tsunami Technical Review Committee, Honolulu, Hawaii, p. 77. Trusdell, F.A., Chadderton, A., Hinchliffe, G., Hara, A., Patenge, B. and Weber, T., 2012. Tohoku-Oki Earthquake Tsunami Runup and Inundation Data for Sites Around the Island of Hawai΄i. U.S. Geological Survey. Open-File Report, p. 42. Vitousek, P.M., Chadwick, O.A., Hilley, G., Kirch, P.V. and Ladefoged, T.N., 2010. Erosion, geological history, and indigenous agriculture: a tale of two valleys. Ecosystems 13, p. 782–793. Witter, R.C., Briggs, R.W., Engelhart, S.E., Gelfenbaum, G., Koehler, R.D. and Barnhart, W.D., 2014. Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska. Geophysical Research Letters 41, p. 2359–2367. Witter, R.C., Carver, G.A., Briggs, R.W., Gelfenbaum, G., Koehler, R.D., La Selle, SP., Bender, A.M., Engelhart, S.E., Hemphill-Haley, E., and Hill, T.D., 2016. Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust. Geophysical Research Letters 43, p. 76–84. Witter, R.C., Briggs, R.W., Engelhart, S.E., Gelfenbaum, G., Koehler, R.D., Nelson, A.R. and Wallace, K.L., 2018. Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust. GSA Bulletin 131, p. 707–729. Wood, N., Church, A., Frazier, T. and Yarnal, B., 2007. Variations in community exposure and sensitivity to tsunami hazards in the State of Hawai΄i. U.S. Geological Survey Scientific Investigation Report 2007-5208, p. 42.

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5.10 Supplementary Material

Appendix 5.S1 Uncalibrated radiocarbon ages of sediments in Anahola, Kahana and Pololū valleys, HI.pdf”: this table contains the uncalibrated radiocarbon ages of all samples submitted from these three sites. Data is also available in La Selle et al. (2019b).

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OxCal Models (Ramsey, 2009) used to determine ages of Sands A3, K1, and P3

Plot(Anahola_Phase_v20) Plot(Kahana_Phase_v5) { { //This is a phase model to estimate age of “Sand A3” using //This is a phase model to estimate age of “Sand K1” just the youngest and oldest bulrush seed above and below Sequence() the sand { Sequence() Boundary("start"); { Phase("Phase 1") Boundary("start"); {

Phase("0.0-0.5 cm below Sand") R_Date("RC3 133.0-133.5 bulrush seed",600,15);

{ };

R_Date("VC6 120-125 bulrush seed", 785,20); Date("Sand");

}; Phase("Phase 2") Date("Sand"); { Phase("0 to 2 cm above Sand") R_Date("gc02b 133-133.5 bulrush seed",375,15); { }; R_Date("GC1 90-92 bulrush and other seeds 6 Phase("Phase 3") mg",530,15); { }; R_Date("RC3 124.0-124.5 bulrush seed",470,20); Boundary("end"); }; }; Boundary("end"); }; };

};

Plot(PololuP3_VC1_Phase-v10) Plot(Pololu_VC1_Phase-v19 ) { { //This is a phase model to estimate age of “Sand P3” in //This is a phase model to estimate age of “Sand P3” core VC1 Sequence() { Sequence() Boundary("start"); { Phase("Phase 7 0-1.5 cm below Sand P3") Boundary("start"); { Phase("below Sand") R_Date("125-126 seeds", 445, 65); { R_Date("125.5-126 round seeds",625,45); R_Date("VC1 125-126 bulk peat",590,15); }; R_Date("VC1 125.5-126 unidentified round Date("Sand"); seeds",625,45); Phase("Phase 10 0-4.0 cm above Sand P3") }; { Date("Sand"); R_Date("121.5-122 brachiaria seeds",825,110); Phase("above Sand") R_Date("121.5-122 brachiaria seeds",740,130); { R_Date("121.5-122 brachiaria seeds",285,100); R_Date("VC1 120-120.5 bulk peat",480,15); R_Date("121.5-122 brachiaria seeds",375,90); R_Date("VC1 121-121.5 bulk peat",410,15); }; }; Boundary("end"); Boundary("end"); }; }; }; };

Appendix 5.S2 “OxCal Models for Sands A3, K1, P3”: the codes for each model used to determine the ages of sand beds A3, K1 and P3. These are simple phase models using maximum and minimum bracketing ages of the sediments below and above each sand.

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Top of Bottom Sand Top of Bottom Top of Bottom Sand Sand Sand of Sand A1 Sand of Sand Sand of Sand A2 A3 A1 A1 Sand A2 A2 A3 A3 Name Lat Lon Thick Thick below below Thick- below below below below -ness -ness surface surface ness surface surface surface surface [cm] [cm] [cm] [cm] [cm] [cm] [cm] [cm] [cm]

gcbj-28 22.148091 -159.308171

gcbj-29 22.148091 -159.308171 15 25 10

607BR/gc29-BR 22.147846 -159.308040 124 127 3

gcbj-26 22.147951 -159.308142 47 49 2

gcbj-27 22.148036 -159.308190 35 43 8

gcbj-24 22.147967 -159.308165 7 8 1

gcbj-20 22.148012 -159.308201 30 31 1 44 49 5

gcbj-25 22.147966 -159.308172 49 51 2 100 102 2

608BR/gc30_BR 22.147773 -159.308077 128 132 4

gcbj-21 22.148017 -159.308220

gcbj-22 22.148017 -159.308220 29 34 5

gcbj-23 22.148016 -159.308219

VC7 22.147990 -159.308210 45 47 2 105 106.5 1.5

gcbj-19 22.148046 -159.308261 46 51 5

gcbj-30 22.147994 -159.308248 14 15 1 29 31 2

gcbj-17 22.148051 -159.308307

gcbj-18 22.148051 -159.308307 29 33 4

609BRgc31-BR 22.147707 -159.308180 139 147 8

gcbj-31 22.147949 -159.308321 12 13 1 42 52 10

gcbj-16 22.148037 -159.308388 49 63 14

610BR/gc32-BR 22.147683 -159.308190

gcbj-14 22.148061 -159.308408 53 57 4

gcbj-15 22.148061 -159.308408 24 27 3

gcbj-32 22.147929 -159.308364 22 24 2 34 39 5

gcbj-12 22.148108 -159.308490 11 13 2 99 102 3

gcbj-13 22.148095 -159.308485 38 41 3

RC1-BR/gc27-BR 22.147924 -159.308478 35 38 3 33 34 1

611BR/gc-33-BR 22.147629 -159.308236 141 146 5

gcbj-9 22.148121 -159.308541

gcbj-10 22.148121 -159.308541

gcbj-11 22.148121 -159.308541 20 22 2

gcbj-33 22.147892 -159.308415 22 24 2 24 32 8

gcbj-7 22.148145 -159.308604

gcbj-8 22.148145 -159.308604 20 22 2 86 102 16

VC6 22.148140 -159.308610 24 26 2 110 123 13 VC8 22.148410 -159.308770 19 20 1 22.5 28 5.5 63 88 25

gcbj-6 22.148165 -159.308644 17 19 2 85 102 17

gcbj-5 22.148163 -159.308696 25 27 2 85 95 10

gcbj-4 22.148160 -159.308751 20 26 6 70 79 9

614BR/gc35-BR 22.147496 -159.308425 117 122 5

gcbj-3 22.148137 -159.308805 19 26 7 83 94 11

gcbj-2 22.148128 -159.308848 24 28 4 83 93 10

gcbj-1 22.148108 -159.308893 23 26 3 79 81 2

RC6-BR/gc36-BR 22.147492 -159.308578 46 49 3 99 111 12

VC1 22.148160 -159.309010 33 34 1

gc8-SP 22.148180 -159.309030 32 36 4

616BR/gc37-BR 22.147381 -159.308671 134 136 2

617BR/gc38-BR 22.147288 -159.308738 133.5 134.5 1

618BR/gc39-BR 22.147219 -159.308838 158 162 4

619BR/gc40-BR 22.147119 -159.308893 41 44.5 3.5 144.5 146.5 2

ANA-15-603CCG 22.147814 -159.309834 132 147 15

ANA-15-604CCG 22.147821 -159.309849 141 153 12

ANA-15-612CCG 22.147728 -159.309800

VC2 22.147500 -159.309800 94 103 9

ANA-15-613CCG 22.147729 -159.309942 123 133.5 10.5

ANA-15-605CCG 22.147858 -159.310058 158 159 1

gc9-SP 22.147490 -159.309880 120 136 16

Appendix 5.S3 A “Sand thicknesses Anahola Kahana Pololū”: this is a Microsoft Excel® (version 16.14.1) file with a tab for each site: Anahola Valley, Kahana Valley and Pololū Valley. Core names, locations, core types and the depths and thicknesses of sand beds in each valley are listed. Data is also available in La Selle et al., (2019b).

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Name Lat Lon Top of Bottom Sand Top of Bottom Sand Top of Bottom Sand Sand of Sand A1 Sand of Sand A2 Sand of Sand A3 A1 A1 Sand A2 A2 Thick- A3 A3 Thick- below below Thick- below below ness below below ness surface surface ness surface surface [cm] surface surface [cm] [cm] [cm] [cm] [cm] [cm] [cm] [cm] ANA-15-614CCG 22.147783 -159.310036 148 152 4

ANA-15-606CCG 22.147797 -159.310135 166 167 1

ANA-15-615CCG 22.147663 -159.310169 158 159.5 1.5

ANA-15-608CCG 22.147733 -159.310277

GC21-SP 22.147210 -159.310140 137 141 4

VC3 22.147190 -159.310160 142 150 8

ANA-15-609CCG 22.147678 -159.310421 168 170 2

GC22-SP 22.147220 -159.310310 152 156 4

gc11-SP 22.146910 -159.310160

ANA-15-610CCG 22.147735 -159.310605 115 120 5

ANA-15-611CCG 22.147715 -159.310603

ANA-15-616CCG 22.147514 -159.310518

GC27-SP/RC3SP 22.147120 -159.310340 148 156 8

GC23-SP 22.147350 -159.310550 136 139 3

GC28-SP 22.146540 -159.310120 101 105.5 4.5

ANA-15-617CCG 22.147587 -159.310689

gc30-SP/RC5SPA 22.146490 -159.310120 22 24.5 2.5 178 180 2

gc29-SP 22.146820 -159.310320

GC26-SP/RCSP4 22.146950 -159.310410

GC24-SP 22.147120 -159.310640 98 108 10

GC25-SP 22.146960 -159.310660 168 175 7

VC4a 22.147330 -159.310880 85 91 6

VC4b 22.147330 -159.310880

gc14-SP 22.147330 -159.310880 132 137 5

GC18-SP 22.147320 -159.310880 113 118 5

GC20-SP 22.147300 -159.310950 150 155 5

GC19-SP 22.147240 -159.310980

gc-17-SP 22.147170 -159.311160

gc16-SP 22.146750 -159.311170

VC5 22.146960 -159.311430 192 195 3

gc15-SP 22.146950 -159.311420 Appendix 5.S3 A (Continuation) “S3 Sand thicknesses Anahola Kahana Pololū.xlsx”: this is a Microsoft Excel® (version 16.14.1) file with a tab for each site: Anahola Valley, Kahana Valley and Pololū Valley. Core names, locations, core types and the depths and thicknesses of sand beds in each valley are listed. Data is also available in La Selle et al., (2019b).

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Name Lat Lon Sample Type Top of Sand K1 Bottom of Sand K1 Sand K1 below surface [cm] below surface [cm] Thickness [cm] gc14 21.552958 -157.872711 60 mm gouge core 125.0 134.5 9.5 gc13 21.55266 -157.872898 60 mm gouge core 83.0 87.5 4.5

gc11 21.551947 -157.873301 60 mm gouge core gc12 21.551979 -157.873335 60 mm gouge core 152.0 155 3.0 gc03 21.55178 -157.873418 60 mm gouge core 110.5 119 8.5 gc04 21.551761 -157.873612 30 mm gouge core 135.0 147 12.0 RC3 2015 21.5516464 -157.8735254 Russian core 108.0 122 14.0 RC02 21.551646 -157.873543 Russian core 103.5 107.5 4.0 gc16-FG 21.551557 -157.873645 30 mm gouge core 113.0 120 7.0 gc18 21.551536 -157.87366 60 mm gouge core 133.0 136 3.0 gc15-FG 21.551498 -157.873693 30 mm gouge core 125.0 126 1.0 gc05-SP 21.551685 -157.873883 30 mm gouge core 119.0 125 6.0 gc05-FG 21.55145 -157.873853 60 mm gouge core 106.0 108 2.0

gc17 21.551414 -157.873856 60 mm gouge core

gc06-FG 21.551272 -157.874021 60 mm gouge core

gc2 2015 21.5506273 -157.8800425 60 mm gouge core

gc07-FG 21.55107 -157.874345 60 mm gouge core

gc06-SP 21.551272 -157.874021 30 mm gouge core

gc08-FG 21.550815 -157.874807 60 mm gouge core

gc07-SP 21.55107 -157.874345 30 mm gouge core

gc09-FG 21.550518 -157.875165 60 mm gouge core

gc10-FG 21.550306 -157.875446 60 mm gouge core

gc09-SP 21.549959 -157.875843 30 mm gouge core

gc08-SP 21.550273 -157.876209 30 mm gouge core

Appendix 5.S3 B (Continuation) “S3 Sand thicknesses Anahola Kahana Pololū.xlsx”: this is a Microsoft Excel® (version 16.14.1) file with a tab for each site: Anahola Valley, Kahana Valley and Pololū Valley. Core names, locations, core types and the depths and thicknesses of sand beds in each valley are listed. Data is also available in La Selle et al., (2019b).

Name Lat Lon Sample Top of Bottom Sand Top of Bottom Sand Top of Bottom Sand Type Sand of Sand P1 Sand of Sand P2 Sand of Sand P3 P2 P1 Sand P2 P2 Thick- P3 P3 Thick- below below Thick below below ness below below ness surface surface -ness surface surface [cm] surface surface [cm] [cm] [cm] [cm] [cm] [cm] [cm] [cm]

VC1 20.2022939 -155.7331385 vibracore 15 15.3 0.3 19.5 42 22.5 121 124 3

VC2 20.2000984 -155.7327316 vibracore 54 64 10

VC3 20.2006196 -155.7328947 vibracore 42 56 14

VC4 20.2007973 -155.7329306 vibracore 305 43 12.5

VC5 20.2009689 -155.7330197 vibracore 31 42 11

PO1 20.2024 -155.73311 gouge core 18 48 30

PO2 20.20209 -155.73331 gouge core 27 29 2 22

PO3 20.20193 -155.73339 gouge core 21

PO4 20.20184 -155.73347 gouge core 16

PO5 20.20165 -155.73359 gouge core 2.5

Appendix 5.S3 C (Continuation) “S3 Sand thicknesses Anahola Kahana Pololū.xlsx”: this is a Microsoft Excel® (version 16.14.1) file with a tab for each site: Anahola Valley, Kahana Valley and Pololū Valley. Core names, locations, core types and the depths and thicknesses of sand beds in each valley are listed. Data is also available in La Selle et al., (2019b).

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Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i

6 Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i

Piero Bellanova1,2, Mike Frenken1,2, Bruce Richmond3, Jan Schwarzbauer1, SeanPaul La Selle3, Frances Griswold3,4, Bruce Jaffe3, Alan Nelson5, Klaus Reicherter2

1 Institute for Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University Lochnerstrasse 4-20, 52056, Aachen, Germany 2 Lehr- und Forschungsgebiet Neotektonik und Georisiken, RWTH Aachen University Lochnerstrasse 4-20, 52056, Aachen, Germany 3 U.S. Geological Survey, Pacific Coastal and Marine Science Center, 2885 Mission Street, Santa Cruz, CA 95060, United States 4 Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA 5 U.S. Geological Survey, Geologic Hazards Science Center, Golden, CO 80401, United States

Abstract Far-field tsunami deposits observed in the Kahana Valley, O‘ahu, Hawai‘i (USA), were investigated for their organic-geochemical content. During short high-energy events, (tsunamis and storms) organic and chemical components are transported with sediment from marine to terrestrial areas. This study investigates the use of anthropogenic based organic geochemical compounds (such as polycyclic aromatic hydrocarbons, pesticides and organochlorides) as a means to identify tsunami deposits. Samples were processed by solid–liquid extraction and analyzed using gas chromatography–mass spectrometry. A total of 21 anthropogenic marker compounds were identified, of which 11 compounds were selected for detailed analysis. Although the tsunami deposits pre-date industrial activity in Hawai‘i by several hundred years, distinct changes were found in the concentrations of anthropogenic marker compounds between sandy tsunami deposits and the surrounding mud/peat layers, which may help in identifying tsunami deposits within cores. As expected, low overall concentrations of anthropogenic markers and pollutants were observed due to the lack of industrial input-sources and little anthropogenic environmental impact at the study site. This geochemical characterization of tsunami deposits shows that anthropogenic markers have significant potential as another high-resolution, multi-proxy method for identifying tsunamis in the sedimentary record.

Keywords Anthropogenic marker, Hawaii, Kahana Valley, organic geochemistry, tsunami This chapter is a slightly modified version of the article published in Sedimentology (2019) DOI: 10.1111/sed.12583

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Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i

6.1 Introduction Located in the centre of the Pacific Ocean, the Hawaiian Islands have experienced several far-field tsunamis of different magnitudes within the past century. Several of these events were destructive, such as the 1946 and 1957 Aleutian tsunamis, the 1952 Kamchatka tsunami, the 1960 Chilean tsunami and the 1964 Alaska tsunami. Low-lying coastal areas of the Hawaiian Islands remain highly susceptible to far-field tsunami hazards. Far-field tsunamis have impacted the Hawaiian Islands (e.g. Atwater et al., 2005; Richmond et al., 2001; Atwater et al., 2005; Richmond et al., 2008a,b,c, 2011a; Wood et al., 2007; Butler, 2012; Chagué-Goff et al., 2012b) and other Pacific Islands (e.g. Jaffe et al., 2010; Fritz et al., 2011; Gelfenbaum et al., 2011; Goff et al., 2011b; Richmond et al., 2011b). As Goff (2011) suggested, a cross-identification of the historical tsunami records between Hawai‘i and other Pacific Islands is essential for developing a comprehensive spatial and temporal tsunami history for the entire Pacific region. The sedimentary record of smaller far-field tsunamis can be difficult to identify and investigate by using conventional methods, such as grainsize analysis and micropaleontology, when only thin (<0.5 cm) sand or muddy deposits are preserved. Therefore, multi-proxy investigations that include the development and application of fine-scale organic geochemical methods can be invaluable to far-field tsunami deposit studies. Inorganic-geochemical proxies (such as water-leachable ions, major elements, δ13C, δ15N or δ34S) have been used in studies of tsunami deposits (e.g. Chagué-Goff et al., 2017). In the last few years, organic geochemical methods, such as marine biomarkers (e.g., Alpar et al., 2012; Mathes-Schmidt et al., 2013; Shinozaki et al., 2015) and anthropogenic markers (e.g., Tipmanee et al., 2012; Reicherter et al., 2015) have been applied in tsunami studies. Because these studies have focused on thick deposits and post-event environmental pollution, however, there is a need to test these methods in more pristine environments and on smaller events (thinner deposits). This study assesses the presence of anthropogenic markers (like pesticides, polycyclic aromatic hydrocarbons and organochlorides) in Kahana Valley, O‘ahu, Hawai‘i, a remote and unindustrialized area containing palaeotsunami deposits. Here, the background organic geochemical signature of the tsunami deposits and the surrounding sediments are characterized, which can be used to compare with modern event deposits in similar environments.

6.2 Study area Kahana Valley is located on the south-eastern slope of the Ko’olau Range on the north-eastern coast of O‘ahu (Fig. 6.1A). Containing 70% of the state population, O‘ahu is the most populous and the most urbanized of the Hawaiian Islands (Mayfield, 2013), and is therefore at a high risk in the event of a large far-field tsunami. Kahana Valley is relatively sheltered and extends inland from the crescent-shaped shoreline to the crest of the Ko’olau Range (Fig. 6.1B; Beggerly, 1990; Mayfield, 2013). The valley is an amphitheatre- headed valley, but is more club-shaped with a narrower mouth than cape (Beggerly, 1990). The valley

87 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i is underlain by the basalt of the Ko’olau Volcanic Series (Beggerly, 1990; Mayfield, 2013). Kahana Stream drains the marshy lowland of the valley through two channels into the bay at the central and eastern portions of the shoreline (Beggerly, 1990; US Army Corps of Engineers, 2010). While the eastern channel is frequently open to the bay, the central channel is usually dammed by beach sand (Beggerly, 1990; US Army Corps of Engineers, 2010). The bay is shielded by a fringing reef (Beggerly, 1990) and cut by a seaward running shallow marine reef passage created by the Kahana Stream during lower sea-level (Fig. 6.1B; Coulbourn, 1971; MacDonald et al., 1947). Recorded run-up heights from the 1946, 1952 and 1960 tsunamis that inundated parts of Kahana Valley ranged from 1 to 3 m (Lander and Lockridge, 1989; Fletcher et al., 2002; Walker, 2004). The highest run-up of 3 m was recorded at the seaward facing parts of the northern ridge (Makali’i Point) during the 1946 tsunami, while the lowest run-up of 1 m was recorded for the same event at the southern ridge (Mahie Point) of the valley (Lander and Lockridge, 1989; Fletcher et al., 2002; Walker, 2004). The low- lying areas in the central part of the Kahana valley were inundated by these events with a run-up height of 2.0 to 2.5 m (Fig. 6.1B; Walker, 2004). Located close to the south-eastern estuary mouth is the Huilua Fishpond, a mixohaline Hawaiian pond (Fig. 6.1C; Beggerly, 1990). The fishpond is used for aquaculture and was built in the 15th to the 17th Centuries before western contact (Mayfield, 2013). The walls of the fishpond were destroyed by several extreme wave events and were restored in 1993; since then it has been used for recreational fishing (Beggerly, 1990; Mayfield, 2013). Historically, Kahana Bay and Valley were used for fishing and farming prior to western contact. Taro was historically cultivated in the Kahana Valley and was replaced by commercial sugar cane cultivation after western contact until agricultural production was stopped during World War II. During this period, the valley was occupied for combat training by the US military (Mayfield, 2013; US Army Corps of Engineers, 2016). Since then the valley has been owned by the State of Hawai‘i and is operated as the Ahupuaʻa ʻO Kahana State Park, with the purposes of educating people on traditional Hawaiian culture and for recreation. However, a few commercial agricultural activities are still practiced in the valley (US Army Corps of Engineers, 1985). A United States Geological Survey (USGS) study (La Selle et al., 2019a) of Kahana Valley identified a landward thinning, carbonate sand sheet in 30 cores between about 240 m and 480 m from the shoreline in the freshwater marsh on the south-east side of Kahana Valley. This sand sheet is mostly composed of fine to medium carbonate sand, overlain by a sandy mud with freshwater (Tyronia sp.) gastropod shells in about half of the cores containing the sand layer, which were used to correlate the sand layers between some cores. Radiocarbon dates from bulrush seeds and bulk sediment just above and below the sand layer informed statistical age models used to bracket the timing of deposition to approximately 690 to 508 cal yr BP (1320 to 1442 CE) at the 95.4% confidence interval which overlaps the ages of tsunami deposits found at multiple field sites on Kauaʻi, the Big Island of Hawaiʻi, and the Aleutians (App. 6.T1; La Selle et al., 2019a; Witter et al., 2016, 2018). Further dating and age modelling is needed to better correlate the carbonate sand sheet between the proposed palaeo-tsunami deposits in Hawaiʻi and the

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Aleutians. A storm or hurricane source of this carbonate sand sheet is unlikely given the lack of observations of historical storm and hurricane washover exceeding 250 m (Fletcher et al., 1995), and models of large storms and hurricanes that do not predict greater than 3 m of storm surge on the coasts of Oʻahu and Kauaʻi (Kennedy et al., 2012). Flooding of Kahana stream results in fluvial sand layers containing basaltic clasts which are easily differentiated from the carbonate-rich marine sand in the palaeo-tsunami deposit. There are no records from the 1946, 1952 and 1960 CE tsunamis that suggest that this part of the valley was inundated by modern events, and no modern tsunami deposit has been observed in cores.

Fig. 6.1 Overview map of the sampling site Kahana Valley, O‘ahu, Hawai‘i. (A) Location of the Kahana Valley on O‘ahu. (B) Overview of the Kahana Valley (imagery by DigitalGlobe®, 2018). (C) Core locations in the Kahana Valley. (D) Transect across the coring locations (imagery by DigitalGlobe®, 2018).

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6.3 Methods 6.3.1 Fieldwork and material storage In February of 2017 gouge auger and Russian cores were collected in Kahana Valley. All cores were collected within <100 m of one another; 25 mm diameter gouge or Russian cores were used to describe stratigraphy and for radiocarbon dating. Because a relatively large (50 to 200 g) amount of sediment is required for organic geochemical analyses, geochemical samples were taken only from gouge cores with a diameter of 60 mm. Samples were collected from four 60 mm cores taken along a linear transect perpendicular to the shoreline within the marsh along the southern edge of the valley. Cores (Fig. 6.1C) were collected with increasing distance from the shoreline starting with core 13 (N 21°33’9.5” W 157°52’22.4″; 380 m from the shoreline) followed by core 03 (N 21°33’6.4” W 157°52’24.3”; 470 m), core 18 (N 21°33’5.5” W 157°52’25.2”; 500 m) and core 17 (N 21°33’5.1” W 157°52’25.8”; 525 m). Sediments for geochemical analyses were subsampled out of the 60 mm gouge cores and were placed into aluminum cups to prevent cross-contamination with plastic. After collection, samples were kept cool during fieldwork and transport, stored in a freezer (at -20°C) for three months and in a refrigerator (between 5°C and 7°C) during sample processing. Freezing or refrigeration of samples is necessary in order to preserve the organic–geochemical signature and to prevent contamination by microbes, especially mold.

6.3.2 Loss of ignition analysis Loss of ignition (LOI) analysis was used to determine the content of total organic carbon (TOC) in each sample. For LOI, 0.1 g was extracted from each sample, then ground and ashed in a furnace (Elementar Liqui TOC II; Elementar UK Limited, Stockport, UK) for 30 min at 550 °C. The difference in mass due to the ashing was used to calculate the organic content (Dean, 1974). The TOC concentration of each sample was used for normalizing geochemical compound concentration to provide comparability between samples (for example, sand has lower TOC, whereas mud has higher TOC).

6.3.3 Solid–liquid extraction To extract anthropogenic organic geochemical compounds from sediment samples, a solid–liquid extraction technique was used using organic solvents modified after Schwarzbauer et al. (2000). Aliquots of 24 to 310 g wet sediment were added to Erlenmeyer flasks and extracted twice with 110 ml acetone dispersed for 24 h and 4 h using an overhead shaker with a rotation-speed of 20 rpm, followed by an extraction with 110 ml of n-hexane dispersed for another 24 h. Each extraction step was followed by centrifugation for 10 min at 5000 g (RCF). The three extracts were combined in a separatory funnel in which the aqueous phase was separated by adding additional n-hexane. The volume of the extract was reduced to 1 ml by using rotary evaporation with a reduced air pressure of 300 mbar. With anhydrous granulated sodium sulphate (Na2SO4) the sample was dried and desulphurized by the addition of activated copper and ultrasonic agitation.

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Extracts were separated into six fractions (B1 to B6) by column chromatography using mixtures of n- pentane, dichloromethane and methanol as eluents following Schwarzbauer et al. (2000). Bakerbond columns filled with 2 g activated silica gel conditioned at 200 °C were used as chromatographic columns. Chromatographic fractionation was carried out by eluting with 5 ml n-pentane (fraction B1), 8.5 ml n-pentane/ dichloromethane 95/5 (fraction B2), 5 ml n-pentane/ dichloromethane 90/10 (fraction B3), 5 ml n-pentane/dichloromethane 40/60 (fraction B4), 5 ml dichloromethane (fraction B5) and 5 ml methanol (fraction B6). For methylation of acidic compounds in fraction B6 0.1 ml methanolic diazomethane solution was added, and the fraction was evaporated and fractionated into two subfractions by column chromatography. Two millilitres of dichlormethane (fraction 6a) and 2 ml methanol (fraction 6b) were used as eluents: 50 µl of surrogate standard solution (5.8 ng µl -1

-1 -1 fluoracetophenone, 6.28 ng µl d10-benzophenone and 6.03 ng µl d34-hexadecane) were added to fractions B1 to B5, and 200 µl to fractions 6a and 6b.

6.3.4 Gas chromatography–mass spectrometry analysis For identification and quantification of organic geochemical compounds, sample concentration was first determined by gas chromatography–flame ionization detection (GC-FID) before being measured using gas chromatography–mass spectrometry (GC-MS). Fraction volumes were reduced by evaporation at room temperature to 50 µl. The GC analyses were performed on a Fisons GC8000 series 8060 (Fisions Instruments SPA, Milan, Italy) equipped with a 30 x 0.25 mm i.d. x 0.25 µm film ZB-5 fused silica capillary column (Zebron capillary GC column, Chrompack) and a flame ionization detector (FID). All fractions were analyzed with chromatographic conditions of 1 µl split/ splitless injection (injector temperature 270 °C) at 60 °C, splitless time 60 s, 3 min hold, then programmed at 5 °C min-1 to 300 °C with a 20 min isothermal time. Due to the high sensitivity of this method, the occurrence of trace concentrations in the samples can be detected (Dsikowitzky, 2002). The injected sample extract is transported in a hydrogen gas stream through the capillary column and separated into its individual organic components, due to different boiling points and polarities (Dsikowitzky, 2002). After separation, eluates are ionized by flame, and total oxidizable organic ions are detected (Dsikowitzky, 2002). For quantification, samples were analyzed with GC-MS performed on quadrupole, benchtop GC-MS instrument (Thermo Finnigan Trace GC/MS; Thermo Fisher Scientific, Waltham, MA, USA). Exactly 1 µl of the sample extract was injected for analysis at a temperature of 60 °C, a split less time of 60 s, with a 3 min hold and a following 3 °C min -1 increase to 310 °C. In GC-MS analysis the fractions are first separated by a gas chromatograph and passed with carrier gas into the mass spectrometer where characteristic mass spectrums are recorded for each organic compound and the mass spectrum of the sample is obtained (Dsikowitzky, 2002). Organic compounds were identified using the software AMDIS32 (AutomatedMass spectral Deconvolution and Identification System) by comparison with known mass spectra from spectral libraries in the NIST MS database (National Institute of Standards and Technology - US Department of Commerce) and verifying the results by comparison of gas

91 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i chromatographic and mass spectral parameters with those of standard reference material. Quantification was carried out by integration of specific ion chromatograms and an external four point calibration with refence material using the software XCALIBUR™ by Thermo Scientific™.

6.4 Results 6.4.1 Sample material Sedimentary material sampled from cores consisted mainly of grey to brown muddy peat or muddy peat with 0 to 50% fine sand (see App. 6.F1 to 6.F4). All cores contained a distinct fine to medium sand layer, which varies in thickness within the valley and is interpreted as a tsunami deposit according to La Selle et al. (2019a). Closest to the shoreline (approximately 380 m), core 13 consists of grey, sandy-silty sediment with a prominent 4 cm thick (83 to 87 cm depth) tsunami deposit of medium to coarse sand with sharp contacts (App. 6.F1). The tsunami deposit is topped by a layer of dark, sandy mud. Below the tsunami deposit is a muddy sand layer containing shells. From 109 to 115 cm depth is another medium sand unit, containing large shell fragments and rounded, weathered basalt clasts (ca 1 x 1 x 2 cm). Core 03 (480 m from the shoreline) consists of muddy peat above an 8.5 cm thick, well-sorted, carbonate sand layer (110.5 to 119.0 cm depth; App. 6.F2) with muddy sand below it containing freshwater shell fragments (Tyronia sp.), a rounded basalt clast and a kukui nut. The carbonate sand layer has a sharp erosional contact and contains several upward fining sequences observed in the field. At a distance of 530 m inland, core 18 (App. 6.F3) contains muddy to silty peat dominated by a high organic content in the upper metre. At 133 to 136 cm depth there is a 3 cm thick deposit of mostly fine sand with a mix of volcanic and carbonate grains, and a sharp lower contact. Above the sand unit is approximately 20 cm of muddy sand with gastropod shells. Below the sand unit is sandy mud and muddy sand containing primarily volcanic grains, that overlies a second sandy tsunami deposit (160 to 175 cm) composed of fine to medium carbonate sand. Core 17 (App. 6.F4) located furthest inland at 555 m from the shoreline, is characterized by muddy peat with a high organic content. The uppermost 70 cm of the core contains alternating layers of dark brown peat and organic rich mud. At 124 to 136 cm depth is a 12 cm thick layer of muddy fine to medium sand with volcanic grains and scattered carbonate shell fragments with sharp upper and lower contacts. Underneath this sand unit is 4 cm of peaty mud, underlain by a another muddy fine to medium sand that is 14 cm thick. A total of 22 samples was taken from these four cores in the Kahana Valley, with five to seven samples per core. Samples were taken from the youngest part (top) of the core, above the tsunami deposits, within the tsunami deposit, from the sediment below the tsunami deposit, and from well below the deposit. In core 18, two additional samples were taken from a thin mud layer below the tsunami deposit and from within the second possible tsunami deposit.

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6.4.2 Identification of organic geochemical proxies Non-target screening applied on all fractions of each sample resulted in a diverse group of chemical compounds, such as polycyclic aromatic hydrocarbons (PAHs), pesticides, squalene, n-alkanes and chlorinated organic compounds (App. 6.F5). A total of 21 organic geochemical compounds in three compound groups (PAHs, UV-absorber and pesticides), which are present in most samples, were selected for further analysis. Of the 23 identified organic compounds, 17 were polycyclic aromatic hydrocarbons (PAHs), of which many are produced from the incomplete combustion of hydrocarbons or from seepage of crude oil or coal and oil spills, and have a variety of industrial and anthropogenic input sources. Their structure consists only of carbon and hydrogen atoms, which are arranged in two or more benzene rings. The benzene rings are single or fused aromatic rings, which are connected by a pair of carbon atoms. The PAHs are divided into two groups: small PAHs (up to six benzene rings) and large PAHs (more than six aromatic rings). Results of all mass-spectra show that small PAHs are dominant in the sediment of Kahana Valley. This study focused on the seven most dominant of the 17 PAHs: phenanthrene, fluoranthene, pyrene, anthracene, benz[a]anthracene, chrysene and perylene (Fig. 6.2).

Phenanthrene (C14H10) consists of three-fused benzene rings and is used in the synthesis of colours, in resins and pesticides (Mostert et al., 2010). Fluoranthene (C16H10), is used frequently in the manufacture of agrochemicals, dyes and pharmaceuticals, and is a combustion product, especially in less efficient and lower-temperature combustion (Mostert et al., 2010). Pyrene (C16H10), a four-fused ring, originates from incomplete combustion of organic compounds, such as automobile exhaust fumes; due to its fluorescent properties it is used in colours and in industrial applications (Mostert et al., 2010). The three- ring PAH anthracene (C14H10) is used for colour synthesis, dyes and coating materials as well as in pesticides, particularly in insecticides for wood preservation (Mostert et al., 2010). Benz[a]anthracene

(C18H12) consists of four benzene rings and is a product of incomplete combustion of organic matter, such as wood, coal, mineral oils and gasoline. Chrysene is characterized by four-fused benzene rings

(C18H12) and is mainly released by incomplete combustion of fossil fuels. The origin of perylene

(C20H12), which consists of two benzene rings connected with two other benzene rings by a five- membered ring, is also released by incomplete combustion of organic matter (Mostert et al., 2010). The present study also focused on organic pesticide compounds which include some PAHs, such as anthracene. Different positional isomers of dichlorodiphenyldichloroethane (C14H10Cl4 - DDD), a DDT metabolite, were detected in some samples. Two of the identified isomers are p,p’-DDD and o,p’-DDD.

Another identified pesticide metabolite is p,p’-DDMS (C14H11Cl3) and occurs in the form of 1-chloro- 2,2 bis(p-chlorophenyl)ethane. The last compound group, only identified in core 13 closest to the beach, are UV-absorbers which are represented by bumetrizole (C17H18ClN3O). Bumetrizole is used in cosmetics and protection for plastic because of its ability for UV-absorption.

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Fig. 6.2 Selected identified anthropogenic organic geochemical marker groups and the selected compounds used for further analysis in this study.

6.4.3 Evaluation of identified proxies and loss of ignition After identification, for indicative organic geochemical compounds quantification has been performed. To establish comparability between individual samples, a normalization based on the samples loss of ignition (LOI) has been conducted. The LOI results (App. 6.T2) show that the content of total organic carbon decreases with depth in all cores, from 12 to 24% TOC in the upper layers too as little as 0.5% in the lowest layers. The ratio between sample weight and total organic content was examined here because organic chemical compound concentrations are related to the total organic content. This ratio varies broadly with values of 0.9 to 2.9 in the upper samples and as much as 56 to 94 near the bottom of the cores. The sandy tsunami deposits, as expected, contain a lower amount of total organic content in relation to sample weight, which is reflected by high sample weight to TOC ratios (App. 6.T2). Therefore, normalization of all samples on basis of the injection volume, the aliquot factor includes: the dry sample weight and the TOC content (in g), as well as the calculated area of each compound peak and the internal standard peak of each individual compound in each fraction of the samples. The Rf-value of each identified chemical compound was also considered. For normalization Formula 6.1 is used (see below):

푛푔 (푎푟푒푎 표푓 푐ℎ푒푚푖푐푎푙 푐표푚푝표푢푛푑 × 푅푓 푣푎푙푢푒 × 푖푛푗푒푐푡푖표푛 푣표푙푢푚푒) 1 푄푢푎푛푡 ( ) = 푎푟푒푎 표푓 푡ℎ푒 𝑖푛푡푒푟푛푎푙 푠푡푎푛푑푎푟푑 × (Formula 6.1) 푔 ( )× 푑푟푦 푤푒푖푔ℎ푡 푑푟푦 푤푒푖푔ℎ푡 × 푇푂퐶 (푖푛 푔) 퐴푙𝑖푞푢표푡푓푎푐푡표푟

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Following normalization, the quantitative results of the same compound of different fractions are summed up and used for interpretation. All of the resulting concentrations are presented in nanogram per gram sample material (ng g-1) in Appendix 6.S3 and in Figs. 6.4 to 6.6.

6.4.4 Data presentation of organic geochemical proxies Normalized delta plots and concentration profiles are used to present and clarify the organic geochemical data. Delta plots represent the variation within each core between compound concentrations of the pre- tsunami and post-tsunami deposits in relation to the compound concentrations of the tsunami deposit. Concentration profiles show the proportion of organic geochemical compound concentrations in relation to depth within a core.

6.4.4.1 Delta plots Delta plots were generated using the normalized data of the PAHs with standard deviation relative to the concentration of the individual tsunami deposit (red line - Fig. 6.3). The delta plots for core 13, the closest site to the shoreline and the stream, generally show higher PAH concentrations in the two post- tsunami samples and lower concentration in the pre-tsunami samples compared to the concentration in the tsunami deposit itself. Cores 03, 17 and 18, do not indicate the same pattern of PAH-concentrations compared with core 13. The delta plot for perylene (Fig. 6.3) in cores 13 and 03 shows an enrichment in the post-tsunami deposits and a depletion for the pre-tsunami deposits. Cores 17 and 18 show a general enrichment of all samples. Pre-tsunami deposits in core 17 contain extremely high perylene enrichment- ratios of 5000 to 10000% (20.6 ng g-1 and 42.8 ng g-1), which are not shown on Fig. 6.3. The phenanthrene delta plot (Fig. 6.3) shows similar characteristics for core 13, with lower compound concentrations detected in the pre-tsunami layer, with the exception of the deposit from right above the tsunami layer, and higher concentrations in the post-tsunami deposits compared with the tsunami deposit. In cores 03 and 18, accumulations and depletions of the pre-tsunami and post-tsunami deposits are recognizable. The youngest sediment sample from core 18 is strongly enriched in phenanthrene concentration (11.16 ng g-1 – 2000%) compared to the tsunami deposit (0.5 ng g-1) and is not shown on the figure. Core 17 shows lower amounts of phenanthrene in all samples compared with the tsunami deposit. Characteristics for fluoranthene (Fig. 6.3) show similar properties to the phenanthrene delta plot. Higher concentrations in post-tsunami deposits and lower concentrations in pre-tsunami deposits characterize core 13. Core 03 exhibits a similar pattern with the exception that the lowermost sample contains a 200% higher concentration (0.6 ng g-1) in relation to the tsunami deposit (0.3 ng g-1). In core 17 all samples except those at the tsunami deposit contact show lower concentrations, while all analyzed samples in core 18 indicate higher concentrations than the tsunami deposit.

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The chrysene delta plot (Fig. 6.3) shows, for most samples, higher concentrations in the post-tsunami sediment than in the pre-tsunami and tsunami deposits. Core 17, however, shows that pre-tsunami and post-tsunami deposits have a lower concentration of chrysene, except for the layer directly below the tsunami deposit. Anthracene has the most irregular delta plot (Fig. 6.3) compared to other PAHs. Irregularities are seen in all cores, especially core 17. Subsamples from these cores show high and low concentrations in post- tsunami and pre-tsunami deposits with no recognizable pattern. An exceptional outlier is found in core 03, where the post-tsunami deposit just above the tsunami contact has a concentration 1600% higher (0.9 ng g-1) than the event deposit itself (0.06 ng g-1). The delta plot for pyrene (Fig. 6.3) generally shows a depletion of the compound with depth. Core 17 indicates that the pre-tsunami and post-tsunami samples have lower concentrations than the tsunami deposit and the pre-tsunami deposit just below the contact. Core 18 samples have overall higher concentrations than the tsunami deposit (0.1 ng g-1) with an exceptional jump (5800%) in concentration at the layer just below the contact (9.0 ng g-1), which might be influenced by the tsunami deposit. The final PAH of focus is benz[a]anthracene (Fig. 6.3), showing similar results in its delta plot as the organic geochemical compound pyrene. All pre-event and post-event samples from core 18 have higher concentrations of benz[a]anthracene than during the event. The pre-event layer just below the contact has a high relative concentration 9400% (2.84 ng g-1) and is an outlier off the chart. Concentrations of benz[a]anthracene shown in samples of core 17, however, are lower than in the event deposit, with the exception of the deepest pre-event deposit. Cores 13 and 03 have high concentrations in all post-event samples and show low concentrations compared to the event deposit in the layers just above and below the contact.

Fig. 6.3 Delta plots of analyzed polycyclic aromatic hydrocarbons (PAH). Concentrations of pre-tsunami deposits (green) and post-tsunami deposits (red) are plotted relative to the concentration of the tsunami deposit (red line = 100%) of each sample core.

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While concentrations vary between compounds and subsamples of each core, general trends can be seen in the delta plots, in terms of the event deposit showing a clear difference in its organic geochemical assemblage compared to the sediments above and below. The only primary exception is marked by the layers directly below and in contact with the event deposit. These layers contain concentrations that are similar to the event deposit or are exceptionally large. Furthermore, some of the shallowest samples show extremely high values of the analyzed organic geochemical compounds.

6.4.4.2 Concentration profiles The concentrations of perylene as a function of depth in each core are much higher compared with the other six PAHs, so these values were reduced by an order of magnitude on Fig. 6.4. All analyzed PAHs in the core closest to the shoreline (core 13) show a general decreasing concentration trend with depth. However, a significant decrease in concentration in all PAHs is displayed in the tsunami deposit. Perylene shows the strongest decline from post-tsunami to the tsunami deposit, while anthracene shows the lowest change. In core 03 the concentration profiles for anthracene, fluoranthene, benz[a]anthracene, pyrene and chrysene are very similar, showing a slight increase in concentration with depth until the tsunami deposit. Here a sudden concentration decrease can be seen, followed by a slight increase in the pre- tsunami deposits below. Outliers are phenanthrene and perylene (decreased by an order of magnitude 10), both of which have distinctly higher concentrations in the upper part of the core, but follow the same pattern of lower concentrations in the tsunami deposit that then increase towards the bottom of the core. Concentrations in core 17 are very different from those in the rest of the cores. The PAHs decrease downward towards the tsunami deposit, but then four of the PAHs (phenanthrene, fluoranthene, pyrene and perylene) are significant within the tsunami deposit or directly below it, before declining again with depth. Anthracene does not markedly increase in concentration until near the bottom of the core. Benz[a]anthracene and chrysene show only a very small concentration increase within the tsunami deposit. Phenanthrene has increased concentrations in the tsunami deposit (11 ng g-1) and pre-tsunami deposits (9 ng g-1 and 10 ng g-1), which are cut from the graph for illustration purposes. The PAHs in core 18 show a significant increase in concentration in the layer below the tsunami deposit. Concentrations within the deposit itself reach a minimum. While anthracene shows the smallest increase in concentration, fluoranthene shows the most significant increase of all analyzed compounds.

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Fig. 6.4 Polycyclic aromatic hydrocarbon (PAH) concentration profiles with depths and graphic sediment description of all cores. 98 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i

6.4.5 Diagnostic ratios and other compounds By using GC–MS analysis, diagnostic ratios were calculated between the PAHs and used to differentiate between possible sources of chemical compounds, such as combustion, petroleum and mixed zones (combustion and petroleum). Three different ratios are used: anthracene and phenanthrene (An/(An + Ph)); benz[a]anthracene and chrysene (BaA/(BaA + Ch)); and phenanthrene and anthracene (Ph/An). These ratios are plotted on the y-axes of Fig. 6.5, and the ratio of fluoranthene and pyrene (Fl/(Fl + Py)) is plotted on the x-axes.

Fig. 6.5 Diagnostic ratios with fluoranthene and pyrene (Fl/(Fl + Py)) plotting on the x-axis of each graph and: (A) anthracene and phenanthrene (An/(An + Ph)); (B) benz[a]anthracene and chrysene (BaA/(BaA + Ch)); and (C) phenanthrene and anthracene (Ph/An) plotting on the y-axis, respectively.

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The diagnostic ratio between anthracene/phenanthrene related to the proportion of fluoranthene/pyrene has six defined areas of possible sources from petroleum, petroleum-combustion and combustion. The diagram shows that most samples are plotting in a mixed area of petroleum (y-axis) and combustion (x- axis), while a smaller number are located in the area of combustion. The results herein plot close to the edges of the areas, which probably reflects a mixture of sources like petroleum and natural combustion. The exception are three outliers of post-tsunami samples and one tsunami deposit sample. Post-tsunami outliers plot very differently, with one sample from core 18 being strongly in the combustion area (An/(An + Ph) = 0.26 – Fl/(Fl + Py) = 0.77) and two samples from core 17, one being more on the petroleum side of the ratio (An/(An + Ph) = 0.03 – Fl/(Fl + Py) = 0.32) and the other in a petroleum leaning mixed zone (An/(An + Ph) = 0.24 – Fl/(Fl + Py) = 0.39). Core 18 also shows an outlier from within the tsunami deposit, with a source solely in the combustion area (An/(An + Ph) = 0.35 – Fl/(Fl + Py) = 0.59). The diagram with the ratio between benz[a]anthracene and chrysene/triphenylene in proportion to the ratio of fluoranthene and pyrene is the second diagnostic ratio, characterized by three subdivisions on each axis displaying nine defined source areas. Most samples plot in the mixed zone (y-axis) and combustion area (x-axis), whereas a few samples plot above the combustion area and two plot below in the petroleum (y-axis) and combustion (x-axis) areas, which indicates a mixture of sources. Two samples, however, plot well within the petroleum area. These samples are from post-tsunami deposits in core 17, with the upper layer (51 to 59 cm) being the rightmost point in the plot (BaA/(BaA + Ch) = 0 09 – Fl/(Fl + Py) = 0.39) and the lower layer (116 to 122 cm) from right above the tsunami deposit being on the right side in the petroleum area (BaA/(BaA + Ch) = 0.11 – Fl/(Fl + Py) = 0.32). These two samples also plot as outliers using the previous ratio, again suggesting a petroleum source. Thirdly, the diagnostic ratio between phenanthrene and anthracene in proportion to fluoranthene and pyrene is characterized by six source areas. With these ratios the samples are more spread out on the diagram. Most plot near the border between petrogenic (>10) and combustion areas (<10) (y-axis), with most plotting in the combustion area (>0.5) but close to the petroleum combustion area (0.4 to 0.5) (x- axis). Again, this is interpreted as a relative mix between natural combustion and petroleum sources. As for the ratios for the two post-tsunami layers from core 17, two outliers show a more petrogenic origin. The lower leftmost point (Ph/An = 3 – Fl/(Fl + Py) = 0.39) represents the uppermost layer in core 17 and the sample from just above the tsunami deposit is the upper leftmost point (Ph/An = 30.7 – Fl/(Fl + Py) = 0.32). Bumetrizole is another compound of interest, although it is only found in core 13 closest to the beach (Fig. 6.6). The use of chemical UV-absorbers in sunscreen was introduced in the 1920s but the first large-scale use was in the Pacific during World War II by the US military. The concentration profile for bumetrizole shows a strong peak of bumetrizole in the tsunami deposit. This may record increasing

100 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i tourism on the Hawaiian Islands beginning after World War II when this compound was introduced through seepage or by groundwater transportation into the pre-industrial deposit. Other identified compounds are the organochlorides p,p’-DDD, o,p’-DDD and p,p’-DDMS. These compounds were only found in the samples below the tsunami deposit in core 17 (p,p’-DDD 0.0 ng g-1; o,p’-DDD 0.04 ng g-1; p,p’-DDMS 0.02 ng g-1). Their presence might be used as a relative dating marker, because the use of organochlorides in the United States is limited to the period between 1939 and 1972. The use of these organochlorides started during World War II and declined rapidly in the 1950s due to stricter regulations. Organochlorides like DDT were used in the military to prevent insect borne diseases like malaria and typhus through delousing and widespread airborne spraying with gas; they were mainly used during World War II on many islands; even before an invasion an airplane would spray islands to prevent insect borne diseases infecting arriving ground troops. This is especially important at the Kahana site because the presence of a military training camp suggests that organochlorides were most likely used for delousing and medical reasons as well as insecticides. Because the concentrations found were relatively low, these diagnostic organochlorides were probably introduced in lower layers through groundwater transport.

Fig. 6.6 Bumetrizole concentration profile with depths and graphic sediment description of core 13.

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6.5 Discussion 6.5.1 Applicability and limitations These results suggest that polycyclic aromatic hydrocarbons (PAH) can be measured with high vertical resolutions in cores, and, therefore, serve as anthropogenic markers. The applicability of other anthropogenic markers, however, is limited for samples from the Kahana Valley. All Kahana samples show relatively low concentrations of anthropogenic geochemical markers, which is an indication that older sediment in the Kahana Valley has not been strongly impacted by humans. The present authors attribute the overall low concentrations to the lack of local industry and populated areas, that would release organic geochemical compounds during a tsunami. The presence of anthropogenic geochemical markers suggests that measurable amounts of PAHs have infiltrated into pre-industrial sediment. The influence of the water levels and groundwater flow, however, is difficult to assess without trackable output sources within the valley. The selection of a sampling site containing a modern tsunami deposit, such as the 1946 sand in Pololu Valley (Chagué-Goff et al., 2012b) or the investigation of other biomarkers, might lead to more information on tsunami characteristics. Inorganic and organic geochemical markers do not determine the origin of a deposit (Chagué-Goff, 2010). In addition, tsunami deposits can vary greatly in their sedimentological characteristics and overall architecture due to different site and depositional conditions, as well as hydrodynamic differences in tsunami waves. On Hawai‘i, both tsunamis and tropical storms have a high frequency and impact on deposition and erosion along shorelines (Kane et al., 2017). Even though tropical storms are capable of depositing massive sandy deposits, the inland extent and other characteristics of carbonate-rich sand layers (e.g., La Selle et al., 2019a) makes the deposits in Kahana Valley unlikely to be storm-related, while deposits of MW 9+ trans-pacific tsunamis can be found and correlated to one another across the Pacific (e.g. Goff et al., 2011b; La Selle et al., 2019a). Tsunamis affecting the Kahana Valley occurred according to La Selle et al. (2019a) at about 581 to 507 cal yr BP and post-WorldWar II (1946 and 1957). At an undeveloped location such as Kahana Valley, with little input of anthropogenic compounds, high- energy events are only capable of transporting small quantities of chemical substances; traces of these compounds cannot be used as stand-alone proxies for the identification of tsunami deposits. Another important limitation of geochemical analyses is the preservation of organic geochemical compounds in sediment. In general, the younger a deposit, the easier and more likely it is to identify anthropogenic markers, due to the steady increase of human pollution into the youngest sediment. However, only a local input of anthropogenic markers ensures the detectability in the sediments. Most anthropogenic pollutants are relatively persistent or create persistent metabolites during degradation. If suitable conditions (preservation, pollution and detection of compounds) are met, the methods used here are applicable in identifying tsunamis, as well as other short-term high energy inundation events, such as storms and river flooding. For identifying tsunami deposits, however, PAHs seem to be more useful

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6.5.2 Organic geochemical markers All investigated organic geochemical markers show concentration variations with depth. Especially between distinct layers of differing lithology within individual cores. The PAHs in particular show both a general concentration decline with depth, and significant changes in concentration within and near sandy tsunami deposits. Core 13 shows an interesting geochemical pattern which is reflected in the concentration profile as well as in the delta plots. A general concentration decline of PAHs with depth is disrupted by a strong decrease in concentration of the tsunami deposit. Below the tsunami deposit many freshwater shells can be found. Bumetrizole is an important marker in this core with a significant peak in the tsunami deposit. The UV-absorbers found in sunscreens increase in nearshore waters because they wash off while swimming. When a tsunami brings nearshore water inland it leads to an increase of UV-absorbers in tsunami deposits. These UV-absorbers should have minimal to non-existent concentrations in normal beach and river sediment because they are unlikely to be distributed far as aerosols. Bumetrizole is in this case an excellent organic geochemical marker, because of its high source specificity In particular, the detection of this UV-absorber in pre-industrial tsunami deposits indicates that this compound is transported through groundwater into older sediment, because its components are partly water soluble and the sandy tsunami deposits are more porous than the surrounding mud. The organic geochemical pattern of core 03 is similar to that of core 13, with unusually high concentrations of two compounds, perylene and phenanthrene. Perylene is present at extremely high concentrations in the post-tsunami deposits. Perylene being sourced from incomplete combustion of fossil fuels is likely, but does not explain concentrations this high. If the only source was the incomplete combustion of hydrocarbons, this would also be reflected in the diagnostic ratio patterns. Instead, all cores show a combination of natural combustion and petrogenic sources. Perylene, however, is known to occur in high concentrations in tropical peats, and the source of perylene through the decomposition of wood and by fungal activities is debated (Grice et al., 2009). Phenanthrene increase in the uppermost 50 cm layers above the tsunami deposit may result from local conditions. Following World War II, Kahana Valley was for a short period of time used for farming. The natural organic chemical phenanthrenoid, which appears in five isomeric phenols from phenanthrene, is naturally occurring in plant families like Dioscoreaceae and Orchidaceae (yams and orchids; Kovács et al., 2008). Yam and taro root farming is relatively common on the Hawaiian Islands due to the good climatic conditions for these plants (Kirch, 1977; Stauffer, 2004; Mayfield, 2013), which probably have been grown for centuries. In the early 20th Century, however, commercial sugar cane farming dominated Kahana Valley. During World War II farming stopped almost completely because Kahana Valley was used by the US Army as a military camp (Mayfield, 2013; US Army Corps of Engineers, 2016). Following the war,

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Ahupua’a ‘O Kahana State Park was established and families once again resided in and farmed the valley. Therefore, the input of natural phenanthrenoids into the system may be the result of farming (at least at a small-scale) of these plants. The organochloride insecticides, p,p’-DDD, o,p’-DDD and p,p’-DDMS, found in cores were also probably related to farming in the Kahana Valley because they were used widely during the mid-20th Century. Several PAHs (for example, anthracene, fluoranthene and phenanthrene) that were found are components of agrochemicals (Abdel-Shafy and Mansour, 2016), which might have been used in the Kahana Valley. Core 17 shows high concentrations of phenanthrene, even exceeding (up to 11.4 ng g-1) values displayed in the concentration profiles, but only in the tsunami deposit and below. This might also be related to yam and taro farming with input of phenanthrenoid during deposition of these deposits. The other PAHs, especially fluoranthene and pyrene, show varying patterns in core 17 that reflect higher concentrations in the tsunami deposit and just below it. In contrast, perylene and anthracene occur at very low concentrations in the upper core and achieve high concentrations only in the layers below the tsunami deposit. This pattern is also observed for all PAHs in core 18 where a significant concentration increase is seen in the muddy deposits below the sandy tsunami deposit, whereas concentrations in the tsunami layer are low. This pattern could be related to either a strong initial pollution of the area or a seeping of organic compounds from the tsunami deposit into the more impermeable layer below it, aided by the high amounts of meteoric water in the Kahana Valley. The delta plots of core 18 are evidence for the migration of pollutants into the underlying layer (Fig. 6.3), because concentrations for all other samples of that core plot above those for the tsunami layer. Even though anthropogenic markers have high source specificities, it can be difficult to determine source locations, especially in areas with relatively little anthropomorphic disturbance. The diagnostic ratios of PAHs in Kahana Valley show a mixture of natural combustion and petrogenic sources. Given the age of the tsunami deposit (581 to 507 cal yr BP; La Selle et al., 2019a), the present authors think that the primary source is natural decomposition and combustion in the sediment of former marshes. Since Kahana Valley has been utilized for different purposes, the source locations and the types of organic geochemical markers released have changed. For Kahana Valley several source locations for the input of PAHs and pesticides can be determined. The Huilua Fishpond at the river mouth, built in the 15th to 17th Centuries (Beggerly, 1990) was operated for centuries and, more recently, used for recreational fishing. In the operation of modern fish ponds, pesticides and antibiotics can be used to prevent diseases and pests in fish; however, this usage is unlikely by native Hawaiians before the 20th Century. The agriculture in the Kahana Valley is the most likely source of PAHs into the system. Another reason for the increased levels of PAHs in the upper and modern sediments could be increased tourism, because the valley and bay have become a state park (Jaworowski, 2001). Creation of the state park resulted in an increased volume of visitors (US Department of Agriculture, 1999; Jaworowski, 2001; US Army Corps of Engineers, 2016), which resulted in an increased amount of waste and therefore an input of pollutants. The settlement located at the lower end of the valley might be another possible input source

104 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i for all kinds of anthropogenic markers, like incomplete combustion related PAHs (Kirch, 1977; Jaworowski, 2001). Car exhausts and other fossil fuel motorized machines, as well as the burning of garbage and excess agricultural harvests, contribute to the total PAH input. Dissolution of airborne anthropogenic markers by the high precipitation rates of the Kahana Valley (Beggerly, 1990) may lead to their transportation via meteoric water into sediment of the marshes. However, occurrence of anthropogenic markers can also take place through direct input of oil, petroleum and gasoline (Mostert et al., 2010), especially during refueling or leaking of machines. Because the Kahana Valley was used during World War II as a military training camp, smoke, oil segregation, and the use of fuels and combustibles originating from the use of vehicles and weapons could have released PAHs. Another factor may be the remains of forgotten ammunition and other items left behind by the military (Fig. 6.7; US Army Corps of Engineers, 1993; US Army Corps of Engineers, 2016). A cartridge casing may contain traces of inflammable matter and residues from firing, which can be absorbed by meteoric water and migrate into the surrounding sediment. The cores herein were not taken near the former military camp, but runoff and sediments from the valley sides which were used by the military, makes this a potential pollution source. The study area is also in the floodplain of the valley, and so river flooding could have led to migration and more widespread distribution of pollutants. The release and distribution of anthropogenic markers of the military camp by meteoric water is another likely input source. Other military-related input sources like fires from attacks on the military base in Kaneohe following the attack on Pearl Harbour or combat training are difficult to assess.

Fig. 6.7 Map of areas in the Kahana Valley used by the US military and munition response sites (modified after US Army Corps of Engineers, 2016).

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Another source of difficulty in assessing PAH input source is the volcanic origin of Kahana Valley sediment. As O‘ahu is composed largely of basaltic rock, small basalt fragments were found in several cores. How much PAHs are preserved in volcanic rocks and released by weathering processes directly into the sediments (Tobiszewski and Namiesnik, 2012) remains an open question. The sources of the anthropogenic markers should be reflected in most cores, nonetheless, concentration variation and declining trends are connected to usage changes of the valley and the impact of events like a tsunami. Therefore, a possible visualization of concentration differences was expected for the tsunami deposits, rather than the detection of imported, new anthropogenic markers into the event deposits, due to the lack of general pollution in the Kahana Bay and the adjacent coastlines. Tsunami inundation into Kahana Valley occurred approximately 550 cal yr BP according to La Selle et al. (2019a) resulting in the deposition of a landward thinning carbonate sand. Despite minor inundation in Kahana Valley from historical tsunamis after World War II (1946 and 1957) and within the usage period of organochlorides, modern tsunami deposits have not been identified in the sedimentary records of Kahana Valley.

6.6 Conclusions This study examines the applicability of using anthropogenic organic geochemical markers to characterize tsunami deposits in four cores from the Kahana Valley, O‘ahu, Hawai‘i. Results from this analysis show how concentrations of polycyclic aromatic hydrocarbons (PAHs), pesticides and UV- absorbers vary downcore and across the field site. The influence of anthropogenic markers within individual cores differs widely with various sediment layers being enriched or depleted in PAHs, pesticides and other chemical compounds. Two main observations are made: a general concentration decline of organic geochemical markers with depth, and significant concentration changes of individual anthropogenic geochemical compounds in or just below tsunami deposits. The applicability of anthropogenic markers for identifying tsunami deposits at the Kahana field site, however, is limited. Low concentrations of anthropogenic markers and pollutants lead to the conclusion that anthropogenic markers are not only limited by their usage in time (limited usage of anthropogenic created chemicals to centuries or decades) but also geographically. In rural areas like the Kahana Valley, with no nearby industry nor large settlements, the concentration of anthropogenic markers is expected to be low. However, the evaluation of input sources for sensitive and persistent markers, even if limited in time, is important in cases like the Kahana Valley. Agricultural and military use of the valley were sources anthropogenic markers when the 1946 and 1957 tsunamis inundated the Kahana Valley. The need for high-resolution methods to identify tsunami deposits and differentiate them from storm deposits is increasing. Anthropogenic markers so far have only been used in a limited way to identify tsunami deposits, but results such as those herein show the potential of organic geochemistry in reconstructing the history of tsunamis. Due to the recent development and very limited testing of these

106 Publication - Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i methods they should be used as supporting methods to other geochemical and sedimentological methods rather than stand-alone proxy methods. These methods have the potential to provide additional information on tsunami deposits (for example, differentiation between onshore and offshore) due to the high source specificity of the compounds identified. By sampling a fine-mesh grid across an area inundated by tsunamis, more information could be collected (like distribution of compounds, a localization of sources and inundation limit). This information, in turn, could be useful for tsunami modelling, tsunami mitigation and post-tsunami environmental assessments. Anthropogenic markers are a promising method already providing a new line of inquiry into the organic geochemical characteristics of tsunami deposits for future multi-proxy studies. However, further testing of these methods is needed to determine the limitations and advantages compared with more widely used methods.

6.7 Acknowledgements Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. Field work was supported by the USGS Tsunami Hazards, Modeling and Sedimentary Record Project. We thank Yvonne Esser and Miriam Birx for their support during sample processing and Anette Schneiderwind for her technical support during GC-MS analysis. This study was granted by the German Research Foundation (DFG, RE1361-32-1, SCHW750-22). We would like to thank the anonymous journal reviewers for their constructive reviews, improving this publication.

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Richmond, B.M., Cochran, S.A. and Gibbs, A.E., 2008a. Geologic resource evaluation of Pu’ukohola Heiau National Historic Site, Hawai‘i; part I, geology and coastal landforms. U.S. Geological Survey Open-File Report 2008-1190, p. 23. Richmond, B.M., Gibbs, A.E. and Cochran, S.A., 2008b. Geologic Resource Evaluation of Kaloko- Honokohau National Historical Park, Hawai‘i; Geology and Coastal Landforms. US Geological Survey Open-File Report 2008–1191, p. 28. Richmond, B.M., Cochran, S.A. and Gibbs, A.E., 2008c. Geologic resource evaluation of Pu’uhonua O Honaunau National Historical Park, Hawai‘i; part I, geology and coastal landforms. U.S. Geological Survey Open-File Report 2008-1192, p. 23. Richmond, B.M., Watt, S., Buckley, M., Jaffe, B.E., Gelfenbaum, G. and Morton, R.A., 2011a. Recent storm and tsunami coarse-clast deposit characteristics, southeast Hawai΄i. Marine Geology 283, p. 79–89. Richmond, B.M., Buckley, M., Etienne, S., Chagué-Goff, C., Clark, K., Goff, J., Dominey-Howes, D. and Strotz, L., 2011b. Deposits, flow characteristics, and landscape change resulting from the September 2009 South Pacific tsunami in the Samoan islands. Earth Science Reviews 107, p. 38–51. Schwarzbauer, J., Littke, R. and Weigelt, V., 2000. Identification of specific organic contaminants for estimating the contribution of the Elbe river to the pollution of the German Bight. Organic Chemistry 31, p. 1713–1731. Shinozaki, T., Fujino, S., Ikehara, M., Sawai, Y., Tamura, T., Goto, K., Sugawara, D. and Abe, T., 2015. Marine biomarkers deposited on coastal land by the 2011 Tohoku-oki tsunami. Natural Hazards 77, p. 445-460. Stauffer, R.H., 2004. Kahana: how the land was lost. University of Hawai‘i Press, Honolulu, Hawai‘i, USA, p. 256. Tipmanee, D., Deelaman,W., Pongpiachan, S., Schwarzer, K., and Sompongchaiyakul, P., 2012. Using Polycyclic Aromatic Hydrocarbons (PAHs) as a chemical proxy to indicate Tsunami 2004 backwash in Khao Lak coastal area, Thailand. Natural Hazards and Earth System Sciences 12, p. 1441–1451. Tobiszewski, M. and Namiesnik, J., 2012. PAH diagnostic ratios for the identification of pollution emission sources. Environmental Pollution 162, p. 110–119. US Army Corps of Engineers, 1985. Kahana Bay Navigation Improvements O‘ahu, Hawai‘i. Honolulu, Hawai‘i, USA. U.S. Army Corps of Engineers Report. US Army Corps of Engineers, 1993. Pacific Jungle Combat Training Center Kahana and Punaluu Valleys, Island of Oahu, Hawaii – Inventory Project Report. Honolulu, Hawai‘i, USA. U.S. Army Corps of Engineers Report. US Army Corps of Engineers, 2010. Oahu Coastal Stream Mouth Map Book. Honolulu Engineering District, O‘ahu, Hawai‘i, USA. United States Army Corps of Engineers Report, p. 70. US Army Corps of Engineers, 2016. U.S. Army Corps of Engineers Proposed Plan Former Pacific Jungle Combat Training Center. O‘ahu, Hawai‘i, USA. U.S. Army Corps of Engineers Report, p. 24.

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US Department of Agriculture, 1999. Contaminants Present in the Original Water Quality Limited Segments. Water Technology Note 10, p. 1–18. Walker, D.A., 2004. Regional Tsunami Evacuation for the State of Hawaii: a Feasibility Study based on historical Runup Data. Science of Tsunami Hazards 22, p. 3–16. Witter, R.C., Carver, G.A., Briggs, R.W., Gelfenbaum, G., Koehler, R.D., La Selle, SP., Bender, A.M., Engelhart, S.E., Hemphill-Haley, E., and Hill, T.D., 2016. Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust. Geophysical Research Letters 43, p. 76–84. Witter, R.C., Briggs, R.W., Engelhart, S.E., Gelfenbaum, G., Koehler, R.D., Nelson, A.R. and Wallace, K.L., 2018. Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust. GSA Bulletin 131, p. 707–729. Wood, N., Church, A., Frazier, T. and Yarnal, B., 2007. Variations in community exposure and sensitivity to tsunami hazards in the State of Hawai΄i. U.S. Geological Survey Scientific Investigation Report 2007-5208, p. 42.

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6.9 Supplementary Material

Appendix 6.F1 Concentration profiles with depths and graphic sediment description of core 13.

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Appendix 6.F2 Concentration profiles with depths and graphic sediment description of core 03.

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Appendix 6.F3 Concentration profiles with depths and graphic sediment description of core 18.

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Appendix 6.F4 Concentration profiles with depths and graphic sediment description of core 17.

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Appendix 6.F5 All 21 organic-geochemical markers identified in the samples.

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Appendix 6.T1 Modelled ages of tsunami deposits at sites in the Aleutians and Hawaii (after Richmond et al., 2019; Witter et al., 2016, 2018).

Appendix 6.T2 TOC results by loss of ignition (LOI) and weight/TOC ratios.

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Appendix 6.T3 Anthropogenic geochemical marker results of all 21 components and the 11 selected (highlighted)

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7 Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan)

Piero Bellanova1,2, Mike Frenken1,2, Klaus Reicherter2, Bruce Jaffe3, Witold Szczuciński4, Jan Schwarzbauer1 1 Institute for Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstrasse 4-20, 52056, Aachen, Germany 2 Lehr- und Forschungsgebiet Neotektonik und Georisiken, RWTH Aachen, Lochnerstrasse 4-20, 52056 Aachen, Germany 3 U.S. Geological Survey, Pacific Coastal and Marine Science Center, 400 Natural Bridges Drive, Santa Cruz, CA 95060, United States 4 Geohazards Lab, Institute of Geology, Adam Mickiewicz University, Bogumiła Krygowskiego 12, 61-680 Poznań, Poland

Abstract Organic geochemistry is commonly used in environmental studies. In tsunami research, however, its applications are in their infancy and it is still rarely used. We present results for two types of organic geochemical markers, biomarkers and anthropogenic markers, present in deposits left by 2011 Tohoku- oki tsunami on the Sendai Plain, Japan. As the tsunami inundated the coastal lowland up to 4.85 km inland, sediments from various sources were eroded, transported and deposited. This led to the distribution of biomarkers from different sources across the Sendai Plain creating a unique geochemical signature in the tsunami deposits. The tsunami also caused destruction along the Sendai coastline, leading to the release of large quantities of environmental pollutants (e.g., fossil fuels, tarmac, pesticides, plastics, etc.) that were distributed across the inundated area. These anthropogenic markers, represented by three main compound groups (polycyclic aromatic hydrocarbons, pesticides, and halogenated compounds), were preserved in tsunami deposits (at least until 2013, prior to land clearing). Their concentrations differed significantly from the pre- and post-tsunami background contamination levels. Organic proxy concentrations can differ for sand and mud deposits due to various factors (e.g., preservation, dilution, microbial alteration). However, it can be concluded that anthropogenic markers and biomarkers have the potential to be a valuable proxy for future studies of recent tsunami deposits because of their high source specificity and relatively good preservation potential providing information about sediment sources and transport pathways (e.g., marine source, evidence of backwash).

Keywords Tsunami deposits; 2011 Tohoku-oki tsunami; anthropogenic pollutants; biomarkers; geochemical signatures This chapter is a slightly modified version of the article published in Marine Geology (2020) DOI: 10.1016/j.margeo.2020.106117

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7.1 Introduction Following the 2004 Indian Ocean tsunami and the 2011 Tohoku-oki tsunami, there was a rapid development in applications of new analytical techniques for the identification and analysis of tsunami deposits (e.g., Chagué-Goff et al., 2017). New methods increase the understanding of processes during tsunami events and provide new insights that are valuable for hazard assessment and improve tsunami mitigation plans. For instance, the analysis of inorganic geochemical tsunami markers following the 2011 Tohoku-oki tsunami by Chagué-Goff et al. (2012a) led to the discovery that the inundation distance determined from muddy tsunami deposits and inundated soils was approximately 1.75 km farther inland than the inundation limit marked by sandy tsunami deposits. In the absence of other inundation markers, deriving tsunami inundation limits from sandy tsunami deposits in low-lying coastal plains typically results in a minimum estimate of inundation (MacInnes et al., 2009; Goto et al., 2011; Morton et al., 2011; Abe et al., 2012; Chagué-Goff et al., 2012a). For this reason, new methods that enhance the investigation of both sandy and muddy tsunami deposits and their identification in the sedimentary record are much needed. Geochemical markers have been used in tsunami research since the 1980s (Minoura et al., 1987). However, studies of geochemical markers are much less common than studies using sedimentological methods. Most of the geochemical applications are based on inorganic compounds detectable with various techniques including core scanners (e.g., Itrax, Aavatech), XRF, ICP-AES etc. (overview by Chagué-Goff et al., 2017). Extreme marine flooding events, however, not only transport inorganic particulate matter (e.g., sand & salts) from marine to terrestrial areas during uprush, and vice versa during backwash, but also associated organic material. Organic geochemical markers incorporated in this organic material may be source-specific and be utilized in characterization and identification of tsunami deposits in the sedimentary record. The use of bulk organic-geochemical parameters, such as the total organic carbon (TOC) content and stable carbon isotopes ratio, has proven useful in tsunami studies (e.g., Chagué-Goff et al., 2012a; Dahanayake et al., 2012; Pilarczyk et al., 2012). The first application of biomarkers (n-alkanes, isoprenoids, fatty acids, n-aldehydes and steroids) for identifying historical tsunami deposits were in coastal areas in southwest Turkey (Alpar et al., 2012) and Greece (Mathes-Schmidt et al., 2013). The most recent use of organic geochemistry in tsunami research is the study of anthropogenic markers (polycyclic aromatic hydrocarbons, pesticides, halogenated industrial compounds) by Bellanova et al. (2019). They successfully identified historical tsunami deposits through analysis of organic anthropogenic proxies augmenting data derived from traditional sedimentological methods, in the Kahana Valley, Oahu, Hawaii. Following the 2011 Tohoku-oki tsunami, organic geochemical biomarkers were detected at the well- studied Sendai Plain (Shinozaki et al., 2015), indicating the difference between tsunami, pre- and post- tsunami layers. The presence or absence, respectively, of source-specific (e.g., dinosterols from marine dinoflagellates) and environment-indicating substances (e.g., pristane/phytane, n-alkanes) were used to

Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan develop scenarios for deposition during the 2011 Tohoku-oki tsunami. While organic indicators are affected by many factors (e.g., preservation, dilution, microbial alteration), that are different for sand and mud layers, Shinozaki et al. (2015) concluded there was great potential for organic biomarker analyses in tsunami research in general. The 2011 Tohoku-oki tsunami caused extensive flooding and destruction in the Sendai area and along the eastern coastline of Japan. To date, it is the best documented tsunami event. For instance, videos taken from helicopters and by survivors on rooftops provided an opportunity to calculate the tsunami run-up current velocities (Hayashi and Koshimura, 2013; Fritz et al., 2012). Furthermore, media coverage documented destruction, burning debris transported with the current, and flooded industrial complexes. Taken as a whole, media coverage provides good information on the overall pollution and distribution of pollutants. As most contaminants are source specific, in particular xenobiotics, they are an ideal proxy for the identification of modern event deposits, contrasting with the less contaminated background sediments. They can also be used for differentiating terrestrial from marine sources on the basis of environment specific chemical compounds. For example, pesticides are frequently used in large quantities in agriculture and can be assigned as terrestrial indicators. Another example is the constituents of anti-fouling paint, which indicate a likely marine or coastal input (e.g., Sousa et al., 2013). Organic geochemical investigations of tsunami deposits have great potential to improve the understanding of tsunami deposits but, so far, lack proof-of-concept studies. Here, we evaluate whether biomarkers and anthropogenic organic markers are capable of identify and characterizing the deposits of the 2011 Tohoku-oki tsunami. While the severe damage on the Sendai Plain cannot be reversed and the sedimentary record there has largely been removed (Chagué-Goff et al., 2018), results of this study will have implications for future tsunamis and the approaches used to study them along the coastline of Japan and elsewhere in the world.

7.2 Study area For the investigation of the utilization of biomarkers and organic anthropogenic markers in the identification of tsunami deposits, the following conditions must be met: (1) a research areas recently impacted by a tsunami; (2) presence of infrastructure – such as villages, highways, industry, harbors, etc. – in the research area that releases pollutants during the tsunami; (3) information about the tsunami inundation and tsunami characteristics in the research area. The Sendai Plain in Miyagi prefecture, Japan (Fig. 7.1), which was impacted by the 2011 Tohoku-oki tsunami, meets all of these requirements. The ca. 5 km wide low-lying alluvial plain is highly modified by human activities. Prior to the 2011 tsunami, beaches (ca. 150 m wide) were separated from the alluvial plain by a 300 m wide control forest of pine trees, which was planted during the Edo period (1603-1867 CE) to protect inland areas from storm surges, windblown sand, and salt spray (Sugawara et al., 2012b). A 5-6 m high artificial dune ridge on the back beach, partly reinforced with nets, stabilized by wood piles, and planted with young pine trees, was flattened by the 2011 Tohoku-oki tsunami (Sugawara and Goto, 2012; Takashimizu et al., 2012).

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The tsunami also left deep scour depressions at some locations behind the dune ridge (Richmond et al., 2012). The control forest was also heavily damaged by the tsunami (Sugawara and Goto, 2012; Sugawara et al., 2012b).

Fig. 7.1 Study site overview. (A) location of Sendai on Honshu Island (Japan) and the epicenter of the 2011 Tohoku-oki tsunami. (B) detail of Sendai Airport field site showing the Sendai airport as well as urban, industrial and agricultural areas. Black dots are sampling locations for former studies (Goto et al., 2011; Chagué-Goff et al., 2012a, 2012c; Jaffe et al., 2012; Jagodziński et al., 2012; Pilarczyk et al., 2012; Richmond et al., 2012; Schneider et al., 2014; Szczuciński et al., 2012), while red dots are sampling locations for this study. The max. limit of tsunami inundation (orange dashed line) is shown according to the Association of Japanese Geographers (2011) report.

The selected field area is located alongside the well-studied Sendai airport transect (e.g., Goto et al., 2011; Chagué-Goff et al., 2012a, 2012c; Goto et al., 2012; Jaffe et al., 2012; Pilarczyk et al., 2012; Richmond et al., 2012; Sugawara and Goto, 2012; Szczuciński et al., 2012 – Fig. 7.1). Most of the studies focused on the origin and distribution of sandy tsunami deposits and their characteristics. However, Goto et al. (2011) pointed out that the trends in deposit thickness and grain size distribution are far more complex on the Sendai Plain compared to sediment distribution pattern found at other locations in previous tsunami studies. The significance and sole reliance on sand deposits was questioned as several studies pointed out that the 2011 tsunami deposits are mud-dominated from 2.9 km from the shoreline to 4.65 km from the shoreline; thus sand deposits are not a good proxy for inundation as they only extended to about 60% of the limit of inundation (Goto et al., 2011; Chagué-Goff et al., 2012a). No significant indicators of offshore sediments were found within tsunami deposits on the Sendai Plain and the evidence of seawater flooding was rather limited (e.g., Chagué-Goff et al., 2012a, 2012c; Richmond et al., 2012; Szczuciński et al., 2012). Szczuciński et al. (2012) demonstrated that the sediment in tsunami deposits from the shoreline to 1 km inland was sourced mainly from beach sand and dunes. From 1 to 2 km inland, sediment sources were local soils, beach and dune sand, and sediment of the Minami-Teizan Canal. Tsunami deposits from 2 km onwards consisted mainly of eroded local soil. Inorganic saltwater indicators (mostly as chlorides and sulphates) were present up to the limit of inundation, at a distance of 4.85 km (Chagué-Goff et al., 2012a, 2012c). In agreement with this also

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δ13C and C/N data indicated the entrainment and deposition of marine organic matter (Chagué-Goff et al., 2012a). Shinozaki et al. (2015) detected marine biomarkers (e.g. pristane/phytane, short chained n- alkanes) exclusively in the tsunami deposits and soil up to 2 cm below the event layer, indicating a marine input by the tsunami and their potential as valuable proxies. However, Shinozaki et al. (2015) pointed as well to a possible leaching of marine biomarkers. Additionally, the deposits were moderately affected by post-depositional processes, mainly by winds, creating a thin eolian sand coverage (Goto et al., 2011; Richmond et al., 2012; Szczuciński, 2020). In the vicinity of the sampled transect there were multiple potential sources of anthropogenic markers such as the airport, agricultural areas, industrial complexes, roadways, and urban residential areas (Table 7.1). There were also natural ecosystems, such as the coastal pine forests, beaches and coastal dunes, that are sources for a variety of biomarkers. Holocene fluvial and coastal sediments (beach ridges), forming the alluvial plain of the research area, are dissected by drainage systems and irrigation channels. Due to the flat and low topography of the Sendai Plain, backwash was weak away from the coast and water brought by the tsunami ponded for several weeks (Chagué-Goff et al., 2012c, 2014; Sugawara et al., 2012b). This effect was amplified by damage to the drainage system (Sugawara et al., 2012b), increasing the preservation potential of biomarkers and anthropogenic markers in the sedimentary record of this event as shown by Shinozaki et al. (2015, 2016).

Table 7.1 Overview of anthropogenic markers and biomarkers, the environments they are found, and the sources they can derive from (visually modified after Bellanova et al., 2020). 7.3 Methods Sediment samples were taken from small trenches in 2013 before clearing of tsunami debris and removal of deposits on the Sendai Plain (Chagué-Goff et al., 2018). Three trenches were excavated as deep as 50 cm at locations 30 m, 800 m and 2500 m from the shoreline along a coast-perpendicular transect (Fig. 7.1) In addition, the upper 0.5 cm of mud deposited in a drainage channel under the Sendai-Tobu

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Highway 4.5 km inland from the shoreline was sampled. The landward fining deposits of the 2011 Tohoku-oki tsunami (e.g., Richmond et al., 2012; Szczuciński et al., 2012) as well as - for comparison of geochemical composition - sediments from below and above the event layer were sampled. Macroscopic sedimentological characteristics were described and (if possible) at least 3 samples were taken (post-tsunami, tsunami and pre-tsunami). For this study a total of 8 sediment samples were collected and placed into 2 oz. Whirl Pak® sampling bags and kept cold at 4 °C during processing and at -20 °C during long-term storage to avoid microbial alteration of the geochemical compounds. The number of samples is limited for this study because of land clearing on the Sendai Plain that resulted in much of the tsunami deposit being removed. Thus, interpretation of spatial distribution outside the analyzed transect is restricted. Samples were analyzed in 9 chemical fractions at the Institute for Geology and Geochemistry of Petroleum and Coal (RWTH Aachen University, Germany) resulting in 72 fraction sets of results. 7.3.1 Total organic carbon (TOC) For TOC determination 1-2 g of sample was dried, homogenized and 100 mg weighed into a quartz boat for analysis. Total organic carbon (TOC), total carbon (TC) and total inorganic carbon (TIC) contents were measured using the liquiTOC II (Elementar Analysesysteme GmbH, Germany) in the single analytical run mode. Calibration was performed before every measurement. 7.3.2 Extraction To extract all environment-sensitive and source specific organic chemical compounds a two-step extraction was applied. First, the non-bound and therefore freely extractable compounds, such as polycyclic aromatic hydrocarbons (PAHs), were extracted. In a second step the bound compounds, such as fatty acid methyl esters or steroids, were extracted via basic hydrolysis out of the sediment.

Free extractable compounds Compounds that are freely available (anthropogenic markers) were extracted from the sediment samples via overhead shaking solid-liquid extraction with organic solvents (Bellanova et al., 2019). Aliquots of 24-310 g wet sediment were added in an Erlenmeyer flask and extracted 3 times, twice with 110 ml acetone (4 and 24 h) and once with 110 ml n-hexane (24 h). Extracts were separated from the sediment via centrifugation and combined in a separatory funnel. As samples were wet, the aqueous phase was separated by a surplus of n-hexane while reducing the total volume via rotary evaporation (300 mbar). The reduced extract was dried over a Bakerbond column filled with anhydrous granulated sodium sulfate and desulphurized with activated copper powder in ultrasonic agitation. Column chromatography with a Bakerbond column, filled with 2 g activated silica gel and conditioned at 200 °C, was used to fractionate extracts into 6 fractions (B1-B6) using different mixtures of the eluents n-pentane, dichloromethane (DCM) and methanol (MeOH) (Schwarzbauer et al., 2000; Bellanova et al., 2019). With increasing polarity, the eluents for each fraction are as following: 1st Fraction 5 ml n- pentane (i.e., aliphatic hydrocarbons); 2nd Fraction 8.5 ml n-pentane/DCM 95/5 (i.e., polychlorinated

125 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan compounds); 3rd Fraction 5 ml n-pentane/DCM 90/10 (i.e., aromatic hydrocarbons); 4th Fraction 5 ml n- pentane/DCM 40/60 (i.e., aromatic hydrocarbons); 5th Fraction 5 ml DCM (i.e., semi-polar organic compounds); 6th Fraction 5 ml MeOH (i.e., polar organic compounds). Acidic compounds of fraction 6 have been methylated by diazomethane prior to gas chromatography (GC) and gas chromatography– mass spectrometry (GC-MS) analyses. Each sample was spiked with 50 μl of internal surrogate standard solution (5.8 ng/μl fluoracetophenone,

6.28 ng/μl d10-benzophenone and 6.03 ng/μl d34-hexadecane) and was reduced to 50 μl of total volume for GC-MS measurements.

Bound compounds The sediment bound compounds (biomarkers) were extracted from the samples via alkaline hydrolysis solid-liquid extraction. For the alkaline hydrolysis 10-25 g of the extracted sediment and 2.5 g of potassium hydroxide were weighted into a closeable centrifuge glass and mixed with 2 ml ultrapure water and 20 ml methanol. Sample tubes were tightly closed, ultrasonic agitated and boiled at 105 °C for extraction (24 h). Aliquots were centrifuged (2500 rpm/5000 g RCF [Relative Centrifugal Force]) and extracts decanted in a separatory funnel with 50 ml ultrapure water. Subsequently, 5 ml of three organic solvents (acetone, dichloromethane and n-pentane) were added to the extracted sediment and mixtures ultrasonically agitated for 15 min, centrifuged and decanted to the separatory for each individual organic solvent. The basic extract was acidified with hydrochloric acid (HCl) to a pH of 4-5. For the solvent exchange 3 × 30 ml of dichloromethane (DCM) were added to the extract, shaken for 5 min and the DCM-phase separated in a pear-shaped flask. The DCM-extract was reduced in volume (1 ml) by using rotary evaporation (300 mbar), dried with anhydrous granulated sodium sulfate and desulphurized with activated copper powder in ultrasonic agitation. Column chromatography with a Bakerbond column was filled with 2 g activated silica gel and conditioned at 200 °C, was used for fractionation of extracts into 3 fractions (BH/B1–BH/B3) using different mixtures of the eluents n-pentane, dichloromethane (DCM) and methanol (MeOH). With increasing polarity, the fractions eluents were as following: Fraction BH1 5 ml n-pentane/DCM 50/50 (i.e., alkanes and triterpenes); Fraction BH2 5 ml DCM (i.e., ketones, aldehydes and alcohols); Fraction BH3 5 ml MeOH (i.e., fatty acids and fatty acid methyl esters). Each sample was spiked with 50 μl of internal surrogate standard solution (5.8 ng/μl fluoracetophenone, 6.28 ng/μl d10-benzophenone and

6.03 ng/μl d34-hexadecane) and was reduced to 50 μl of total volume for GC-MS measurements.

7.3.3 GC and GC-MS analysis To identify and determine the concentration of organic compounds of both anthropogenic markers (free- extractable) and biomarkers (bound-compounds), concentrations of all samples' fractions were examined using gas chromatography and measured by gas chromatography-mass spectrometry.

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GC-FID analysis was performed on a Fisons GC8000 series 8060 equipped with a flame ionization detector (FID) and a 30 m × 0.25 mm i.d. × 0.25 μm film ZB-5 fused silica capillary column (Zebron capillary GC column, Chrompack). Of each sample 1/50 μl of extract was injected at 60 °C (injector temperature 270 °C), splitless time 60 s, heating rate of 5 °C/min to 300 °C with 20 min isothermal time. Based on different boiling points and polarities, compounds are then ionized by flame, transported and separated by a hydrogen gas stream through the capillary, and total oxidizable ions detected (Dsikowitzky, 2002). The concentration of particular compounds was quantified with GC-MS analysis and was performed on a quadrupole, GC-MS instrument (Thermo Finnigan Trace GC/MS) with helium as carrier gas. Therefore, 1 μl of sample extract of each fraction was injected at a start temperature of 60 °C with a splitless time of 60 s, a temperature hold of 3 min, followed by a temperature ramp of 3 °C/min to 310 °C and another hold for 20 min. The mass spectrometers operated in full scan mode achieving a range from 35 to 500 m/z (mass-to-charge ratio) in positive electron impact ionization mode (EI+) with 7 eV electron energy. Identification of compounds was achieved by comparison with mass spectra of the NIST MS database (National Institute of Standards and Technology – U.S. Department of Commerce), and a subsequent verification of mass spectral parameter with those of standard reference materials. Applying the integration of specific ion chromatograms in combination with external four-point calibration with reference material, the quantification of organic compounds concentrations was accomplished.

7.3.4 Metrics to determine the source of tsunami deposits Three ratios are useful for determining the source of the tsunami deposits: (1) the terrigenous to aquatic ratio (TAR), (2) the carbon preference index (CPI), and (3) the odd-to-even-predominance ratio (OEP). The TAR, which is the ratio between different n-alkanes, is an indicator of terrestrial versus aquatic organic matter in the sediment. High values of the TAR reflect an increase of odd long-chained n- alkanes, which indicate a higher terrestrial input by vascular plants (Peters et al., 2005). Low values reflect the dominance of odd short-chained n-alkanes, indicating marine input. The TAR, however, must be applied carefully. Biodegradation has an effect on the ratios. Land plants can strongly influence the TAR as they typically contain more n-alkanes (Peters et al., 2005). TAR was calculated with concentrations of the respective n-alkanes (CX) normalized by TOC as inputs using Formula (1) (Peters et al., 2005): C +C +C TAR= 27 29 31 C15+C17+C19 Formula 1 The carbon preference index is a common biomarker ratio used to distinguish biogenic from petrogenic n-alkane sources. A higher CPI indicates a shift to odd-numbered n-alkanes, which are derived primarily from biogenic sources, such as the cuticular waxes of higher land plants (Schwarzbauer et al., 2018).

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Following Peters et al. (2005) the CPI was calculated for n-alkanes with chain length C24 to C30 with concentrations normalized to TOC as input values: C +C +C +C CPI=2 · ( 23 25 27 29 ) C22+2 · (C24+C26+C28)+C30 Formula 2 Odd-to-even-predominance (OEP) indicates the biogenic or petrogenic source of n-alkanes in sediments, similar to the CPI. The OEP ratio was calculated using Formula (3) (Peters et al., 2005) with concentrations of the respective n-alkanes normalized by TOC: C +6·C +C OEP= 25 27 29 4·C26+4·C28 Formula 3

7.4 Results 7.4.1 Sample description and TOC Samples were collected to characterize variability in anthropogenic pollutants and biomarkers along a transect from the beach to the Sendai-Tobu Highway at ca. 4.5 km inland. Trench 1 (T1 – 0-3 cm) is at the beach and consists of angular medium to coarse sand with marine shell debris. T1 is used as a coastal reference for this study. Trench 2 (T2) is located in a rice paddy 800 m inland close to the Minami- Teizan Canal. Four samples were collected at T2: (sample 1) a post-tsunami eolian top layer (3-7 cm) comprised of silty fine sand, followed by a brown sandy silt with roots and plant residues (sample 2, 9- 14 cm); the ~10-cm-thick tsunami deposit consisting of yellowish fine to medium sand with few shell fragments (sample 3, 16-21 cm); and (sample 4, 22-27 cm) a pre-tsunami sediment comprised of a brown fine-sandy silt. Samples from Trench 3 (T3) were collected about 2.5 km inland in an urban area north of the Sendai airport and close to Yashimari Canal. This site may also be influenced by nearby agricultural activity. The tsunami deposit (0-4 cm) at T3 is a sandy silt while the pre-tsunami soil (8- 12 cm) consists of homogenous organic-rich silt with macroscopic plant residues. No sediment had accumulated on top of the tsunami deposit from the time of the tsunami to the time of sample collection. The most landward (4.5 km inland) sample (G1), is the upper 0.5 cm of organic-rich brown muddy silt deposited within the 2011 inundated area on a path in a tunnel under the Sendai-Tobu Highway next to an irrigation canal draining nearby rice paddies. Table 7.2 Total organic carbon (TOC) and total inorganic carbon (TIC) results from liquiTOC II analysis (visually modified after Bellanova et al., 2020).

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Total organic carbon varies between samples and sampling sites, with the lowest TOC (0.17%) in the beach sample of T1 and the highest TOC (6.5%) in the deposit 4.5 km inland (G1, Table 7.2). Both tsunami and non-tsunami samples at T2 had TOC values between 0.24 and 0.33%. The TOC of the tsunami deposit at T3 (1.1%)

7.4.2 Organic markers Based on an extended non-target screening, a total of >320 biological markers and > 130 anthropogenic markers were identified. Indicative compounds were assigned to their respective compound group and quantified. Organic markers are a part of the organic matter. In general, sands contain lower amounts of organic matter than finer grain size fractions (mud & silt). Thus, the grain size has an indirect influence on the organic marker concentration. We normalize the results by the total content of organic carbon (TOC [%]; Table 7.2) to make them comparable to each other. About 75% of the analyzed organic compounds, however, were not assigned to a particular compound group, were below the quantification limit, or were present in only one sample, and thus were not discussed in this study.

Fig. 7.2 Specific anthropogenic markers, biomarkers, and compound groups analyzed in this study.

129 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan

Biomarkers A total of 30 specific biological compounds (biomarkers) were selected for analyses (Fig. 7.2) and compared between samples of the two trenches (T2 & T3). The selected analyses were carried out to represent six of the most prominent biomarker groups: n-alkanes, terpenes, n-aldehydes, ketones, as well as fatty acids and their methyl esters (Table 7.3).

Table 7.3 Biomarker marker results of the six analyzed compound groups and the calculated indicative ratios: terrigenous aquatic ratio (TAR), carbon preference index (CPI), odd-even-predominance (OEP) (visually modified after Bellanova et al., 2020). n-Alkanes are excellent environmental indicators as they differentiate terrestrial (> C25), aquatic (C23-

C25) and marine (C23 <) environments (Peters et al., 2005). All terrestrial, aquatic and marine nalkanes are summarized in Table 7.3 and Fig. 7.3. In pre-tsunami sediments the TAR increases landward up to 101.7, which indicates dominance of terrestrial sources (Table 7.3; Fig. 7.3C). There is a general landward decrease in the contribution of marine n-alkanes, however, the tsunami deposits have an increased marine n-alkane input as indicated by low TAR values (Table 7.3; Fig. 7.3B&C). Short- chained n-alkanes indicative of a marine environment were predominant in the coastal sample (T1), which had the lowest TAR value (0.38). In samples of T2, T3 and G1, terrestrial n-alkanes are dominant, however in the tsunami deposits a distinct increase in marine n-alkanes was detected. In some samples (T2 and T3) high n-alkanes amounts of aquatic origin (aquatic macrophyte - mid length n-alkanes) are detected (Fig. 7.3B). An odd-over-even predominance is visible in all chromatograms as well as in the CPI and OEP (Fig. 7.3A, D) as the odd-numbered n-alkanes outweigh the even-numbered n-alkanes, indicating the dominating biogenic nature of n-alkanes in the deposits. In trench T2 the tsunami deposit has a lower ratio between odd and even-numbered n-alkanes than pre- and post-sediments. However, in the tsunami deposit of T3 the OEP value is lower, suggesting a possible petrogenic input of fossil fuels during the tsunami (Table 7.3 & Fig. 7.3). Odd-over-even n-alkanes predominance across the samples reflects a predominant biogenic source from vascular plant leaf waxes (Schwarzbauer et al., 2018). The OEP results confirm results of the CPI with similar patterns for both T2 and T3 and their respective tsunami deposits (Table 7.3 & Fig. 7.3).

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Fig. 7.3 Overview of results of n-alkanes with (A) representative chromatograms (trench 2) showing the n-alkane distribution of mass (m/z)= 85; (B) marine, aquatic and terrestrial n-alkane concentrations of each sample; (C) results of the terrigenous:aquatic ratio (TAR); (D) the carbon preference index (CPI) and odd-even predominance (OEP).

Terpenes are biological compounds produced primarily by plants. They are represented in the analyzed samples by their most prominent member - squalene. The linear triterpene squalene (C30H50), consists of six isoprene's and is a universal biological marker, as it is produced in various concentrations by all plants and animals (e.g., as skin lipids and waxes) (e.g. Schwarzbauer and Jovančićević, 2016). In most samples squalene occurred in relatively high concentrations, however it is depleted by about 50% in the tsunami deposits of T3 compared to pre- and post-tsunami sediments and only accounts for 4-6% of the pre- and post-event concentration in the tsunami deposit of T2 (Fig. 7.4). Only the beach sample, T1, and the immediate post-tsunami sediment in T2 show similarly low concentrations of squalene relative to the tsunami deposits (Table 7.3).

131 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan

Fig. 7.4 Concentrations of the five analyzed biomarkers groups in trenches T2 and T3 for tsunami deposits (blue bars) and pre- and post-event sediments (green and red).

The dehydrated alcohols, n-aldehydes, are common in nature as they are the basis of many lipids and essential oils. In the samples from the Sendai Plain the n-aldehyde nonanal (C9H10O) was commonly found (Fig. 7.4). With its citrus-like smell it is common to many plants and is frequently used in food production (as flavor) and in pharmaceutical applications (e.g., Buettner and Schieberle, 2001; Zavala- Sánchez et al., 2008). Nonanal concentrations were relatively low, except for in the tsunami deposits.

Benzylideneacetone (C10H10O), naturally occurring in soybeans, was present in high concentrations in the pre- and post-tsunami sediments, with the exception of the beach (T1) (Table 7.3). High values reflect possible soybean farming in the agricultural areas of the Sendai Plain before and after the tsunami (Sekine, 2016; Chagué-Goff et al., 2018). Tsunami deposits had low concentrations of benzylideneacetone. Fatty acids, saturated or unsaturated long-chained carboxylic acids, are common biological compounds that are building blocks of cells and play a role in metabolic processes (e.g., Alpar et al., 2012; Ünlü et al., 2012; Schwarzbauer et al., 2018). Three fatty acids were selected as indicator biomarkers (Fig. 7.4).

Palmitic acid (C16H32O2), a saturated fatty acid, a primary component of palm oil, meat and dairy products, was detected in T2, T3 and G1. The highest concentrations, however, were in the pre-tsunami

132 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan sample of T3 (Table 7.3 & Fig. 7.4). The odd-numbered nonanoic acid (C9H18O2), naturally occurring in thorny Rosaceae and other plants, but industrially used as plasticizers and lacquers, was identified in low concentrations in most samples (Table 7.3). Within the beach sample T1 it is to be found in high amounts, which might be related to its natural occurrence in leaf waxes and essential oils of thorny plants on coastal dunes. An increase of nonanoic acid was measured in the tsunami deposit of T3, while in T2 it occurred in a general decreasing trend from pre-tsunami to the most modern post-tsunami sediment (Fig. 7.4). Heneicosanoic acid (C21H42O2) is a long-chained, odd-numbered fatty acid typically found in vascular land plants, trees, legumes, mushrooms, and is also used in technical applications. The concentrations of heneicosanoic acid varied (Table 7.3, Fig. 7.4). The lowest values occurred in the beach sample of T1, while in T2 the lowest concentration was detected in the tsunami deposits. The highest value was in the pre-tsunami soils of T3. Fatty acid methyl esters (FAME) derived by esterification of fatty acids, are well known due to their usage in the production of biofuels but they are as common as fatty acids in natural environments. The two most prominent representatives of fatty acid methyl esters in the samples of the Sendai Plain were methyl myristate and palmitic acid methyl ester (Fig. 7.4). Methyl myristate (C15H30O2) and the fatty acid myristic acid (C14H28O2) are prominent in many plants and animal fats, such as coconut oil and butter, and therefore are frequently used in cosmetics, soaps and seasonings. Results showed methyl myristate to be present across the studied sites, with low concentrations in T1 and relatively low concentrations in the tsunami deposits (Table 7.3). Methyl palmitate (C17H34O2) is used in cosmetics, detergents and resins based of its chemical properties. Generally high but strongly varying concentrations of methyl palmitate have been quantified in all samples (Table 7.3). The lowest concentration was found in beach sediments (T1). The pre- and immediate post-tsunami samples of T2 have highest concentrations, while the tsunami deposit and most modern deposit have the lowest concentrations. On the contrary, the T3 tsunami deposit was enriched in comparison to the pre-tsunami soil.

Anthropogenic markers A total of 17 specific organic substances considered to be anthropogenic pollutants were identified. They belong to three of the most commonly found compound groups (Fig. 7.2): PAHs, pesticides and halogenated compounds (Table 7.4).

Table 7.4 Anthropogenic geochemical marker results of the three analyzed compound groups polycyclic aromatic hydrocarbons, pesticides and halogenated compounds (visually modified after Bellanova et al., 2020). 133 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan

PAH are persistent and toxic organic pollutants found in all samples. We present results for 9 indicative

PAHs. Acenaphthylene (C12H8), originating from fossil fuel combustion, was enriched in the tsunami deposit of T2 (up to 95×) and T3 relative to adjacent sediments. Fluorene (C13H10), used in pharmaceuticals, pesticides, paints and in diodes based of its fluorescence properties, was found in both higher (T2) and lower (T3) concentrations in the tsunami deposits than in the pre- and post-tsunami sediments and soils. Phenanthrene (C14H10), with industrial application in the synthesis of paints, was noticeably common in the tsunami deposits; however, it was also common, although in lower concentrations, in local soils. The linear-fused anthracene (C14H10) is used in dyes, coating material or as an insecticide. It was enriched in tsunami deposits (> 25×) relative to the adjacent sediments and soils in T2, but not in T3. Fluoranthene (C16H10), is a carcinogen pollutant produced by incomplete combustion and was found in higher concentrations in tsunami deposits, in particular in T2 (> 25× higher than in adjacent sediments and soils). The four-ring PAH pyrene (C16H10), used in industrial applications due to its fluorescent properties and a product of incomplete combustion, was enriched in tsunami deposits compared to the pre- and post-event layers. The next analyzed PAH, derived by incomplete combustion of organic matter (e.g., of gasoline, cigarettes, coal combustion, mineral oils and wood), was benz[a]anthracene (C18H12). It was found in increased concentrations in tsunami deposits. Chrysene

(C18H12) originates from the incomplete combustion of organic matter, industrially used in paints and as UV-filters. Higher concentrations of chrysene distinguish the tsunami deposit from adjacent sediments and soils, with especially high concentrations in T2. Triphenylene (C18H12), derived by incomplete combustion of fossil fuels, is enriched in both tsunami deposits of trenches 2 and 3 in comparison with the pre-tsunami soils. Pesticides, in the form of herbicides, insecticides and plant growth regulators, were identified and four indicative representative compounds are presented (Table 7.4). 2,4-Dichlorophenylacetate (2,4-D;

C8H6Cl2O2) is an herbicide and fungicide with a low acute toxicity but leading to serious long-term health risks. It was found in relative high concentration in the pre-tsunami soil of T3 and in the tsunami deposit of T2. The chlorinated herbicide 2,6-dichlorobenzonitrile (C7H3Cl2N) was identified in the soil of G1 near the rice paddies and was enriched in the tsunami deposit of T2, while it was not found in T3.

The fungicide dibenzyl (C14H14) was detected in all samples along the transects, except for the beach (T1), suggesting usage in local agriculture. However, it was only slightly increased in the tsunami deposits. Chlornitrofen (C12H6Cl3NO3) is an herbicide that was widely used in rice paddy fields in Japan between 1965 and 1994 until it was discovered to disrupt the endocrine function of wildlife and humans (Kojima et al., 2003). It was found only in low quantities in the pre-tsunami soil and within the tsunami deposit. Halogenated compounds, mostly industrial and pharmaceutical compounds, were identified in the samples. Four of them are presented here (Table 7.4). The halogenated 4-chlorodiphenylether

(C12H9ClO), used in pharmaceuticals and as an anti-fouling agent, was found in low concentrations in all samples. Dichlorodiphenylether (C12H8Cl2O), a pharmaceutical compound used as an anti-asthmatic

134 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan and in dermatological products, was found in the tsunami deposits sample of T2 to be 27× higher concentrated compared to the pre-tsunami and 18× higher to the post-tsunami sediment. In T3 the contrast is lower, although the concentration is still 5× higher in tsunami deposits than in pre-tsunami soil. Pentachloroaniline (C6H2Cl5N) was generally, in relatively low concentrations, but it was enriched in the tsunami layers. 2,4,6-Trichloroaniline (C6H4Cl3N) an intermediate product of synthetic colors production was also detected and in T3 was enriched in the tsunami deposits.

Fig. 7.5 Delta plots of analyzed anthropogenic markers. Concentrations of pre-tsunami sediments (green) and post-tsunami sediments (red) are plotted relative to the concentrations in the tsunami deposit (blue line =100%) of each trench. For trench 3 (T3) no post-tsunami sediment was present above the tsunami deposit.

To visualize the levels of pollution in the samples of the Sendai Plain with respect to tsunami deposits, delta plots and whisker box plots were used. Delta plots normalized to the concentration of the respective tsunami deposits, reflected both the concentration increases and decreases for trench 2 and 3 (Fig. 7.5). In most cases, the concentrations in the tsunami deposits were higher than in the samples of soils and sediments from pre- and post-tsunami, especially in T2. Among PAHs, the concentrations of fluorene and anthracene in T3 were outliers, as the concentration of fluorene was much higher in the pre-tsunami soils and the concentrations of anthracene were very similar to the concentrations in tsunami deposits. Concentrations of pesticides and halogenated compounds were generally much higher in tsunami

135 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan deposits, with the exception of 2,4,6-trichloroaniline which was found in higher concentrations in the pre- and post-tsunami sediments of T2.

Fig. 7.6 Normalized anthropogenic marker concentrations in trenches T2 and T3 for tsunami deposits (blue bars) and pre- and post-event sediments (dark-gray bars). Whiskers encompass the range of concentrations detected while boxes show 1 σ standard deviations from the mean concentration. Note that y-axes are either linear or logarithmic.

In order to improve data presentation, the pollution by compound groups and key organic compounds found in trenches 2 and 3 are shown in whisker box plots (Fig. 7.6). These plots use both normal and logarithmic scales. For PAHs the total amount of PAHs within the tsunami deposits were higher than in the sediments from before and after the 2011 Tohoku-oki tsunami. PAH pollutants in the post-tsunami sediments were higher than in the pre-tsunami sediments. Similar observations were made for individual PAHs, for instance phenanthrene and pyrene had concentrations of up to 976.4 ng/g (normalized to TOC [%]) in the tsunami deposits. In the case of the sum of pesticides (Fig. 7.6), the tsunami deposits appeared to contain and preserve pesticides in higher concentrations compared to the surrounding pre- and post-tsunami soils. This difference is well supported, for instance, by dibenzyl with relatively high concentrations in the post-tsunami sediments and a maximum concentration in the 2011 tsunami deposit. Among the major types of pesticides, only 2,4-dichlorophenylacetate had a different pattern, with

136 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan highest concentrations in the oldest sediments and lowest concentrations in the youngest sediments (Fig. 7.6). The sum of halogenated compounds was in general higher than that of pesticides and revealed the highest concentration within the tsunami deposit (Fig. 7.6), although, the difference was less pronounced than in other compound groups. However, in the case of specific halogenated compounds such as dichlorodiphenylether and pentachloroaniline the concentrations in the tsunami deposits were several times higher than in the remaining samples. Dichlorodiphenylether can be considered a specific marker of the Sendai Plain tsunami deposits as it occurred in extremely low concentrations in pre- and post- tsunami layers.

7.5 Discussion 7.5.1 Geochemical organic markers on the Sendai Plain In this study a wide variety of biomarkers and anthropogenic markers (Figs. 7.2 and 7.7) were detected in samples from the well-studied Sendai Plain, permitting discussion on their applicability in the context of other studies on the 2011 Tohoku-oki tsunami in this area This allows an evaluation of the significance of biomarkers and anthropogenic markers. As the beach was the major sediment source for tsunami deposits within at least 1-2 km inland from the shoreline (Szczuciński et al., 2012), the concentration of biomarkers and anthropogenic markers in beach sediments serves as a reference point. Beach sediments for the most part had low concentrations of biomarkers and anthropogenic markers. However, a marine dominance of short-chained n-alkanes distinguishes the beach from all other sampled environments. In addition, the specific biomarker nonanoic acid indicates the presence of vegetation of thorny plants that stabilize coastal dunes and are typical for this environment (e.g., Samejo et al., 2013; Sridhar and Niveditha, 2014). Trench T2 located within the first kilometer from the coast and east of the Minami-Teizan Canal contains a sandy tsunami deposit as described by Szczuciński et al. (2012). As the organic content increases inland (Chagué-Goff et al., 2012a) so do the concentrations of terrestrial biomarkers and anthropogenic markers. A likely marine input or beach source of the tsunami deposit is reflected by n-alkanes, with still dominant terrestrial characteristics, but an increased concentration of short-chained n-alkanes compared to pre- and post-tsunami sediments, matching observations by Shinozaki et al. (2015) about n-alkane distributions and by Chagué-Goff et al. (2012a) about δ13C distributions and C/N ratios. Most biomarkers of the tsunami deposit in trench T2 occur in lower concentrations than in the pre- and post-tsunami sediment. In addition, lower values of TAR, CPI and OED suggest that the beach is the source material. On the contrary, the enrichment in anthropogenic markers and especially of PAHs records the destruction by the tsunami, reflecting possible source areas further inland in urban, agricultural or industrial areas (Fig. 7.7).

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Fig. 7.7 Conceptual model for distribution of anthropogenic chemical compounds in a pre-tsunami setting, during tsunami inundation and in a post-tsunami setting. With concentration differences of three indicative anthropogenic marker (dibenzyl – pesticide; pyrene – PAH; pentachloroaniline – halogenated compound) analyzed samples of each setting. Inundation limit marks the max. distance water reached, limit of tsunami recognition marks the max. distance deposits

can be detected (for comparison see Chagué-Goff et al., 2012a). Model is not to scale. The documented destruction and release of environmental pollutants via the demolition of infrastructure, fires and countless sources, is best captured by the unique helicopter footage of waves travelling over land during the event (e.g., Japanese Coast Guard; referenced by Tappin et al., 2012). The increased presence of pesticides (some exclusively in the tsunami layer; Fig. 7.7) supports the assumption of soil erosion of agricultural land. However, for trench T2, which is located relatively close to the coast, the source of pesticides can be traced back to greenhouse farms located in the trench's vicinity (Fig. 7.1B). An extreme outlier is the relatively high concentration of 2,6-dichlorobenzonitrile, which is restricted or prohibited in many countries and the E.U. (Pohanish, 2015). Further inland at trench T3, Szczuciński et al. (2012) described a less distinctive tsunami deposit, which is mostly silt, and contains local soil and traces of beach and dune sand. The previously described soil erosion and transport across the Sendai Plain can be confirmed by most biomarkers and anthropogenic markers, showing similar concentrations between tsunami deposit and pre-tsunami soil in samples of T3 (Fig. 7.7). However, short-chained n-alkanes present a very distinct marine signature for the tsunami deposit. This can be explained by observations of Chagué-Goff et al. (2012a, 2012c), who report lower salinities in porous sandy tsunami deposits within 1 km from the shoreline, while S and Cl concentrations (even though sharply decreasing landwards of ~4 km) were detectable in fine-grained tsunami deposits. High porosity allowing leaching of biomarkers from sandy tsunami deposits was suggested by Shinozaki et al. (2015), however, as organic compounds are not water-soluble the likely

138 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan sink of compounds can be better explained by degeneration or microbial decomposition, especially of relatively instable short-chained n-alkanes. Our results suggest that these short-chained n-alkanes, similar to inorganic ions (S, Cl) that indicate marine influence (Chagué-Goff et al., 2012a), were highly enriched in the tsunami deposit of T3. This high concentration is linked to two observations: (1) the grain size (as described by Chagué-Goff et al., 2012a) or, in case of organic compounds, the organic carbon content (TOC) control on the presence and preservation of respective compounds; and (2) the long term ponding of seawater after the tsunami (e.g. described by Richmond et al., 2012; Sugawara and Goto, 2012; Chagué-Goff et al., 2012c, 2014; Fig. 7.7) may have contributed to the higher concentrations and preservation of certain biomarkers. Even the influence of the canals (Yashimanri Canal) is observable in trench T3, based on the high concentrations of mid-chain-length n-alkanes, representing freshwater macrophyte (as described by Szczuciński et al., 2012). Results of n-alkanes suggest the source of freshwater representing n-alkanes in pre-tsunami soils is related to seasonal flooding of local rice paddies with the water from the irrigation canal. Tsunami deposits reflect the increased marine input during inundation with the erosion and mixture of freshwater canal sediments based on the n-alkane results. This is corresponding to results of Szczuciński et al. (2012) who associated the source tsunami deposits of the 1-2 km inundation zone west of the Minami-Teizan Canal to be a mixture of decreased input from beach and dune, local soils and canal sediments, based on grain size distributions and the presence of freshwater-brackish microfossils in the tsunami deposit. Also, Chagué- Goff et al. (2012a) observed based on δ13C and C/N ratios the mixture of marine an terrestrial organic matter being entrained and deposited by the tsunami. Anthropogenic markers indicate, on the one hand, contamination of the pre-tsunami local soil with PAHs and the herbicide 2,4-dichlorophenylacetate. On the other hand, PAHs and especially halogenated industrial compounds show an increase in the tsunami deposit indicating local destruction and distribution of environmental pollutants from industrial areas across the Sendai Plain due to the tsunami inundation (Fig. 7.7).

7.5.2 Implications and applicability of organic compounds Prior studies (especially Chagué-Goff et al., 2012a, 2012c and Shinozaki et al., 2015) on geochemical characteristics of the 2011 Tohoku- oki tsunami broadened the accessible information about the tsunami from its deposits. Similar to Chagué-Goff et al. (2012a) and Shinozaki et al. (2015) who extended the proxy of biomarkers to the well-studied inorganic proxies along the airport transect on the Sendai Plain, our results contribute a spatial analysis of biomarkers and the introduction of anthropogenic markers. Few studies carrying out organic analyses have been conducted on tsunami deposits before the 2011 Tohoku-oki tsunami. Following the 2004 Indian Ocean tsunami, Tipmanee et al. (2012), Pongpiachan et al. (2013), Pongpiachan (2014) and Pongpiachan and Schwarzer (2013) used PAHs to identify backwash deposits in the nearshore offshore area of the Andaman Sea. While these studies were important steps towards the introduction of anthropogenic marker to tsunami research, they were lacking the clear identification of the sediments as being derived by the tsunami, as well as a comparison of

139 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan concentrations between tsunami deposits and prior contamination. These studies all used surface grab samplers, which do not allow for a description of sediment stratigraphic and layer-specific sampling. On the contrary, the first tsunami studies utilizing biomarkers (e.g., Alpar et al., 2012; Mathes-Schmidt et al., 2013) reported on their capability to identify and characterize paleo-tsunami deposits. The analyzed compounds were (due to their age) limited to the differentiation between marine and terrestrial origin, which was sufficient for tsunami identification but not to gain additional information about the complex behavior during run-up or backwash. In comparison to former studies we were able to show that during tsunamis, the large amounts of water and sediments transferred inland contain natural (biomarker) and anthropogenic organic compounds. These compounds are transported in various forms - adsorbed on mineral grains or organic matter, or as free substances in water. During the tsunami, compounds may be released from sediment and soil erosion, as well as from damage of infrastructure and industry. A portion of the compounds is ultimately buried with the tsunami deposits. Thus, the results allow us to be the first to confirm the findings of Shinozaki et al. (2015) at a single location in the Sendai Plain. The results also confirm, with a new proxy, observations of soil erosion by Richmond et al. (2012) and Szczuciński et al. (2012). Limitations of both inorganic and organic geochemical proxies in tsunami research have previously been documented (Chagué-Goff et al., 2017; Shinozaki et al., 2015; Bellanova et al., 2019). Application limitation caused by an insufficient supply of anthropogenic markers due to a remote location as described by Bellanova et al. (2019) analyzing anthropogenic markers of tsunami deposits in Hawaii, is not a factor for the Sendai Plain. The preservation potential of organic compounds is of importance for analysis, especially if compared to inorganic analyses. Chagué-Goff et al. (2012a) documented inorganic markers (salts - chlorides and sulphates) that almost covered the entire inundation distance of the 2011 Tohoku-oki tsunami at the Sendai Plain. While chlorides and sulphates were better preserved in mud than in sandy deposits their preservation was often limited to a few months after the tsunami (Chagué-Goff et al., 2012a, 2012c). However, their transformation to organic form lead to a better preservation in fine-grained organic-rich sediments (Chagué-Goff et al., 2012a). Biomarkers showed great preservation potential based upon their detectability and capability of identifying paleo-tsunami deposits in the sedimentary record of Dalaman delta (Turkey; Alpar et al., 2012) and the Thracian coast (Greece; Mathes-Schmidt et al., 2013). A good preservation of anthropogenic markers was documented by Bellanova et al. (2019) in historic tsunami deposits from the Kahana Valley (Hawaii). Organic anthropogenic compounds are generally persistent or create persistent metabolites as degradation products (Bellanova et al., 2019). However, these authors state that preservation and occurrence of anthropogenic markers is better, the younger a deposit is and if the input of pollutants was local. Nevertheless, anthropogenic markers are not being designed to identify and study paleo-tsunamis in the sedimentary record. Dilution effects and flushing of compounds by rainfall, as described by Chagué-Goff et al. (2012a, 2014) do not affect organic components significantly as they are not water-soluble. Leaching of organic

140 Publication – Application of anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku- oki tsunami deposits on Sendai Plain, Japan compounds was nonetheless described in porous sands (Shinozaki et al., 2015). Though our results suggest that some organic compounds have lower concentrations in the tsunami deposit at certain sites or depths, we attribute this to their limited availability (i.e. by a point source). Moreover, in tsunami deposits a lower concentration of a specific compound may be attributed to the mixture of different sediment sources that the tsunami encounters as it moves inland. The beach sample in this case represented a sedimentary and organic geochemical source to be entrained during the tsunami, identified earlier as major source of tsunami sands found inland (Szczuciński et al., 2012), which was enriched in compounds from local sources during the inundation.

7.6 Conclusion This study at a site near Sendai Airport, Japan, that was flooded during the 2011 Tohoku-oki tsunami, examines two types of organic geochemical markers: biomarkers and anthropogenic markers. Our results demonstrate that: (1) the different characteristics of n-alkanes and other biomarkers in tsunami deposits may help in their identification, as suggested by Shinozaki et al. (2015). Moreover, in this work additional biological markers were tested, and (2) anthropogenic markers were shown to be useful in the characterization of modern tsunami deposits. These anthropogenic markers, represented by three main compound groups (polycyclic aromatic hydrocarbons, pesticides, and halogenated compounds), were preserved in tsunami deposits two years after the event. Their concentrations differed significantly from the pre- and post-tsunami background contamination levels due to the tsunami on the Sendai Plain. The studied compounds are capable of differentiating tsunami layers, and they also provide additional information about their origin (e.g., soil erosion, beach sediment source), and environmental information (e.g., agricultural use). Anthropogenic markers have especially great potential in tsunami investigations because of their high-source specificity. Organic markers have relatively good preservation potential, as many compounds are persistent, not water-soluble or sediment-bound compounds that required intensive extraction to be released. With anthropogenic markers, however, there is an ethical hardship. Although they are useful in the identification of recent and historic extreme flooding events, thus potentially helping in the mitigation of future disasters, most anthropogenic markers may pose health-risks as many compounds are xenobiotics. As tsunami research advanced over the last decades so did the methods used to gain more and more information on the past events. The search for new methods for the identification and characterization of tsunami deposits no matter if recent, historic or paleo is crucial. Every piece of new information we gain from event deposits leads us a step further to a better understanding of mechanisms acting during a tsunami. This will help to improve countermeasures and relief efforts.

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7.7 Acknowledgements Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank the head of lab Yvonne Esser for her contribution in analyzing parts of the samples, as well as Kerstin Windeck and Miriam Birx for their support during sample processing and Annette Schneiderwind for her technical support during GC-MS analysis. This study was granted by the German Research Foundation (DFG, RE1361/32-1, SCHW750/22-1). Lastly, we would like to thank Pedro Costa, Catherine Chagué and an anonymous reviewer for their constructive reviews, as well as SeanPaul La Selle for providing invaluable comments in the USGS internal review that substantially improved the paper.

7.8 References Abe, T., Goto, K., and Sugawara, D., 2012. Relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 Tohoku-oki tsunami on the Sendai Plain, Japan. Sedimentary Geology 282, p. 142-150. Aktar, W., Sengupta, D., and Chowdhury, A., 2009. Impact of pesticides use in agriculture: their benefits and hazards. Interdisciplinary Toxicology 2, p. 1-12. Alpar, B., Ünlü, S., Altınok, Y., Özer, N., and Aksu, A., 2012. New approaches in assessment of tsunami deposits in Dalaman (SW Turkey). Natural Hazards 60, p. 27-41. Association of Japanese Geographers, 2011. Map of tsunami inundation reported by Tsunami Damage Team. http://danso.env.nagoya-u.ac.jp/20110311/map/574017Sendaikukou.jpg. Bellanova, P., Frenken, M., Richmond, B., Schwarzbauer, J., La Selle, SP., Griswold, F., Jaffe, B., Nelson, A., and Reicherter, K., 2019. Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i. Sedimentology, DOI: 10.1111/sed.12583 Bianchi, T.S., and Canuel, E.A., 2011. Chemical Biomarkers in Aquatic Ecosystems, Princeton University Press, p. 396. Buettner, A., and Schieberle, P., 2001. Evaluation of key aroma compounds in hand-squeezed grapefruit juice (Citrus paradisi Macfayden) by quantitation and flavor reconstitution experiments. Journal of Agricultural and Food Chemistry 49, p. 1358-1363. Chagué-Goff, C., Andrew, A., Szczuciński, W., Goff, J, and Nishimura, Y., 2012a. Geochemical signatures up to the maximum inundation of the 2011 Tohoku-oki tsunami – Implications for the 869 AD Jogan and other palaeotsunamis. Sedimentary Geology 282, p. 65-77. Chagué-Goff, C., Niedzielski, P., Wong, H.K.Y., Szczuciński, W., Sugawara, D., and Goff, J., 2012c. Environmental impact assessment of the 2011 Tohoku-oki tsunami on the Sendai plain. Sedimentary Geology 282, p. 175-187. Chagué-Goff, C., Wong, H.K.Y., Sugawara, D., Goff, J., Nishimura, Y., Beer, J., Szczuciński, W. and Goto, K., 2014. Impact of tsunami inundation on soil salinisation – up to one year after the 2011 Tohoku-oki tsunami. In: Kontar, Y., Santiago-Fandiño, V., Takahashi, T. (Eds.), Tsunami Events and Lessons Learned: Environmental and Societal Significance. Springer, Dordrecht, p. 193-214.

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Chagué-Goff, C., Szczuciński, W., and Shinozaki, T., 2017. Applications of geochemistry in tsunami research: A review. Earth-Science Reviews 165, p. 203-244. Chagué-Goff, C., Goto, K., Sugawara, D., Nishimura, Y., and Komai, T., 2018. Restoration measures after the 2011 Tohoku-oki tsunami and their impact on tsunami research. In: Santiago-Fandiño, V., Sato, S., Maki, N., Iuchi, K. (Eds.), The 2011 Japan Earthquake and Tsunami: Reconstruction and Restoration, Advances in Natural and Technological Hazards Research 47, p. 229-247. Cranwell, P.A., 1982. Lipids of aquatic sediments and sedimenting particulates. Progress in Lipid Research 21, p. 271-308. Dahanayake, K., Kulasena, N., Ravi Prasad, G.V., Dutta, K., and Ray, D.K., 2012. Sedimentological and 14C dating studies of past tsunami events in Southern Sri Lanka. Natural Hazards 63, p. 197-209. Douben. P.E.T., 2003. PAHs: An Ecotoxicological Perspective. John Wiley and Sons Ltd, p. 392. Dsikowitzky, L., 2002. Umweltgeochemische Charakterisierung der niedermolekularen organischen Fracht des Flußsystems Lippe. RWTH Aachen, Germany. unpublished Ph.D. thesis, p. 178 (in German with English abstract). Eglinton, G., and Hamilton, R.J., 1967. Leaf epicuticular waxes. Science 156, p. 1322-1335. Frische, K., Schwarzbauer, J., and Ricking, M., 2010. Structural diversity of organochlorine compounds in groundwater affected by an industrial point source. Chemosphere 81, p. 500-508. Fritz, H.M., Phillips, D.A., Okayasu, A., Shimozono, T., Liu, H., Mohammed, F., Skanavis, V., Synolakis, C.E., and Takahashi, T., 2012. The 2011 Japan tsunami current velocity measurements from survivor videos at Kesennuma Bay using LiDAR. Geophysical Research Letters 39, L00G23, DOI: 10.1029/2011GL050686. Goto, K., Chagué-Goff, C., Fujino, S., Goff, J., Jaffe, B., Nishimura, Y., Richmond, B., Sugawara, D., Szczuciński, W., Tappin, D.R., Witter, R. and Yulianto, E., 2011. New insights of tsunami hazard from the 2011 Tohoku-oki event. Marine Geology 290, p. 46-50 Goto, K., Chagué-Goff, C., Goff, J., and Jaffe, B., 2012. The future of tsunami research following the 2011 Tohoku-oki event. Sedimentary Geology 282, p. 1-13. Hayashi, S., and Koshimura, S., 2013. The 2011 Tohoku Tsunami Flow Velocity Estimation by the Aerial Video Analysis and Numerical Modeling. Journal of Disaster Research 8, p. 561-572. Heim, S., Ricking, M., Schwarzbauer, J., and Littke, R., 2005. Halogenated compounds in a dated sediment core of the Teltow canal, Berlin: Time related sediment contamination. Chemosphere 61, p. 1427-1438. Hoffman, E.J., Mills, G.L., Latimer, J.S., and Quinn, J.G., 1984. Urban runoff as a source of polycyclic aromatic hydrocarbons to coastal waters. Environmental Science Technology 18, p. 580-587. Jaffe, B.E., Goto, K., Sugawara, D., Richmond, B.M., Fujino, S., and Nishimura, Y., 2012. Flow speed estimated by inverse modeling of sandy tsunami deposits: results from the 11 March 2011 tsunami on the coastal plain near the Sendai Airport, Honshu, Japan. Sedimentary Geology 282, p. 90-109.

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Jagodzinski, R., Sternal, B., Szczucinski, W., Chagué-Goff, C., and Sugawara, D., 2012. Heavy minerals in the 2011 Tohoku-oki tsunami deposits – insights into sediment sources and hydrodynamics. Sedimentary Geology 282, p. 57-64. Jones, K.C., Stratford, J.A., Tidridge, P., Waterhouse, K.S., and Johnston, A.E., 1989. Polynuclear aromatic hydrocarbons in an agricultural soil: Long-term changes in profile distribution. Environmental Pollution 56, p. 337-351. Kojima, H., Iida, M., Katsura, E., Kanetoshi, A., Hori, Y., and Kobayashi, K., 2003. Effect of a diphenyl ether-type herbicide, chlornitrofen, and its amino derivative on androgen and estrogen receptor activities. Environmental Health Perspectives 111, p. 497-502. MacInnes, B.T., Bourgeois, J., Pinegina, T.K., and Kravchunovskaya, E.A., 2009. Tsunami geomorphology: Erosion and deposition from the 15 November 2006 Kuril Island tsunami. Geology 37, p. 995-998. Mathes-Schmidt, M., Schwarzbauer, J., Papanikolaou, I., Syberberg, F., Thiele, A., Wittkopp, F., and Reicherter, K., 2013. Geochemical and micropaleontological investigations of tsunamigenic layers along the Thracian Coast (Northern Aegean Sea, Greece). Zeitschrift für Geomorphologie 57, p. 5- 27. Minoura, K., Nakaya, S., and Sato, H., 1987. Traces of tsunamis recorded in lake deposits. An example from Jusan, Shiura-mura, Aomori. Zisin Journal of the Seismological Society of Japan 40, p. 183- 196 (in Japanese with English abstract). Morton, R.A., Gelfenbaum, G., Buckley, M.L., and Richmond, B.M., 2011. Geological effects and implications of the 2010 tsunami along the central coast of Chile. Sedimentary Geology 242, p. 34- 51. Peters, K.E., Walters, C.C., and Moldowan, J.M., 2005. The Biomarker Guide: Volume 2, Biomarkers and Isotopes in Petroleum Systems and Earth. Cambridge University Press, History, p. 1132. Pilarczyk, J.E., Horton, B.P., Witter, R.C., Vane, C.H., Chagué-Goff, C., and Goff, J., 2012. Sedimentary and foraminiferal evidence of the 2011 Tōhoku-oki tsunami on the Sendai coastal plain, Japan. Sedimentary Geology 282, p. 78-89. Pohanish, R.P., 2015. Sittig's Handbook of Pesticides and Agricultural Chemicals 2nd Edition, Elsevier, p. 1006. Pongpiachan, S., 2014. Application of binary diagnostic ratios of polycyclic aromatic hydrocarbons for identification of tsunami 2004 backwash sediments in Khao Lak, Thailand. Thee Scientific World Journal 485068, p. 14. Pongpiachan, S., and Schwarzer, K., 2013. A critical review and evaluation of applying semivolatile organic compounds (SVOCs) as a geochemical tracer to indicate tsunami backwash. Science of Tsunami Hazards 32, p. 236-280.

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Pongpiachan, S., Tipmanee, D., Deelaman, W., Muprasit, J., Feldens, P., and Schwarzer, K., 2013. Risk assessment of the presence of polycyclic aromatic hydrocarbons (PAHs) in coastal areas of Thailand affected by the 2004 tsunami. Marine Pollution Bulletin 76, p. 370-378. Richmond, B., Szczuciński, W., Goto, K., Sugawara, D., Witter, R.C., Tappin, D.R., Jaffe, B., Fujino, S., Nishimura, Y., Chagué-Goff, C. and Goff, J., 2012. Erosion, deposition and landscape change on the Sendai coastal plain, Japan resulting from the March 11, 2011 Tōhoku-oki tsunami. Sedimentary Geology 282, p. 27-39. Samejo, M.Q., Memona, S., Bhanger, M.I., and Khan, K.M., 2013. Essential oil constituents in fruit and stem of Calligonum polygonoides. Industrial Crops and Products 45, p. 293-295. Schiff, K., Diehl, D., and Valkirs, A., 2004. Copper emissions from antifouling paint on recreational vessels. Marine Pollution Bulletin 48, p. 371-377. Schneider, J.L., Chagué-Goff, C., Bouchez, J.L., Goff, J., Sugawara, D., Goto, K., Jaffe, B., and Richmond, B., 2014. Using magnetic fabric to reconstruct the dynamics of tsunami deposition on the Sendai Plain, Japan - The 2011 Tohoku-oki tsunami. Marine Geology 358, p. 89-106. Schwarzbauer, J., and Jovančićević, B., 2016. Isoprenoids. In: Schwarzbauer, J., and Jovančićević, B. (Eds.), From Biomolecules to Chemofossils. Fundamentals in Organic Geochemistry, 2016. Springer, Cham, p. 27-76. Schwarzbauer, J., Littke, R. and Weigelt, V., 2000. Identification of specific organic contaminants for estimating the contribution of the Elbe river to the pollution of the German Bight. Organic Chemistry 31, p. 1713-1731. Schwarzbauer, J., Stock, F., Brückner, H., Dsikowitzky, L., and Krichel, M., 2018. Molecular organic indicators for human activities in the Roman harbor of Ephesus, Turkey. Geoarchaeology 33, p. 498- 509. Sekine, R., 2016. Agricultural damage in the Sendai Plan and the road to recovery. In: Karan, P.P., Suganuma, U. (Eds.), 2016. Japan after 3/11: Global Perspectives on the Earthquake, Tsunami and Fukushima Meltdown. University Press of Kentucky, Lexington, pp. 477. Shinozaki, T., Fujino, S., Ikehara, M., Sawai, Y., Tamura, T., Goto, K., Sugawara, D. and Abe, T., 2015. Marine biomarkers deposited on coastal land by the 2011 Tohoku-oki tsunami. Natural Hazards 77, p. 445-460. Shinozaki, T., Sawai, Y., Hara, J., Ikehara, M.,Matsumoto, D., and Tanigawa, K., 2016. Geochemical characteristics of deposits from the 2011 Tohoku-oki tsunami at Hasunuma, Kujukuri coastal plain, Japan. Island Arc 25, p. 350-368. Sindern, S., Lima, R.F.S., Schwarzbauer, J., and Petta, R.A., 2007. Anthropogenic heavy metal signatures for the fast growing urban area of Natal (NE-Brazil). Environmental Geology 52, p. 731- 737.

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Sousa, A.C.A., Pastorinho, R.M., Takahashi, S., and Tanabe, S., 2013. Organotin compounds from snails to humans. In: Lichtfouse, E., Schwarzbauer, J., and Robert, D. (Eds.), 2013. Pollutant Diseases, Remediation and Recycling. Springer, Cham, p. 215-275. Sridhar, K.R., Niveditha, V.R., 2014. Nutritional and bioactive potential of coastal sand dune wild legume Canavalia maritima (Aubl.) Thou.- an overview. Indian Journal of Natural Products and Resources 6, p. 107-120. Sugawara, D. and Goto, K., 2012. Numerical modeling of the 2011 Tohoku-oki tsunami in the offshore and onshore of Sendai Plain, Japan. Sedimentary Geology 282, p. 110-123. Sugawara, D., Goto, K., Imamura, F., Matsumoto, H., and Minoura, K., 2012b. Assessing the magnitude of the 869 Jogan tsunami using sedimentary deposits: Prediction and consequence of the 2011 Tohoku-oki tsunami. Sedimentary Geology 282, p. 14-26. Szczuciński, W., 2020. Postdepositional changes to tsunami deposits and their preservation potential. In: Engel, M., Pilarczyk, J., May, S.M., Brill, D., Garrett, E., (Eds.), Geological Records of Tsunamis and Other Extreme Waves. Elsevier, DOI: 10.1016/B978-0-12-815686-5.00022-5. Szczuciński, W., Kokociński, M., Rzeszewski, M., Chagué-Goff, C., Cachão, M., Goto, K., and Sugawara D., 2012. Sediment sources and sedimentation processes of 2011 Tohoku-oki tsunami deposits on the Sendai Plain, Japan - Insights from diatoms, nannoliths and grain size distribution. Sedimentary Geology 282, p. 40-56. Takashimizu, Y., Urabe, A., Suzuki, K., and Goto, Y., 2012. Deposition by the 2011 Tohoku-oki tsunami on coastal lowland controlled by beach ridges near Sendai, Japan. Sedimentary Geology 282, p. 124-141. Tappin, D.R., Evans, H.M., Jordan, C.J., Richmond, B., Sugawara, D., and Goto, D., 2012. Coastal changes in the Sendai area from the impact of the 2011 Tōhoku-oki tsunami: Interpretations of time series satellite images, helicopter-borne video footage and field observations. Sedimentary Geology 282, p. 151-174. Tashiro, Y., and Kameda, Y., 2013. Concentration of organic sun-blocking agents in seawater of beaches and coral reefs of Okinawa Island, Japan. Marine Pollution Bulletin 77, p. 333-340. Tipmanee, D., Deelaman,W., Pongpiachan, S., Schwarzer, K., and Sompongchaiyakul, P., 2012. Using Polycyclic Aromatic Hydrocarbons (PAHs) as a chemical proxy to indicate Tsunami 2004 backwash in Khao Lak coastal area, Thailand. Natural Hazards and Earth System Sciences 12, p. 1441-1451. Ünlü, S., Alpar, B., Altınok, Y., and Özer, N., 2012. Rapid coastal changes and tsunami impacts at the Patara Harbour (Turkey). Proceedings of the International Conference. Land-Sea Interaction in the Coastal Zone LANDSI-2012, Jounieh, Lebanon, p. 411-418. Zavala-Sánchez, M.A., Pérez-Gutiérrez, S., Pérez-González, C., Sánchez-Saldivar, D., and Arias- García, L., 2008. Antidiarrhoeal Activity of Nonanal, an Aldehyde Isolated from Artemisia ludoviciana. Pharmaceutical Biology 40, p. 263-268.

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8 Resume Methodological development of organic markers as an identification proxy of tsunamites preserved in the sedimentary record combined with the proof-of-concept application by comparing this new proxy to standard techniques (sedimentary and inorganic geochemistry), to test the potential and to provide new insights into tsunami research are the fundamental aim of this doctoral thesis. With the multi-proxy results of the three main study areas in Portugal, Hawaii and Japan (Chapters 4-7) the capabilities and potential of sedimentary standard techniques, biomarkers and anthropogenic markers have been examined.

8.1 Applicability and preservation potential of organic markers Throughout this doctoral thesis organic markers, both anthropogenic markers and biomarkers, have been tested in two contrasting sedimentary and environmental settings. The Kahana Valley (Hawaii) represents a rural and natural environment, while the Sendai Plain (Japan) is densely populated and exposed to strong anthropogenic influence (Fig. 8.1). A direct comparison between field sites remains difficult, similar to almost all techniques applied in tsunami research. This is mainly attributed to the ever-changing face of tsunami inundation and tsunamites, both strongly dependent on local settings, such as bathymetry, topography, sediment sources and supply, as well as anthropogenic modifications (e.g., Morton et al., 2007; Peters and Jaffe, 2010; Fritz et al., 2011). These local factors need to be taken into consideration for the study of organic geochemical parameters in tsunami deposits. Concentrations are strongly influenced by the background concentration or pollution due to soil and sediment erosion, destruction-based pollutant emission during the event (see Fig. 8.1), and post-event anthropogenic modifications, namely component migration, soil removal and clean-up measures. Whilst remaining a difficult task, the results and observations from the Kahana Valley and the Sendai Plain led to general observations regarding the applicability of organic proxies. Despite expected difficulties in assessing the concentration and distribution of anthropogenic markers in natural settings (Fig. 8.1), compounds were detected in significant concentrations enabling indicative observations. In particular polycyclic aromatic hydrocarbons (PAHs) remained in relatively high concentrations in the soil presenting a vertical distribution pattern in the obtained cores (see Chapter 6). Other anthropogenic markers were limited as the Kahana Valley has not been strongly anthropogenically influenced and population is still rural. Nonetheless, biomarkers (e.g., n-alkanes) are the favorable organic geochemical proxy for tsunami investigations in natural or pre-industrial environments. On the contrary, the 2011 Tohoku-oki tsunami deposits of the Sendai Plain present high concentration of both biomarkers and anthropogenic markers (see Chapter 7; Fig. 8.1). The partly sharp contrasts to background sedimentation indicate the investigative potential of organic-geochemical proxies for research on modern tsunami deposits in urban or populated coastal settings.

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Fig. 8.1 Conceptual model of erosion, transport, distribution and deposition of sediments and organic-geochemical compounds/ pollutants during tsunami inundation and backwash in rural environments (left – Kahana Valley) and urbanized environments (right – Sendai Plain).

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The applicability of organic-geochemical markers faces the same cost-benefit consideration as other proxies. While most sedimentary and inorganic methods are relatively easy in terms of sampling, sample conservation, laboratory processing and result interpretation, organic geochemical applications are more complex. Samples need to be taken and preserved contamination free and stored at low temperatures to avoid microbial alterations (see Chapters 6 and 7). Laboratory processing is time consuming (several weeks until first results and limited samples processable) and resource-intensive (e.g., GC-MS, solvents, etc.) followed by elaborate data analysis based on multiple non-target screenings to ensure the detection of all indicative compounds. These need to be considered when applying organic geochemistry on tsunami samples, although, the scientific output and new insights (discussed in the next Chapter) deems the costs worth it. As all used methods for the identification and characterization of tsunami deposits, organic-geochemical markers cannot and are not designed to act as a stand-alone proxy for a sufficient identification. Therefore, first applications and the proof-of-concept in this doctoral thesis have been carried out at locations with either complementary studies or known and documented deposits of tsunami origin. Organic geochemistry, similar to inorganic geochemical applications, will likely remain a supplementary proxy, despite its analytical and investigative potential, until sustainable establishment in the scientific community. General preservation of organic markers at the studied sites show relatively good preservation. Some compounds of rather anthropogenic influence (e.g., PAH congener) have been found in deeper layers in the Kahana Valley, thus a limited amount of infiltration and compound transport cannot be fully excluded. A connection between compound preservation and sediment grain size or composition needs to be further discussed. In most geochemical studies, both inorganic and organic, normalization to TOC or organic matter is used to correct for grain size distribution and the resulting effects. Many components present higher concentrations in the fine fraction (mud/ silt; e.g., Chagué-Goff et al., 2002; Chagué-Goff et al., 2012a) or diluted and washed out signatures in coarse sediments (e.g., Chagué-Goff et al., 2012b; Mathes-Schmidt et al., 2013; Shinozaki et al., 2015; Bellanova et al., 2019). While Van der Weijden (2002) indicates that normalization can lead to incorrect or misleading correlations between normalized elements. Its benefit to correct the grain size due error or imbalance in concentration lead to the almost exclusive use of normalization in geochemical characterization of tsunami deposits (e.g., Chagué-Goff, 2010; Chagué-Goff et al., 2012a,b; Tipmanee et al., 2012; Shinozaki et al., 2015; 2016; Bellanova et al., 2019; Bellanova et al., 2020). This proves that the interpretation of geochemical signatures is not as straightforward as simple sedimentological methods and an understanding of geochemical affinities, effects and preservation is required as Chagué-Goff (2010) correctly concluded. The working hypothesis of this thesis, that organic compounds are marked by a higher preservation potential over inorganic proxies (such as water-leachable ions, salts; see also Chagué-Goff et al., 2017), has been confirmed by the results of studies conducted in both environmental settings (natural vs. urban). The promising application of biomarker on historic deposits has been adequately proved by Mathes- Schmidt et al. (2013) and Schwarzbauer et al. (2018). The application of anthropogenic markers on

149 Resume historic and paleo-tsunami deposits may be limited to biomarkers hinting towards an anthropogenic use or influence, as prior to industrialization only little to no complex or synthetized compounds were emitted. A still promising anthropogenic related organic proxy are the PAH congener which may be traced back further in time than other organic anthropogenic-related compounds, based on their formation processes. The consideration of preservation potential and the primary occurrence of compounds is critical for historic and paleo-tsunami studies, because most of the coastal areas affected by tsunamis (especially across the Pacific) were not colonialized or significantly populated until in relatively recent history, resulting in incomplete or lacking tsunami records. A Holy Grail in tsunami research remains the difficult task to identify tsunami deposits in the geological record with unequivocal criteria that differentiate them from other events (like storms). Although many methodological approaches have been applied, to date it is not possible to definitively differentiate tsunami sediments without written or visible records of their formation. Because tsunami deposits vastly differentiate from event to event or have a different appearance (e.g., thickness, distribution, composition, microfossil content, internal structures, etc.) along a coastline affected by the same event, it remains intricate to definitively identify tsunami deposits. This is critical, especially in the field of paleo-tsunami research, where no written or eye-witness accounts of the deposit formation exist. Organic-geochemical proxies may contribute to a positive identification of event deposits in general but limit the same capability in definite characterizing a deposit as of tsunami origin. Thus, the scientific discussion regarding tsunami vs. storm origin of respective deposits will remain, likewise the search for an unequivocal proxy for a positive identification will likely continue.

8.2 Identification potential and new insights Sedimentological standard proxies are ubiquitous for the identification of tsunami deposits. To extend the present identification tool kit, it must be tested before the addition of promising but cost intensive proxies. Therefore, the Boca do Rio Valley (Portugal – Chapter 4) sets a research area to test standard sedimentary methods and inorganic geochemistry to its full extend. Reconstructing the environmental changes and depositional facies of the past ~4000 years. uncovered the natural hazard history of the Gulf of Cadiz. The AD 1755 Lisbon tsunami was positively detected, dated and characterized as expected. A yet unknown event deposit (older than 985-1147 cal. CE) was found with sedimentological evidences and characterized by micropaleontology and inorganic geochemistry (XRF – detailed in Chapter 4). As a result of this, the Portuguese tsunami catalogue (Baptista and Miranda, 2009) was extended with a new entry, which can be assigned to similar event evidence for an event at 881 CE along the Spanish coastal areas in the Gulf of Cadiz (Morales et al., 2008; Reicherter et al., 2010). This positive identification of a new tsunami deposit consolidates why standard sedimentological proxies are the most common used due to their ease of use during field work and by providing fast results. However, it arouses the question: Why this deposit was not detected prior to the study in this doctoral thesis (Chapter 4) as the Boca do Rio Valley is the best-studied location regarding tsunamis in the Gulf of

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Cadiz? The low physical preservation potential of small scale events may be the major reason, but is compensable by inorganic geochemistry. A problem which is not discussed in the tsunami community is the limited study at field sites considered ‘difficult’ with no or little visual evidence for tsunami deposits. In part this may be a reason for the still restrictive research and identification of tsunami deposits in the offshore domain. This is not questioning the powerfulness and the past research providing the fundament of today’s tsunami research; observations only hint towards the limitation of these proxies and the declared need for new investigative proxies (e.g., by Goff et al., 2012; Chagué-Goff et al., 2011; 2015; 2017). For the Boca do Rio Valley further research is evidently required and the application of organic geochemistry (mainly biomarker) might provide valuable insight into the newly identified tsunami deposit and potentially uncovering further event deposits from the past. Following the remarkable evidence found at Boca do Rio Valley solely by standard tools, a step further towards the implementation and testing of organic geochemistry was accomplished at Kahana Valley (Hawaii – Chapter 5 and 6). Sedimentological and stratigraphic evidence combined with radiocarbon dating across three field sites on different Hawaiian Islands discovered numerous previously unidentified prehistoric tsunami deposits (La Selle et al., 2019a). The marine carbonate sand layers have been connected via ‘Oxcal’-age modelling to far-field tsunamis originating in the Aleutian Islands. Alternative potential tsunami source areas, such as Kamchatka (Nanayama et al., 2003; Pinegina et al., 2003; Bourgeois et al., 2006), Peru-Chile (Atwater et al., 2013; Kempf et al., 2017) and Cascadia (Priest et al., 2017), cannot be ruled out without further tsunami modeling and extension of the age models. Following the event deposits sudden environmental changes have been observed in the sediments by the presence of Tryonia porrecta shells. The lack of these shells in the stratum predating the tsunami layer indicates the erosion, transport and redeposition of allochthonous sediment by the tsunami. In transported allochthonous sediments from stream channels, lagoons, fishponds and (or) taro fields into marsh environments during the tsunami, Tryonia found environmental conditions to colonize. Storms and river floods of the marshy lowlands have been discussed as potential causes of the event deposits. River floods have been excluded based on the marine origin of the carbonate sands and storms (while present in Hawaii – e.g., Hurricane Iniki 1992; Fletcher et al., 1995) were neglected as the nearshore shallow water reef protects the valley from storm waves inundating the bay. After primary identification of the Kahana Valley event deposits via standard sedimentary proxies (Chapter 4), the continuing focus was on the organic geochemical characterization of aforementioned tsunami deposits. While tsunamis affecting the Kahana Valley predate the industrial era, a significant and characteristic distinction from background sediments was possible based on anthropogenic markers (see Chapter 6). It is noteworthy that the study presented by Bellanova et al. (2019) presents the first application of organic anthropogenic markers on tsunami deposits. By examination of potential and limitations of organic markers, new insights (e.g., petrogenic ratios, source specificity of compounds) were discussed and effects during and after an event (e.g., compound migration, dilution, preservation) evaluated. Prior inorganic geochemical studies by Chagué-Goff et al. (2012) on Hawaiian tsunami

151 Resume sediments resulted in mixed results. Many inorganic components were washed out of the coarse and sandy tsunami deposits, corrupted by occasional saltwater intrusion through and over the sand berm or were potentially misinterpreted by the presence and input of element-rich volcanic black sand (Chagué- Goff et al., 2012). Similar observations were made for PAHs in the Kahana Valley. The volcanic origin of PAHs is difficult to assess. Because the islands are mainly composed of basaltic rock, small basalt fragments and black sand were found across sediments of the field site. The preservation of PAHs in volcanic rocks and their release into the surrounding sediments (e.g. by weathering - Tobiszewski and Namiesnik, 2012) remains a matter of discussion. Diagnostic PAH ratios suggest a mixture of natural combustion and petrogenic sources, although, the primary source for the Kahana Valley remains natural decomposition and combustion. For the Kahana Valley multiple input sources for PAHs and pesticides were determined, such as the Huilua Fishpond operating for centuries, the past agricultural use of the floodplain, increased settlement and the prior military use of the valley. This way a geochemical record of the changing usage of the valley and the impact of events like tsunamis was established. Even though anthropogenic markers have high source specificities, it can be challenging to determine source locations, especially in areas with relatively little anthropomorphic disturbance. Nonetheless, this first application of anthropogenic markers on tsunami deposits indicates their potential, while still remaining a complementary proxy in its application to the initial identification by La Selle et al. (2019). At the Kahana Valley, which is industrially underdeveloped, tsunamis showed a capability of transporting organic anthropogenic markers, whilst only small quantities were available. Under these circumstances an additional analysis of biomarkers is recommended by Bellanova et al. (2019). Testing the organic geochemistry as an identification proxy, the proof-of-concept study (Chapter 7) at the Sendai Plain detected a wide variety of biomarkers and anthropogenic markers. A limitation in the applicability caused by an insufficient supply of anthropogenic markers due to a remote location as described for the Kahana Valley (Bellanova et al., 2019) can be neglected for the Sendai Plain. Tsunami deposits reflected a strong marine signal of short-chained n-alkanes while still presenting a dominance of terrestrial long-chained n-alkanes. TAR, CPI and OEP, indicative biomarker ratios (Chapter 7), all present distinguishing characteristics for n-alkane biomarker results, confirming biomarker results of Shinozaki et al. (2015). Of the detected and applied biomarkers, n-alkanes seem the most promising as they provide answers to one of most pressing questions: the marine signature of tsunami deposits in terrestrial sedimentary environments (see Fig. 7.3). Thus, n-alkane can be used as an organic equivalent with (possibly) better preservation potential to inorganic geochemistry (e.g., salts, water-leachable ions). The documented leaching of biomarkers (i.a., n-alkanes) from sandy tsunami deposits (Shinozaki et al., 2015) could not be confirmed. While organic compounds are little to insoluble in water, the reasoning for a sink of biomarkers by Shinozaki et al. (2015), the porosity of the sediment, was not confirmable. It is much likelier, that biomarker concentrations are altered by degeneration or microbial decomposition, especially of relatively instable short-chained n-alkanes. On the contrary, our results present well-preserved indicative distribution of organic proxies years after the tsunami linking to two

152 Resume main observations: (1) the grain size (as described by Chagué-Goff et al., 2012a) and the organic carbon content (TOC) control the presence and preservation of respective compounds; and (2) the long-time ponding of seawater (e.g. described by Richmond et al., 2012; Sugawara and Goto, 2012) may have contributed to higher concentrations and preservation of organic proxies at the Sendai Plain. Furthermore, anthropogenic markers are higher concentrated and in broader variety at the Sendai Plain compared to the Hawaiian samples. Preexisting pollution with pesticides, halogenated compounds and PAHs is indicated by pre-tsunami deposits. Nonetheless, concentrations suggest the release of additional pollutants into the environment by destruction of infrastructure during the tsunami. The documented release of environmental pollutants by the destruction, fires and countless sources, is best emphasized by the unique helicopter footage of the inundating waves captured during the event. Another source of pollutants may be the release from sediment and soil erosion. This is corresponding to results of Szczuciński et al. (2012) who associated the source tsunami deposits of the 1-2 km inundation zone to be a mixture of decreased input from beach and dune, local soils and canal sediments. Most biomarkers and anthropogenic markers indicate soil erosion and the distribution across the Sendai Plain shows similar concentrations between tsunami and pre-tsunami deposit in samples. However, the proportion of destructively released anthropogenic proxies is not neglectable. As major point-sources for release of pesticides, agricultural sites and greenhouse farms in the vicinity of sampled trenches were located. Altogether, the proof-of-concept study presents promising results in confirming, with a new proxy, observations of biomarker distributions by Shinozaki et al. (2015) as well as soil erosion by Richmond et al. (2012) and Szczuciński et al. (2012). Organic geochemistry in tsunami research can be outlined as one of the more promising proxies in identifying and characterizing tsunami deposits for the years to come. Capable of providing additional information on tsunamites of the present and the past, the high preservation potential of organic compounds is one of the tools strongest assets. Inorganic geochemistry proved to be a valuable complementary proxy in the past, despite the limited preservation of some markers leading to a significant disadvantage, especially in association of the recent prominence of paleo-tsunami research. It must be noted that the best results for anthropogenic markers are expected in fine-grained and organic- rich recent tsunami sediments along urbanized coastlines, as displayed for the Sendai Plain, Japan (Fig. 8.1). As presented rural areas still feature reasonable concentrations of anthropogenic proxies for a positive identification of event layers, which might not be the case for extremely remote locations, such as the Aleutian Islands or Kuril–Kamchatka, without any prior population. Background contamination prior to the tsunami always needs to be considered, as soil erosion has shown to be an effective way of redistributing preexisting anthropogenic markers during an event, but a strong influence of local emission sources affected by destruction remains. At these settings the source specificity of certain anthropogenic markers may be used in the future to determine exact locations of pollutant release and potentially give insight into direction and movements of the inundation and the backwash.

153 Resume

Organic geochemistry shows promising evidence of detecting not only tsunamites in the sedimentary record, but to track the telltale organic signature of the backwash (Figs. 3.2 and 8.1). This is groundbreaking, as to date no method of the proxy toolkit, with the exception of few found but little discussed sedimentary or micropaleontological features, such as current ripples or cross-lamination (e.g., Paris et al., 2007; Bahlburg and Spiske, 2012; Goto et al., 2012; Takashimizu et al., 2012), is capable of distinctively describing backwash deposits and distinguish them from inundation signatures. The backwash is hardly considered in tsunami research, but the erosive potential is underestimated and the little research into backwash neglects almost half of the processes during a tsunami flooding coastal lowlands. The backwash must be considered especially in offshore tsunami research, but there has been limited research into determining complex backwash processes. This might change with the potential high-resolution insights promised by organic proxies, biomarkers and anthropogenic markers. The limit of tsunami recognition has long been restricted to sandy deposits. Following the findings by Chagué-Goff et al. (2012a) that only 60% of the inundated distance in the Sendai Plain was covered with deposits composed of sandy sediments. This research represents significant improvements to existing research because most paleo-tsunami studies base their analysis exclusively on sandy deposits, which do not represent the full tsunami event. Inorganic proxies already showed that they are capable of recognizing 95% of the inundation distance by analyzing respective samples. They indicate low preservation when they were only limited or non-detectable anymore a few months after the 2011 Tohoku-oki tsunami (Chagué-Goff et al., 2012a). In that, organic markers present their full capabilities, not being as easily washed-out or leached out of the sediment and therefore having a higher preservation potential. Thus, organic markers present a potential proxy for future analysis of ‘invisible’ tsunami deposits beyond the visible sand limit, and therefore are a valuable addition to the paleo-tsunami identification toolkit. The use of standard proxies is indispensable and proved numerous times to deliver upon the need to identify tsunami deposits in the sedimentary record (as shown in Chapter 4). With advancing sampling and analysis techniques, needs in identification and characterization will change. This will lead to the need of additional, high-resolution proxies providing significantly new but mainly site-specific information on the hydrodynamic processes associated with tsunamis as organic geochemical proxies applied in this doctoral thesis confirmed to be capable of. New techniques and applications, such as biomarker and anthropogenic marker, do not intend to replace veteran tsunami identification techniques, rather to complement them in closing the knowledge gap.

154 Conclusion and outlook

9 Conclusion and outlook

9.1 Conclusion Presented and discussed results of this doctoral thesis acknowledge the need for a continuation of research for the investigation of (paleo-) tsunamis in the sedimentary records of coastal areas with a high hazard potential. The acquisition of knowledge about characteristics and extent of modern, historic or paleo-tsunamis is crucial for any hazard mitigation effort, therefore a full identification of all past events is neccessary, which is apparently not the case for all previously studied sites, as presented in this thesis (Chapter 4 and 5). Commonly used sedimentological, micropaleontological and inorganic geochemical proxies are regarded as standard proxies. Nonetheless, in recent years they have reached their detection limits with a shift in scientific focus on paleo-tsunami deposits and the gained knowledge by the 2004 Indian Ocean tsunami and 2011 Tohoku-oki tsunami that visually recognizable sand deposits reach only about 60% of the total inundated distance (Goto et al., 2011; Chagué-Goff et al., 2012a) results in a drastic change of needed analytical tools. While the visual recognition limit is site- and event-specific, it still questions conclusions as well as developed emergency and evacuation plans based solely on the study of sandy historic or paleo-tsunami deposits. In 2011 it emerged that the predecessor of the 2011 Tohoku-oki tsunami was significantly underestimated as maximum extent of the sand deposits is not a well-chosen representation of the minimum inundation extend contrary to previous assumptions (Goto et al., 2011; 2012; Sugawara et al., 2011). This is emphasizing the need of proxies capable to answer these unresolved scientific questions and possibly lead to new discoveries in tsunami research. Geochemistry in its entirety presents novel approaches by shining a bright future on the future paths of investigation into tsunamites. The most recent addition into the analytical toolkit is the organic branch of geochemistry. However, the number of successful applications of organic proxies to investigate tsunami deposits is still countable on one hand. Amongst these, two novel studies have been presented as the core of this doctoral thesis exploring the scope and significance of biomarkers and anthropogenic markers in meeting the present and future needs of tsunami research (Chapters 6 and 7).

In this, the overall work hypothesis of this doctoral thesis – Organic markers, both biomarkers and anthropogenic markers, provide a powerful supplementary approach to sedimentary standard techniques, improving the knowledge on tsunami deposits in the sedimentary records, essential for future mitigation efforts of tsunami hazards – was positively confirmed. Organic marker compounds of recent and historic tsunami events have been identified and quantified at two separate locations with contrasting environmental settings. Results from sedimentological, paleontological and inorganic geochemical results have been compared to organic geochemical characterization of the respective tsunami deposits, were validated and the pre-existing dataset has been extended. Certain technical and analytical limitations of organic geochemical markers have to be taken into consideration, such as special sampling, storage and careful but labor intensive treatment to avoid contamination or alterations, the detection limitations of anthropogenic markers at rural field locations, and potential leaching of

155 Conclusion and outlook certain biomarkers as documented (Shinozaki et al., 2015). While leaching of components has not been confirmed by this doctoral thesis its possibility still should be considered during sample analysis. Based on the recent development and yet limited testing of these proxies they should be used (for now) as supporting methods to other geochemical and sedimentological methods rather than stand-alone proxy methods. On that note organic geochemistry is not designed to act as a stand-alone tsunami identification tool. Nevertheless, for a full establishment of the organic geochemistry in the tsunami community more research and a continuation in broad application on multiple event deposits of different ages and environmental settings is necessary. In summary the following main objectives of this doctoral thesis were successfully met: I) apply organic marker compounds for the identification of recent and historic tsunami events in sedimentary records alongside of sedimentary standard methods.

II) provide a characterization of tsunamites based on specific organic marker compounds (anthropogenic markers and biomarkers).

III) Contrast organic geochemical results with sedimentary evidences and inorganic geochemical applications

IV) evaluate the complementary application of biomarker and anthropogenic markers in their ability of identifying tsunami deposits and their contribution to the existing dataset.

V) build up and establish the organic-geochemical tool for a wide range usage in tsunami research, assessment of spatial inundation distribution and quantitative estimation of recent, historic and prehistoric tsunami impacts.

VI) Identification of yet undiscovered tsunami deposits in the sedimentary record based on multi-proxy analyses.

With the application of standard sedimentary, micropaleontological and inorganic geochemical proxies detecting new insights into known and before unknown tsunami deposits. In times of rising negligence against imposing threats and more frequent climate-induced flooding events, improved coastal protection measures are needed more than ever. However, devastating events in the past have shown that an underestimation, due to lack of knowledge and incomplete assumption, can cause a false sense of protection ultimately endangering thousands of lifes. In attempting to close this and other scientific gaps, organic geochemical proxies present one of the most promising approaches introduced to tsunami research in the last years.

156 Conclusion and outlook

9.2 Outlook While promising a broad applicability and new insights, organic geochemical proxies in tsunami research are still in their infancy. Thus, before take-off basic questions need to be and are planned to be addressed in the near future. Most importantly the connection between grain size, composition and content or distribution of organic proxies in tsunami and non-tsunami deposits need to be explored further. This would tackle the question if leaching or a washing-out effect can be eventually validated or falsified. Therefore, a long-term post-tsunami survey of a recent event should be taken into consideration, monitoring the preservation potential and potential migration effects in coarse versus fine-grained tsunami deposits over the course of days to years. The reasonably presentable number of detected and significant compounds for a single publication is in some ways limited. But a general extension and in-depth analysis of additional, potentially more information providing site-specific compounds should be a main achievement in the future, as is the continuing application in different sedimentary, climatic and populated environments, which all influence local tsunami deposits to a varying degree. Additionally, the temporal effect on preservation of organic proxies, both anthropogenic markers and biomarkers, and their presence and distribution need to be analyzed further in historic and paleo-tsunami settings to gain approval and establishment by the tsunami community. We plan to engage in all of the mentioned above in multiple studies to come. Specifically, we are currently analyzing samples from the Boca do Rio field site (Chapter 4) in order to comprehensively characterize the geochemical footprint of the AD 1755 Lisbon tsunami. Coinciding with the onshore investigations, we conducted an offshore survey with the RV METEOR (M-152) to examine the offshore sedimentary archive for its tsunami record. With a full multi-proxy approach, including sedimentology, micropaleontology, geochemistry (both inorganic and organic) and dating techniques the current tsunami database for Portugal will be provided with an overdue extension. Similarly, the Hawaiian field site of the Kahana Valley will play a role in future enhancement of the organic proxies, as we are currently evaluating results of a broader set of extraction techniques using additional alkaline hydrolysis and pyrolysis to extract chemically bound components from the sediment. These techniques, giving a closer perspective into more persistent and even better-preserved compounds, might lead to the extension of powerful biological organic compound proxies for identification of historic and paleo-tsunami deposits and their in-depths analysis. Scientifically unfortunate is the land clearing and soil removal, as well as the invasive reforestation efforts along the Japanese coastline but especially at the Sendai Plain. The permanent loss of the yet best-studied but now inaccessible tsunami deposits complicates future studies comparing newly developed proxies and test their capability of reproducing existing research result in order to validate their application. However, we were able to conduct field work at the auspicious location of Misawa in Northern Japan. Along the coastal control forest, which got inundated during the 2011 Tohoku-oki tsunami, a grid of 50 coring location was laid and numerous samples for a detailed geochemical analysis

157 Conclusion and outlook have been gathered. Preliminary results and field observations hint towards the detection of the ‘invisible’ tsunami deposit beyond the maximum sand limit. New observations of a potential inflow or outflow deposit comprising of floating woody material has been detected and can be assigned to be part of the tsunami deposit. Further research will be conducted at the field site of Misawa, with a special interest in disclosing the specific sources of anthropogenic pollutants distributed during the tsunami, getting greater insights into the backwash processes and visualizing hydrochemical flow movements of the tsunami across the field site through the detailed grid-sampling. Capturing the bigger picture in flooding events we intent to elevate organic geochemical markers to a higher level. By combining applied markers with in-depths environmental studies and ecotoxicological applications we attempt to overcome limitations of standard proxies. We will not solely study the geochemical signatures of tsunamites but also of other flood events such as storms and river floods. We conducted field surveys along the southeastern coast of India, where all three types of events have occurred and were detected in the sedimentary record. Altogether, there is no ubiquitous tool distinctively differentiating tsunamis from other toxic flood events, however, organic geochemistry has not been taken for consideration so far. In this I am looking forward to the continuation in the development and the application of organic proxies for tsunami identification and characterization, as the applications in this doctoral thesis only scratched the surface of the proxy’s full potential.

158 References

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186

Contribution in publications and additional publications

Contribution in publications and additional publications Peer-reviewed publications

Feist, L., Frank, S., Bellanova, P., Laermanns, H., Cämmerer, C., Mathes-Schmidt, M., Biermanns, P., Brill, D., Costa, P.J.M., Teichner, F., Brückner, H., Schwarzbauer, J., Reicherter, K. (2019) The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal. Sedimentary Geology 389, p. 147-160. Field work 30% Laboratory data acquisition: 10% Evaluation and interpretation: 25% Publication authoring and composition: 65%

La Selle, SP., Richmond, B., Jaffe, B., Nelson, A., Griswold, F., Arcos, B., Chagué, C., Bishop, J., Bellanova, P., Kane, H., Lunghino, B., Gelfenbaum, G. (2019) Sedimentary Evidence of Distant Source Tsunamis in the Hawaiian Islands. Sedimentology, DOI: 10.1111/sed.12623 Field work 30% Laboratory data acquisition: 25% Evaluation and interpretation: 25% Publication authoring and composition: 10%

Bellanova, P., Frenken, M., Richmond, B., Schwarzbauer, J., La Selle, SP., Griswold, F., Jaffe, B., Nelson, A., Reicherter, K. (2019) Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley, O‘ahu, Hawai‘i. Sedimentology, DOI: 10.1111/sed.12583 Field work 100% Laboratory data acquisition: 50% Evaluation and interpretation: 50% Publication authoring and composition: 85%

Bellanova, P., Frenken, M., Reicherter, K., Jaffe, B., Szczuciński W., Schwarzbauer, J. (2020) Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan). Marine Geology, DOI: 10.1016/j.margeo.2020.106117 Field work 0% Laboratory data acquisition: 100% Evaluation and interpretation: 100% Publication authoring and composition: 100%

189 Contribution in publications and additional publications

Additional publications and conference contributions

Peer-reviewed publications

Bellanova, P., Bahlburg, H., and Nentwig, V., Spiske, M., 2016. Test of the microtextural analysis of quartz grains of tsunami and non-tsunami de-posits- an unsuitable method for a valid tsunami identification in Tirúa (Chile). Sedimentary Geology (2016) 343, p. 72-84.

Nentwig, V., Bahlburg, H., Górecka, E., Huber, B., Bellanova, P., Witkowski, A., and Encinas, A., 2018. Multiproxy analysis of tsunami deposits—The Tirúa example, central Chile. Geosphere 14, p. 1067-1086.

Vött, A., Bruins, H.J., Gawehn, M., Goodman-Tchernov, B.N., De Martini, P.M., Kelletat, D., Mastronuzzi, G., Reicherter, K., Röbke, B.R., Scheffers, A., Willershäuser, T., Av-ramidis, P., Bellanova, P., Costa, P.J.M., Finkler, C., Hadler, H., Koster, B., Lario, J., Reinhardt, E., Mathes- Schmidt, M., Ntageretzis, K., Pantosti, D., Papanikolaou, I., Sansò, P., Scicchitano, G., Smedile, A., and Szczuciński, W., 2017. Publicity waves based on manipulated geoscientific data suggesting climatic trigger for majority of tsunami findings in the Mediterranean – Response to ‘Tsunamis in the geological record: Making waves with a cautionary tale from the Mediterranean’ by Marriner et al. (2017). Zeitschrift für Geomorphologie (2018), DOI: 10.1127/zfg_suppl/2018/0547

Conference contributions

Bellanova, P., Bahlburg, H., and Nentwig, V., 2015. Test of the microtextural analysis of quartz grains of tsunami and non-tsunami de-posits in Tirúa (Chile) - an unsuitable method for a valid tsunami identification. AGU-Fall Meeting 2015 - NH33A-1898 (Conference abstract)

Bellanova, P., Schwarzbauer, J., Reicherter, K., Jaffe, B., and Szczucinski W., 2016. Our fingerprint in tsunami deposits – anthropogenic markers as a new tsunami identification tool. AGU-Fall Meeting 2016 – NH009-NH41A-1770 (Conference abstract)

Bellanova, P., Schwarzbauer, J., Reicherter, K., Jaffe, B., and Szczucinski, W., 2017a. Identification of tsunami deposits using organic markers. EGU General Assembly 2017 - EGU2017-8636 – Poster (Wed, 26 Apr, 17:30–19:00, Hall X3, X3.170 - NH5.3/GM12.8/OS5.8/SSP3.14) (Conference abstract)

Bellanova, P., Richmond, B., La Selle, S.P., Griswold, F., Gelfenbaum, G., Jaffe, B., Nelson, A., Schwarzbauer, J. and Reicherter, K., 2017b. Organic geochemical investigation of far-field tsunami. 5th International Tsunami Field Symposium (ITFS), Lisbon - (Public Talk)

190 Contribution in publications and additional publications

Bellanova, P., Jarmulkowicz, D., Eickers, C., Frenken, M., Gökdemir, T., Fischer, N., Schwarzbauer, J., and Reicherter, K., 2018a. Organic-geochemical characteristics of 2011 Tohoku-Oki tsunami deposits in northern Japan. GeoBonn 2018 – Oral Presentation – Session 06a) Natural Hazards: earthquakes, tsunamis, landslides (Conference abstract)

Bellanova, P., Schwarzbauer, J., and Reicherter, K., 2018b. Tracing toxic flood events in sedimentary archives - the potential of organic indicators. Humboldt Kolleg Serbia, 19-22.09.2018 - „Sustainable Development and Climate Change: Connecting Research, Education, Policy and Practice“ (Conference abstract)

Bellanova, P., Frenken, M., Nishimura, Y., Schwarzbauer, J., and Reicherter, K., 2019a. Telltale geochemical signatures of tsunami deposits (Northern Japan). 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

Bellanova, P., Laermanns, H., Feist, L., Frank, S., Mathes-Schmidt, M., Brill, D., Brückner, H., and Reicherter, K., 2019b. The unknown event deposit – a predecessor to the AD 1755 tsunami?. INQUA 2019 Dublin - Coastal and Marine Processes: Sea-level changes from minutes to millennia - P3053 (Conference abstract)

Bellanova, P., Frenken, M., Schwarzbauer, J., Reicherter, K., and Nishimura, Y., 2019c. Organic geochemical signature of deposits by the 2011 Tohoku-oki tsunami (North-ern Japan). INQUA 2019 Dublin - Coastal and Marine Processes: Sea-level changes from minutes to millennia - P3054 (Conference abstract)

Bellanova, P., Frenken, M., Nishimura, Y., Schwarzbauer, J., Reicherter, K., 2019d. Tracing the “lost” deposits of the 2011 Tohoku-oki tsunami (Northern Japan). EGU General Assembly 2019 - EGU2019-10048 - NH5.5/GM11.11/OS2.15/SSP3.15 (Conference abstract)

Eichner, D., Feist, L., Val-Péon, C., Bellanova, P., Costa, P.J.M., Brückner, H., Reicherter, K., and M- 152 cruise team, 2019. The offshore footprint of the 1755 Lisbon tsunami - micropaleontological and paly-nological analyses. 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

Feist, L., Bellanova, P., Mathes-Schmidt, M., Reicherter, K., Laermanns, H., and Brückner, H., 2018. The AD 1755 tsunami and other extreme wave events in Boca do Río, Portugal. GeoBonn 2018 – Poster No. Tue-33 – Session 06a) Natural Hazards: earthquakes, tsunamis, landslides (Conference abstract)

Feist, L., Eichner, D., Bellanova, P., Costa, P.J.M., Brückner, H., Reicherter, K., and M-152 cruise team, 2019. Offshore deposits of the 1755 Lisbon tsunami – RV METEOR cruise M-152. 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

191 Contribution in publications and additional publications

Frank, S., Laermanns, H., Feist, L., Bellanova, P., Reicherter, K., and Brückner, H., 2019. Palaeoenvironmental evolution and extreme wave events during the last four mil-lennia at Boca do Río, Algarve coast, Portugal. 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

Frenken, M., Bellanova, P., Schwarzbauer, J., and Reicherter, K., 2018. Organic geochemical investigation of far-field tsunami deposits of Hawai’i. GeoBonn 2018 – Oral Presentation – Session 06a) Natural Hazards: earthquakes, tsunamis, landslides (Conference abstract)

Frenken, M., Bellanova, P., Schwarzbauer, J., and Reicherter, K., 2019a. Biomarkers & anthropogenic markers – an approach for the identification of tsuna-mis in Hawaii (Kahana Valley). 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

Frenken, M., Bellanova, P., Nishimura, Y., Schwarzbauer, J., and Reicherter, K., 2019b. Organic geochemical evidences of the 2011 Tohoku-oki tsunami (Northern Japan). EGU General Assembly 2019 - EGU2019-12611 - NH5.5/GM11.11/OS2.15/SSP3.15 (Conference abstract)

Griswold, F., La Selle, S.P., Richmond, B., Jaffe, B., Gelfenbaum, G., Chagué-Goff, C., LeVeque, R., Kane, H., Bishop, J., Bellanova, P., Sugawara, D., and Nelson, A., 2016. Summary of Paleotsunami Investigations in Aliomanu, Anahola, Kauai. AGU-Fall Meeting 2016 – NH009- NH43A-1815 (Conference abstract)

Huber, B., Nentwig, V., Bahlburg, H., Bellanova, P., and Jungheim, V., 2014. Comparative sedimentology and geochemistry of tsunami sediments in the Tubul-Raquí estuary, Central Chile. GEO-Frankfurt 2014 (GV Annual Meeting) (Conference abstract)

La Selle, S.P., Gelfenbaum, G., Jaffe, B., Costa, P., Lunghino, B., and Bellanova, P., 2015. Hurricane Sandy deposits on Fire Island, NY: Using washover deposit stratigraphy to understand sediment transport during large storms. AGU-Fall Meeting 2015 - NH23D-08 (Conference abstract)

Nentwig, V., Bahlburg, H., Huber, B., Bellanova, P., Montecinos, M., Encinas, A., Tsukamoto, S., and Frechen, M., 2014. The onshore tsunami record of Tirúa, central Chile. GEO-Frankfurt 2014 (GV Annual Meeting) (Conference abstract)

Nentwig, V., Bahlburg, H., Tang, H., Weiss, R., Gorecka, E., Witkowski, A., Encinas, A, Huber, B., and Bellanova, P., 2015. Multi-proxy analysis of tsunami deposits – the Tirúa, Chile, example. AGU-Fall Meeting 2015 - NH24A-05(Conference abstract)

Nentwig, V., Bahlburg, H., Tsukamoto, S., Bellanova, P., and Encinas, A. (2017) Young vs. old onshore tsunami records in Central Chile. GeoBremen 2017 (Conference abstract)

192 Contribution in publications and additional publications

Rasteiro da Silva, D., Figueirinhas, L., Costa, P.J.M., Lira, C., Bellanova, P., and Lario-Gomez, J., 2016. Developing a new microtextural classification in the study of tsunami deposits. 32nd IAS International Meeting of Sedimentology 2016 - Session SS4 - Paper ID 164 (Conference abstract)

Reicherter, K., Costa, P., Bellanova, P., and M-152 cruise team, 2019. The off-shore Lisbon 1755 tsunami sediments. EGU General Assembly 2019 - EGU2019-18827 - NH5.5/GM11.11/OS2.15/SSP3.15 (Conference abstract)

Schwarzbauer, J., Frenken, M., Bellanova, P., and Reicherter, K., 2019. Biomarkers – Indicators for the identification of ancient tsunami deposits (Kahana, Hawaii). EGU General Assembly 2019 - EGU2019-8915 - NH5.5/GM11.11/OS2.15/SSP3.15 (Conference abstract)

Wagner, B., Laermanns, H., Bellanova, P., Scheder, J., Frank, S., Feist, L., Reicherter, K., and Brückner, H., 2019. The Lagoa de Santo André – An archive for reconstructing the palaeoenvironmental development of the SW coast of Portugal. 37. Annual Conference of the Working Group 'Geography of Seas and Coasts' 09 - 10 May 2019 Köln (Cologne) (Conference abstract)

193

194 Declaration

Declaration Hereby, I declare that the presented doctoral thesis (dissertation) was authored independently, the acquired and presented dataset is complete, and all sources and resources are completely stated. Passages of this doctoral thesis – including tables, maps and figures – drawn or modified from other studies and sources have been individually cited in full and are labeled as so throughout the thesis. This doctoral thesis has prior not been submitted to any faculty or university for examination. This dissertation – with the exception of the marked sub-publications of chapters 4-7 – has not yet been published and will not before completion of the doctoral procedure. I am aware of the provisions of the doctoral degree regulatory of the Faculty of Georessources and Material Engineering (Faculty 5) at the RWTH Aachen University. The presented doctoral thesis (dissertation) has been supervised and supported by Prof. Dr. Klaus Reicherter and Prof. Dr. Jan Schwarzbauer.

Aachen ______

(Piero Bellanova)

195