The tsunami phenomenon

Abstract With human activity increasingly concentrating on coasts, tsunamis (from Japanese tsu = harbour, nami = wave) are a major natural hazard to today’s society. Stimulated by disastrous tsunami impacts in recent years, for instance in south-east Asia (2004) or in Japan (2011), tsunami science has significantly flourished, which has brought great advances in hazard assessment and mitigation plans. Based on tsunami research of the last decades, this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view. Starting with the wave features, tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy l…

Impact of Holocene tsunamis detected in lagoonal environments on Corfu (Ionian Islands, Greece): Geomorphological, sedimentary and microfaunal evidence

Abstract In this paper, we present for the first time geomorphological, sedimentary and microfaunal evidence of palaeotsunami impact on Corfu (Ionian Islands, Greece). The island of Corfu is located in an area of exceptional tectonic stress: towards the south, the African oceanic plate is being subducted underneath the Aegean plate, whereas towards the north, the Adriatic and European plates form a continental collision zone. Recent publications provide evidence of earthquake related co-seismic movements that potentially trigger extreme wave events as well as relative sea level fluctuations. In this context, we investigated two selected near-coast geological archives – the Chalikiopoulou La…

Mid-Holocene tectonic geomorphology of northern Crete deduced from a coastal sedimentary archive near Rethymnon and a Late Bronze Age Santorini tsunamite candidate

Abstract The Late Bronze Age (LBA) tsunami and the A.D. 365 tsunami are supposed to have affected the northern coasts of Crete. However, near-coast sedimentary archives have been rarely investigated in this area, and sedimentary archives including palaeotsunami fingerprints are still unknown. The main objective of our research was to search for appropriate tsunami sediment traps in order to gain detailed insights into the Holocene palaeotsunami history of northern Crete. We found an excellent fine sediment archive near Pirgos, located to the west of Rethymnon. Based on a multi-electrode geoelectrical survey and an 11-m-deep sediment core, we analysed the event-geochronostratigraphical recor…

Landscape reconstruction and major flood events of the River Main (Hesse, Germany) in the environs of the Roman fort at Groβkrotzenburg

Abstract Detailed geoarchaeological studies were conducted at the Groβkrotzenburg floodplain (Southern Hesse, Germany) in order to reconstruct the fluvial palaeogeography and search for Roman harbour installations. Another objective was to reconstruct the local flood history based on stratigraphic and geochronological data. Prospection based on electrical resistivity tomography, vibracoring and direct push electrical conductivity logging were carried out to detect and analyze subsurface stratigraphies. Altogether, 6 sediment cores, up to 7 m long, were drilled along transects along and perpendicular to the present course of the River Main. Based on sedimentological and geochemical data, we …

Geoarchaeological investigations of a prominent quay wall in ancient Corcyra: Implications for harbour development, palaeoenvironmental changes and tectonic geomorphology of Corfu Island (Ionian Islands, Greece)

Abstract In antiquity, the harbour-city of Corcyra (modern: Corfu) was a prevailing naval power in the Mediterranean and had several harbours to host a considerable fleet. Today, these harbours are totally or partly silted and concealed under modern urban infrastructure. Comprehensive geoarchaeological studies were conducted on the northeastern fringe of the Analipsis Peninsula where excavations have revealed the archaeological remains of a massive quay wall (Pierri and Arion sites). These remains are located east of known ancient harbour structures that belong to the Alkinoos Harbour. Our study aimed to reconstruct the palaeoenvironmental setting of the harbour facilities at the Pierri sit…

Potential and limits of combining studies of coarse- and fine-grained sediments for the coastal event history of a Caribbean carbonate environment

The coastal deposits of Bonaire, Leeward Antilles, are among the most studied archives for extreme-wave events (EWEs) in the Caribbean. Here we present more than 400 electron spin resonance (ESR) and radiocarbon data on coarse-clast deposits from Bonaire’s eastern and western coasts. The chronological data are compared to the occurrence and age of fine-grained extremewave deposits detected in lagoons and floodplains. Both approaches are aimed at the identification of EWEs, the differentiation between extraordinary storms and tsunamis, improving reconstructions of the coastal evolution, and establishing a geochronological framework for the events. Although the combination of different method…

River channel evolution and tsunami impacts recorded in local sedimentary archives – the ‘Fiume Morto’ at Ostia Antica (Tiber River, Italy)

The Palaeoanthropocene – The beginnings of anthropogenic environmental change

Abstract As efforts to recognize the Anthropocene as a new epoch of geological time are mounting, the controversial debate about the time of its beginning continues. Here, we suggest the term Palaeoanthropocene for the period between the first, barely recognizable, anthropogenic environmental changes and the industrial revolution when anthropogenically induced changes of climate, land use and biodiversity began to increase very rapidly. The concept of the Palaeoanthropocene recognizes that humans are an integral part of the Earth system rather than merely an external forcing factor. The delineation of the beginning of the Palaeoanthropocene will require an increase in the understanding and …

Millennial-scale terrestrial ecosystem responses to Upper Pleistocene climatic changes: 4D-reconstruction of the Schwalbenberg Loess-Palaeosol-Sequence (Middle Rhine Valley, Germany)

Abstract Loess-Palaeosol-Sequences (LPS) in the Central European region provide outstanding terrestrial polygenetic and multiphase archives responding to past climate and environments over various spatial and temporal scales. As yet, however, the geomorphological and pedogenic processes involved in LPS formation, and their interplay with changes in ecological conditions, impede robust correlation with other palaeoenvironmental archives. The Schwalbenberg LPS, which drape a hillslope in the Middle Rhine Valley in western Central Europe, provide unique high-resolution records highly suitable for investigating the processes involved in their formation and the relationship to climatic influence…

Identifying sedimentary structures and spatial distribution of tsunami deposits with GPR - examples from Spain and Greece

Shallow drilling in coastal areas like southern Spain and different parts of Greece (Corinth region and Argolis Gulf) proved evidence for tsunamis. Sedimentary analyses were conducted to identify tsunamigenic deposits, but did not reveal sedimentary structures or spatial distribution of tsunamites in a regional scale. Since drilling is time-intensive and expensive (depending on extend), this method can by far not cover an entire coastal area. On the other hand, distribution and preservation of tsunamigenic deposits seems to be highly variable. We used ground penetrating radar (GPR) in combination with electrical resistivity tomography (ERT) measurements and sedimentological research methods…

Tracing tsunami signatures of thead551 andad1303 tsunamis at the Gulf of Kyparissia (Peloponnese, Greece) using direct pushin situsensing techniques combined with geophysical studies

Natural and human induced environmental changes preserved in a Holocene sediment sequence from the Etoliko Lagoon, Greece: New evidence from geochemical proxies

Abstract A key feature of Greece is the large amount of historical and archaeological records. The sedimentary record of the Etoliko Lagoon, Aetolia, Western Greece, offers an ideal opportunity to study human–environment interaction and to disentangle natural and anthropogenic imprints in the sedimentary record. By applying an interdisciplinary approach of combining geoscientific methods (XRF, LOI, grain size analysis) with archaeological and historical records, the 8.8 m long sedimentary sequence ETO1C reveals the palaeoenvironmental history of the lagoon and its catchment since 11,670 cal BP. With a thorough chronology based on 14 C age-depth-modelling including varve counting, different …

Quartz OSL dating of late quaternary Chinese and Serbian loess: A cross Eurasian comparison of dust mass accumulation rates

© 2018 Elsevier Ltd and INQUA. Reconstructing dust Mass Accumulation Rate (MAR) from loess deposits is critical to understanding past atmospheric mineral dust activity and requires accurate independent age models from loess deposits across Europe and Asia. Previous correlations of loess in Europe and China have tended to focus on multi-millennial timescales, with no detailed examination of dust MAR at the two ends of the Eurasian loess belt on shorter, sub-orbital scales. Here we present a detailed quartz optically stimulated luminescence (OSL) chronology from the Serbian Titel Loess Plateau (Veliki Surduk loess core) and the Chinese Loess Plateau (Lingtai section). The luminescence ages pa…

Sedimentology of a Late Quaternary lacustrine record from the south-eastern Carpathian Basin

The Upper Pleistocene geoarchives in the south‐eastern Carpathian Basin are represented predominantly by loess–palaeosol records. In 2015, a 10 m sediment core composed of clay‐rich lacustrine sediments was recovered by vibracoring a dry lake basin located between the Vršac Mountains (Serbia) and the Banat Sands in the south‐eastern Carpathian Basin; a location relevant for placing regional archaeological results in a palaeoenvironmental context. Here, we present results from geoelectrical prospection and a lithostratigraphic interpretation of this sequence supported by a detailed granulometric study supplemented by ostracod analysis. An age model based on luminescence dating is discussed a…

Dyke failures in the Province of Groningen (Netherlands) associated with the 1717 Christmas flood: a reconstruction based on geoscientific field data and numerical simulations

AbstractThe 1717 Christmas flood is one of the most catastrophic storm surges the Frisian coast (Netherlands and Germany) has ever experienced. With more than 13,700 casualties it is the last severe storm surge with a death toll of this order. At the same time, little is known about the hydrodynamic conditions and the morphological effects associated with this storm surge.In this study, 41 potential dyke failures in the Province of Groningen (Netherlands) associated with the 1717 Christmas flood were systematically reconstructed and mapped by using historical maps and literature and by analysing the recent topography in search of typical pothole structures and sediment fans. The dimensions …

Temple-complex post-dates tsunami deposits found in the ancient harbour basin of Ostia (Rome, Italy)

Abstract Detailed geophysical and geoarchaeological investigations carried out in Ostia, ancient harbour of Rome, revealed two different generations of harbour basins and also proved the repeated impact of high-energy wave events on the study area. West of Ostia, at the southern bank of the Tiber, a lagoonal harbour existed from the 4th and 2nd cent. BC but was affected by strong siltation. At the same site, a river harbour was subsequently established from the 1st cent. AD onwards. Fluvial deposits of medieval age finally document Tiber river bank erosion affecting the abandoned site. Within the sedimentary record, distinct high-energy event deposits were found and seem to be related to ts…

Combined Electrical Resistivity Tomography (ERT), Direct-Push Electrical Conductivity (DP-EC) Logging and Coring - A New Methodological Approach in Geoarchaeological Research

Non-invasive geophysical methods have been increasingly applied in geoarchaeological research commonly showing the need of data calibration based on stratigraphical information deduced from outcrops or sediment cores. In this contribution, a methodological approach combining two-dimensional (2D) electrical resistivity tomography (ERT) and stratigraphical data based on coring and, for the first time in geoarchaeological research, direct-push electrical conductivity (DP-EC) logging is presented and discussed. The approach yields high resolution data based on studies of two different types of archives, the Holsterburg site in central Germany located in a fluvio-terrestrial zone and the Corfu C…

The sedimentary and geomorphological imprint of the AD 365 tsunami on the coasts of southwestern Crete (Greece): Examples from Sougia and Palaiochora

Abstract The southwestern coast of Crete, one of the most seismically active regions in Europe, experienced co-seismic crust uplift by 9 m during the Ms = 8.3 mega-earthquake that struck the eastern Mediterranean world on 21 July AD 365. An associated tsunami event caused thousands of fatalities and destroyed many coastal settlements and infrastructure between the Levante in the east and the Adriatic Sea in the northwest. So far, coastal sedimentary archives in southwestern Crete including distinct palaeotsunami fingerprints are rarely investigated. Therefore, a multi-proxy study including sedimentological, geochemical, geochronological, and microfaunal methods was conducted in order to det…

The river harbour of Ostia Antica - stratigraphy, extent and harbour infrastructure from combined geophysical measurements and drillings

Abstract We performed a combined geophysical and geoarchaeological survey of the harbour of ancient Ostia, Italy, to investigate the extent of the former harbour basin, the sedimentary infill and possible building remains around the harbour. Besides geoarchaeological results the paper highlights the advantage of combining vibracore drilling with different geophysical prospection methods, which are sensitive to different physical soil parameters. Geophysical methods applied were electrical resistivity tomography (ERT), ground penetrating radar (GPR) and seismics with shear and compressional waves. The extent and shape of the harbour basin were determined by ERT profiling. The ERT profiles we…

Taken from the sea, reclaimed by the sea: The fate of the closed harbour of Elaia, the maritime satellite city of Pergamum (Turkey)

Abstract During Hellenistic times, when the Pergamenian kingdom was prospering, Pergamum was operating an important harbour, used by merchants and military at the city of Elaia. This paper focuses on the development, utilisation and decay of the closed harbour of Elaia, which is discussed in the context of the landscape evolution of the environs of the ancient settlement. Based on geoarchaeological, archaeological and literary evidence, the construction of two harbour moles in order to provide shelter against wave action and enemies can be attributed to the early Hellenistic period. Geoelectric measurements revealed the construction profile of the moles. Coring evidence indicated that toget…

Detection and localization of chamber tombs in the environs of ancient Olympia, Peloponnese, Greece, based on a combination of archaeological survey and geophysical prospection

The Purpose and Age of Underwater Walls in the Bay of Elaia of Western Turkey: A Multidisciplinary Approach

Pergamum (modern: Bergama) was operating an important harbour used by military forces and merchants at the city of Elaia during Hellenistic and Roman Imperial times. Harbour-related facilities such as warehouses, breakwaters and wharfs document the importance of this harbour site not only for the Pergamenians. This paper focuses on the purpose and age of six submerged wall structures situated approximately 1 km south of the ancient closed harbour basin of Elaia. Geoelectric cross-sections and semi-aquatic coring near these walls failed to detect any solid basement under the walls which excludes their possible use as breakwaters or wharfs. Instead, the walls were most likely delineating and …

The Mediterranean Sea and the Gulf of Cadiz as a natural laboratory for paleotsunami research: Recent advancements

International audience; After the 2004 Indian Ocean (IOT) and the 2011 Tohoku-oki tsunamis, new research in tsunami-related fields was strongly stimulated worldwide and also in the Mediterranean. This research growth yields substantial advancements in tsunami knowledge.Among these advancements is the “Paleotsunami” research that has marked particular progress on the reconstruction of the tsunami history of a region. As an integration of the historical documentation available in the Mediterranean and the Gulf of Cadiz areas, geological and geoarchaeological records provide the insights to define the occurrence, characteristics, and impact of tsunamis of the past. Here, we present the recent …

Effects of different boundary conditions and palaeotopographies on the onshore response of tsunamis in a numerical model – A case study from western Greece

Abstract Hydrodynamic numerical models are essential in modern tsunami hazard assessment. They allow the economical simulation of possible tsunami scenarios for areas at risk and provide reliable and detailed insights into local onshore dynamics. This is especially true when simulations are calibrated with field traces of past tsunami inundation events. Following this approach, the current study focuses on palaeotsunami events indicated by sedimentary and geomorphological field traces in the northern Gulf of Kyparissia (NW Greece). Based on three different digital elevation models (DEM) – reflecting the recent and two palaeotopographies – various tsunami wave constellations according to the…

Geoarchaeological evidence of marshland destruction in the area of Rungholt, present-day Wadden Sea around Hallig Südfall (North Frisia, Germany), by the Grote Mandrenke in 1362 AD

Abstract Geophysical and geoarchaeological investigations were carried out in the Wadden Sea of North Frisia (Schleswig-Holstein, Germany) to elucidate major environmental changes that considerably altered the coastal landscape since medieval times. Between the 12 th and 14 th cent. AD, the present-day tidal flats around the marsh island Hallig Sudfall belonged to the historical Edomsharde district and its main settlement Rungholt . For North Frisia, it is well known that during medieval and early modern times, extreme storm surges caused major land losses associated with a massive landward shift of the coastline. Today, cultural traces like remains of dikes, drainage ditches, terps or even…

Automated facies identification by Direct Push-based sensing methods (CPT, HPT) and multivariate linear discriminant analysis to decipher geomorphological changes and storm surge impact on a medieval coastal landscape

In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north‐western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long‐term as well as event‐related short‐term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) wer…

Hydro- and morphodynamic tsunami simulations for the Ambrakian Gulf (Greece) and comparison with geoscientific field traces

Tracing the Alkinoos Harbor of ancient Kerkyra, Greece, and reconstructing its paleotsunami history

International audience

The Mycenaean drainage works of north Kopais, Greece: a new project incorporating surface surveys, geophysical research and excavation

The attempt to drain the Kopais Lake was one of the most impressive and ambitious technical works of prehistoric times in Greece, inspiring myths and traditions referring to its construction and operation. The impressive remnants of the Mycenaean hydraulic works represent the most important land reclamation effort during prehistoric Greek antiquity, thus attracting the attention of the international scientific community. Nevertheless, in spite of the minor or extended contemporary surveys, the picture of the prehistoric drainage works in Kopais has remained ambiguous. Concerning the function of these works and their precise date within the Bronze Age, the proposed theories were based solely…

Sediment Transport and Hydrodynamic Parameters of Tsunami Waves Recorded in Onshore Geoarchives

In regions with a short historical tsunami record, the assessment of long-term tsunami risk strongly depends on geological evidence of prehistoric events. Whereas dating tsunami deposits is already well established, magnitude assessment based on remaining sedimentary structures is still a major challenge. In this study, two approaches were applied to deduce transport processes and hydrodynamic parameters of tsunami events from onshore deposits found in the coastal plain of Ban Bang Sak, SW Thailand: (1) The maximum offshore sediment source was determined using granulometry, geochemistry, mineralogy and foraminifera of the tsunamites, and reference samples from various marine and terrestrial…

TERRESTRIAL LASER SCANNING FOR COASTAL GEOMORPHOLOGIC RESEARCH IN WESTERN GREECE

We used terrestrial laser scanning (TLS) for (i) accurate volume estimations of dislocated boulders moved by high-energy impacts and for (ii) monitoring of annual coastal changes. In this contribution, we present three selected sites in Western Greece that were surveyed during a time span of four years (2008-2011). The Riegl LMS-Z420i laser scanner was used in combination with a precise DGPS system (Topcon HiPer Pro). Each scan position and a further target were recorded for georeferencing and merging of the point clouds. For the annual detection of changes, reference points for the base station of the DGPS system were marked. Our studies show that TLS is capable to accurately estimate volu…

Constraining electric resistivity tomography by direct push electric conductivity logs and vibracores: An exemplary study of the Fiume Morto silted riverbed (Ostia Antica, western Italy)

The inversion of geoelectric data is nonunique. Therefore, electric resistivity tomography (ERT) usually results in different subsurface models that fit observed apparent resistivity values equally well. To reduce the uncertainty, constraints on the geometry and resistivity of subsurface structures can be incorporated into the ERT inversion. We test different ways of constraining ERT by applying (1) improved starting models, (2) structural constraints, and (3) structural and resistivity constraints. A priori information is needed for these approaches, which is acquired from direct push electrical conductivity (DP-EC) logs and vibracores in our study. We found that adapting high vertical re…

Sedimentological and geoarchaeological evidence of multiple tsunamigenic imprint on the Bay of Palairos-Pogonia (Akarnania, NW Greece)

Abstract This paper presents evidence of multiple tsunami impact on the Bay of Palairos-Pogonia, NW Greece, during the Holocene based on detailed geo-scientific studies. Altogether, 41 vibracores were drilled to detect high-energy influence in the stratigraphical record. Layers of coarse-grained allochthonous marine deposits were found intersecting autochthonous fine-grained back beach sediments in the Palairos coastal plain, on top of beach or marly bedrock units at Pogonia beach and along the Pogonia cliff section. High-energy deposits are associated with specific sedimentary structures such as fining upward sequences, rip up-clasts, basal erosional contact, bi- to multimodal grain size d…

Combining inorganic and organic carbon stable isotope signatures in the Schwalbenberg Loess-Palaeosol-Sequence near Remagen (Middle Rhine valley, Germany)

Western Central European Loess-Palaeosol-Sequences (LPS) provide valuable terrestrial records of palaeoenvironmental conditions, which formed in response to variability in the North Atlantic climate systems. Over the last full glacial cycle (∼130 ka), climate oscillations within these systems are best documented in deep sea- and ice cores; the responses of terrestrial systems are not yet fully understood. A better understanding of metabolism governing input and output variables of organic- and inorganic C pools is, however, crucial for investigating landscape-atmospheric feedback processes and in particularly, for understanding the formation of calcareous LPS as environmental archives. Here…

The Lefkada barrier and beachrock system (NW Greece) — Controls on coastal evolution and the significance of extreme wave events

Abstract The Lefkada–Preveza coastal zone, NW Greece, is characterised by an active barrier system and related extensive beachrock sequences. Besides the gradual coastal processes of longshore drift and spit evolution, the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system. In this paper, we present the results of detailed multi-proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back-beach positions. Our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary br…

Potential and limits of combining studies of coarse- and fine-grained sediments for the coastal event history of a Caribbean carbonate environment

The coastal deposits of Bonaire, Leeward Antilles, are among the most studied archives for extreme-wave events (EWEs) in the Caribbean. Here we present more than 400 electron spin resonance (ESR) and radiocarbon data on coarse-clast deposits from Bonaire’s eastern and western coasts. The chronological data are compared to the occurrence and age of fine-grained extreme-wave deposits detected in lagoons and floodplains. Both approaches are aimed at the identification of EWEs, the differentiation between extraordinary storms and tsunamis, improving reconstructions of the coastal evolution, and establishing a geochronological framework for the events. Although the combination of different metho…

Sedimentology of a profile from Etoliko Lagoon, Western Greece

A key feature of Greece is the large amount of historical and archaeological records. The sedimentary record of the Etoliko Lagoon, Aetolia, Western Greece, offers an ideal opportunity to study human-environment interaction and to disentangle natural and anthropogenic imprints in the sedimentary record. By applying an interdisciplinary approach of combining geoscientific methods (XRF, LOI, grain size analysis) with archaeological and historical records, the 8.8 m long sedimentary sequence ETO1C reveals the palaeoenvironmental history of the lagoon and its catchment since 11,670 cal BP. With a thorough chronology based on 14C age-depth-modelling including varve counting, different evolutiona…