Tephrabase: tephrochronology and the development of a centralised European database (original) (raw)
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Encyclopedia of Scientific Dating Methods, 2014
Tephrochronology is the use of primary, characterized tephras or cryptotephras as chronostratigraphic marker beds to connect and synchronize geological, paleoenvironmental, or archaeological sequences or events, or soils/paleosols, and, uniquely, to transfer relative or numerical ages or dates to them using stratigraphic and age information together with mineralogical and geochemical compositional data, especially from individual glass-shard analyses, obtained for the tephra/cryptotephra deposits. To function as an age-equivalent correlation and chronostratigraphic dating tool, tephrochronology may be undertaken in three steps: (i) mapping and describing tephras and determining their stratigraphic relationships, (ii) characterizing tephras or cryptotephras in the laboratory, and (iii) dating them using a wide range of geochronological methods. Tephrochronology is also an important tool in volcanology, informing studies on volcanic petrology, volcano eruption histories and hazards, and volcano-climate forcing. Although limitations and challenges remain, multidisciplinary applications of tephrochronology continue to grow markedly.
Tephra, tephrochronology and archaeology – a (re-)view from Northern Europe
2013
Volcanic eruptions are often, although by no means always, associated with a profuse output of fine pyroclastic material, tephra. While residence time in the atmosphere of the very finest of these particles can be substantial, the deposition of the bulk of volcanic ejecta can be considered instantaneous from a geological, archaeological, and evolutionary perspective. Often these volcanic products can be identified by various chemical and non-chemical means and if the eruption date is known, the occurrence of tephra from a given eruption in stratigraphic sequences provides a powerful means of dating such deposits, or of refining available dating schemes. Furthermore, the occurrence of tephra from the same eruption across sites, regions and in various types of depositional contexts (ice-cores, terrestrial, marine, cultural) holds the potential of linking and thus elucidating the tempi and causes of both environmental and cultural change. Recent years have seen considerable advances in tephrochronology studies, especially regarding the detection of macroscopically invisible micro-or cryptotephras. In parallel with the possibility of detecting hitherto invisible tephras over vastly increased areas, the overall potential of tephrochronology as a major dating tool for both palaeoenvironmental scientists and archaeologists is greatly expanded. The aim of this paper is not to be comprehensive, but to provide a brief and timely general review of tephra studies and their methodologies, and to make a case for better linking tephra research to archaeology, all from a primarily Scandinavian perspective. We argue that the identification of tephra in archaeological sediments should, in due time, become as routine as other types of geo-archaeological analyses, especially given that tephra cannot only act as a useful chronostratigraphic marker, but can also play a role in changing patterns of environmental and cultural change at the level of the site or the region. In order to move towards such integration, a series of methodological challenges have to be met. We outline some of these, and provide pointers as to how and where tephrochronologists and archaeologists can work together more closely.
2021
Modern tephra studies per se began almost 100 years ago (in the late 1920s) but the first collective of tephrochronologists, with a common purpose and nascent global outlook, was not formed until 7 September, 1961, in Warsaw, Poland. On that date, the inaugural 'Commission on Tephrochronology' (COT) was ratified under the aegis of the International Union for Quaternary Research (INQUA). COT's formation can be attributed largely to the leadership of Kunio Kobayashi of Japan, the commission's president for its first 12 years. We were motivated to record COT's heritage for posterity and also because the discipline of tephrochronology, including the study of cryptotephras, continues to grow globally at a significant rate. This is recognition of tephrochronology as both a unique correlational and age-equivalent dating method, and as a complementary method in other fields, such as volcanology, in which tephra research has been employed to develop eruption histories and hazards and to help understand volcano-climate interactions. In this article, we review the history of COT (which also functioned under other names, abbreviated as COTS, CEV, ICCT, COTAV, SCOTAV, INTAV) under the umbrella of INQUA for 53 of the last 60 years, or under IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior) for seven of the last 60 years, including since 2019. We describe the development of the commission and its subsequent activities that include organising nine specialist tephra-field meetings in seven different countries, numerous conference sessions or workshops, and generating tephra-themed issues of journals/books or specialist internet documents or websites. The commission began to prosper after 1987 when key changes occurred, and it has blossomed further, especially in the past decade or so as an entire new cohort of specialists has emerged alongside new analytical and dating techniques to become a vibrant global group today. We name 29 elected officers involved with COT since 1961 and their roles, and 15 honorary life members. We also document the aims of the commission and conclude by evaluating its legacies and current and future work. Short summary. The Commission on Tephrochronology, formed in 1961, comprises global researchers who characterize, map, and date tephra (volcanic ash) layers and use them stratigraphically as linking and dating tools in geological, palaeoenvironmental, and archaeological research, and volcanology. We review the commission's historyits growth, leadership, and activities for 60 years that include hosting specialist meetings, symposia, and workshops, developing new analytical and dating methods and protocols, and encouraging ECRs.
Integrating the INTIMATE records using tephrochronology: rising to the challenge
Quaternary Science Reviews, 2012
Little has challenged our understanding of climate change more so than the abruptness with which large-scale shifts in temperature occurred during the Late Quaternary. The causal mechanisms driving these rapid changes are poorly understood, largely due to the inherent difficulties of integrating palaeoclimate records which represents the key focus of the INTIMATE 1 project. Tephrochronology has become central to the synchronisation goals of INTIMATE, the overall aim of which is to test the degree of climatic synchroneity in relation to these rapid climatic events. Here we present a European framework of 12 volcanic events that hold considerable promise for achieving the INTIMATE goals and effecting precise correlation of widespread palaeoarchives. These tephras are widespread and fall stratigraphically in close association to rapid climatic changes. We believe that these represent the most valuable tephras for the European INTIMATE project, but also highlight those that require urgent investigation to refine their geochemical signatures, eruptive context and chronological and stratigraphical uncertainties. For instance, new data are presented for the Saksunarvatn Ash that question the sole reliance on majorelement analysis for tephra characterisation and highlights some of the challenges that remain for tephra studies. Accordingly, we outline a number of key recommendations relating to geochemical characterisation, data comparison, assessing the depositional integrity of tephra horizons as well as methods for improving age estimates e all of which will optimise the application of tephrochronology to meet the INTIMATE goals.