Marine tephrochronology: a personal perspective

Abstract

IntroductionThis special volume on marine tephrochronology is remarkable, and timely, because it marks a concerted step towards what might be informally termed 'phase 3' of a revolution in Quaternary geosciences that began around 40 years ago. The ten articles collectively represent a re-focussed examination of tephras and cryptotephras preserved in ocean sediments at various locations and the authors describe their significance for a range of subdisciplines. Eight provide a new understanding of the origin, distribution, and ages of various tephra and cryptotephra deposits and their stratigraphic inter-relationships; how the terrestrial ages of the tephra/crypotephra deposits relate to those of enclosing sediments and inform the ongoing development of the marine radiocarbon time-scale; mechanisms for the emplacement, remobilisation, or bioturbation of the tephras or cryptotephras; and volcanic eruption history. Two further articles document the characterization of tephra-derived glass shards using microbeam techniques to analyse 3040 elements from individual shards as small as 10 µm in diameter. The collection thus provides snapshots of many aspects of the latest developments and directions in tephra studies -volcanology, primary and secondary dispersal, stratigraphy, single-grain characterization, chronology -through the medium of marine sediments. My personal perspective reflects briefly on how this point was reached and identifies a few of the important milestones on the way from 'phase 1' to 'phase 3'. I am privileged to write it.3

Cryptotephras: the revolution in correlation and precision dating

“…A Geological Society Special Publication (No. 398) has been dedicated to capturing recent work in the marine realm (Austin et al , ; Lowe, ).…”

Crossing new frontiers: extending tephrochronology as a global geoscientific research tool

“…Sparse, ‘non‐visible’ occurrences of volcanic glass shards or crystals (minerals) in sedimentary deposits or soils had been documented in northwestern Europe/Scandinavia since the 1950s (Davies, 2015), in New Zealand from the early 1980s (Lowe, 2014) and Canada from the late 1980s (Zoltai, 1989). However, the rise in systematic, ‘modern’ cryptotephra studies began in the late 1980s, initially driven by research conducted on peat and lake sequences in the British Isles to identify Icelandic eruptives (e.g.…”

Identifying cryptotephra units using correlated rapid, nondestructive methods: VSWIR spectroscopy, X‐ray fluorescence, and magnetic susceptibility

“…When preserved subaerially, in ice cores, or in marine and lacustrine sedimentary records, these layers can serve as stratigraphic marker beds that can be used to infer the timing and magnitude of eruptive activity [e.g., Federman and Carey , ; Dugmore , ; Brown et al ., ; Carter et al ., ; Eden et al ., ; Knudsen and Eirı´ksson , ; Larsen et al ., ; Svensson et al ., ], provide independent chronological constraints [e.g., Kristjánsdóttir et al ., ; Stoner et al ., ; Ólafsdóttir et al ., ; Austin et al ., ], and can be spatially correlated to provide event‐coeval tie points [e.g., Brown et al ., ; van den Bogaard et al ., ; Grönvold et al ., ; Kristjánsdóttir et al ., ]. Assuming conservative tracer properties, sedimentological, petrological, and geochemical analysis of tephra can be used to inform about the timing and source of eruptive events [e.g., Shane , ; van den Bogaard and Schmincke , ; Lowe , ], identify systematic patterns or variance in terms of eruptive style, eruption magnitude, and repose periods [e.g., Bonadonna et al ., ; Larsen and Eiríksson , ; Le Friant et al ., ], assess the completeness of terrestrial records [e.g., Carter et al ., ; Le Friant et al ., ], and examine the nature and evolution of volcanism during the construction of a volcanic complex [e.g., Larsen , ; Shane et al ., ]. While subaerially deposited tephra records can be obscured by burial and/or dense vegetation, and may be subject to extensive erosion [e.g., Le Friant et al ., ; Shane and Wright , ], evaluation of tephra incorporated into continuously accumulating sediment records can often make for the most complete archive of explosive volcanic events.…”