Tracing marine cryptotephras in the North Atlantic during the last glacial period: Protocols for identification, characterisation and evaluating depositional controls

Type Article
Date 2018-07
Language English
Author(s) Abbott Peter M.1, 2, 3, 4, Griggs Adam J.1, Bourne Anna J.1, 5, Davies Siwan M.1
Affiliation(s) 1 : Swansea Univ, Coll Sci, Dept Geog, Singleton Pk, Swansea SA2 8PP, W Glam, Wales.
2 : Cardiff Univ, Sch Earth & Ocean Sci, Pk Pl, Cardiff CF10 3AT, S Glam, Wales.
3 : Univ Bern, Inst Geol Sci, Baltzerstr 1 3, CH-3012 Bern, Switzerland.
4 : Univ Bern, Oeschger Ctr Climate Change Res, Baltzerstr 1 3, CH-3012 Bern, Switzerland.
5 : Univ Southampton, Geog & Environm, Univ Rd, Southampton SO17 1BJ, Hants, England.
Source Marine Geology (0025-3227) (Elsevier Science Bv), 2018-07 , Vol. 401 , P. 81-97
DOI 10.1016/j.margeo.2018.04.008
WOS© Times Cited 12
Keyword(s) Quaternary, Palaeoceanography, Tephrochronology, North Atlantic, Transport and deposition, Marine cores, Glass shard concentrations

Tephrochronology is increasingly being utilised as a key tool for improving chronological models and correlating disparate palaeoclimatic sequences. For many sedimentary environments, however, there is an increased recognition that a range of processes may impart a delay in deposition and/or rework tephra. These processes can affect the integrity of tephra deposits as time-synchronous markers, therefore, it is crucial to assess their isochronous nature, especially when cryptotephras are investigated in a dynamic marine environment. A methodology for the identification and characterisation of marine cryptotephras alongside a protocol for assessing their integrity is outlined. This methodology was applied to a wide network of North Atlantic marine sequences covering the last glacial period. A diverse range of cryptotephra deposits were identified and, based on similarities in physical characteristics (e.g. glass shard concentration profiles and geochemical homogeneity/heterogeneity), indicative of common modes of tephra delivery and post-depositional reworking, a deposit type classification scheme was defined. The presence and dominance of different deposit types within each core allowed an assessment of spatial and temporal controls on tephra deposition and preservation. Overall, isochronous horizons can be identified across a large portion of the North Atlantic due to preferential atmospheric dispersal patterns. However, the variable influence of ice-rafting processes and an interplay between the high eruptive frequency of Iceland and relatively lower sedimentation rates can also create complex tephrostratigraphies in this sector. Sites within a wide sector to the south and east of Iceland have the greatest potential to be repositories for isochronous horizons that can facilitate the synchronisation of palaeoclimatic records.

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