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

Tracing marine cryptotephras in the North Atlantic during the last glacial period: protocols for identification, characterisation and evaluating depositional controls
Tracing marine cryptotephras in the North Atlantic during the last glacial period: protocols for identification, characterisation and evaluating depositional controls
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.
0025-3227
81-97
Abbott, Peter
96c9555e-5fa7-4077-a9d0-d68fd141d3ed
Griggs, Adam
62020c90-90e1-4b83-901c-f6fa66942140
Bourne, Anna
ca184ead-1dc3-4b0f-8a01-cb427838d996
Davies, Siwan
8e31ea52-fca6-427f-a4c6-76bdef15c6bc
Abbott, Peter
96c9555e-5fa7-4077-a9d0-d68fd141d3ed
Griggs, Adam
62020c90-90e1-4b83-901c-f6fa66942140
Bourne, Anna
ca184ead-1dc3-4b0f-8a01-cb427838d996
Davies, Siwan
8e31ea52-fca6-427f-a4c6-76bdef15c6bc

Abbott, Peter, Griggs, Adam, Bourne, Anna and Davies, Siwan (2018) Tracing marine cryptotephras in the North Atlantic during the last glacial period: protocols for identification, characterisation and evaluating depositional controls. Marine Geology, 401, 81-97. (doi:10.1016/j.margeo.2018.04.008).

Record type: Article

Abstract

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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Abbott et al. TRACE Controls Open Access Version - Accepted Manuscript
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More information

Accepted/In Press date: 16 April 2018
e-pub ahead of print date: 19 April 2018
Published date: July 2018

Identifiers

Local EPrints ID: 420140
URI: http://eprints.soton.ac.uk/id/eprint/420140
ISSN: 0025-3227
PURE UUID: 51a97f19-dff6-4942-9ec6-790a3b69538c
ORCID for Anna Bourne: ORCID iD orcid.org/0000-0003-1506-6160

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Date deposited: 27 Apr 2018 16:30
Last modified: 23 Apr 2020 04:01

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Author: Peter Abbott
Author: Adam Griggs
Author: Anna Bourne ORCID iD
Author: Siwan Davies

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