The University of Southampton
University of Southampton Institutional Repository

Construction of volcanic records from marine sediment cores: A review and case study (Montserrat, West Indies)

Construction of volcanic records from marine sediment cores: A review and case study (Montserrat, West Indies)
Construction of volcanic records from marine sediment cores: A review and case study (Montserrat, West Indies)
Detailed knowledge of the past history of an active volcano is crucial for the prediction of the timing, frequency and style of future eruptions, and for the identification of potentially at-risk areas. Subaerial volcanic stratigraphies are often incomplete, due to a lack of exposure, or burial and erosion from subsequent eruptions. However, many volcanic eruptions produce widely-dispersed explosive products that are frequently deposited as tephra layers in the sea. Cores of marine sediment therefore have the potential to provide more complete volcanic stratigraphies, at least for explosive eruptions. Nevertheless, problems such as bioturbation and dispersal by currents affect the preservation and subsequent detection of marine tephra deposits. Consequently, cryptotephras, in which tephra grains are not sufficiently concentrated to form layers that are visible to the naked eye, may be the only record of many explosive eruptions. Additionally, thin, reworked deposits of volcanic clasts transported by floods and landslides, or during pyroclastic density currents may be incorrectly interpreted as tephra fallout layers, leading to the construction of inaccurate records of volcanism. This work uses samples from the volcanic island of Montserrat as a case study to test different techniques for generating volcanic eruption records from marine sediment cores, with a particular relevance to cores sampled in relatively proximal settings (i.e. tens of kilometres from the volcanic source) where volcaniclastic material may form a pervasive component of the sedimentary sequence. Visible volcaniclastic deposits identified by sedimentological logging were used to test the effectiveness of potential alternative volcaniclastic-deposit detection techniques, including point counting of grain types (component analysis), glass or mineral chemistry, colour spectrophotometry, grain size measurements, XRF core scanning, magnetic susceptibility and X-radiography. This study demonstrates that a set of time-efficient, non-destructive and high-spatial-resolution analyses (e.g. XRF core-scanning and magnetic susceptibility) can be used effectively to detect potential cryptotephra horizons in marine sediment cores. Once these horizons have been sampled, microscope image analysis of volcaniclastic grains can be used successfully to discriminate between tephra fallout deposits and other volcaniclastic deposits, by using specific criteria related to clast morphology and sorting. Standard practice should be employed when analysing marine sediment cores to accurately identify both visible tephra and cryptotephra deposits, and to distinguish fallout deposits from other volcaniclastic deposits.
Tephrostratigraphy, Tephrochronology, Eruption history, Cryptotephras, Tephra fallout, Reworked volcaniclastic
0012-8252
137-155
Cassidy, Michael
fc0e9729-9c71-477d-a4e3-39698155e6fc
Watt, Sebastian F.L.
8cde9189-35d1-450c-bff8-f7c9107eb635
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Trofimovs, Jessica
f77f3f44-6fbd-4efb-ba3a-d4818b229b10
Symons, William
054e7f1e-b187-4caf-bb5f-2b16895d2388
Maclachlan, Suzanne E.
a6c1b5e7-066a-45f5-a6bd-15cbcf127758
Stinton, Adam J.
6631cd87-cf40-47b0-b2a3-422509379b22
Cassidy, Michael
fc0e9729-9c71-477d-a4e3-39698155e6fc
Watt, Sebastian F.L.
8cde9189-35d1-450c-bff8-f7c9107eb635
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Trofimovs, Jessica
f77f3f44-6fbd-4efb-ba3a-d4818b229b10
Symons, William
054e7f1e-b187-4caf-bb5f-2b16895d2388
Maclachlan, Suzanne E.
a6c1b5e7-066a-45f5-a6bd-15cbcf127758
Stinton, Adam J.
6631cd87-cf40-47b0-b2a3-422509379b22

Cassidy, Michael, Watt, Sebastian F.L., Palmer, Martin R., Trofimovs, Jessica, Symons, William, Maclachlan, Suzanne E. and Stinton, Adam J. (2014) Construction of volcanic records from marine sediment cores: A review and case study (Montserrat, West Indies). Earth-Science Reviews, 138, 137-155. (doi:10.1016/j.earscirev.2014.08.008).

Record type: Article

Abstract

Detailed knowledge of the past history of an active volcano is crucial for the prediction of the timing, frequency and style of future eruptions, and for the identification of potentially at-risk areas. Subaerial volcanic stratigraphies are often incomplete, due to a lack of exposure, or burial and erosion from subsequent eruptions. However, many volcanic eruptions produce widely-dispersed explosive products that are frequently deposited as tephra layers in the sea. Cores of marine sediment therefore have the potential to provide more complete volcanic stratigraphies, at least for explosive eruptions. Nevertheless, problems such as bioturbation and dispersal by currents affect the preservation and subsequent detection of marine tephra deposits. Consequently, cryptotephras, in which tephra grains are not sufficiently concentrated to form layers that are visible to the naked eye, may be the only record of many explosive eruptions. Additionally, thin, reworked deposits of volcanic clasts transported by floods and landslides, or during pyroclastic density currents may be incorrectly interpreted as tephra fallout layers, leading to the construction of inaccurate records of volcanism. This work uses samples from the volcanic island of Montserrat as a case study to test different techniques for generating volcanic eruption records from marine sediment cores, with a particular relevance to cores sampled in relatively proximal settings (i.e. tens of kilometres from the volcanic source) where volcaniclastic material may form a pervasive component of the sedimentary sequence. Visible volcaniclastic deposits identified by sedimentological logging were used to test the effectiveness of potential alternative volcaniclastic-deposit detection techniques, including point counting of grain types (component analysis), glass or mineral chemistry, colour spectrophotometry, grain size measurements, XRF core scanning, magnetic susceptibility and X-radiography. This study demonstrates that a set of time-efficient, non-destructive and high-spatial-resolution analyses (e.g. XRF core-scanning and magnetic susceptibility) can be used effectively to detect potential cryptotephra horizons in marine sediment cores. Once these horizons have been sampled, microscope image analysis of volcaniclastic grains can be used successfully to discriminate between tephra fallout deposits and other volcaniclastic deposits, by using specific criteria related to clast morphology and sorting. Standard practice should be employed when analysing marine sediment cores to accurately identify both visible tephra and cryptotephra deposits, and to distinguish fallout deposits from other volcaniclastic deposits.

Text
Cassidy et al 2014_Construction of volcanic records from marine sediment cores_unformatted.pdf - Accepted Manuscript
Restricted to Registered users only
Download (2MB)
Request a copy

More information

Published date: 2014
Keywords: Tephrostratigraphy, Tephrochronology, Eruption history, Cryptotephras, Tephra fallout, Reworked volcaniclastic
Organisations: Geology & Geophysics, Marine Geoscience

Identifiers

Local EPrints ID: 370736
URI: http://eprints.soton.ac.uk/id/eprint/370736
ISSN: 0012-8252
PURE UUID: 46c7fcf6-d465-44b3-9d4a-e6d6e46b6879

Catalogue record

Date deposited: 05 Nov 2014 11:10
Last modified: 22 Jul 2022 19:11

Export record

Altmetrics

Contributors

Author: Michael Cassidy
Author: Sebastian F.L. Watt
Author: Jessica Trofimovs
Author: William Symons
Author: Suzanne E. Maclachlan
Author: Adam J. Stinton

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×