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Tracking Holocene palaeostratification and productivity changes in the Western Irish Sea: a multi-proxy record

Tracking Holocene palaeostratification and productivity changes in the Western Irish Sea: a multi-proxy record
Tracking Holocene palaeostratification and productivity changes in the Western Irish Sea: a multi-proxy record

The Western Irish Sea preserves an exceptionally thick (ca. 40 m) Holocene succession that is ideally suited to understanding the pattern of palaeostratification and water mass productivity changes in the region, and their relationship with sea level, sedimentation, and biota. Additionally, the presence of shallow-buried methane provides an opportunity to explore its potential impact on the local pattern of Holocene marine environmental change. Multi-proxy investigation of a cored borehole succession through the Holocene interval tracks changes from mixed to seasonally stratified conditions. In the earliest Holocene (11.2–10 ka), high productivity, mixed water conditions prevailed, with abundant and diverse foraminifera and dominant heterotrophic dinoflagellate cysts. Productivity was probably driven by high nutrient fluxes related to high rates of sedimentation (>1600 cm/kyr), in turn influenced by relatively low sea level and restricted sediment accommodation space across shelf areas to the east of the borehole site (eastern Irish Sea Basin). With rising sea level in the later part of the Early Holocene, the region evolved into a relatively lower productivity mixed water mass system, with significant changes in ecology revealed by dinoflagellate cysts and foraminifera. In the latest Early Holocene and earliest Mid Holocene (ca. 8.4–8.2 ka) a return to higher productivity is signalled by dinoflagellate cyst data; a result of seasonal stratification becoming established, evidenced by sharply increased summer sea surface temperature estimates (typically 16–17 °C) that contrast with an opposite (more positive) trend in δ18O values for benthic foraminifera. Reductions in turbulent mixing associated with stratification might have exacerbated the palaeoecological impact of shallow-buried methane associated with the borehole site, potentially evidenced by a significant change in dominant benthic foraminifera and strong, localised excursions in the benthic δ13C/δ18O record.

Methane, Microfossils, Palaeotidal modelling, Rock-Eval, Sea surface temperature, Stable isotopes
0031-0182
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Woods, Mark A.
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Wilkinson, Ian P.
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Leng, Melanie J.
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Riding, James B.
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Vane, Christopher H.
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Lopes dos Santos, Raquel A.
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Kender, Sev
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De Schepper, Stijn
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Hennissen, Jan A.I.
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Ward, Sophie L.
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Gowing, Charles J.B.
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Wilby, Philip R.
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Nichols, Matthew D.
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Rochelle, Christopher A.
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Woods, Mark A.
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Wilkinson, Ian P.
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Leng, Melanie J.
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Riding, James B.
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Vane, Christopher H.
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Lopes dos Santos, Raquel A.
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Kender, Sev
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De Schepper, Stijn
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Hennissen, Jan A.I.
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Ward, Sophie L.
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Gowing, Charles J.B.
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Wilby, Philip R.
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Nichols, Matthew D.
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Rochelle, Christopher A.
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Woods, Mark A., Wilkinson, Ian P., Leng, Melanie J., Riding, James B., Vane, Christopher H., Lopes dos Santos, Raquel A., Kender, Sev, De Schepper, Stijn, Hennissen, Jan A.I., Ward, Sophie L., Gowing, Charles J.B., Wilby, Philip R., Nichols, Matthew D. and Rochelle, Christopher A. (2019) Tracking Holocene palaeostratification and productivity changes in the Western Irish Sea: a multi-proxy record. Palaeogeography, Palaeoclimatology, Palaeoecology, 532, 1-16. (doi:10.1016/j.palaeo.2019.06.004).

Record type: Article

Abstract

The Western Irish Sea preserves an exceptionally thick (ca. 40 m) Holocene succession that is ideally suited to understanding the pattern of palaeostratification and water mass productivity changes in the region, and their relationship with sea level, sedimentation, and biota. Additionally, the presence of shallow-buried methane provides an opportunity to explore its potential impact on the local pattern of Holocene marine environmental change. Multi-proxy investigation of a cored borehole succession through the Holocene interval tracks changes from mixed to seasonally stratified conditions. In the earliest Holocene (11.2–10 ka), high productivity, mixed water conditions prevailed, with abundant and diverse foraminifera and dominant heterotrophic dinoflagellate cysts. Productivity was probably driven by high nutrient fluxes related to high rates of sedimentation (>1600 cm/kyr), in turn influenced by relatively low sea level and restricted sediment accommodation space across shelf areas to the east of the borehole site (eastern Irish Sea Basin). With rising sea level in the later part of the Early Holocene, the region evolved into a relatively lower productivity mixed water mass system, with significant changes in ecology revealed by dinoflagellate cysts and foraminifera. In the latest Early Holocene and earliest Mid Holocene (ca. 8.4–8.2 ka) a return to higher productivity is signalled by dinoflagellate cyst data; a result of seasonal stratification becoming established, evidenced by sharply increased summer sea surface temperature estimates (typically 16–17 °C) that contrast with an opposite (more positive) trend in δ18O values for benthic foraminifera. Reductions in turbulent mixing associated with stratification might have exacerbated the palaeoecological impact of shallow-buried methane associated with the borehole site, potentially evidenced by a significant change in dominant benthic foraminifera and strong, localised excursions in the benthic δ13C/δ18O record.

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Accepted/In Press date: 3 June 2019
e-pub ahead of print date: 6 June 2019
Published date: 15 October 2019
Keywords: Methane, Microfossils, Palaeotidal modelling, Rock-Eval, Sea surface temperature, Stable isotopes

Identifiers

Local EPrints ID: 432381
URI: https://eprints.soton.ac.uk/id/eprint/432381
ISSN: 0031-0182
PURE UUID: bb26186e-7375-47d7-8711-5c6bc8216e5a

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Date deposited: 12 Jul 2019 16:30
Last modified: 15 Oct 2019 16:30

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Contributors

Author: Mark A. Woods
Author: Ian P. Wilkinson
Author: Melanie J. Leng
Author: James B. Riding
Author: Christopher H. Vane
Author: Raquel A. Lopes dos Santos
Author: Sev Kender
Author: Stijn De Schepper
Author: Jan A.I. Hennissen
Author: Sophie L. Ward
Author: Charles J.B. Gowing
Author: Philip R. Wilby
Author: Christopher A. Rochelle

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