Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland
Radiocarbon dating marine sediments is complicated by the strongly heterogeneous age of ocean waters. Tephrochronology provides a well-established method to constrain the age of local radiocarbon reservoirs and more accurately calibrate dates. Numerous ultra-distal cryptotephra deposits (non-visible...
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ftcopernicus:oai:publications.copernicus.org:egusphere107824 2023-06-11T04:14:12+02:00 Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland Monteath, Alistair Bolton, Matthew Harvey, Jordan Seidenkrantz, Marit-Solveig Pearce, Christof Jensen, Britta 2023-05-04 application/pdf https://doi.org/10.5194/egusphere-2022-1273 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1273/ eng eng doi:10.5194/egusphere-2022-1273 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1273/ eISSN: Text 2023 ftcopernicus https://doi.org/10.5194/egusphere-2022-1273 2023-05-08T16:23:13Z Radiocarbon dating marine sediments is complicated by the strongly heterogeneous age of ocean waters. Tephrochronology provides a well-established method to constrain the age of local radiocarbon reservoirs and more accurately calibrate dates. Numerous ultra-distal cryptotephra deposits (non-visible volcanic ash more than 3000 km from source) have been identified in peatlands and lake sediments across north-eastern North America and correlated with volcanic arcs in the Pacific north-west. Previously, however, these isochrons have not been identified in sediments from the north-west Atlantic Ocean. In this study, we report the presence of two ultra-distal cryptotephra deposits; Mazama Ash and White River Ash eastern lobe (WRAe), in Placentia Bay, North Atlantic Ocean. We use these well-dated isochrons to constrain the local marine radiocarbon reservoir offset ( Δ R) and develop a robust Bayesian age–depth model with a Δ R that varies through time. Our results indicate that the marine radiocarbon offset in Placentia Bay was - 126 ± 151 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="cae5bdecf7af0978e53d2c4c9289ec09"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-5-229-2023-ie00001.svg" width="58pt" height="10pt" src="gchron-5-229-2023-ie00001.png"/></svg:svg> years (relative to the Marine20 calibration curve) at the time of Mazama Ash deposition (7572 ± 18 yr BP) and −396 ± 144 years at the time of WRAe deposition (1098–1097 yr BP). Changes in Δ R appear to coincide with inferred shifts in relative influences of the inner Labrador Current and the Slopewater Current in the bay. An important conclusion is that single-offset models of Δ R are easiest to apply and often hard to disprove. However, such models may oversimplify reservoir effects in a core, even over relatively short timescales. Acknowledging potentially varying offsets is critical when ocean circulation and ventilation characteristics ... Text Newfoundland North Atlantic North West Atlantic Copernicus Publications: E-Journals Newfoundland Pacific |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Radiocarbon dating marine sediments is complicated by the strongly heterogeneous age of ocean waters. Tephrochronology provides a well-established method to constrain the age of local radiocarbon reservoirs and more accurately calibrate dates. Numerous ultra-distal cryptotephra deposits (non-visible volcanic ash more than 3000 km from source) have been identified in peatlands and lake sediments across north-eastern North America and correlated with volcanic arcs in the Pacific north-west. Previously, however, these isochrons have not been identified in sediments from the north-west Atlantic Ocean. In this study, we report the presence of two ultra-distal cryptotephra deposits; Mazama Ash and White River Ash eastern lobe (WRAe), in Placentia Bay, North Atlantic Ocean. We use these well-dated isochrons to constrain the local marine radiocarbon reservoir offset ( Δ R) and develop a robust Bayesian age–depth model with a Δ R that varies through time. Our results indicate that the marine radiocarbon offset in Placentia Bay was - 126 ± 151 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="cae5bdecf7af0978e53d2c4c9289ec09"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-5-229-2023-ie00001.svg" width="58pt" height="10pt" src="gchron-5-229-2023-ie00001.png"/></svg:svg> years (relative to the Marine20 calibration curve) at the time of Mazama Ash deposition (7572 ± 18 yr BP) and −396 ± 144 years at the time of WRAe deposition (1098–1097 yr BP). Changes in Δ R appear to coincide with inferred shifts in relative influences of the inner Labrador Current and the Slopewater Current in the bay. An important conclusion is that single-offset models of Δ R are easiest to apply and often hard to disprove. However, such models may oversimplify reservoir effects in a core, even over relatively short timescales. Acknowledging potentially varying offsets is critical when ocean circulation and ventilation characteristics ... |
format |
Text |
author |
Monteath, Alistair Bolton, Matthew Harvey, Jordan Seidenkrantz, Marit-Solveig Pearce, Christof Jensen, Britta |
spellingShingle |
Monteath, Alistair Bolton, Matthew Harvey, Jordan Seidenkrantz, Marit-Solveig Pearce, Christof Jensen, Britta Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
author_facet |
Monteath, Alistair Bolton, Matthew Harvey, Jordan Seidenkrantz, Marit-Solveig Pearce, Christof Jensen, Britta |
author_sort |
Monteath, Alistair |
title |
Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
title_short |
Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
title_full |
Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
title_fullStr |
Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
title_full_unstemmed |
Ultra-distal tephra deposits and Bayesian modelling constrain a variable marine radiocarbon offset in Placentia Bay, Newfoundland |
title_sort |
ultra-distal tephra deposits and bayesian modelling constrain a variable marine radiocarbon offset in placentia bay, newfoundland |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2022-1273 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1273/ |
geographic |
Newfoundland Pacific |
geographic_facet |
Newfoundland Pacific |
genre |
Newfoundland North Atlantic North West Atlantic |
genre_facet |
Newfoundland North Atlantic North West Atlantic |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2022-1273 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1273/ |
op_doi |
https://doi.org/10.5194/egusphere-2022-1273 |
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1768392039097958400 |