Improving the reliability of bulk sediment radiocarbon dating
Radiocarbon dated chronologies are the most extensively applied dating technique when investigating the last ∼45,000 years. In lake and marine sediments, a single macrofossil or several microfossils are the preferred sample material because they have a 14 C age that accurately reflects the time of d...
Published in: | Quaternary Science Reviews |
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2020
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ftcopenhagenunip:oai:pure.atira.dk:publications/119b226b-692f-45da-ae12-1a747126967d 2024-05-19T07:41:19+00:00 Improving the reliability of bulk sediment radiocarbon dating Strunk, Astrid Olsen, Jesper Sanei, Hamed Rudra, Arka Larsen, Nicolaj K. 2020 https://curis.ku.dk/portal/da/publications/improving-the-reliability-of-bulk-sediment-radiocarbon-dating(119b226b-692f-45da-ae12-1a747126967d).html https://doi.org/10.1016/j.quascirev.2020.106442 eng eng info:eu-repo/semantics/closedAccess Strunk , A , Olsen , J , Sanei , H , Rudra , A & Larsen , N K 2020 , ' Improving the reliability of bulk sediment radiocarbon dating ' , Quaternary Science Reviews , vol. 242 , 106442 . https://doi.org/10.1016/j.quascirev.2020.106442 Age offset. Bulk sediment Greenland Organic geochemistry Paleolimnology Pyrolysis Quaternary Radiocarbon dating Radiogenic isotopes Stable isotopes article 2020 ftcopenhagenunip https://doi.org/10.1016/j.quascirev.2020.106442 2024-05-02T00:33:11Z Radiocarbon dated chronologies are the most extensively applied dating technique when investigating the last ∼45,000 years. In lake and marine sediments, a single macrofossil or several microfossils are the preferred sample material because they have a 14 C age that accurately reflects the time of deposition. However, absence of macro- or microfossils are a recurring challenge. Often, it is necessary to use bulk sediment samples for radiocarbon dating, but they frequently yield ages clearly exceeding the depositional timeframe due to occurrence of organic material of older origin. Until now, it has not been possible to assess if the dating result of a bulk sediment sample is reliable, or to adequately explain the mechanisms behind age disagreement between bulk and macro- and microfossils. In this study, we investigate the age offset between paired bulk and macrofossil ages in sediment cores from three lakes in SE and E Greenland. Furthermore, we distinguish three quantifiable main carbon sources in the samples: a) recent terrestrial organic fragments, b) recent aquatic organic matter, and c) reworked land-derived old carbon, through pyrolysis organic geochemistry, organic petrographic microscopy, and isotopic fractionization. Our results show that the offset between bulk (humic fraction) and macrofossil radiocarbon ages in three similar lakes range from 9 14 C yr to 20.1 14 C kyr. We observe a reduced age offset between bulk- and macrofossil ages, and thereby a higher reliability of bulk (humic fraction) ages, correlated with increased values of TOC, C/N ratio, and high CO 2 release in pyrolysis (S3 value). We recommend that future studies presenting bulk sediment chronologies apply pyrolysis organic geochemistry, organic petrographic microscopy, and isotopic fractionization as demonstrated here, to select reliable sediment intervals for bulk dating and retrieve more robust results. Article in Journal/Newspaper Greenland University of Copenhagen: Research Quaternary Science Reviews 242 106442 |
institution |
Open Polar |
collection |
University of Copenhagen: Research |
op_collection_id |
ftcopenhagenunip |
language |
English |
topic |
Age offset. Bulk sediment Greenland Organic geochemistry Paleolimnology Pyrolysis Quaternary Radiocarbon dating Radiogenic isotopes Stable isotopes |
spellingShingle |
Age offset. Bulk sediment Greenland Organic geochemistry Paleolimnology Pyrolysis Quaternary Radiocarbon dating Radiogenic isotopes Stable isotopes Strunk, Astrid Olsen, Jesper Sanei, Hamed Rudra, Arka Larsen, Nicolaj K. Improving the reliability of bulk sediment radiocarbon dating |
topic_facet |
Age offset. Bulk sediment Greenland Organic geochemistry Paleolimnology Pyrolysis Quaternary Radiocarbon dating Radiogenic isotopes Stable isotopes |
description |
Radiocarbon dated chronologies are the most extensively applied dating technique when investigating the last ∼45,000 years. In lake and marine sediments, a single macrofossil or several microfossils are the preferred sample material because they have a 14 C age that accurately reflects the time of deposition. However, absence of macro- or microfossils are a recurring challenge. Often, it is necessary to use bulk sediment samples for radiocarbon dating, but they frequently yield ages clearly exceeding the depositional timeframe due to occurrence of organic material of older origin. Until now, it has not been possible to assess if the dating result of a bulk sediment sample is reliable, or to adequately explain the mechanisms behind age disagreement between bulk and macro- and microfossils. In this study, we investigate the age offset between paired bulk and macrofossil ages in sediment cores from three lakes in SE and E Greenland. Furthermore, we distinguish three quantifiable main carbon sources in the samples: a) recent terrestrial organic fragments, b) recent aquatic organic matter, and c) reworked land-derived old carbon, through pyrolysis organic geochemistry, organic petrographic microscopy, and isotopic fractionization. Our results show that the offset between bulk (humic fraction) and macrofossil radiocarbon ages in three similar lakes range from 9 14 C yr to 20.1 14 C kyr. We observe a reduced age offset between bulk- and macrofossil ages, and thereby a higher reliability of bulk (humic fraction) ages, correlated with increased values of TOC, C/N ratio, and high CO 2 release in pyrolysis (S3 value). We recommend that future studies presenting bulk sediment chronologies apply pyrolysis organic geochemistry, organic petrographic microscopy, and isotopic fractionization as demonstrated here, to select reliable sediment intervals for bulk dating and retrieve more robust results. |
format |
Article in Journal/Newspaper |
author |
Strunk, Astrid Olsen, Jesper Sanei, Hamed Rudra, Arka Larsen, Nicolaj K. |
author_facet |
Strunk, Astrid Olsen, Jesper Sanei, Hamed Rudra, Arka Larsen, Nicolaj K. |
author_sort |
Strunk, Astrid |
title |
Improving the reliability of bulk sediment radiocarbon dating |
title_short |
Improving the reliability of bulk sediment radiocarbon dating |
title_full |
Improving the reliability of bulk sediment radiocarbon dating |
title_fullStr |
Improving the reliability of bulk sediment radiocarbon dating |
title_full_unstemmed |
Improving the reliability of bulk sediment radiocarbon dating |
title_sort |
improving the reliability of bulk sediment radiocarbon dating |
publishDate |
2020 |
url |
https://curis.ku.dk/portal/da/publications/improving-the-reliability-of-bulk-sediment-radiocarbon-dating(119b226b-692f-45da-ae12-1a747126967d).html https://doi.org/10.1016/j.quascirev.2020.106442 |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Strunk , A , Olsen , J , Sanei , H , Rudra , A & Larsen , N K 2020 , ' Improving the reliability of bulk sediment radiocarbon dating ' , Quaternary Science Reviews , vol. 242 , 106442 . https://doi.org/10.1016/j.quascirev.2020.106442 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.1016/j.quascirev.2020.106442 |
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Quaternary Science Reviews |
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242 |
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106442 |
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