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Biases in radiocarb...
Biases in radiocarbon dating of organic fractions in sediments from meromictic and seasonally hypoxic lakes
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- Ojala, Antti E. K. (författare)
- Geol Survey Finland, Vuorimiehentie 5, FIN-02151 Espoo, Finland,Geological Survey of Finland
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- Saarnisto, Matti (författare)
- Mikonkatu 22 D 46, FIN-00100 Helsinki, Finland
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- Jungner, Hogne (författare)
- Univ Helsinki, POB 64, FIN-00014 Helsinki, Finland,Helsinki University of Technology
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- Snowball, Ian, 1963- (författare)
- Uppsala University,Uppsala universitet,Naturresurser och hållbar utveckling
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- Muscheler, Raimund (författare)
- Lund University,Lunds universitet,Kvartärgeologi,Geologiska institutionen,Naturvetenskapliga fakulteten,Quaternary Sciences,Department of Geology,Faculty of Science
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(creator_code:org_t)
- 2019-12-04
- 2019
- Engelska.
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Ingår i: Bulletin of the Geological Society of Finland. - : GEOLOGICAL SOC FINLAND. - 0367-5211 .- 1799-4632. ; 91, s. 221-235
- Relaterad länk:
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https://doi.org/10.1...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- We present here radiocarbon dating results from two boreal lakes in Finland, which are permanently (meromictic) or seasonally stratified and contain continuous sequences of annually laminated sediments that started to form in the early Holocene. The radiocarbon dating results of different organic components were compared with the varve-based sediment chronologies. The deviation between the Lake Valkiajarvi varve chronology (8400 varve years 2-3% error estimate) and 33 C-14 dates taken from insoluble and soluble organic phases vary inconsistently throughout the Holocene. In extreme cases mean calibrated radiocarbon dates with 95.4% confidence levels (2 sigma) are -2350 and +2040 years offset when compared with the varve chronology. On average, the radiocarbon dates are offset by ca. +550 years. The deviation between the Lake Nautajarvi varve chronology (9898 varve years +/- 1% error estimate) and 26 C-14 dates analyzed with conventional and AMS methods indicates that radiocarbon dates are systematically older by 500-1300 years (about 900 years on average). This significant offset mean that radiocarbon dates obtained from organic bulk sediment of meromictic and seasonally hypoxic lakes must be cautiously interpreted because of the reservoir effect and carbon cycling at the sediment-water interface. Direct evidence was obtained from the dating of soluble fraction and insoluble organic matter from near bottom water in the monimolimnion of Lake Valkiajarvi, which yielded C-14 ages of 560 +/- 80 BP and 2070 +/- 140 BP, respectively. Our study reinforces previous results that age-depth models based on bulk sediment radiocarbon dates obtained on sediments of stratified lakes are of limited value for accurate dating of changes in land use and especially the commence of agriculture.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
Nyckelord
- lake sediment
- dating
- radiocarbon
- varves
- anoxia
- Finland
- Anoxia
- Dating
- Finland
- Lake sediment
- Radiocarbon
- Varves
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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