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A new method for constructing Pb-210 chronology of young peat profiles sampled with low frequency

Jarosław Sikorski
Jarosław Sikorski
   | Feb 06, 2019
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Article Category: Regular Articles
Published Online: Feb 06, 2019
Page range: 1 - 14
Received: Jul 04, 2018
Accepted: Jan 04, 2019
DOI: https://doi.org/10.1515/geochr-2015-0101
Keywords
© 2019 J. Sikorski published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Location of the sites.
Location of the sites.

Fig. 2

Specific activity of the 210Pb for measured samples (black circles) and using approximation of activity (red squares).
Specific activity of the 210Pb for measured samples (black circles) and using approximation of activity (red squares).

Fig. 3

Activities (the upper chart) and age-depth models (the lower chart), obtained for different values of c parameter (c = 2 – black diamonds, c = 2.5 – red squares, c = 3 – blue circles), for BB3 core.
Activities (the upper chart) and age-depth models (the lower chart), obtained for different values of c parameter (c = 2 – black diamonds, c = 2.5 – red squares, c = 3 – blue circles), for BB3 core.

Fig. 4

Specific activity of the 210Pb obtained using the approximation of activity (red squares) for BB3 and BB4 cores, and after their shortening (black circles).
Specific activity of the 210Pb obtained using the approximation of activity (red squares) for BB3 and BB4 cores, and after their shortening (black circles).

Fig. 5

Age calculated from the CRS dating model for measured activity (black circles) and using approximation of activity (red squares).
Age calculated from the CRS dating model for measured activity (black circles) and using approximation of activity (red squares).

Fig. 6

Age-depth models obtained by activity approximation (red) and SIT (brown), Mod-Age (black), OxCal (green), Clam (blue), Bacon (purple) models. For the sake of clarity, the presented charts show the uncertainties (68.2%) for activity approximation only, as well as in the lower layers of the cores for the models that diverge most seriously from the proposed model. This is the case for SIT model for all the cores, and for BB3 and BM4 in the case of Bacon model, and BB4, BM3, and BM4 in the case of Mod-Age model.
Age-depth models obtained by activity approximation (red) and SIT (brown), Mod-Age (black), OxCal (green), Clam (blue), Bacon (purple) models. For the sake of clarity, the presented charts show the uncertainties (68.2%) for activity approximation only, as well as in the lower layers of the cores for the models that diverge most seriously from the proposed model. This is the case for SIT model for all the cores, and for BB3 and BM4 in the case of Bacon model, and BB4, BM3, and BM4 in the case of Mod-Age model.

Fig. 7

Examples of age-depth models obtained by Bacon model for cores TW1 (left) and BM4 (right). Note that the models are not matched to the points corresponding to the maximum probability; they only tend to the linearization.
Examples of age-depth models obtained by Bacon model for cores TW1 (left) and BM4 (right). Note that the models are not matched to the points corresponding to the maximum probability; they only tend to the linearization.

Parameters a, b, c of the functions obtained in TableCurve program.

Core a b c
BB3 6.093(45) –0.391(52) 2.5
BB3 shortened 6.148(52) –0.486(77) 2.5
BB4 6.175(26) –0.499(38) 2.5
BB4 shortened 6.220(26) –0.618(45) 2.5
BM3 6.063(39) –0.420(61) 2.5
BM3 shortened 6.062(49) –0.417(80) 2.5
BM4 6.022(36) –0.198(35) 3.0
BM4 shortened 6.018(40) –0.187(41) 3.0

Average growth rates of the investigated peat bogs.

Average growth rates (mm/y)
Core by 1967 from 1967 to present times
weighted average weighted average
BB3 1.03(12) 1.10(13) 3.41(19) 3.21(18)
BB4 1.21(15) 3.04(18)
BM3 1.15(13) 0.99(12) 3.26(18) 3.40(18)
BM4 0.87(11) 3.54(18)
TW1 1.34(16)
TW2 1.41(17)

Comparison of measured and approximated values of supported 210Pb.

Core Depth (cm) Measured values of supported 210Pb (Bq/kg) Approximated values of supported 210Pb (Bq/kg) t-test p-value
BB3 29.5 12.2(81) 14.7(91) 0.21 0.84
BB4 29.5 15.3(83) 13.8(90) 0.12 0.91
BM3 31.5 20.8(95) 22.9(99) 0.15 0.88
BM4 29.5 23.4(96) 23.1(98) 0.02 0.98
eISSN:
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Language:
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