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Residual Dose of K-Feldspar post-IR Irsl of Beach-Shoreface Sands at Kujukuri, Eastern Japan

Toru Tamura
Toru Tamura
, 
Junko Komatsubara
Junko Komatsubara
, 
Saiko Sugisaki
Saiko Sugisaki
 and 
Naohisa Nishida
Naohisa Nishida
   | Dec 31, 2021
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Published Online: Dec 31, 2021
Page range: 364 - 378
Received: Feb 15, 2019
Accepted: Mar 13, 2020
DOI: https://doi.org/10.2478/geochr-2020-0036
Keywords
© 2019 Toru Tamura et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

A) Location map of the study area and plate boundaries between the Eurasian (EUR), Okhotsk (OKH), Philippine Sea (PHS), and Pacific Ocean (PAC) plates. B) Morpho-sedimentary map of the Kujukuri beach-ridge plain and offshore showing the locations of modern samples and drill cores (modified from Tamura et al., 2008b). Five modern samples (Katakai, BS9, 10, 23, and 34) and two drill cores (GS-QYH-1 and GS-QAS-2) were used for the analysis. The red line shows the location of the cross section in Fig. 2. The definition of beach-ridge groups I–III is after Moriwaki (1979) and their formative durations were determined based on radiocarbon chronology in a cross section near the Makame and Sakuta rivers (Masuda et al., 2001b; Tamura et al., 2007).
A) Location map of the study area and plate boundaries between the Eurasian (EUR), Okhotsk (OKH), Philippine Sea (PHS), and Pacific Ocean (PAC) plates. B) Morpho-sedimentary map of the Kujukuri beach-ridge plain and offshore showing the locations of modern samples and drill cores (modified from Tamura et al., 2008b). Five modern samples (Katakai, BS9, 10, 23, and 34) and two drill cores (GS-QYH-1 and GS-QAS-2) were used for the analysis. The red line shows the location of the cross section in Fig. 2. The definition of beach-ridge groups I–III is after Moriwaki (1979) and their formative durations were determined based on radiocarbon chronology in a cross section near the Makame and Sakuta rivers (Masuda et al., 2001b; Tamura et al., 2007).

Fig. 2

Cross section across the Kujukuri beach-ridge plain and offshore area (see location in Fig. 1b). The positions of the two drill cores and five modern sediment samples analyzed herein were projected onto a single section. Six samples were taken for analysis from each drill core. Radiocarbon dates of molluscan shells and a plant fragment are shown beside the columns of the cores. Dashed lines indicate the isochrones of the beach-ridge group boundary. The stratigraphic outline was defined on the basis of drill cores and compilations of previous studies in the central part of the plain (e.g., Tamura et al., 2003, 2007, 2008a, 2008b). FS: foreshore and backshore facies; US: upper shoreface facies; LS: lower shoreface facies; T.P.: Tokyo Peil, the standard datum for elevation measurements in Japan.
Cross section across the Kujukuri beach-ridge plain and offshore area (see location in Fig. 1b). The positions of the two drill cores and five modern sediment samples analyzed herein were projected onto a single section. Six samples were taken for analysis from each drill core. Radiocarbon dates of molluscan shells and a plant fragment are shown beside the columns of the cores. Dashed lines indicate the isochrones of the beach-ridge group boundary. The stratigraphic outline was defined on the basis of drill cores and compilations of previous studies in the central part of the plain (e.g., Tamura et al., 2003, 2007, 2008a, 2008b). FS: foreshore and backshore facies; US: upper shoreface facies; LS: lower shoreface facies; T.P.: Tokyo Peil, the standard datum for elevation measurements in Japan.

Fig. 3

Fading-corrected final luminescence age estimates of samples taken from (A) core GS-QAS-2 and (B) core GS-QYH-1. Radiocarbon ages of molluscan shells are also shown for comparison. Radiocarbon ages at the ground surface were assumed to be 5.7 ka and 0 ka for cores GS-QAS-2 and GS-QYH-1, respectively, to define the expected ages (red lines).
Fading-corrected final luminescence age estimates of samples taken from (A) core GS-QAS-2 and (B) core GS-QYH-1. Radiocarbon ages of molluscan shells are also shown for comparison. Radiocarbon ages at the ground surface were assumed to be 5.7 ka and 0 ka for cores GS-QAS-2 and GS-QYH-1, respectively, to define the expected ages (red lines).

Fig. 4

Decay curves and dose–response curves (inset) of IR50, pIRIR150, and pIRIR290 measured on samples (A) gsj15259 and (B) gsj17282. The intersections of the natural OSL intensity with the dose–response curve and the corresponding equivalent dose are highlighted with red dashed lines.
Decay curves and dose–response curves (inset) of IR50, pIRIR150, and pIRIR290 measured on samples (A) gsj15259 and (B) gsj17282. The intersections of the natural OSL intensity with the dose–response curve and the corresponding equivalent dose are highlighted with red dashed lines.

Fig. 5

Fading test results of IR50, pIRIR150, and pIRIR290 signals measured for sample gsj15258. A regression line was defined for each signal based on the least-squares method and then applied to estimate the g-value.
Fading test results of IR50, pIRIR150, and pIRIR290 signals measured for sample gsj15258. A regression line was defined for each signal based on the least-squares method and then applied to estimate the g-value.

Fig. 6

Plots of fading-corrected De derived from (A) IR50, (B) pIRIR150, and (C) pIRIR290 against expected De. The y-intercept of the regression line for pIRIR290 represents the average residual dose, which is estimated as 24.2 Gy. Dotted lines indicate the 95% confidence interval.
Plots of fading-corrected De derived from (A) IR50, (B) pIRIR150, and (C) pIRIR290 against expected De. The y-intercept of the regression line for pIRIR290 represents the average residual dose, which is estimated as 24.2 Gy. Dotted lines indicate the 95% confidence interval.

Fig. 7

Plots of residual dose estimated for pIRIR290 against depositional water depth of the sample. The regression line exhibits only a very weak correlation; however, a few samples taken from less than 5 m water depth exhibit slightly lower residual doses than others. Dotted lines indicate the 95% confidence interval.
Plots of residual dose estimated for pIRIR290 against depositional water depth of the sample. The regression line exhibits only a very weak correlation; however, a few samples taken from less than 5 m water depth exhibit slightly lower residual doses than others. Dotted lines indicate the 95% confidence interval.

Details of modern samples. Equivalent doses (De) were determined from IR50, pIRIR150, and pIRIR290.

Site Lab code Latitude Longitude Water depth (m) De from IR50 (Gy) De from pIRIR150 (Gy) De from pIRIR290 (Gy)
Katakai gsj15160 N35°32′28.2″ E140°27′55.8″ 0 0.09 ± 0.01 0.93 ± 0.08 11.93 ± 1.66
BS9 gsj17282 N35°37′42.1″ E140°37′13.9″ 13 0.04 ± 0.01 1.80 ± 0.16 27.28 ± 1.08
BS10 gsj17283 N35°37′42.3″ E140°40′16.6″ 14 0.07 ± 0.003 2.45 ± 0.13 29.09 ± 1.44
BS23 gsj17284 N35°35′11.9″ E140°41′48.5″ 23 0.18 ± 0.01 3.25 ± 0.33 29.27 ± 1.47
BS34 gsj17273 N35°32′40.0″ E140°45′39.4″ 34 0.06 ± 0.01 2.26 ± 0.14 23.92 ± 1.60

Details of Holocene samples taken from drill cores: sample level, water, U, Th, K, and Rb contents, estimated dose rates, and expected ages from radiocarbon dates. The internal dose rate was estimated to be 0.738±0.123 Gy/ka for all samples.

Lab code Depth (m) Water content (%) U (ppm) Th (ppm) K (%) Rb (ppm) Cosmic dose rate (Gy/ka) Total dose rate (Gy/ka) Expected age (ka)
GSJ-QAS2 (N35°43′17.3″ E140°37′52.0″ Elevation: +5.2 m)
gsj15149 2.2 21 0.67 2.9 1.1 39 0.15 ± 0.02 2.07 ± 0.14 5.89 ± 0.08
gsj15151 4.2 31 0.89 3.6 1.3 48 0.12 ± 0.01 2.17 ± 0.14 6.01 ± 0.08
gsj15154 7.5 20 0.7 3.0 1.4 55 0.09 ± 0.01 2.28 ± 0.14 6.26 ± 0.08
gsj15155 10.2 39 1.1 4.3 1.6 62 0.07 ± 0.01 2.26 ± 0.14 6.88 ± 0.08
gsj15157 14.4 34 0.89 3.8 1.6 60 0.05 ± 0.01 2.28 ± 0.14 7.13 ± 0.08
gsj15158 14.8 42 1.2 3.8 1.6 62 0.05 ± 0.00 2.21 ± 0.14 7.15 ± 0.08
GSJ-QYH1 (N35°37′00.0″ E140°32′29.2″ Elevation: +2.1 m)
gsj15254 2.3 20 0.91 4.8 0.97 34 0.15 ± 0.02 2.13 ± 0.14 0.23 ± 0.08
gsj15255 4.9 33 0.88 3.1 1.6 58 0.11 ± 0.01 2.30 ± 0.14 0.45 ± 0.08
gsj15256 7.2 30 0.67 3.3 1.5 52 0.09 ± 0.01 2.23 ± 0.14 0.66 ± 0.08
gsj15257 10.7 33 0.76 4.0 1.5 50 0.06 ± 0.01 2.16 ± 0.14 1.13 ± 0.08
gsj15258 14.6 31 0.73 3.1 1.6 50 0.05 ± 0.01 2.21 ± 0.14 1.74 ± 0.08
sj15259 19.2 31 0.8 3.5 1.6 51 0.03 ± 0.00 2.24 ± 0.14 2.44 ± 0.08

Equivalent dose (De), uncorrected age, g-value, corrected age, offset from expected age, and De offset from expected for pIRIR150 signals of Holocene samples.

Lab code Depth (m) De (Gy) Uncorrected age (ka) g-value (%/decade) Corrected age (ka) Age offset from expected (ka) De offset from expected (Gy)
GS-QAS-2
gsj15149 2.2 22.83 ± 1.25 11.0 ± 0.9 1.13 ± 0.17 12.0 ± 1.2 6.1 ± 1.2 12.64 ± 0.16
gsj15151 4.2 34.00 ± 1.51 15.7 ± 1.2 1.28 ± 0.09* 17.3 ± 1.3 11.3 ± 1.3 24.46 ± 0.18
gsj15154 7.5 28.50 ± 1.17 12.5 ± 0.9 1.16 ± 0.08 13.7 ± 1.0 7.4 ± 1.0 16.88 ± 0.15
gsj15155 10.2 40.57 ± 1.17 17.9 ± 1.2 1.28 ± 0.09* 19.8 ± 1.3 12.9 ± 1.3 29.21 ± 0.18
gsj15157 14.4 39.51 ± 1.36 17.3 ± 1.2 1.28 ± 0.09* 19.2 ± 1.3 12.0 ± 1.3 27.40 ± 0.19
gsj15158 14.8 39.62 ± 1.03 17.9 ± 1.2 1.28 ± 0.09* 19.8 ± 1.3 12.7 ± 1.3 27.95 ± 0.18
GS-QYH-1
gsj15254 2.3 18.08 ± 0.60 8.5 ± 0.6 1.45 ± 0.37 9.4 ± 0.7 9.2 ± 0.7 19.58 ± 0.10
gsj15255 4.9 26.42 ± 1.38 11.5 ± 0.9 1.11 ± 0.16 12.5 ± 0.9 12.0 ± 0.9 27.69 ± 0.12
gsj15256 7.2 21.50 ± 0.85 9.6 ± 0.7 1.05 ± 0.32 10.4 ± 0.7 9.8 ± 0.7 21.78 ± 0.10
gsj15257 10.7 28.89 ± 0.79 13.4 ± 0.9 1.07 ± 0.12 14.5 ± 1.0 13.3 ± 1.0 28.85 ± 0.14
gsj15258 14.6 26.99 ± 1.02 12.2 ± 0.9 1.96 ± 0.36 14.3 ± 1.2 12.6 ± 1.2 27.81 ± 0.17
gsj15259 19.2 25.46 ± 0.64 11.4 ± 0.8 1.31 ± 0.18 12.5 ± 0.9 10.1 ± 0.9 22.66 ± 0.13

Radiocarbon dating results for drill core samples.

Access code Core depth (m) Sample Conventional 14C age (yr BP) Calibrated age (2s) (cal yr BP) Probability
GS-QAS-2
IAAA-153551 7.3 Shell (Mactra chinensis) 5720 ± 30 6019–6239 1.000
IAAA-153282 9.1 Shell (M. chinensis) 6290 ± 30 6653–6843 1.000
IAAA-153552 21.3 Shell (Raetellops pulchellus) 6970 ± 30 7411–7540 1.000
IAAA-153283 25.4 Shell (R. pulchellus) 7850 ± 30 8224–8388 1.000
IAAA-153284 38.9 Shell (Glossaulax didyma) 8950 ± 30 9511–9708 1.000
IAAA-153553 41.8 Shell (Dosinia angulosa) 9570 ± 40 10295–10551 1.000
IAAA-151461 43.6 Plant fragment 9700 ± 40 10878–10933 0.097
11080–11212 0.903
GS-QYH-1
IAAA-153560 3.4 Shell (Chion semigranosa) 620 ± 20 146–164 0.026
187–312 0.974
IAAA-153288 8.4 Shell (M. chinensis) 1150 ± 20 649–749 1.000
IAAA-153561 19.1 Shell (Siliqua pulchella) 2680 ± 30 2303–2456 1.000
IAAA-153289 25.8 Shell (R. pulchellus) 7220 ± 30 7596–7761 1.000
IAAA-153562 27.3 Shell (Macoma tokyoensis) 8020 ± 30 8393–8556 1.000
IAAA-153290 32.4 Shell (Dentalium octangulatum) 9010 ± 40 9540–9822 1.000

Summaries of the IR50, pIRIR150, and pIRIR290 single-aliquot regenerative dose protocols used in this study.

Step post-IR IRSL (150°C) Signal post-IR IRSL (290°C) Signal
1 Preheat at 180°C for 60 s Preheat at 320°C for 60 s
2 IR stimulation at 50°C for 100 s Lx for IRSL50 IR stimulation at 50°C for 200 s
3 IR stimulation at 150°C for 100 s Lx for post-IR IRSL150 IR stimulation at 290°C for 200 s Lx for post-IR IRSL290
4 Test dose Test dose
5 Preheat at 180°C for 60 s Preheat at 320°C for 60 s
6 IR stimulation at 50°C for 100 s Tx for IRSL50 IR stimulation at 50°C for 200 s
7 IR stimulation at 150°C for 100 s Tx for post-IR IRSL150 IR stimulation at 290°C for 200 s Tx for post-IR IRSL290
8 Dose and return to step 1 IR stimulation at 325°C for 200 s
9 Dose and return to step 1

Equivalent dose (De), uncorrected age, g-value, corrected age, offset from expected age, and De offset from expected for IR50 signals of Holocene samples.

Lab code Depth (m) De (Gy) Uncorrected age (ka) g-value (%/decade) Corrected age (ka) Age offset from expected (ka) De offset from expected (Gy)
GS-QAS-2
gsj15149 2.2 5.25 ± 0.09 2.5 ± 0.2 8.48 ± 0.73 5.8 ± 1.0 −0.1 ± 1.0 −0.17 ± 0.14
gsj15151 4.2 6.78 ± 0.11 3.1 ± 0.2 7.96 ± 0.15* 6.8 ± 0.5 0.8 ± 0.5 1.6 ± 0.07
gsj15154 7.5 7.64 ± 0.20 3.4 ± 0.2 7.51 ± 0.45 6.9 ± 0.8 0.6 ± 0.8 1.5 ± 0.11
gsj15155 10.2 7.89 ± 0.13 3.5 ± 0.2 7.96 ± 0.15* 7.6 ± 0.5 0.7 ± 0.5 1.6 ± 0.07
gsj15157 14.4 8.10 ± 0.09 3.6 ± 0.2 7.96 ± 0.15* 7.8 ± 0.6 0.6 ± 0.6 1.5 ± 0.09
gsj15158 14.8 7.82 ± 0.11 3.5 ± 0.2 7.96 ± 0.15* 7.7 ± 0.6 0.6 ± 0.6 1.3 ± 0.08
GS-QYH-1
gsj15254 2.3 0.28 ± 0.01 0.13 ± 0.01 8.21 ± 0.42 0.2 ± 0.0 0.0 ± 0.1 0.01 ± 0.01
gsj15255 4.9 0.40 ± 0.01 0.18 ± 0.01 8.26 ± 0.28 0.3 ± 0.0 −0.1 ± 0.1 −0.29 ± 0.01
gsj15256 7.2 0.67 ± 0.02 0.30 ± 0.02 7.39 ± 0.10 0.5 ± 0.0 −0.1 ± 0.1 −0.27 ± 0.01
gsj15257 10.7 1.46 ± 0.03 0.68 ± 0.05 8.93 ± 0.90 1.5 ± 0.3 0.4 ± 0.3 0.77 ± 0.04
gsj15258 14.6 1.95 ± 0.02 0.88 ± 0.06 7.20 ± 0.13 1.6 ± 0.1 −0.1 ± 0.1 −0.26 ± 0.02
gsj15259 19.2 2.49 ± 0.03 1.1 ± 0.1 7.73 ± 0.73 2.2 ± 0.3 −0.3 ± 0.3 −0.57 ± 0.05
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