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Comparison of Equivalent Doses Obtained with Various post-IR IRSL Dating Protocols of K-Feldspar

Junjie Zhang

Junjie Zhang

Department of Earth Sciences, The University of Hong KongHong Kong, China
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Zhang, Junjie
, 
Sheng-Hua Li

Sheng-Hua Li

Department of Earth Sciences, The University of Hong KongHong Kong, China
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Li, Sheng-Hua
, 
Xulong Wang

Xulong Wang

State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of SciencesXi’an, China
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Wang, Xulong
, 
Qingzhen Hao

Qingzhen Hao

  • Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of SciencesBeijing, China
  • University of Chinese Academy of SciencesBeijing, China
  • CAS Center for Excellence in Life and PaleoenvironmentBeijing, China
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Hao, Qingzhen
, 
Guiming Hu

Guiming Hu

Department of Earth Sciences, The University of Hong KongHong Kong, China
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Hu, Guiming
 and 
Yiwei Chen

Yiwei Chen

State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of SciencesGuangzhou, China
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Chen, Yiwei
  
Dec 31, 2021
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Article Category: Conference Proceedings of the 5Asia Pacific Luminescence and Electron Spin Resonance Dating Conference October 15–17, 2018, Beijing, China. Guest Editor: Grzegorz Adamiec
Published Online: Dec 31, 2021
Page range: 129 - 137
Received: Jan 15, 2019
Accepted: Oct 29, 2019
DOI: https://doi.org/10.2478/geochr-2020-0010
Keywords
© 2019 Junjie Zhang et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

a) Locations of the Jingbian and Luochuan loess sections. b) Photograph of the sampling of section B at Jingbian.
a) Locations of the Jingbian and Luochuan loess sections. b) Photograph of the sampling of section B at Jingbian.

Fig. 2

Residual doses of IRSL signals stimulated at different temperatures using the SAR MET-pIRIR protocol. After 8 hr of bleaching with the solar simulator, the residual doses were reduced to ∼10 Gy for the MET-pIRIR300 signal.
Residual doses of IRSL signals stimulated at different temperatures using the SAR MET-pIRIR protocol. After 8 hr of bleaching with the solar simulator, the residual doses were reduced to ∼10 Gy for the MET-pIRIR300 signal.

Fig. 3

Standard growth curve (SGC) of the ‘MAR with heat’ protocol. The re-normalisation dose was 500 Gy. SGC curves were fitted with the single saturating exponential (SSE) function: y = y0 + A*(1-exp(-x/D0)) and the double saturating exponential (DSE) function: y = y0 + A1*(1-exp(-x/D1)) + A2*(1-exp(-x/D2)), respectively. The fitted results are shown in the graph. Note that the two SGCs only begin to diverge when the dose exceeds 2000 Gy.
Standard growth curve (SGC) of the ‘MAR with heat’ protocol. The re-normalisation dose was 500 Gy. SGC curves were fitted with the single saturating exponential (SSE) function: y = y0 + A*(1-exp(-x/D0)) and the double saturating exponential (DSE) function: y = y0 + A1*(1-exp(-x/D1)) + A2*(1-exp(-x/D2)), respectively. The fitted results are shown in the graph. Note that the two SGCs only begin to diverge when the dose exceeds 2000 Gy.

Fig. 4

De values and age versus depth relationship for section B. The SAR pIR50IR290 protocol has the youngest ages; the SAR pIR50IR290, MET-pIRIR250 and MET-pIRIR300 protocols have similar ages; and the ‘MAR with heat’ protocol has the oldest ages.
De values and age versus depth relationship for section B. The SAR pIR50IR290 protocol has the youngest ages; the SAR pIR50IR290, MET-pIRIR250 and MET-pIRIR300 protocols have similar ages; and the ‘MAR with heat’ protocol has the oldest ages.

Fig. 5

De values with different stimulation temperatures for the two SAR protocols with MET-pIRIR stimulation to 250°C or 300°C, and the ‘MAR with heat’ protocol. Note that the MAR De values always exceed the SAR De values.
De values with different stimulation temperatures for the two SAR protocols with MET-pIRIR stimulation to 250°C or 300°C, and the ‘MAR with heat’ protocol. Note that the MAR De values always exceed the SAR De values.

Fig. 6

Results of dose-recovery-like experiments for sample B-1000. (a) The growth curves of the L1/T1 and L2/T2 signals fitted with a single saturating exponential (SSE) function: y= y0+a*(1-exp(-x/D0)). (b) Regenerative doses of the first cycle are taken as unknown and recovered by the growth curve of L2/T2. The recovery ratios are plotted versus the recovery doses. Note that the recovery ratios are slightly overestimated when the doses exceed 600 Gy.
Results of dose-recovery-like experiments for sample B-1000. (a) The growth curves of the L1/T1 and L2/T2 signals fitted with a single saturating exponential (SSE) function: y= y0+a*(1-exp(-x/D0)). (b) Regenerative doses of the first cycle are taken as unknown and recovered by the growth curve of L2/T2. The recovery ratios are plotted versus the recovery doses. Note that the recovery ratios are slightly overestimated when the doses exceed 600 Gy.

Dose rates and ages of the samples using the five protocols_

Sample Water (%) K20 (%) Alpha count Dose rate (Gy/ka) Age (ka)
SAR pIR50IR290 SAR pIR200IR290 SAR MET-pIRIR250 SAR MET-pIRIR300 MAR with heat
A-570 15 ± 5 2.03 9.55 ± 0.15 3.21 ± 0.12 116 ± 12 132 ± 6 129 ± 6 \ 119 ± 6
A-1050 15 ± 5 2.19 10.83 ± 0.16 3.44 ± 0.13 179 ± 17 206 ± 13 206 ± 9 \ 217 ± 17
B-0 15 ± 5 1.95 10.14 ± 0.18 3.30 ± 0.12 165 ± 8 204 ± 19 194 ± 8 216 ± 19 260 ± 24
B-610 19.3 ± 5 2.50 11.88 ± 0.19 3.55 ± 0.13 183 ± 9 206 ± 10 212 ± 9 217 ± 15 260 ± 20
B-640 19.3 ± 5 2.40 11.85 ± 0.19 3.59 ± 0.13 171 ± 16 206 ± 9 215 ± 10 209 ± 18 251 ± 17
B-1000 15 ± 5 2.22 10.74 ± 0.18 3.43 ± 0.13 189 ± 19 240 ± 14 222 ± 11 233 ± 16 261 ± 23

De values obtained using the five protocols_ In the ‘MAR with heat’ protocol, the first ‘n’ indicates the aliquots used to measure the natural signal, and the second refers to the aliquots used to measure the signal of a regenerative dose_

Sample Depth (cm) SAR pIR50IR290 SAR pIR200IR290 SAR MET-pIRIR250 SAR MET-pIRIR300 MAR with heat
De ± σ n De ± σ n De ± σ n De ± σ n De ± σ n
A-570 570 373 ± 35 7 424 ± 11 19 415 ± 9 15 \ \ 381 ± 11 12;12
A-1050 1050 615 ± 54 7 706 ± 34 8 706 ± 17 8 \ \ 747 ± 53 16;8
B-0 220 543 ± 17 6 673 ± 57 4 640 ± 13 8 712 ± 57 6 856 ± 73 24;14
B-610 830 652 ± 20 10 734 ± 21 14 753 ± 17 9 773 ± 45 6 925 ± 62 24;20
B-640 860 613 ± 51 6 741 ± 18 9 773 ± 22 7 749 ± 57 6 901 ± 51 14;10
B-1000 1190 649 ± 61 6 822 ± 35 5 762 ± 25 7 800 ± 47 6 897 ± 71 24;20

The five post-IR IRSL dating protocols used in this study_ The first four are the SAR protocols with pIR50IR290, pIR200IR290, MET-pIRIR250 and MET-pIRIR300 signals, respectively_ The fifth is the MAR protocol with the MET-pIRIR300 signal and a ‘cutheat to 500°C’ treatment added before the test dose, simplified as ‘MAR with heat’ (modified from Li et al_ (2013))_

Step SAR pIR50/200IR290 SAR MET-pIRIR250/300 ‘MAR with heat’
Treatment Observed Treatment Observed Treatment Observed
1 Regenerative dose, Di Regenerative dose, Di Regenerative dose, Di
2 Preheat at 320°C, 60 s Preheat at 300°C or 320°C, 60 s Preheat at 320°C, 60 s
3 IRSL 200 s at 50/200°C IRSL 100 s at 50°C IRSL 100 s at 50°C
4 IRSL 200 s at 290°C Lx (290) IRSL 100 s at 100°C IRSL 100 s at 100°C
5 IRSL 100 s at 150°C IRSL 100 s at 150°C
6 IRSL 100 s at 200°C IRSL 100 s at 200°C
7 IRSL 100 s at 250°C Lx (250) IRSL 100 s at 250°C
8 IRSL 100 s at 300°C or not Lx (300) IRSL 100 s at 300°C Lx (300)
9 Cutheat to 500°C
10 Test dose, Dt Test dose, Dt Test dose, Dt
11 Preheat at 320°C, 60 s Preheat at 300°C or 320°C, 60 s Preheat at 320°C, 60 s
12 IRSL 200 s at 50/200°C IRSL 100 s at 50°C IRSL 100 s at 50°C
13 IRSL 200 s at 290°C Tx (290) IRSL 100 s at 100°C IRSL 100 s at 100°C
14 IR at 325°C, 200 s IRSL 100 s at 150°C IRSL 100 s at 150°C
15 Return to step 1 IRSL 100 s at 200°C IRSL 100 s at 200°C
16 IRSL 100 s at 250°C Tx (250) IRSL 100 s at 250°C
17 IRSL 100 s at 300°C or not Tx (300) IRSL 100 s at 300°C Tx (300)
IR at 320 or 325°C, 100 s
Return to step 1
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