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

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

Geochronometria
Volume 48 (2021): Issue 1 (January 2021)
By: Junjie Zhang,  Sheng-Hua Li,  Xulong Wang,  Qingzhen Hao,  Guiming Hu and  Yiwei Chen  
Open Access
|Dec 2021

Figures & Tables

Fig. 1

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.

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.

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.

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.

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.

Dose rates and ages of the samples using the five protocols_

SampleWater (%)K20 (%)Alpha countDose rate (Gy/ka)Age (ka)
SAR pIR50IR290SAR pIR200IR290SAR MET-pIRIR250SAR MET-pIRIR300MAR with heat
A-57015 ± 52.039.55 ± 0.153.21 ± 0.12116 ± 12132 ± 6129 ± 6\119 ± 6
A-105015 ± 52.1910.83 ± 0.163.44 ± 0.13179 ± 17206 ± 13206 ± 9\217 ± 17
B-015 ± 51.9510.14 ± 0.183.30 ± 0.12165 ± 8204 ± 19194 ± 8216 ± 19260 ± 24
B-61019.3 ± 52.5011.88 ± 0.193.55 ± 0.13183 ± 9206 ± 10212 ± 9217 ± 15260 ± 20
B-64019.3 ± 52.4011.85 ± 0.193.59 ± 0.13171 ± 16206 ± 9215 ± 10209 ± 18251 ± 17
B-100015 ± 52.2210.74 ± 0.183.43 ± 0.13189 ± 19240 ± 14222 ± 11233 ± 16261 ± 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_

SampleDepth (cm)SAR pIR50IR290SAR pIR200IR290SAR MET-pIRIR250SAR MET-pIRIR300MAR with heat
De ± σnDe ± σnDe ± σnDe ± σnDe ± σn
A-570570373 ± 357424 ± 1119415 ± 915\\381 ± 1112;12
A-10501050615 ± 547706 ± 348706 ± 178\\747 ± 5316;8
B-0220543 ± 176673 ± 574640 ± 138712 ± 576856 ± 7324;14
B-610830652 ± 2010734 ± 2114753 ± 179773 ± 456925 ± 6224;20
B-640860613 ± 516741 ± 189773 ± 227749 ± 576901 ± 5114;10
B-10001190649 ± 616822 ± 355762 ± 257800 ± 476897 ± 7124;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))_

StepSAR pIR50/200IR290SAR MET-pIRIR250/300‘MAR with heat’
TreatmentObservedTreatmentObservedTreatmentObserved
1Regenerative dose, Di Regenerative dose, Di Regenerative dose, Di
2Preheat at 320°C, 60 s Preheat at 300°C or 320°C, 60 s Preheat at 320°C, 60 s
3IRSL 200 s at 50/200°C IRSL 100 s at 50°C IRSL 100 s at 50°C
4IRSL 200 s at 290°CLx (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°CLx (250)IRSL 100 s at 250°C
8 IRSL 100 s at 300°C or notLx (300)IRSL 100 s at 300°CLx (300)
9 Cutheat to 500°C
10Test dose, Dt Test dose, Dt Test dose, Dt
11Preheat at 320°C, 60 s Preheat at 300°C or 320°C, 60 s Preheat at 320°C, 60 s
12IRSL 200 s at 50/200°C IRSL 100 s at 50°C IRSL 100 s at 50°C
13IRSL 200 s at 290°CTx (290)IRSL 100 s at 100°C IRSL 100 s at 100°C
14IR at 325°C, 200 s IRSL 100 s at 150°C IRSL 100 s at 150°C
15Return to step 1 IRSL 100 s at 200°C IRSL 100 s at 200°C
16 IRSL 100 s at 250°CTx (250)IRSL 100 s at 250°C
17 IRSL 100 s at 300°C or notTx (300)IRSL 100 s at 300°CTx (300)
IR at 320 or 325°C, 100 s
Return to step 1
DOI: https://doi.org/10.2478/geochr-2020-0010 | Journal eISSN: 1897-1695
Journal RSS Feed
Language: English
Page range: 129 - 137
Submitted on: Jan 15, 2019
|
Accepted on: Oct 29, 2019
|
Published on: Dec 31, 2021
Published by: Sciendo
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year
Keywords:
Chinese loess,
Potassium feldspar,
pIRIR protocols,
age underestimations
Related subjects:
Geosciences,
Geosciences, other

© 2021 Junjie Zhang, Sheng-Hua Li, Xulong Wang, Qingzhen Hao, Guiming Hu, Yiwei Chen, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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