CW-OSL, LM-OSL and TL Dating of Bricks from Karakorum, Mongolia: Insights from TL Spectra

Saran Solongo; Saran Tengis; Günther A. Wagner; Hans-Georg Hüttel

doi:10.2478/geochr-2020-0003

Figures & Tables

TL contour map recorded after laboratory β-irradiation and storage for 4 weeks. (a) heated quartz samples HD3 (red coloured brick), and (b)HD2-57 (grey coloured brick).

TL emission spectra for heated quartz (a, c) HD3 and (b, d) HD2-57. Deconvolution into Gaussian components of the thermoluminescence emission spectra of HD3 showed a broad UV emission band peaking at 366 nm, and the blue emission band peaking at 474 nm. HD2-57 showed typical for quartz blue emission bands peaking at 470 nm for a temperature 200–350°C, and 490 nm emission at 125–175°C. There is peak with low intensity at 600 nm. The UV emission band is absent in TL spectra of HD2-57.

(a, b) Fitting of CW-OSL decay curves and (c, d) pseudo-LM-OSL decay curves for quartz HD3 and HD2-57. The insets show the relative contribution of fast and medium components. (e) Deconvolution of experimental LM-OSL curves HD3 and K02-08.

(a), (c) The representative natural, regenerated and test dose CW-OSL decay curves recorded during the SAR cycles for quartz HD3 and K02/08, respectively, N-natural OSL, R3, R4 - regenerated OSL, TD1, TD5 – test dose OSL. (b), (d) The corresponding dose-response curve fitted by exponential fit.

Preheat plateau test K02/08. a) dose-response curves obtained for preheat temperatures from 200°C to 280°C and the corresponding pre-heat plot De=f(T). b) TL glow curves obtained at the end of SAR protocol after giving a dose of 1.1 Gy. Inset shows sensitivity changes occurring during SAR.

LM-OSL measurements on HD3 and K02-02 using SAR. (a, e) The natural (N) and regenerated (Reg) LM-OSL curves; (b, f) test dose LM-OSL; (c) LM-OSL dose-response curve derived by integrating fast (0–200 s) and slow (last 100 s) for HD3 and by integrating medium (0–100 s) and slow (last 100 s) for K02-02; (d) The sensitivity changes occurring during SAR cycles. Test dose TD – signal (0–200 s), Reg and TD signals of slow components derived as integer of last 100 s.

a) SAR-TL und c) regenerated TL measurements on heated quartz K02/08. TL signal was derived by integrating 325–370°C and 300–350°C, correspondingly. (b, c) corresponding dose-response curves. Inset in b) shows sensitivity changes during SAR. SAR TL De is 3.81±0.33 Gy (n=10). Regenerated TL gives De of 3.5±0.20 Gy.

Fragments of bricks for luminescence dating and concentration of radionuclides measured by high-resolution gamma-spectrometry_

Sample Description	²³²Th (ppm)	²³⁵U (ppm)	⁴⁰K (%)	β (mGy/a), β counter	γ (mGy/a)
K02/01, brick, Great Hall floor, red colored	12.79 ± 0.22	3.43 ± 0.09	2.77 ± 0.015	3.16 ± 0.07	1.73 ± 0.02
HD12B, brick, Great Hall red colored	14.88 ± 0.32	4.26 ± 0.18	2.77 ± 0.10	3.02 ± 0.015	1.86 ± 0.07
HD3, brick, red-colored	13.45 ± 0.29	3.98 ± 0.12	2.68 ± 0.09	2.93 ± 0.15	1.74 ± 0.09
HD3-1, brick, red-colored	13.73 ± 0.26	4.52 ± 0.12	2.59 ± 0.08	2.93 ± 0.15	1.78 ± 0.09
B288B, brick, red-colored, basement, manufacturing	14.66 ± 0.28	4.23 ± 0.09	2.87 ± 0.085	3.03 ± 0.15	1.84 ± 0.080
K02/02, brick, Buddhist ground, grey colored	12.86 ± 0.022	3.71 ± 0.09	2.79 ± 0.08	2.92 ± 0.15	1.60 ± 0.04
K02/08 wallbrick, Stupa basement, grey colored	13.87 ± 0.17	4.05 ± 0.07	2.70 ± 0.05	2.99 ± 0.15	1.81 ± 0.04
HD2-57, grey colored 3-B2027, P202, format 45mm	13.68 ± 0.28	4.24 ± 0.13	2.74 ± 0.09	2.82 ± 0.14	1.79 ± 0.09
K36, brick, small kiln, grey colored	12.97 ± 0.20	3.49 ± 0.08	2.85 ± 0.06	2.972 ± 0.15	1.77 ± 0.02

Age estimates and dose De obtained using different luminescence methods (n number of aliquots, all doses are obtained for coarse quartz)_ * CW-OSL dates were taken from Solongo et al_ (2006a)_

Sample description	Method	N aliqouts	D_e (Gy)	D_r (Gy/ka)	Date (AD)
K02/01, brick, Great Hall floor, red colored	CW-OSL*	12	3.16 ± 0.07	4.56 ± 0.32	1310 ± 45
	LM-OSL	3	2.90 ± 0.10		1370 ± 50
	TL-SAR	6	3.48 ± 0.09		1250 ± 55

HD12B, brick, Great Hall basement, red colored	CW-OSL	24	2.90 ± 0.09	4.58 ± 0.30	1340 ± 45
HD12B, brick, Great Hall basement, red colored	LM-OSL	3	2.98 ± 0.07	4.58 ± 0.30	1350 ± 45

HD3, brick, red colored, Great Hall area	CW-OSL	24	3.07 ± 0.06	4.61 ± 0.28	1340 ± 40
HD3, brick, red colored, Great Hall area	LM-OSL	4	3.20 ± 0.10	4.61 ± 0.28	1310 ± 50

HD3-1, brick, red-colored, Great Hall area	CW-OSL	44	3.28 ± 0.04	4.60 ± 0.29	1290 ± 40
HD3-1, brick, red-colored, Great Hall area	LM-OSL	10	3.00 ± 0.10	4.60 ± 0.29	1345 ± 55

B288B brick, red-colored, basement, manufacturing quarter	CW-OSL	21	3.30 ± 0.14	5.19 ± 0.31	1370 ± 55
B288B brick, red-colored, basement, manufacturing quarter	LM-OSL	3	2.90 ± 0.10	5.19 ± 0.31	1450 ± 50

HD2/57, grey colored, Great Hall area	CW-OSL	6	-	4.43 ± 0.30	-
HD2/57, grey colored, Great Hall area	TL reg	6	2.89 ± 0.17	4.43 ± 0.30	1360 ± 70

K02/08 wall brick, stupa basement, grey colored HD12	CW-OSL*	14	1.90 ± 0.33	4.87 ± 0.28	1610 ± 70
	LM-OSL	2	1.90 ± 0.25		1620 ± 60
	TL-SAR	10	3.81 ± 0.33		1220 ± 85
	TL-REG	6	3.65 ± 0.23		1260 ± 70

K02/02, brick, Buddhist Lotus trone, grey colored	CW-OSL	10	2.08 ± 0.32	4.7 ± 0.28	1560 ± 80
	LM-OSL	2	2.10 ± 0.20		1560 ± 50
	TL-SAR	6	3.63 ± 0.30		1340 ± 80

K36, brick, small kiln, grey colored	CW-OSL	12	2.18 ± 0.51	4.87 ± 0.29	1560 ± 120
K36, brick, small kiln, grey colored	TL-SAR	6	4.10 ± 0.05	4.87 ± 0.29	1190 ± 70

SAR procedure using CW-OSL, LM-OSL, TL used in this study_

Step	CW-OSL	LM-OSL	TL
1	Give dose (3.0; 4.7; 6.5;0;3.0 Gy)	Give dose (3.0; 4.7; 6.5; 0; 3.0 Gy)	Give dose (1.59; 3.59; 5.19; 0; 1.59 Gy)
2	Preheat (220°C for 10 s)	Preheat (220°C for 10 s)	Preheat (180°C for 10 s at 5°C/s)
3	CW-OSL for 20 s at 125°C, *L_x*	LM-OSL for 500 s (or 3000 s) at 125°C, *L_x*	TL 495°C, *L_x*
4	Test dose (0.18Gy /or 0.64Gy)	Test dose (e.g. 0.26 Gy)	Test dose (e.g. 0.39 Gy)
5	Cutheat to 220°C	Cutheat to 220°C	Preheat (180°C for 10 s at 5°C/s)
6	CW-OSL for 20 s at 125°C, *T_x*	LM-OSL for 500 s (3000 s) at 125°C,*T_x*	TL 495°C, 5°C/s, *T_x*
7		Seq. LM-OSL for 500 s (3000 s) at 125°C (x 5)
8	Return to step 1	Return to step 1	Return to step 1

CW-OSL, LM-OSL and TL Dating of Bricks from Karakorum, Mongolia: Insights from TL Spectra

Figures & Tables

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Fragments of bricks for luminescence dating and concentration of radionuclides measured by high-resolution gamma-spectrometry_

Age estimates and dose De obtained using different luminescence methods (n number of aliquots, all doses are obtained for coarse quartz)_ * CW-OSL dates were taken from Solongo et al_ (2006a)_

SAR procedure using CW-OSL, LM-OSL, TL used in this study_

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