Abstract
The yardangs in arid region are important records for paleoclimatic changes and aeolian geomorphology changes. However, their formation ages are rarely studied due to the limitation of dating methods. The postIRSL IRSL (pIRIR) dating of feldspar, with a wider dating range than quartz, is a key method in dating mid- and late Quaternary sedimentations. This method has been applicated to various sediments all over the world. In this paper, pIRIR dating of feldspar were tested to find a suitable dating method for the paleo-lacustrine sediment, which have been carved into Yardangs, in Qarhan Salt Lakes Region, Qaidam Basin, NE QinghaiTibetan Plateau. Two main method of feldspar luminescence dating (the two-step pIRIR dating [1] which might be affected by anomalous fading, and the Multi-elevated-temperature (MET) pIRIR dating [2] which might offer non-fading ages with a De plateau between different stimulating temperatures) were applied. The finegrain size polymineral and coarse-grain size K-feldspars were extracted from paleo-lacustrine sediment, and five samples were studied. The pIR50IR250 (preheat at 280 ℃ for 60s; stimulated at 50℃ for 500 s, and then
stimulated at 250℃ for 500s) and MET-pIRIR (preheat at 320℃ for 60 s, and stimulated at 50, 100, 150, 200, 250 and 290℃ for 100s, respectively) dating results show that: (1) there is an obvious De plateau for METpIRIR dating between the stimulation temperature of 250 and 290 ℃, revealing that the sediments were well bleached before buried, and the results are non-fading and reliable; (2) the pIR50IR250 ages are underestimated compared with MET-pIRIR250 dating for all our samples, indicating that there is still anomalous fading in pIR50IR250 signals, so fading correction (measured average g-valve is 2.1%/decade) is needed; (3) the corrected pIR50IR250 ages are accordant to MET-pIRIR250 ages for both fine-grain size polymineral and coarse-grain size Kfeldspars, suggesting both method are reliable for paleo-lacustrine sediments in this region; (4) the dating results of ~200-330 Ka might indicate existence of mega lakes during interglacial periods of MIS9 and MIS7 in the Qaidam Basin, which is accordant with the paleoclimatic background; (5) The absent of paleo-lacustrine sediments during glacier period might demonstrate a erosional environment, and formation of yardangs should mainly since MIS6, especially MIS4
stimulated at 250℃ for 500s) and MET-pIRIR (preheat at 320℃ for 60 s, and stimulated at 50, 100, 150, 200, 250 and 290℃ for 100s, respectively) dating results show that: (1) there is an obvious De plateau for METpIRIR dating between the stimulation temperature of 250 and 290 ℃, revealing that the sediments were well bleached before buried, and the results are non-fading and reliable; (2) the pIR50IR250 ages are underestimated compared with MET-pIRIR250 dating for all our samples, indicating that there is still anomalous fading in pIR50IR250 signals, so fading correction (measured average g-valve is 2.1%/decade) is needed; (3) the corrected pIR50IR250 ages are accordant to MET-pIRIR250 ages for both fine-grain size polymineral and coarse-grain size Kfeldspars, suggesting both method are reliable for paleo-lacustrine sediments in this region; (4) the dating results of ~200-330 Ka might indicate existence of mega lakes during interglacial periods of MIS9 and MIS7 in the Qaidam Basin, which is accordant with the paleoclimatic background; (5) The absent of paleo-lacustrine sediments during glacier period might demonstrate a erosional environment, and formation of yardangs should mainly since MIS6, especially MIS4
| Original language | English |
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| Publication status | Published - 2018 |
| Event | The 5th Asia Pacific Conference on Luminescence and Electron Spin Resonance Dating (APLED2018) - Peking University, Beijing, China Duration: 15 Oct 2018 → 17 Oct 2018 http://webues.pku.edu.cn/apled2018/index.html |
Conference
| Conference | The 5th Asia Pacific Conference on Luminescence and Electron Spin Resonance Dating (APLED2018) |
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| Abbreviated title | APLED2018 |
| Country/Territory | China |
| City | Beijing |
| Period | 15 Oct 2018 → 17 Oct 2018 |
| Internet address |