Quartz OSL chronology and dust accumulation rate changes since the Last Glacial at Weinan on the southeastern Chinese Loess Plateau

The fine-grained (4-11m) quartz Optically Stimulated Luminescence (OSL) dating technique was applied to the Weinan section on the southeastern Chinese Loess Plateau (CLP) with a high luminescence sampling resolution (10- and 20-cm intervals). Fifty-eight OSL ages, spanning c. 1-74ka, were obtained for the 10-m loess-palaeosol sequences. The reliability of the OSL dating and the constructed chronology was confirmed by comparing the OSL ages with independent dates from other studies and by correlation with palaeoclimatic time series. The closely spaced OSL ages at Weinan indicate that the mean dust accumulation rate (DAR) of L1-1 (MIS 2, 7.0 +/- 0.9cmka(-1)) is lower than those of L1-3 (MIS 4, 19.1 +/- 6.1cmka(-1)) and L1-2 (MIS 3, 16.0 +/- 0.7cmka(-1)) and that the mean DARc. 30-20ka ago (11.4 +/- 2.4cmka(-1)) is higher than that c. 20-10ka ago (3.0 +/- 0.1cmka(-1)) in L1-1. The subsequent calculation of the mass accumulation rate (MAR) indicates that the MAR of L1-1 (107gm(-2)a(-1)) is much lower than those of L1-2 (247gm(-2)a(-1)) and L1-3 (307gm(-2)a(-1)). By comparing the mean DAR results during the Last Glacial at Weinan with those at a further six sites from other studies, we observed that the mean DAR of L1-2 is higher (lower) than that of L1-1 on the eastern (western) CLP, and that the mean DAR during MIS 2 has an evident transition from high to low at c. 20ka on the entire CLP. Possible mechanisms for the above mean DAR changes at orbital and sub-orbital time scales are presented.</p

Closely-spaced recuperated OSL dating of the last interglacial paleosol in the southeastern margin of the Chinese Loess Plateau

The objective of this study is to construct a numerically dated chronology of the last interglacial paleosol (Si) in Chinese loess using luminescence dating. The recuperated optically stimulated luminescence (ReOSL) dating approach was applied to 18 closely-spaced (20 cm intervals) samples, with 15 of these collected from the S(1) unit at the Weinan site, which is located at the southeastern margin of the Chinese Loess Plateau (CLP). By using the multiple-aliquot regenerative-dose (MAR) approach, 18 fine-grained quartz ReOSL equivalent dose (D(E)) values, spanning about 249-466 Gy, were obtained. The validity of ReOSL MAR protocol was checked by dose recovery measurements and recycling ratio tests. By comparison of the dose-response curves of all the samples, we found that it is feasible to construct a standardized growth curve (SGC) for the ReOSL signal at the Weinan site. Considering the effects of pedogenesis of the S(1) unit during formation, the dose rate during the last interglacial was corrected, which should be beneficial for constructing a more reliable chronology. Finally, a detailed chronology of the S(1) unit was established. The results show that S(1) was deposited between approximately 76-127 ka, which confirms the early suggestion that the S(1) unit in Chinese loess corresponds to the whole marine oxygen-isotope stage (MIS) 5. The detailed ReOSL chronology of S(1) indicates the consistency of the substrata of S(1) with MIS 5a-e, but cannot determine whether they are exactly coeval. According to the present ReOSL age results, it is suggested that dust deposition is continuous at timescales larger than 14.1 +/- 11.8 ky during the last interglacial and there is no hiatus longer than 4.4 +/- 13.0 ky at the L(2)/S(1) transition. Further work, e.g. minimizing the errors on ages and reducing the luminescence sampling intervals, is needed to understand the more detailed dust deposition conditions during the last interglacial in Chinese loess. (C) 2011 Elsevier B.V. All rights reserved.</p

A high-resolution quartz OSL chronology of the Talede loess over thepast ~30 ka and its implications for dust accumulation in the Ili Basin,Central Asia

Similar to the loess deposits on the Chinese Loess Plateau (CLP), a reliable chronology plays also an important role in revisiting past climate and environment changes recorded by the loess in Central Asia. Previously, a few luminescence and 14C ages, mainly covering the last glacial, were obtained for several loess sections in Central Asia, which are often controversial. Until now, there is still a lack of reliable high-resolution chronologies covering the late Pleistocene, especially the Holocene. Here, the fine-grained (4&ndash;11&nbsp;&mu;m) quartz single-aliquot regenerative-dose (SAR) optically stimulated luminescence (OSL) dating protocol is used to establish a detailed chronology of the uppermost part (&sim;5&nbsp;m) of Talede loess in the Ili Basin Central Asia. Conventional tests of the SAR protocol and the general luminescence characteristics indicate that this protocol is suitable for dating the Talede loess. Finally, 15 closely-spaced quartz OSL ages, ranging from 0.72&nbsp;&plusmn;&nbsp;0.05 to 28.9&nbsp;&plusmn;&nbsp;2.12&nbsp;ka and with no reversals, were obtained. Consistent with previous studies in the Ili Basin, two of the three 14C ages show discrepancy when compared with quartz OSL ages for the Talede loess section. The constructed OSL chronology of the Talede loess reveals that the dust accumulation is rapid during marine isotope stage (MIS) 2, especially during the Last Glacial Maximum (LGM), and is also continuous during the Holocene, with the dust accumulation rate exhibiting a relatively low level and an increasing trend. Comparison of the dust accumulation at Talede with that at other sites in the Ili Basin indicates that the rapid dust accumulation during the LGM is not universal, and the slow dust accumulation during the Holocene is probably true for the entire Ili Basin. Comparison of different grain sized quartz OSL ages from Central Asian loess show characteristics of both consistency and inconsistency, which needs to be further investigated.</p