Quartz and K-feldspar optical dating chronology of eolian sand and lacustrine sequence from the southern Ulan Buh Desert, NW China: Implications for reconstructing late Pleistocene environmental evolution Guoqiang Li a, ⁎, Ming Jin a , Lijuan Wen a , Hui Zhao b , David Madsen a , Xiaokang Liu a , Duo Wu a , Fahu Chen a a MOE Key Laboratory of Western China's Environmental Systems, Research School of Arid Environment and Climate change, Lanzhou University, Lanzhou 73000, China b Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China abstract article info Article history: Received 21 August 2013 Received in revised form 29 October 2013 Accepted 5 November 2013 Available online 16 November 2013 Keywords: Ulan Buh Desert China Pleistocene Arid landscape evolution Optical stimulated luminescence dating The Ulan Buh Desert (UBD), in southwestern Inner Mongolia, is one of the main dune fields and dust source areas in northern China. In the southern UBD, consisting primarily of high pyramidal and complex sand dunes, the process of desert evolution remains unclear due to a lack of depositional records and adequate age controls. In this study, we present the stratigraphic record of a 120.5 m deep core (WL12ZK-1) collected in this sandy desert region. A 22.6 m thick deposit of lacustrine clay/silty clay bracketed between 37 m (top) and 54.7 m (bottom) thick layers of eolian sand, provides evidence of a desert–lake–desert sequence in the southern UBD. Quartz Optical Stimulated Luminescence (OSL) and K-feldspar multi-elevated-temperature post-IR IRSL (Met-pIRIR) dating technologies were employed to provide a chronology for this sequence. Internal checks of the quartz OSL dating indicate that the quartz single-aliquot regenerative-dose protocol is appropriate for equivalent dose determination and that the quartz ages younger than 60 ka are acceptable. The reliability of the K-feldspar ages is confirmed by both internal checks and an age-temperature plot. The combined stratigraphy and chronol- ogy indicate a sand desert landscape developed in the southern UBD at least ~232 ka ago, and that a paleolake was present beginning sometime before ~155 ka and lasting until ~87 ka, with several possible lake level fluctu- ations. Desert landforms developed synchronously in the southern and northern UBD after the paleolake regressed. A combination of tectonic activity and climate change may be responsible for this sequence. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The sand deserts and sandy lands in China form the eastern portion of the Asian desert belt which extends east from the desert basins of Kazakhstan, Uzbekistan and Turkmenistan. Sand deserts in China consist of the Taklimakan, Kumtag, Qaidam, Badain Jaran, Tengger, Ulan Buh and Hobq deserts, and sand lands include the Gurbantunggut, Mu Us, Otindag, Keerqin and Hulunbeier regions. The Helan Mountains, stretching N–S (~106°E), act as a boundary between the arid and semi- arid zones. Six of the seven sand deserts of China are located west of this mountain range, while four of the five large sandy lands of China occur east of the range. The sandy deserts in northern and northwestern (NW) China are thought to have formed before Quaternary (Sun et al., 2009; Yang et al., 2011), while the sandy lands east of the Helan Moun- tains are generally believed to have formed during the late Holocene due to human activity (Qin, 2002). Sand deserts cover approximately 1,000,000 km 2 in the arid and semiarid regions of northern and northwestern (NW) China (Zhu et al., 1988), providing huge amounts of atmospheric dust and aerosols which influence regional and even global climate change (Uno et al., 2009). Rapid shifts between sand deserts and lakes in geologically and environmentally diverse settings suggest that the drylands of China are very sensitive ephemeral systems, and not as long-lasting as previously thought (Yang et al., 2011). In addition, the sand deserts in China account for a large portion of deserts in the middle latitudes of the Northern Hemisphere. Knowledge of past changes in these sand deserts is thus of importance for understanding climatic changes in the terrestrial regions of mid- latitudes (Yang et al., 2012). The Ulan Buh Desert (UBD), located just east of the Helan Mountains, is one of the main sand deserts in NW China, consisting of active high dunes in the south and fixed low-dunes in the north. This area experi- enced dramatic environmental change during the late Quaternary and paleoshorelines and lacustrine deposits in the region indicate a Jilantai-Hetao Mega-paleolake covered the modern Jilantai Salt Lake, the UBD and the Hetao Plain sometime before 50–60 ka (Chen et al., 2008a). A drill core (WL10ZK-1) study in the northern UBD suggests the sand deserts formed during MIS 2 and the early Holocene after the paleolake disappeared, and was related to summer monsoon changes (Chen et al., 2013). Yang et al. (1991) suggest the UBD formed during the late Pleistocene to early Holocene and that the driving force was a change in the course of the Yellow River. Other studies considered the Palaeogeography, Palaeoclimatology, Palaeoecology 393 (2014) 111–121 ⁎ Corresponding author at: 505 Yifu Science Building, Research School of Arid Environment and Climate Change, Lanzhou University, 222 Tianshuinanlu, Lanzhou, Gansu, China 730000. Tel.: +86 13893140191 (mobile); fax: +86 931 8912330. E-mail address: gqli@lzu.edu.cn (G. Li). 0031-0182/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2013.11.003 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo