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

Abstract

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 120.5m deep core (WL12ZK-1) collected in this sandy desert region. A 22.6m thick deposit of lacustrine clay/silty clay bracketed between 37m (top) and 54.7m (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 60ka are acceptable. The reliability of the K-feldspar ages is confirmed by both internal checks and an age-temperature plot. The combined stratigraphy and chronology indicate a sand desert landscape developed in the southern UBD at least ~232ka ago, and that a paleolake was present beginning sometime before ~155ka and lasting until ~87ka, with several possible lake level fluctuations. 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.