High-resolution magnetostratigraphy of the Neogene Huaitoutala section in the eastern Qaidam Basin on the NE Tibetan Plateau, Qinghai Province, China and its implication on tectonic uplift of the NE Tibetan Plateau

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The closed inland Qaidam Basin in the NE Tibetan Plateau contains possibly the world's thickest (∼ 12,000 m) continuous sequence of Cenozoic fluviolacustrine sedimentary rocks. This sequence contains considerable information on the history of Tibetan uplift and associated climatic change. However, work within Qaidam Basin has been held back by a paucity of precise time constraints on this sequence. Here we report on a detailed paleomagnetic study of the well exposed 4570 m Huaitoutala section along the Keluke anticline in the northeastern Qaidam Basin, where three distinct faunas were recovered and identified from the middle Miocene through Pliocene. Constrained by these faunal ages, the observed thirty-three pairs of normal and reversed polarity zones can be readily correlated with chrons 2n-5Br of the GPTS. This study assigns the age of the section to the interval between ca. 15.7 Ma to 1.8 Ma. In addition, the widely used stratigraphic units the Xia Youshashan, Shang Youshashan, the Shizigou and Qigequan Formations were formed at > 15.3 Ma, 15.3-8.1 Ma, 8.1-2.5 Ma and < 2.5 Ma, respectively. We obtained a very high average sedimentation rate of ∼ 33 cm/ka over the entire interval 15.7 to 1.8 Ma. Furthermore, the average sedimentation rate is punctuated by three intervals of persistent rapid increases starting at about ∼ 14.7 Ma, 8.1 Ma and 3.6 Ma. These intervals are interpreted as times of rapid uplift and fast exhumation of the NE Tibetan Plateau. © 2007.

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Earth and Planetary Science Letters