PUBLICATIONS Geochemistry, Geophysics, Geosystems RESEARCH ARTICLE 10.1002/2017GC006945 Key Points: Paleomagnetism and fossil mammals determined the sequence deposited from approximately 12.7 to 4.8 Ma Sedimentation rates with paleocurrents and simultaneously changes of facies indicate uplifts of the eastern Qilian Shan at 8.1 and 6.3 Ma Paleomagnetic results provide an age constraint on the river terraces and eolian dust deposition on the basin Supporting Information: Supporting Information S1 Data Set S1
Correspondence to: X. Fang,
[email protected] Citation: Yang, R., Fang, X., Meng, Q., Zan, J., Zhang, W., Deng, T., . . . Li, B. (2017). Paleomagnetic constraints on the Middle Miocene-Early Pliocene stratigraphy in the Xining Basin, NE Tibetan Plateau, and the geologic implications. Geochemistry, Geophysics, Geosystems, 18, 3741–3757. https://doi. org/10.1002/2017GC006945 Received 4 APR 2017 Accepted 24 SEP 2017 Accepted article online 28 SEP 2017 Published online 3 NOV 2017
Paleomagnetic Constraints on the Middle Miocene-Early Pliocene Stratigraphy in the Xining Basin, NE Tibetan Plateau, and the Geologic Implications Rongsheng Yang1,2, Xiaomin Fang1,2 , Qingquan Meng3, Jinbo Zan1, Weilin Zhang1, Tao Deng4, Yibo Yang1, Xiaobai Ruan1,2, Liye Yang1,2, and Bingshuai Li1,2 1
CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China, 2University of Chinese Academy of Science, Beijing, China, 3School of Earth Sciences and Key Laboratory of Western China’s Mineral Resources of Gansu Province, Lanzhou University, Lanzhou, China, 4Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
Abstract The Xining Basin lies in the transitional zone between the arid Asian interior and the East Asian monsoon region. The continuous Cenozoic sediments in the basin provide a unique archive recording the uplift of the Tibetan Plateau and its environmental effects on central Asian aridification and Asian monsoon evolution. However, sediments deposited since the middle Middle Miocene have not been precisely dated, hindering our ability to address these issues. Here we dated a 336 m-thick section containing many Late Miocene fossil mammals from the eastern basin. High-resolution paleomagnetism revealed 16 normal and 16 reversed zones that correlate well with chrons 3n to 5Ar.1r of the Geomagnetic Polarity Time Scale, constraining the section to 12.7–4.8 Ma. The changes in lithofacies from floodplain to braided river at 8.6 Ma and to thick alluvial fan at 6.3 Ma with predominantly southerly paleocurrent directions occur simultaneously with an increase in the sedimentation rates, representing two periods of rapid uplift in the eastern Qilian Shan to the north. Our results provide a robust oldest age constraint (
