Link between global cooling and mammalian transformation across the Eocene–Oligocene boundary in the continental interior of Asia
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Evidence in the world’s ocean current system indicates an abrupt cooling from 34.1 to 33.6 Ma across the Eocene–Oligocene boundary at 33.9 Ma. The remarkable cooling period in the ocean, called the Eocene–Oligocene transition (EOT), is correlated with pronounced mammalian faunal replacement as shown in terrestrial fossil records. For the first time within Asia, a section is magnetostratigraphically dated that also produces mammalian fossils that span the Late Eocene—Early Oligocene transition. Three fossil assemblages revealed through the EOT (34.8, 33.7, and 30.4 Ma) demonstrate that perissodactyl faunas were abruptly replaced by rodent/lagomorph-dominant faunas during climate cooling, and that changes in mammalian communities were accelerated by aridification in central Asia. Three fossil assemblages (34.8, 33.7, and 30.4 Ma) within the north Junggar Basin (Burqin section) tied to this magnetostratigraphically dated section, reveal that perissodactyl faunas were abruptly replaced by rodent/lagomorph-dominant faunas during climate cooling, and that changes in mammalian communities were accelerated by aridification in central Asia. The biotic reorganization events described in the Burqin section are comparable to the Grande Coupure in Europe and the Mongolian Remodeling of mammalian communities. That is, the faunal transition was nearly simultaneous all over the world and mirrored global climatic changes with regional factors playing only a secondary role.
KeywordsEocene–Oligocene boundary Eocene–Oligocene transition Junggar Basin Magnetostratigraphy Paleomagnetism
We thank Drs. Jin Meng (American Museum of Natural History), Jie Ye, Wenyu Wu, Xijun Ni, Bin Bai (Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences), Shundong Bi (Indiana University of Pennsylvania), and Jianqi Wang (Northwest University, Xi’an) for their valuable help during the fieldwork. We thank Dr. Brian Kraatz and Dr. Thomas Martin for providing their constructive comments that led to substantial improvement of our manuscript. We thank Marcia Craig for her editing of the text before our submission to the journal. The study was partially funded by the Natural Sciences and Engineering Research Council of Canada’s support of V.A.K. Measurements were funded through support for V.A.K. by the Canadian Foundation for Innovation and the University of Alberta and for L.Y. by the National Natural Science Foundation of China (grant 41072136).
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