Taphonomy of Early Cretaceous freshwater bivalve concentrations from the Sihetun area,western Liaoning,NE China |
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| Institution: | 1. Department of Entomology, China Agricultural University, Beijing 100193, China;2. College of Life Sciences, Capital Normal University, Beijing 100048, China;1. Institute of Geological Sciences, Jagiellonian University, Gronostajowa 3a, 30387 Kraków, Poland;2. Senckenberg am Meer, Marine Research Department, 26382 Wilhelmshaven, Germany;3. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Spain;1. Department of Entomology, China Agricultural University, Beijing 100193, China;2. College of Life Sciences, Capital Normal University, Beijing 100048, China;1. State Key Laboratory of Biocontrol, School of Life Science, Sun Yat-Sen University, Guangzhou 510275, China;2. Australian National Insect Collection, CSIRO, GPO Box 1700, Canberra, ACT 2601, Australia;3. College of Life Sciences, Capital Normal University, Xisanhuanbeilu 105, Haidian District, Beijing, 100048, China;1. College of Life Sciences, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing 100048, China;2. Palaeontological Institute, Russian Academy of Sciences, Moscow 117997, Russia;3. Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK;1. Key Lab of Insect Evolution and Environmental Change, College of Life Sciences, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing, 100048, China;2. Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, No. 1 Beichen West Road, Chaoyang District, Beijing, 100101, China |
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| Abstract: | The Early Cretaceous Yixian Formation at Sihetun, Beipiao, western Liaoning, northeastern China, is well-known for yielding diverse and excellently preserved fossils of the Jehol Biota. The lower unit of Yixian Formation, dominated by lacustrine deposits, is rich in concentrations of two freshwater bivalves: Sphaerium anderssoni and Arguniella ventricosa. These bivalve concentrations can be divided into three types that comprise either paucispecific A. ventricosa or S. anderssoni, or both bivalves in similar amounts. The lithological, biotic, and taphonomic features of 12 bivalve concentrations are recorded, and the taphonomic signatures (such as shell articulation, size-frequency distribution, and orientation) are analyzed. Autochthonous as opposed to allochthonous bivalve concentrations are discriminated. A very short time-averaging effect is recognized in some concentrations, which was probably caused by seasonal or episodic water-level fluctuations and hypoxia. Three factors operated on the bivalve concentrations before final burial: in-situ reworking, transport, and time-averaging. Although time-averaging of the death assemblages was limited to several years, it is in this way that several generations of the two bivalve species could become preserved together. Reworking of the bivalve concentrations was most likely caused by storm action. |
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