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Stratigraphy and age of the Daohugou Bed in Ningcheng, Inner Mongolia
Recent fieldwork has extended the distribution of the Daohugou Bed deposits from the Daohugou Village to its several neighboring areas. The fossil-bearing Daohugou deposits uncomformably overlie complex bedrocks, and comprise three major parts. The red shales in the lower part were misidentified as belonging to the Tuchengzi Formation. Field excavation has indicated that the shales of upper part of the bed are the major fossil-bearing horizon. Due to strong tectonic activities, sediments were often folded with the sequences inverted in the region. Some newly recognized contacts between the Daohugou Bed and the volcanic rocks showed that the ignimbrite of the Tiaojishan Formation (159―164 Ma) underlies the Daohugou deposits, rather than overlying the latter as previously proposed. Thus, the age of the Daohugou deposits should be younger than the age of the ignimbrite, and thus it was incorrect to correlate the Daohugou Bed with the Middle Jurassic Jiulongshan Formation. Although biostratigraphic studies based on conchostracans and insects support a Middle Jurassic-early Late Jurassic age for the Daohugou deposits, vertebrate fossils such as Liaoxitriton, Jeholopterus and feathered maniraptorans show much resemblance to those of the Yixian Formation. In other words, despite the absence of Lycoptera, a typical fish of the Jehol Biota, the Daohugou vertebrate assemblage is closer to that of the Early Cretaceous Jehol Biota than to any other biota. We propose that the Daohugou fossil assemblage probably represents the earliest evolutionary stage of the Jehol Biota based on both vertebrate biostratigraphy and the sedimentological and volcanic features which suggest the Daohugou deposit belongs to the same cycle of volcanism and sedimentation as the Yixian Formation of the Jehol Group.
作 者： WANG Xiaolin ZHOU Zhonghe HE Huaiyu JIN Fan WANG Yuanqing ZHANG Jiangyong WANG Yuan XU Xing ZHANG Fucheng 作者單位： WANG Xiaolin,ZHOU Zhonghe,JIN Fan,WANG Yuanqing,ZHANG Jiangyong,WANG Yuan,XU Xing(Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China)HE Huaiyu,ZHANG Fucheng(Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China)
刊 名： 科學通報（英文版） SCI 英文刊名： CHINESE SCIENCE BULLETIN 年，卷(期)： 2005 50(20) 分類號： P5 關鍵詞： Inner Mongolia Daohugou Bed Yixian Formation stratigraphic sequence Early Cretaceous Jehol Biota【Stratigraphy and age of the Daohugou】相關文章：