辽宁凌源及内蒙古宁城地区下白垩统义县组脊椎动物生物地层

辽宁凌源及相邻内蒙古南部宁城地区义县组发现多个重要脊椎动物化石地点，通过岩 石地层、脊椎动物生物地层和同位素年代地层对比，建立了该地区义县组地层层序。凌源一宁 城地区义县组有 ２个脊椎动物化石层位：下部道虎沟层含 Ｌｙｃｏｐｔｅｒａｅｒ Ｉｃｈｔｈｙｏｆａｕｎａ， Ｐｓｉｔｔａｃｏｓａｕｒｕｓ Ｆａｕｎａ和Ｃｏｎｆｕｃｉｕｓｏｒｎｉｓ Ａｖｉｆａｕｎａ等３个动物群，可以与北票尖山沟层的四合 屯脊椎动物化石群对比，层位相当于义县组一、三段；上部大王杖子（大新房子）层含 Ｌｙｃｏｐｔｅｒａ Ｉｃｈｔｈｙｏｆａｕｎａ和Ｌｉａｏｘｉｏｒｎｉｓ Ａｖｉｆａｕｎａ等２个动物群，为义县组中部沉积，在四合屯地 区缺失。冀北丰宁四岔口－森吉图地区义县组脊椎动物化石层对应于凌源大王杖子层；滦平 大北沟组为义县组最下部沉积，其上覆的大店子组相当于宁城道虎沟层和北票四合屯义县组 一、三段。热河群义县组和九佛堂组发现３个连续的鸟类群；义县组下部Ｃｏｎｆｕｃｉｕｓｏｒｎｉｓ Ａｖｉｆａｕｎａ、义县组中部Ｌｉａｏｘｉｏｒｎｉｓ Ａｖｉｆａｕｎａ和九佛堂组Ｃａｔｈａｙｏｒｎｉｓ－Ｃｈａｏｙａｎｇｉａ Ａｖｉｆａｕｎａ。义 县组和九佛堂组Ｌｙｃｏｐｔｅｒａ　Ｉ

VERTEBRATE BIOSTRATIGRAPHY OF THE LOWER CRETACEOUS YIXIAN FORMATION IN LINGYUAN, WESTERN LIAONING AND ITS NEIGHBORING SOUTHERN NEI MONGOL (INNER MONGOLIA), CHINA

Summary:Several important vertebrate fossil localities have been discovered from the Early Cretaceous deposits in Lingyuan, western Liaoning Province and neighboring Ningcheng areas of southern Nei Mongol. In this paper, we discuss these deposits of the aforementioned areas, which are referable to the Yixian Formation, and correlate their stratigraphic sequence on the basis of lithostrahgraphy, veftebrate biostratigraphy and radiometric dating. The Cretaceous deposits consist of two fossiliferous beds. The lower one, the Daohugou Bed, is characteristic of Lycoptera Ichthyofauna, Psittacosaurus Fauna and Confuciusornis Avifauna and comparable to the vertebrate fauna of the Jianshangou Bed in Sihetun area of Beipiao. Based on similar components, therefore, the Deohugou Bed is correlated with members 1 and 3 of the Yixian Formation of Sihetun area. Both represent the deposits of the lower Yixian Formation. The upper one, the Dawangzhangzi Bed (Daxinfangzi Bed), is characteristic of Lycoptera Ichthyofauna and Liaoxiornis Avifauna, representing the deposits of the middle Yixian Formation which is absent at Sihetun. The vertebrate fossils in Sichakou-Senjitu area of Fengning, northern Hebei Province are comparable to those from the Dawangzhangzi Bed in Lingyuan, Liaoning Province. The Dabeigou Formation in Luanping, Hebei Province represents the earliest deposits of the Yixian Formation, and the overlying Dadianzi Formation is comparable to the Daohugou Bed in Ningcheng or members 1 and 3 of the Jianshangou Bed at Sihetun on the basis of the lithostratigraphic correlation and the presence of Lycoptera Ichthyofauna, and Psittacosaurus Fauna. Three distinctive Avifaunas have been recognized from the two formations (the lower Yi-clan Formation and the upper Jiufotaflg Formahon) of the Jehol GrouP; from bottom up, they are: Confuciusornis Avifauna of the lower Yixian Formation, Liaoxiornis Avifauna of the middle Yixian Formation and the Cathayornis-Chaoyangia Avifauna of the Jiufotang Formation. The Ichthyofauna from the Yixian Formation characterized by Lycoptera-Protopsephurus can be well distinguished from the Jinanichthys- Longdeichthys Ichthyofauna of the Jiufotang Formation. Three fossil zones can be recognized based on different species of the genus Lycoptera: the lower Lycoptera sinensis Zone of the Jianshangou Bed, the middle Lycoptera davidi Zone of the Dawangzhangzi Bed and the upper Lycoptera muroii Zone of the Jingangshan Bed. Lycoptera Ichthyofauna, the Psittacosaurus Fauna and three avifaunas (Confuciusornis, Liaoxiornis and Cathayornis-Chaoyangia Avifauna) are probably most indicative of the Early Cretaceous (?Berriasian or Valanginian-Barremian) Jehol Biota.