摘要
热河生物群是世界闻名的陆相生物化石宝库,保存了大量特异埋藏化石,为研究早白垩世脊椎动物、昆虫和植物的演化提供了绝佳的素材.依据古生物组合的不同,将其分为早、中、晚三期,分别赋存于河北丰宁花吉营组、辽西义县组和九佛堂组及其周边地区相当层位.河北承德—围场地区处于早-中期热河生物群分布地区的过渡地带,近年来不断的化石发现为研究华北克拉通破坏及其对陆地生态系统的影响提供了关键证据.但由于缺乏准确的年龄约束,对于含化石层位的准确时代及其与邻区地层对比存在较大争议.本文利用来自于河北北部承德盆地袁家庄剖面的3个安山岩样品的锆石,进行化学熔蚀-离子探针(CA-SIMS)锆石U-Pb定年,获得年龄为129.6~128.7 Ma.结合前人发表的磁性地层学结果建立了新的磁性地层学对比方案和新的综合年代框架,揭示了该剖面火山-沉积序列记录了古地磁极性序列M8n-M7n,进一步证明了袁家庄剖面的陆相火山-沉积层序属于欧特里夫晚期.结合区域内前人年代学结果,将该区域热河生物群化石层时代限定为130~127 Ma.年代地层学对比结果显示,承德盆地早白垩世火山-沉积序列与滦平盆地大店子组和森吉图—四岔口盆地花吉营组上部时代相当,明显老于辽西义县组时代,揭示了华北克拉通北缘早白垩世陆相地层的自西向东逐渐年轻的特征.
Jehol Biota in northern China is one of the most interesting terrestrial biotas in the world because it preserves exceptional well-preserved fossils,which provide rare opportunities for evolutionary history of the Early Cretaceous vertebrates,insects,and plants.Considering the taphonomy and fossil contents,it can be subdivided into three phases:the Early Jehol Biota preserved in the Huajiying Formation,the Middle and Late Jehol Biota preserved in the Yixian and Jiufotang formations in western Liaoning and its equivalent strata in adjacent areas.The transitional fauna in the Chengde-Weichang area,northern Hebei between the Early and Middle Jehol Biota distribution areas,yielding a variety of fossils.It has advanced our knowledge of the destruction of the North China Craton and its impact on the terrestrial ecosystem.However,the precise age constraints on the fossiliferous layers and the chronology consensus in this area remain an open question.Here,we present chemical abrasion-secondary ion mass spectrometry(CA-SIMS)U-Pb zircon analysis results of three andesite samples from the volcano-sedimentary sequences outcrops at the Yuanjiazhuang section in the Chengde Basin,northern Hebei.These ages suggest that the volcano-sedimentary sequences in Chengde Basin were deposited at ca.129.6~128.7 Ma.Our integrated new chronology,published magnetostratigraphic results and correlation suggest the geomagnetic polarity time scale from upper Chron M8n to lower Chron M7n,further demonstrating terrestrial volcanic-sedimentary sequence of the Yuanjiazhuang section is of late Hauterivian age.The age of the fossil layers of the Jehol Biota in this area is constrained to 130~127 Ma based on our new chronology and published data.The chronostratigraphic comparison shows that the volcano-sedimentary sequences in Chengde Basin are coeval with the upper Huajiying Formation in the Senjitu-Sichakou basins and the Dadianzi Formation in the Luanping Basin,northern Hebei,and thus are undoubtedly deposited earlier than the Yixian Formation in we
作者
俞志强
贺怀宇
周忠和
YU ZhiQiang;HE HuaiYu;ZHOU ZhongHe(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Key Laboratory of Vertebrate Evolution and Human Origin of Chinese Academy of Sciences,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044,China;College of Earth and Planetary Sciences,University of the Chinese Academy of Sciences,Beijing 101400,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第11期4639-4653,共15页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(42203024,42288201)资助。
