冀北滦平盆地大北沟组叶肢介生物地层特征与大北沟阶单位层型的建立  

Conchostracan biostratigraphy of the Dabeigou Formation in the Luanping basin, northern Hebei, China and establishment of a Dabeigou-aged stratotype section

作　　者：牛绍武[1] 

机构地区：[1]中国地质调查局天津地质矿产研究所,天津300170

出　　处：《地质通报》2008年第3期326-344,共19页Geological Bulletin of China

基　　金：国家自然科学基金项目<侏罗系-白垩系界线过渡期大北沟阶至义县阶连续剖面及化石分带研究>(编号:40472019);全国地层委员会项目<中国主要断代地层建阶研究>(编号:200113900076)联合资助

摘　　要：滦平县火斗山乡张家沟榆树下村大北沟组(J3d)剖面地层连续,顶底清楚,化石丰富,以沉积岩为主夹少量火山岩,可分为3个岩性段。1段含孢粉化石;2至3段化石极为丰富,有叶肢介、昆虫、介形类、双壳、腹足类、鲎虫、鱼、植物等化石。其中叶肢介化石自大北沟组近底部一直分布于顶部,可见至少25个化石层,计5科9属36种,统属于尼斯托叶肢介群(NestoriaFauna)。自下而上又可进一步划分为3个叶肢介化石带。以最底部化石带中Nestoriapissovi,Jibeilimnadiaovata的首现为标志,即为大北沟阶的开始,榆树下剖面可作为大北沟阶理想的单位层型剖面。根据化石组合、地层层序、区域地层对比及同位素年代资料,大北沟阶的时代应为晚侏罗世,可能更近于晚侏罗世晚期。文中描述了一些叶肢介属种。The section of the Dabeigou Formation at Yushuxia Village, Zhangjiagou, Huodoushan Township, Luanping County, Hebei, is characterized by the continuation of strata, clear top and bottom and abundant contained fossils. The formation consists predominantly of sedimentary rocks with small amount of volcanic rocks and may be divided to three members from the bottom to top. The first member contains sporopollen, and the second and third members contain very abundant fossils, including conchostracans, ostracods, bivalves, gastropods, Limulus, fishes and plants. Of these, conchostracans, which are distributed in at least 25 fossil beds from near the bottom up to top of the Dabeigou Formation, include 5 families, 9 genera and 36 species. Among these, the genus Nestoria predominates and occurs throughout the Dabeigou Formation, so these fossils may be called the Nestoria fauna. The Nestoria fauna may be further divided in ascending order into three conchostracan zones： the Nestoria pissovi-Jibeilimnadia ovata assemblage zone in the lower part, and the Nestoria pissovi-Keratestheria gigantea assemblage zone and Yanshania xishunjingensis-Yanshania subovata assemblage zone in the upper part of Dabeigou Formation.. The beginning of the Dabeigouan Stage is marked by the first appearance of Nestoria pissovi-Jibeilimnadia ovata in the bottommost conchostracan assemblage zone. The Yushuxia section may serve as an ideal stratotype section of the Dabeigouan Stage. According to the fossil assemblages, sequence of strata, regional stratigraphic correlation and isotopic age data, the age of the Dabeigouan Stage should be Late Jurassic, possibly closer to late Late Jurassic. The paper describes some genera and species of conchostracans.

关 键 词：冀北 滦平盆地 大北沟组 叶肢介 大北沟阶 上侏罗统 

分 类 号：P534.52[天文地球—古生物学与地层学] Q915[天文地球—地质学]