冀北滦平盆地陆相侏罗系—白垩系界线候选层型剖面初步研究  

Terrestrial Jurassic-Cretaceous boundary stratotype candidate in Luanping basin, northern Hebei

作　　者：田树刚[1] 庞其清[2] 牛绍武[3] 李佩贤[1] 柳永清[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]石家庄经济学院,河北石家庄050031 [3]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》2004年第12期1170-1179,共10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>(No.40472019);全国地层委员会项目<中国主要断代地层建阶研究>联合资助。

摘　　要：在发现陆相侏罗系—白垩系界线地层连续剖面的基础上,补充大北沟组和大店子组的含义,将2组系统分为7个岩段,命名4个标志层;确定年代地层层序,完善大北沟阶和义县阶定义内容;研究重点门类化石分布和演化,建立系统生物地层分带序列,包括7个介形虫带和6个叶肢介带;划分陆相生物群发展阶段,将侏罗系—白垩系界线置于“早期热河生物群”阶段的底部;开展旋回地层和层序地层学研究,建立地层等时格架,识别盆地演化的3个阶段和5个构造期;测得界线层型剖面点存在O同位素高值异常;锆石206Pb/238U测得张家口组顶部年龄为135.4Ma±1.6Ma,大北沟组中部为133.9Ma±2.5Ma和130.1Ma±2.5Ma。综合多学科研究成果,将界线层型剖面点定在张家沟剖面第9层底,以介形虫化石Cyprideastenolonga的首现为标志。Based on the discovery of the successive sections of Jurassic-Cretaceous transitional strata, a boundary stratotype candidate has been preliminarily erected in the Luanping basin of northern Hebei. The Dabeigou and Dadianzi formations are divided to 7 members, in which 4 marker beds are distinguished and named. A chronostratigraphic sequence has been determined and the definitions of the Dabeigouan and Yixianian stages improved. A systematic biostratigraphic zone sequence, including seven ostracod zones and 6 conchostracan zones, has been distinguished according to the occurrence and evolution of fossils. The faunal developmental stages have been defined and the J-K boundary is placed at the base of the 'earlier Jehol (Rehe) fauna stage' (earlier Yixianian). Cyclostratigraphy and sequence-stratigraphy have been studied and an isochrononic framework of strata has been constructed. Three stages and five tectonic phases for basin have been recognized. An O-isotope high-value anomaly appears at the boundary stratotype. The zircon 206Pb/238U dating gave a age of 135.4 Ma±1.6 Ma for the top of the Zhangjiakou Formation and ages of 133.9 Ma±2.5 Ma and 130.1 Ma±2.5 Ma for the middle part of the Dabeigou Formation. According to an integration of multidisciplinary research results, the boundary stratotype point is placed at the bottom of bed 9 of the Zhangjiagou section and marked by the first-occurrence of the ostracod Cypridea stenolanga.

关 键 词：陆相侏罗系—白垩系界线 候选层型剖面 冀北滦平盆地 

分 类 号：P534.52[天文地球—古生物学与地层学] P534.53[天文地球—地质学]