北票-义县地区义县组珍稀化石层位对比及时代

张立东; 金成洙; 郭胜哲; 张长捷; 彭艳东; 贾斌; 陈树旺; 邢德和; 丁秋红; 郑月娟

北票-义县地区义县组珍稀化石层位对比及时代

THE PRECIOUS FOSSIL-BEARING BEDS OF YIXIAN FORMATION IN BEIPIAO-YIXIAN AREA: THIER AGES AND CORRELATION

摘要

摘要: 北票-义县地区义县组以火山-沉积地层为主体,具有4个火山活动亚旋回,生物化石主要形成于第一、第二、第四亚旋回期间,构成了3个产出层位.以中华龙鸟、孔子鸟、辽宁古果为代表的珍稀化石组合产在义县组二段中,形成于125~127Ma期间.枕状熔岩、淬火岩等特殊岩石的出现和高频层序地层研究表明,北票、义县地区的含珍稀化石沉积层(义县组二段)都处于相对较深的湖盆沉积环境,表现为湖扩展体系域沉积,两地含珍稀化石沉积地层层位基本相当.义县组形成于135~120Ma期间,属于早白垩世.多方面证据表明侏罗系-白垩系界限应当置于义县组底界.

Abstract: The Yixian formation in Beipiao-Yixian area, composed mainly of volcano-sedimentary strata, contains four volcanic subcycles.The organic fossils, which formed mainly in the periods of the 1st, 2nd and 4th subcycles, are found in three beds.The precious fossil assemblage represented by Sinosuaropteryx, Confuciusornis and Archaefructus liaoningensis in the 2nd member of Yixian formation and formed during the period of 125 to 127 Ma.The pillow lavas, quenched rocks and high frequency sequence strata all indicate that the precious fossil-bearing beds (the 2nd member of Yixian formation) of Beipiao-Yixian area were situated in a relatively deep lake environment, to show the lake expansive system tract.The precious fossil-bearing beds of both Beipiao and Yixian areas are basically equivalent and correlatable.The Yixian formation was formed during the period of 135 to 120 Ma, i.e.Early Cretaceous in age.Many evidences have revealed that the boundary between Jurassic and Cretaceous should be set in the basal boundary of Yixian formation.

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