辽宁北票地区义县组地层划分与对比

Stratigraphic division and correlation of the Yixian Formation in Beipiao area, Liaoning Province

辽宁北票地区义县组是一套中生代陆相火山沉积岩系,主要由中-基性火山熔岩、火山碎屑岩及陆相沉积岩构成。依据火山活动的规律性,将本区义县组划分为4个岩性段,自下而上分别为:一段:底砾岩、基性-中基性火山岩段;二段:湖相沉积(或称珍稀化石层)岩段;三段:基性火山岩段;四段:砾岩段。其中,义县组一段产丰富的以鹦鹉嘴龙为主的古脊椎动物化石。二段产大量热河生物群化石,包括著名的中华龙鸟、孔子鸟和辽宁古果等珍稀化石,是义县组最重要的化石产出层位。从西向东,义县期火山活动具明显的由早到晚、由基性-中性-酸性(偏碱性)的演化特征。

The Yixian Formation in the Beipiao area, Liaoning Province, consists of a series of volcanic-sedimentary rocks, including basic and intermediate-basic volcanic lava, pyroclasts and terrestrial sedimentary rocks. Based on the regularity of volcanic activity, the Yixian Formation was divided into four members from bottom to top. The first member is of basal conglomerate, basic and intermediate-basic volcanic rocks; the second member is of lacustrine sedimentary rocks, or in another word, precious fossil-rich sedimentary beds; the third is of basic volcanic rocks and the fourth is of upper conglomerate. Field mapping and comprehensive study also indicate that there are abundant vertebrate fossils (mainly of Psittacosaurus) in the first member of Yixian Formation. 'Jehe Biota' (include Sinosauropterxy,Confuciusorns sanctus, Archaefructus,etc.) was yielded in the second member. From west to east, the volcanic activity of the Yixian Formation took place regularly from early to late and from basic and intermediate-basic to acid(alkali).