辽西金羊盆地北票组孢粉组合及其时代和古气候意义

Palynological Assemblages of Beipiao Formation in Jinyang Basin of West Liaoning, and Their Age and Paleoclimatic Significances

金羊盆地内的北票组是辽西地区重要的含煤及生烃潜力层,确定其时代和古气候环境对进一步研究北票组有非常重要的意义.在坤头营子地区北票组剖面中采集到20件孢粉样品进行孢粉学研究,并对侵入北票组的花岗斑岩及该组地层下部的兴隆沟组安山岩进行了锆石U Pb同位素测年.系统的分析、鉴定和研究表明:北票组自下而上可划分为3个孢粉组合,下部以Monosulcites Chasmatosporites Polycingulatisporites为代表,中部以Protopinus Paleoconiferus Alisporites为代表,上部以Monosulcites Protopinus Paleoconiferus为代表.锆石U Pb同位素测年结果分别为172.6 Ma和189 Ma.最终确定北票组的形成时代为早侏罗世中、晚期,自下而上反映了从半湿润的北亚热带气候向湿润的温带气候转变的特征.

The Beipiao Formation within the Jinyang basin at West Liaoning is an important coal bearing and hydrocarbongenerating potential bed,the determination of its formation age and paleoclimatic environment is very important for its research.At present study,20 palynological samples were collected from the section of Beipiao Formation at Kuntouyingzi area,and the zircon U Pb ages of granite porphyry which intruded in the Beipiao Formation and andesite that from the lower strata of Xinglonggou Formation were analyzed.3 sporo-pollen assemblages which represented by Monosulcites Chasmatosporites Polycingulatisporites of lower part,Protopinus Paleoconiferus Alisporites of middle part and Monosulcites Protopinus Paleoconiferus of upper part were identified from Beipiao Formation after systematical analysis,identification and research.The U Pb dating results of zircon are 172.6 Ma and 189 Ma,respectively.The formation age of Beipiao Formation is determined as middle and late Early Jurassic and the bottom-up reflects the characteristics of the transition from a subhumid north subtropical climate to a humid temperate climate.