Abstract:

Eighty one species of fossil spores and pollen assigned to 52 genera are found from the Middle Jurassic Xishanyao,Sanjianfang and Qiketai Formations of boreholes Le 1, Mi 1, Shan 1 and Dun 1 in the northern Turpan Depression, Xinjiang, northwest China. Three assemblages have been proposed as:Cyathidites Psophosphaera Cycadopites assemblage, Cyathidites Quadraeculina Classopollis assemblage and Cyathidites Callialasporites Classopollis assemblage obtained from the Xishanyao Formation, the Sanjianfang Formation and Qiketai Formation respectively. Based on the sporopollen assemblage features and correlation,their geological ages are regarded as of Middle Jurassic,probably Aalenian to Bathonian.The results of the study indicate that the vegetation of early Middle Jurassic in this region consisted mainly of Gymnospermae of Ginkgoaceae of Cycadales, Podocarpaceae, Pinaceae and Pteridophyta of Cyatheaceae, Osmundaceae, Lycopodiaceae and Dicksoniaceae, etc. They reflect a warm moist subtropic climate.To the middle late Middle Jurassic, Cheirolepidaceae was dominant in the vegetation, which indicates that the climate was in the trend of becoming dry.

吐鲁番拗陷北部中侏罗世孢粉植物群

尹凤娟¹  张子福²

(1.西北大学地质系,西安,710069 ；2中国地质科学院西安地质矿产研究所,西安,710054)

报道了新疆吐鲁番拗陷北部勒1、米1 、山1和墩1井中侏罗世孢粉化石52属81种.建立了本区中侏罗世孢粉组合: Cyathidites-Psophosphaera-Cycadopite 组合、 Cyathidites-Quadraeculina-Classopollis 组合和 Cyathidites-Callialasporites-Classopollis 组合.它们分别产自西山窑组、三间房组和七克台组.根据孢粉组合特征及其对比, 认为3个组合的地质时代属阿林-巴通期.经研究表明, 中侏罗世早期的植被是以银杏、苏铁类和松柏类等乔木为主体, 并伴有桫椤科树蕨及紫萁科和卷柏科等草本植物.古气候应属温暖潮湿的亚热带气候.至中侏罗世中晚期, 掌鳞杉科植物在植被中占主导地位, 指示当时的气候趋于干旱.

关键词 孢子花粉 气候 中侏罗世 中国西北