新疆四棵树地区西山窑组孢粉组合及古气候意

四棵树凹陷位于准噶尔盆地南缘西段乌苏市境内，蕴含丰富的油气和煤炭资源。由于匮乏化石证据,制约四棵树凹陷侏罗纪地层的地质时代的确定。对西山窑组沉积环境和孢粉分析研究，恢复重建了其古环境，探讨了本区中西山窑时期的植被演替及环境演变。西山窑组岩性以泥质细砂岩、浅灰绿色泥岩、粉砂岩、泥岩为主。通过对孢粉化石分析研究，建立了Cyathidites minor—Osmundacidites —Cycadopites—Disacciatrileti（COCD）孢粉组合。组合中蕨类植物孢子与裸子植物花粉含量大体相当，蕨类植物孢子以紫萁科的Osmundacidites为主，桫椤科孢子也有一定含量，其他常见分子包括Deltoidospora、Neoraistrickia等，裸子植物以松柏类两气囊花粉含量为主，均为我国侏罗纪常见属种。通过对西山窑组孢粉植物群的分析，认为西山窑组孢粉组合时代属于中侏罗世早期,该孢粉植物群总体上反映了温暖湿润的热带—亚热带气候特点，植被类型以针阔混交林为主。

Palynological assemblage from the Xishan yao Formation in Sikeshu area,Xinjiang and its paleoclimate significance

The Sikeshu sag is located in Wusu City,western part of southern margin of Junggar Basin,which contains rich oil,gas and coal resources.The lack of fossil evidence restricts the determination of the geological age of Jurassic strata in Sikeshu sag.Methods: The sedimentary environment and palynology of the Xishanyao Formation are analyzed,the paleoenvironment is reconstructed,and the vegetation succession and environmental evolution during the Middle Xishanyao period are discussed. Results: The lithology of the Xishan yao Formation is mainly argillaceous fine sandstone,light grayish green mudstone,siltstone and mudstone.The Cyathidites minority-Osmundacidite-Cycadopites-Disacciatrileti(COCD)spore assemblage was established by analyzing the sporopollen fossils.The contents of fern spores and gymnosperms pollen in the combination were roughly equal.The fern spores were mainly Osmundacidites of opteraceae,while the podophylla spores also had a certain content.Other common molecules included Deltoidospora and Neoraistrickia,and the gymnosperms were mainly conifer and cypress pollen.All are common species of Jurassic in China.Conclusions: Based on the analysis of the palynological flora of the Xishanyao Formation,it is considered that the palynological assemblage of the Xishanyao Formation belongs to the early Middle Jurassic.The palynological flora of the Xishanyao Formation reflects the characteristics of warm and humid tropical-subtropical climate,and the vegetation type is mainly coniferous and broad-leaved mixed forest.