新疆准噶尔盆地南缘郝家沟组和八道湾组底部孢粉组合及三叠系—侏罗系界线  

Triassic—Jurassic Sporopollen Assemblages on the Southern Margin of the Junggar Basin, Xinjiang and the T—J Boundary

作　　者：卢远征[1,2] 邓胜徽[2] 

机构地区：[1]中国地质大学 [2]中国石油勘探开发研究院,北京100083

出　　处：《地质学报》2005年第1期15-27,i005,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目 (编号 40 3 72 0 2 1);中国国土资源部地调局;地层委员会和中国科学院知识创新工程项目 (编号 KZCX2 -SW-12 9)资助的成果

摘　　要：新疆乌鲁木齐郝家沟剖面郝家沟组及八道湾组底部的孢粉分为 3个组合。即郝家沟组的 Alisporites-Chordasporites- Chasmatosporites组合和 Aratrisporites- Alisporites- Chasmatosporites组合以及八道湾组底部的Asseretospora- Dictyophyllidites- Cycadopites组合。前两个组合主要由常见或仅见于三叠系的属种组成 ,时代属于晚三叠世无疑 ;后一组合中前期分子大量消失 ,蕨类孢子迅速崛起 ,反映植物群出现显著变化 ,其中常见和仅见于晚三叠世的分子不复存在 ,主要成分为晚三叠世到侏罗纪常见的分子 ,具有晚三叠世到早侏罗世的过渡特点 ,时代趋向于早侏罗世。因此 ,本文提出三叠系—侏罗系的界线划在郝家沟组之顶是合适的。The present paper deals with the Late Triassic—Early Jurassic sporopollen assemblages from the Haojiagou Formation and the base of the Badaowan Formation in the southern margin of the Junggar Basin, Xinjiang. The Alisporites-Chordasporites-Chasmatosporites assemblage and Aratrisporites-Alisporites-Chasmatosporites assemblage, yielded from the mid-upper parts of the Haojiagou Formation, are characterized by predominance of gymnospermous pollen that consists mainly of coniferous bisaccate pollen. These two assemblages are assigned to the Late Triassic based on the appearance of many typical Triassic elements, such as Aratrisporites, Kraeuselisporites, Bharadwajapollenites, Taeniaesporites and Chordasporites. The Asseretospora-Dictyophyllidites-Cycadopites assemblage from the base of the Badaowan Formation is markedly different from the two assemblages from the Haojiagou Formation in being dominated by spores of ferns. The fern spores, which consist mainly of Asseretospora, Crassitudisporites and Dictyophyllidites, occupy 57.14% of the assemblage. Those typical Triassic elements of the above two assemblages are absent, while some Jurassic ones appear. The spore spike is considered to be similar to that of the Passaic Formation of the Newark basin, eastern North America, which indicates the beginning of the Jurassic in that basin. Therefore, this assemblage is assigned an Early Jurassic age. Consequently, the Triassic—Jurassic boundary should be placed at the contact between the Haojiagou Formation and the Badaowan Formation.

关 键 词：三叠系 晚三叠世 侏罗系 早侏罗世 界线 孢粉组合 侏罗纪 植物群 属种 底部 

分 类 号：Q913[天文地球—古生物学与地层学]