内蒙古东胜煤田延安组侏罗纪植物群

A Jurassic Flora from the Yan'an Formation in Dongsheng Coal Field,Inner Mongolia

为确定内蒙古东胜煤田延安组的地质时代,对东胜煤田钻孔中产出的大量古植物化石进行了详细研究和鉴定,该植物群组成包括节蕨纲、真蕨纲、种子蕨纲、苏铁纲、银杏纲、松柏纲的25属68种,以真蕨纲、银杏纲为主,其次为苏铁纲和松柏纲,节蕨纲和种子蕨纲较为少见。可建立Coniopteris(锥叶蕨)—Cladophlebis(枝脉蕨)植物组合,并可进一步划分为2个亚组合:延安组一段的Coniopteris(锥叶蕨)—Neocalamites(新芦木)亚组合和延安组二段的Cladophlebis(枝脉蕨)—Phoenicopsis(拟刺葵)亚组合。经与国内、外其它地区植物群对比,延安组一段的地质时代为早侏罗世晚期土阿辛期,延安组二段的地质时代为中侏罗世早期阿林期和巴柔期。

In order to determine the geological age of Yan＇ an formation in Dongsheng coalfield Inner Mongolia, the great majority of plant fossils from drills in this area were studied and identified in detail. The flora consisted of 25 genuses 68 species belong to Arth ropsida, Filices, Pteridospermae , Cycadopsida, Ginkdopsida, Coni f eropsida. Fi- lices as well as Ginkdopsida appeared to be the important component of the flora. Cycadopsida and Coniferopsida rank next in importance. Arthropsida and Pteridospermae were scarce. Coniopteris Cladophlebis assemblage was set up. This assemblage was divided into two subassemblage：Coniopteris--Neocalamites subassemblage in the first member of Yan^an formation and Cladophlebis--Phoenicopsis subassemblage in the second member of Yah＇an for- mation. Through correlation with the flora of other areas home and abroad,the first member of Yan＇an formation＇s age was Toarcian of the late Early Jurassic,and the second member of Yan＇an formation＇s age was Aalenian to Bajoclan of the early Middle Jurassic.