内蒙古查干敖包地区上石炭—下二叠统宝力高庙组特征及时代

提要：笔者在查干敖包地区开展1∶5万区域地质调查工作时，发现本区出露的宝力高庙组层序齐全、植物化石丰富、划分标志明显，通过路线调查、剖面测量对其进行了重新划分，即据岩性组合、生物面貌等特征划分为4个岩性段，一段为河湖相灰色、灰绿色碎屑岩夹少量中性火山岩，在粉砂岩中采到了大量安格拉植物化石；二段为中偏碱性-酸性砖红色、紫色火山岩夹砂（砾）岩，其中粗面岩获得锆石U-Pb同位素年龄为(297.0±1.2) Ma；三段为灰色、灰紫色安山质火山岩夹碎屑；四段以灰白色流纹质火山岩为特征，夹砂岩、泥灰岩等，在砂岩中采到了大量安格拉植物群化石。据植物化石鉴定结果、同位素年龄资料将其形成时代确定为晚石炭—早二叠世。

Stratigraphic division and age of Upper Carboniferous - Lower Permian Baoligaomiao Formation in Qagan Obo area, Sonid Left Banner, Inner Mongolia

Abstract: During the 1:50 000 regional geological survey in Qagan Obo area, the authors found that the sequence of Baoligaomiao Formation exposed in Qagan Obo area is complete, and the strata have abundant plant fossils and clear division marks. Baoligaomiao Formation was reclassified during route survey and profile measurement into four lithologic members according to the lithological and biological appearance. The first member is lacustrine and gray, grayish green clastic rocks with a little mild volcanic rock, and there are a large number of Angela plant fossils in the siltstones; the second member is alkaline-acidic brick red rock intercalated with purple volcanics with sand (gravel) rock, and the U-Pb dating of zircon from the trachyte and rhyodacite yielded ages of (297.0±1.2)Ma and (323.0±1.4)Ma; the third member is gray and purple gray andesitic volcanics with clastic rock; the fourth member is gray rhyolitic volcanic rocks with sandstone and marl, and the sandstone also has a large number of Angela plant fossils. Based on the results of the identification of plants fossils and isotopic data, the authors hold that the formation age of the Baoligaomiao Formation is Late Carboniferous - Early Permian .