华北地块南缘白大山群的层序、时代及地质意义

笔者等近期对华北地块南缘豫皖交界处出露的一套层序连续完整的白大山群进行了剖面测制，在该套地层的碳酸盐岩中发现了中、晚奥陶世牙形刺分子Belodina compressa，Panderodus gracilis，Pseudobelodina dispansa(?)以及苔藓虫、海绵骨针、小壳类、古介形类等化石，填补了该地区一直无可靠化石记录的空白。同时依据地层层序特征、岩性组合、生物群面貌、古地理沉积环境，并结合大量灰岩薄片鉴定结果，将白大山群时代划归早古生代。同时，将华北地块南缘界限向北推移至蒋集-龙潭一线，并认为本区牙形刺生物群应属北方型牙形刺地理分区。

New progress and understanding of the Baidashan group,southern margin of the North China Block

Recently, the author has measured Baidashan group section which exposed a sequence of complete and continuous layer on the Henan Anhui border of southern margin on the north China Block. There are conodonts molecules of the Middle Late Ordovician in carbonatite of Baidashan group: Belodina compressa,Panderodus gracilis,Pseudobelodina dispansa(?) and Bryozo, Calthrop, Small shells, Archaeostraca etc., which filled the blank of the region that has been no fossil record. According to the characteristics of stratigraphic sequence, lithologic combination, the biota appearance, the ancient sedimentary environment of geography, and combined with a large number of limestone thin section results, it is concluded that the Baidashan group belongs to the Early Paleozoic era. The southern margin of North China massif line was redrawn to Jiangji Longtan sets. We consider that the conodonts biota in this area should belong to the northern type conodonts geographical partition.