摘要：

我国西北地区由不同地体组成，构造运动复杂。由于缺乏充分的古生物学证据，古生物区系的识别和归属一直是有待解决的问题。本文在前人工作的基础上，依据各类动物群特征的分析，较详细地探讨了我国祁连和秦岭地区相关地层区中-晚寒武世和奥陶纪动物群的性质及其古生物类型的归属，确定了过渡型动物群在祁连和秦岭地区的大体分布范围。同时，结合地球动力学和古地理学研究成果的分析，探讨了导致在祁连和秦岭地区中—晚寒武世和奥陶纪时存在着与华南相似过渡类型动物群的两种可能原因。一种可能是中—晚寒武世和奥陶纪时塔里木板块位于扬子板块西边，中朝板块位于扬子板块之北，祁连和秦岭可能位于扬子和塔里木板块之间，存在与华南及华北动物群交流的基本条件，产生了大体相近的动物群。另一种可能是中—晚寒武世和奥陶纪时祁连和秦岭地区存在一些原位于扬子板块北部边缘的地体，在这些沿扬子板块北缘分布的地体上发育了与南部边缘相似的生物群或生物类型。中生代之前，沿扬子板块主体和北部边缘地体之间的走滑活动，可能使扬子板块主体向东移动了几百公里，而其边缘那些属于祁连和秦岭的地体向东移动的幅度不大，从而造成现今祁连和秦岭地区存在与扬子板块东南部地区大体相似的具过渡性质的生物群或生物类型，而扬子板块北部边缘又缺少边缘过渡相带的现状。

Abstract:

The northwestern China is composed of several terranes，where the tectonic movements are complexBecause of the lack of paleontological proof，the recognition and relegation of paleobiogeographical division still remain to be solvedBased on the analysis of fauna characters，the authors studied the Middle  and Late Cambrian and Ordovician fauna nature of different stratigraphic provinces in Qilianand Qinling areas，as well as relegation of paleontological types，and ascertain the distribution of faunas of transitional type in Qilian and Qinling areasAccording to the analyses in geodynamics and paleogeography researches，twopossible reasons，which resulted in the similar faunas of transitionaltypes between the Qilian and Qinling areas and South China during the Middle and Late Cambrian and Ordovician，are discussed One is that Tarim Plate lay to the west of Yangtze Plate,SinoKorean Plate lay to the north of the Yangtze Plate,the Qilian andQinling areas were situated between the Yangtze Plate and Tarim Plate during the Middle and Late Cambrian and Ordovician，and were qualified for interchange between South China fauna and North China fauna，and thus roughly similar faunasemergedAnother is that there were some terranes，which were situated along northern margin of the Yangtze Plate in the Qilian and Qinling areas during the Middle and Late Cambrian and Ordovician，and the faunas or biotic types，which were similar to those in southern margin of the Yangtze Plate，were developed on the terranesBefore the Mesozoic，the slip movement between the main part and the northern margin of the Yangtze Plate caused the mainpart of the Yangtze Plate to shift several hundred kilometres eastwardBut the movement of the terranes of northern margin of the Yangtze Plate，which belonged to the Qilian and Qinling areas，was within a narrow rangeTherefore，the current situation，that the transitional faunas or biotic types appeared in the Qilian and Qinling areas and the transitional zones along the northern margin of the Yangtze Plate were absent，was created