内蒙古锡林浩特宝力根地区哲斯腕足动物群的发现及其生物古地理分区

Discovery of the Zhesi brachiopods fauna in Bolgensume area,Xilinhot,Inner Mongolia,and its biogeographical division

内蒙古锡林浩特宝力根苏木乌勒吉图剖面哲斯组灰岩中发现大量腕足化石,共计18属23种。该腕足群落以长身贝目、石燕目为主,化石组合面貌具有典型的哲斯动物群特征。可将其由下至上划分为2个组合:ⅠYakovlevia mammata-Anidanthus rugousa组合;ⅡAnidanthus ussuricus-Rhombospirifer zhesiensis组合。其中,组合Ⅰ地质年代为Kungurian期—Roadian期,组合Ⅱ地质年代为Wordian期。通过对腕足冷暖属性特征研究,发现组合Ⅰ属于凉水型-分异型,组合Ⅱ属于凉水型-微渗型。对比其他地区的哲斯腕足动物群可以看出,Kungurian期—Wordian期哲斯腕足动物群由单一的凉水型向混生型演化,造成该变化的原因可能是西伯利亚板块和华北板块间的构造运动和晚古生代冰期作用。

Lots of brachiopods which include 18 genera and 23 species were discovered in Zhesi Formation,Wulejitu section,Bolgensume,Xilinhot,Inner Mongolia.The brachiopod community is mainly composed of Productida and Spiriferida,which show typical Zhesi fauna characteristics.It can be divided into two assemblages from bottom to top:ⅠYakovlevia mammata-Anidanthus rugousa assemblage;ⅡAnidanthus ussuricus-Rhombospirifer zhesiensis assemblage.The geological age of assemblageⅠis assigned to the Kungurian to Roadian,with the characteristic of cool water facies-differentiation type.The geological age of assemblageⅡis assigned to the Wordian,with the characteristic of cool water facies-micro-osmosis type.A comparison of Zhesi brachiopods fauna from other regions shows that the Zhesi brachiopods fauna evolved from the cold water type to the mixed type mixed type from Kungurian to Wordian.The cause of this change may be the tectonic movement between the Siberian plate and the North China plate or the Late Paleozoic glaciation.