Carboniferous Brachiopod Biostratigraphy In North Of Qilian

Based on the actually surveying over three profiles of Carboniferous System inHexi corridor and the identification of brachiopod fossils there,this thesis establishedfive brachiopod fossils assemblages in that area.This research still did some contrastwith the Brachiopod assembleges in other areas in or out of China at the same age.The main achievements and knowledge in this thesis are as follows:1.This thesis identified more than one thousand brachiopod fossils, which belongto55genus139species,described the40characteristic species systematicly,andproducted12fossils charts.This research inriched the Carboniferous brachiopodfossils’ content in the area significantly.2.According to the characteristics,diversity, abundance of the brachiopoda fossilsand combined with the phases of evolution as well as the development of thebrachiopods,this research established five assembleges.The assemblage, from bottomto top,are list as follows.⑤Choristites pavlovi-Antiquatonia taiyuanfuensis assemblage④Choristites yanghukouensis-Plicatifera minor assemblage③Gigantoproductus edelburgensis-Striatifera striata assemblage②Kansuella kansuensis-Gigantoproductus geniculatus assemblage①Megachonetes papilionacea-Pugilis subeiensis assemblage3.According to characteristic fossils in each assemblage as well as their evolution,drawing on other kinds of fossils, and still using the analysis of typical molecules andthe community combination faces, this thesis did some contrast with the brachiopodassembleges of other areas in China at the same age and ascertained the geologic agesof the assembleges.It can reach the conclusion that the five assembleges,from bottomto top,belong to early Visean, late Visean, Serpukhovian,Bashkirian, Moscovian-Gzelian.4.Based on the discussion about the ages of each brachiopod assemblage,combining with the conodonts data,this thesis studied on the main biostratigraphicboundaries.Through the contrast with the chronostratigraphic, it can be acknowledged that the diachronism of Chouniugou Formation,from Tianzhu Qilian Mshigouprofile to Sunan Qinglong Daqinggou profile is from early Visean to Serpukhovian;the diachronism of Jingyuan Formation is early Bashkirian; the diachronism ofYanghugou Formation is Bashkirian;and that of Taiyuan Formation isMoscovian-Gzelian.