鄂尔多斯盆地石炭纪(竹蜓)类研究新进展及其古地理面貌初探

A NEW ADVANCE OF CARBONIFEROUS FUSULINID STUDY AND PRELIMINARY EXPLORATION OF THE PALEOGEOGRAPHY IN THE ORDOS BASIN

文章对鄂尔多斯盆地地面和井下6条含?石炭纪地层剖面中的?类动物群作了详细的研究,自上而下建立了5个?带5个?亚带:(5)Sphaeroschwagerina带(可细分为3个亚带,即下部的Pseudofusulina fecunda-Rugosofusulina valida亚带,中部的 Schwagerina sulnathorsti亚带,和上部的Sphaeroschwagerina Sphaerica-Boultonia gracilis亚带);(4)Triticites带;(3)Fusulina-Fusulinella带(包括2个亚带,下部的Beedeina teilhardi亚带和上部的Fusulina cylindrica-F.quasicylindrica亚带);(2)Profusulinellaparva带;(1)Eostaffella paraparva带。根据这些?类资料,对鄂尔多斯盆地石炭系合?地层及其划分、对比和古地理面貌都作了探讨。

Carboniferous rocks of western and eastern Ordos Basin, well exposed and continual instratigraphic succession, are composed of a suite of coal series typical of alternating marine andcontinental facies. With the exception of a few fusulinids reported from the late Late Carboniferous ofa few localities, the Carboniferous fusulinids over rather large areas have not yet been found andstudied in the basin. During the past three years, many collections of fusulinids have been obtainedfrom the western and eastern parts of the basin, comprising 122 species and varieties belonging to 18genera. Based on the characters of the fusulinid fauna, 5 fusulinid aasemblage zones with 5 subzonesare established in descending order as follows: 5. Sphaeroschwagerina Zone (5)Sphaeroschwagerina sphaerica--Boultonia gracilis Subzone (4)Schwagerina subnathorsti Subzone (3)Pseudofusulina fecunda--Rugosofusulina valida Subzone 4. Triticites Zone 3. Fusulinella--Fusulina Zone (2)Fusulina cylindrica--F. quasicylindrica Subzone (1)Beedeina teilhardi Subzone 2. Profusulinella parva Zone 1. Eostaffella paraparva Zone 1. Eostaffella paraparva Zone The first appearance and the end of the zonal species are regarded as the lower and upper limits ofthis zone. This zone is only distributed in the Zhongwei Formation of the Guoyuchu section in the western basin and is characterized by having a greater number of species and individuals of Eostaffellawhich has a smaller, discoid shell and a form ratio of less than one. 2. Profusulinella parva Zone The first appearance and extinction of the zonal species ate considered as the range of this zone,while the first appearance of Fusulinella is regarded as the end of this zone. The fusulinids of this zoneare dominated by Profusulinella and Ozawainella which are more in the number of species andcharacterized by the 3--layered spirotheca, the plane of weakly folded septa in the poles and the robustchomata. Only a few elements of the genera Millerella and Eosluffella are present in this zone. 3. Fusulinella--Fusulina zone The first appearance of Fusulinella and the extinction of Fusulina mark the beginning and the endof this zone. The fusulinid fauna of this zone shows an even greater diversity of 9 genera and 28species and is composed of two different types. The fusulinid fauna from the Hulstai section of thewestern basin is characterized by having more primitive species of Fusulinella, Beedeina andPseudostaffella with lighter septal folds, robust chomata and a few individuals, and by having morespecies of Profusulinella surviving from the lower zone. These are characters of the more primitivefusulinid assemblage which is named the Beedeina teilhardi Subzone. The fusulinid fauna from two localities of western Shanxi in the eastern basin belongs to the mostadvanced forms of Fusulina which is characterized by having a thinner spirotheca, more extensive septalflutings and primitive alveolar structure on the outer volutions in some more developed species. In thisfauna also occur Protriticites and Neostaffella, whereas Profusulinella and Ozawainella surviving from thelower zone are markedly few in number of species. This fauna is called the Fusulina cylindrica--F.quasicylindrica Subzone. 4. Triticites Zone The fusulinids of this zone are only distributed in the basal limestone of the Taiyuan Formationnear the city of Liulin County in the eastern basin. This fusulinid fauna is monotonous and containsonly one genus,Triticites, which is characterized by having a smaller fusiform shell, simple folded septaand robust chomata. No schwagerinids and pseudoschwagerinids have been found in this zone. 5. Sphaeroschwagerina Zone Based on the fusulinid characters,this zone may be divided into 3 fusulinid subzones as follows: (1)Pseudofusulina fecunda--Rugosofusulina valida Subzone This subzone corresponds to the Mugou limestone of the Taiyuan Formation in the typical section.The fusulinid fauna of this subzone is composed of 5 genera and 46 species, among which Schwagerinacontains 22 species,while Pseudofusulina, Rugosofusulina and Quasifu