Studies On Later Paleozoic Radiolarian Fauna And Stratigraphy From Nongba Section In Gengma Area, South-Western Yunnan

Since twenty years, with the information accumulation, geologists had already cognizant that the transformation of the Asia-Australia-Pacific Ocean area during entire virtually is a process of disorganization of Gawana landmass and hyperplasia of Asia continent. The most complex and important terra segment in the area is the location which links up the eastern part of Tethyan and Pacific Ocean. The Changning-Menglian belt, located the drape belt of three river in structure territory of Tethyan-Himalayan, is the one of most pivotal areas which is redounded to research and resolve the problem.The study of Gengma area have been get more and more attention and recognition for near yeard, because Nongba area is located in the weatern part of the Changning-Menglian belt. The author choose the area as study object as the result of the requirement of regional geological surveying and the aim at the disputed hotspot problem recently.The stratum, deposited in Nongba which in eastern part of Gengma area and composed by sandstone, mudstone and silicate and tuff interlayers, was named by former man as Nanpihe Formation and Papai Formation, and their age were Later Permian and Early Triassic respectively. Since the long time, different scholars had different viewpoints on stratigraphic succession^ sedimentary environment and especially chronology evidences of the stratum, that effected infinitely the reconstruction of the tectonic evolutions and paleolithofacies palaeogeography pattern.The author studied meticulously the Nongba sections, abundant data was achieved. Besides the basic sreatigraphy study, on the aspects of paleontolgoy, organic geochemistry and thrust slice type stratigraphy, et al., our research work was carried out effectively and fruitfully. This will give exact chronology and sedimentary evidence to the research of the biostratigraphy and thrust slice type stratigraphy of the Nongba area; will provide more full and accurate geological gist for the tectonic evolutions of paleotethyan located in southern part of "three rivers"; and will provide new reference to the paleolithofacies palaeogeography pattern reconstruction of the Changning- Menglian oceanic basin.The author ultimately achieves the following goals:1. Studied the Nongba section, and correlated many sedimentary information and pteridophyta, graptolite, conodont and radiolaria etc. palaeontology fossils. Study on palaeontology paleontology fossils of Nongba section is carried out. The pteridophyta fauna includes 3 genara and 6 species (including 5 unnamed species ), the graptolite fauna includes 3 genara and 4 species, the conodont fauna includes 10 genara and 17 species and the radiolarian fauna includes 12 genara and 28 species. According to the fossils, we found one graptolite zone: Mongraptus yukonensis-Neomongraptus himalayensis zone; two radiolariancombinations: Entactinia-Entactinosphaera, Entqctinia itsukaichiensis combination, and three radiolarian zones: Albaillella paradoxa zone, Albaillella indensis zone and Albaillella cartalla zone.2. The new cognition about the sedimentary environment of the original Nanpihe Formation.The two early Carboniferous fragments are composed of Basalt and ash-black, fuchsia radiolaria silicalite, siliceous mudstone, tuff. The geochemical study on silicalite illustrate that the content of SiO2 is more than 80 per cent, the average value of MnO/TiO2 is 0.58, the average value of Al/ (Al+Fe+Mn) is 0.48, the average value of radio Ce/Ce* is 0.91. Contrasted to the geochemical characteristic of silicalite which has known geotectonic setting, the result indicates the studied silicalites formed in the margin of the oceanic basin near the continental margin.The geochemistry characteristic of fuchsia radiolarian silicalite indicates that they deposited in the of edge of oceanic basin near the continental margin, not the typical caontinental margin environment. Obviously, these samples effected by continental substances in different degree.The study of sedimentary basis and sedimental geoc...