REMARKS ON THE CARBONIFEROUS-PERMIAN LITHOSTRATIGRAPHIC DIVISION IN THE SHENZHA AREA, TIBET, CHINA
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Abstract:
The term formation is the basic lithostratic unit which is divided based on the lithological characters. The Carboniferous Permian strata developed well in the Deriangma Xiala section and the Angjie section in Shenzha, Tibet. All the lithostratic units of the Carboniferous and Permian strata in this area were named after them. However, some of them were not defined based on the lithological characters but on the fossil assemblages in the sections, and do not accord with the principle of the multiple stratigraphical classification. And the lithostratic system of the Carboniferous Permian has been a controversial subject for a long time. The lithostratic systems of the Carboniferous Permian in the area are manily remarked by the author in the present paper, and the Carboniferous Permian boundary is discussed briefly.Keywords:
Section (typography)
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Permian strata are widely spread with complete sequences and obvious contact relations in Nileke region. It is a typical region for researching Permian strata in west of the Tianshan mountains. Based on analyses of remeasured the five type sections and colleetion of the samples,authors obtained results in researching cycle of volcanic eruption, fossils,facies analysis, and making the detailed stratigraphic division, providing reliable evidences for stratigraphic division and correlation of Permian strata in west of the Tianshan mountains.
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Lithostratigraphy
Sequence Stratigraphy
Sequence (biology)
Macrofossil
Stratigraphic unit
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The stratigraphic division in the Kumtag sand-ridge, East Tianshan, has long been in dispute. During 1∶50,000 regional geological and mineral survey, the conodonts Streptognathodus suberectus and Idiognathoides sinuate and the corals Pelalaxis intermedia, Lithostrotionella rarivesicula and Fomichevella kiaeri were found in two sequences of carbonate rocks in the Kumtag sand-rigde area north of the Kanggurtag deep fault, East Tianshan. The two sequences of strata are Late Carboniferous Luosuan-Dalaanian and Dalaanian-Xiaodushanian in age respectively, assigned to the Dikan'er Formation and Qishan Formation in the Karlik stratigraphic area respectively. Two suites of volcanic rocks are separated by the two sequences of sedimentary rocks. They are very easy to recognize and distinguish in the field and correlate at a regional scale because their spatial distributions are relatively fixed and the features of rock associations are distinct. Their ages are Early Carboniferous and Late Carboniferous respectively. The Qi'eshan Group can be further divided in ascending order into the Xiaorequanzi, Dikan'er, Qi'eshan and Qishan formations.
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The intervals from 1822m To 1977m and 1977 m to 2094.5 m have been divided into Nanzha Group of the Early Permian(P1n) and Group of the Late Carboniferous(C2x) in well BC1.As the 7th and 8th national 5-year projects invoicing exploration,by fossil datas we know that it contains Pseudoschwagerina, triticites from 1910m to 2075m in well BC1, but it contains triticites, Fusulinella in the same interval in well BC1. According to rock, logging, seismic stratigraphy and contact relation,and based on comprehensive analysis, we consider that the interval from 1882m to 2094.5 m should be regarded as the lute Carboniferous, it is named: Xiaohaizi group as the statigraphic unit temporarily.
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This study revises the lithostratigraphic units from Ganzhai Section,Pingtang County,Guizhou Province and subdivides the Permian of this section into 6 formations from bottom up according to the results of regionally lithostratigraphic liquidation as:Maping Fm.,Liangshan Fm.,Qixia Fm.,Maokou Fm.,Heshan Fm.and Dalong Fm.Unusually diverse fossil assemblages of Permian from Ganzhai section,and 60 fusulinacean species belonging to 17 genera are found from this section,nine fusulinid zones have been recognized according to the changes of components of the fusulinid.Chronostratigraphic subdivision of this section is discussed by comparing these fossil zones with the contemporary ones from adjacent area and other places in the world,using 8 stages belonging to 3 Series of the Permian.On the international geological time scale it is proved that the Maping Fm.is a diachronous unit which belongs to the Upper Carboniferous—Lower Permian.The Maokou Fm.is also diachronic,and this section is conjectured to lack the strata of the Longlinian Stage according to the output of fusulinid fossils.We also discuss the P/T boundary according to the conodont and ammonite fossils from the top of the section.
Conodont
Section (typography)
Diachronous
Chronostratigraphy
Ammonite
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The confirming and blocking of Carboniferous stratigraphic units is disputed for more. The 1:50000 Regional Geologic and Mineral surveying discovers a suit of shallow marine carbonate rock—clastic rock building,it abundanted early Carboniferous wrists(Gangamophyllum vetiforme、corals(Gigantopra ductus)et al. fossils in the clastic rock which the age is early Carboniferous later DaTang late-DeWu time. The two suit volcanic rock which intervaled by the Akehsake Formation,which distributing are comparatively tranquilization,the characteristic of rock association are evidence,easily identified and distinguished,easily contrasted in the lage area,which just belong to early Carboniferous and late Carboniferous. The contact connection of three formations are angular unconformity,so the Carboniferous more disintegration three Formations rock-stratigraphic unit,thire are Dahalajunshan Formation、Akeshake Formation and Yishijilike Formation form old to new.
Viséan
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The results are here presented of the biostratigraphic and lithological investigations of the uppermost Devonian and Lower Carboniferous from the Chojnice region. They are based chiefly on a detailed analysis of brachiopod and conodont assemblages. The Upper Famennian (Fa2) with deposits equivalent to the Etroeungt beds of France and BeIgium (Tn1a), also the proper Touraisian (sensu Heerlen 1935) have been distinguished. The stratigraphic position of the Devonian/Carboniferous passage beds of Europe are discussed in the light of paleontological studies. Consideration is given to the sediments of this age in Poland. A description is given of the facial-paleogeographic development in the sedimentary basin of the Chojnice region at the Devonian/Carboniferous turn, two sedimentary zones being differentiated there. All the faunal remains here worked out have been figured, but descriptions are given only of forms whose generic or specific assignment is controversial. A survey of all the phenomena noted on the Devonian/Carboniferous passage beds, also the exceptionally great depth of the sediments – the age equivalents in the Chojnice area of the Etroeungt beds (Tn1a) – reasonably suggest that this area is of essential all-European importance for the clearing up of the problems of the Dewonian/Carboniferous passage beds and the boundary between these two systems.
Devonian
Conodont
Late Devonian extinction
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Abstract The Lower Permian and Triassic successions of the offshore East Irish Sea Basin are probably the thickest of the United Kingdom Continental Shelf or UK mainland, but currently, no hierarchical lithostratigraphy exists for this offshore area. A summary is presented of the first comprehensive hierarchical lithostratigraphical nomenclature scheme to be established for the Carboniferous, Permian and Triassic rock successions of the offshore East Irish Sea Basin. This scheme, which has been sponsored by interested exploration companies, identifies 25 formal lithostratigraphical divisions following the methodology already established in BGS-UKOOA (British Geological Survey-United Kingdom Offshore Operators’ Association) revisions of North Sea lithostratigraphy. Sixteen new lithostratigraphical names are introduced (nine in the Mercia Mudstone Group, one in the Sherwood Sandstone Group, three each within the Permian and Carboniferous successions). The lithology, wireline log characteristics and nature of the lower boundary are discussed briefly for each lithostratigraphical unit, together with correlations to the adjacent onshore successions where appropriate. Formal definitions of lithostratigraphic units, including type and reference sections are fully documented elsewhere. The aims of this study are to rationalize the existing terminology and to provide a practical scheme that will have the widest acceptance within the oil industry.
Irish sea
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In Nileke region of Xinjiang, Permian strata are widespread and form complete sequences. The contact relations are obvious and all stratotypes of the five formations are found in the region. It is a classic location for the research of Permian strata in west of the Tianshan mountains. The authors re-measured and systematically sampled the five type sections to study the cycle of volcanic eruption, fossils and facies to make dependable criteria for stratigraphic division and correlation of Permian strata in the west Tianshan mountains.
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