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1.
The Yehlangian of Ting and Graban includes the Paoan shale,the Yülungshanlimestone,the Feihsienkuan shale and the Sanchiao limestone.In their opinion theseformations would represent the Upper Permian of south-western China.The presentpaper tries to show that both by their stratigraphical relation and their faunal contentsthe Yülungshan limestone and the Feihsienkuan shale belong undoubtedly to the LowerTriassic and that the Sanchiao limestone is much younger,probably of Upper Triassicage.The Paoan shale...  相似文献   

2.
With abundant deep-water upper Permian sediments,Guizhou is an ideal place for the re-search of radiolarian biostratigraphy of Upper Permian.The sections of Sidazhai and Lekang in southern Guizhou Province are studied.Lithology and biostratigraphy of the siliceous rock sequence of uppermost Permian in the two sections are introduced.Radiolarian assemblage zones,Neoalbaillella optima assem-blage zone and Klaengspongus spinosus assemblage zone in ascending order are established for the top-most Permian of southern Guizhou.The Klaengspongus spinosus zone has been the topmost radiolarian assemblage zone of Permian,which is also correlated with former ones in a considerable depth.  相似文献   

3.
In western Henan, Late Palaeozoic coal measures are completely developed and well exposed. A great deal of research work on biostratigraphy was done by predecessors. After systematic palaeomagnetic studies, we have confirmed the existence of the Permian Kiaman reversed polarity epoch in the study region. Its palaeolatitude varied from 11.2° N(P,) to 15.6°N(P2). This provides important evidence for the view that this region was situated in a low latitude climatic zone in this period and gradually moved northwards from the tropic rain forest climate area to the tropic arid-humid seasonal climate area during this stage.  相似文献   

4.
The Menghai batholith (Yunnan Province, China) is the southern extension of the ~370 km long Lincang granite body that syntectonically intruded the collisional zone between Gondwana (Baoshan block) and Laurasia (Simao block) terranes during closure of the Palaeo-Tethyan Ocean. Eight Menghai granodiorites were analysed across an ~45 km E–W transect from the pluton’s central region to eastern perimeter. Each rock was imaged in cathodoluminescence and geochemically analysed for major and trace elements. A minimum 30 zircons per sample were dated using laser ablation inductively coupled plasma–mass spectrometry. Samples are peraluminous to strongly peraluminous, magnesian, calcic or calc-alkalic granodiorites. Trace element suggest a high pressure (12–15 kbar) low clay source with >20–30% volume interaction with basalt. Crustal anatexis was likely related to post-collisional lithosphere delamination and upwelling of hot asthenosphere, forming large-volume melts. Zircon ages (207Pb–206Pb and 238U–206Pb) range from 3234 ± 42 to 171.7 ± 5.4 Ma (±2σ). Inherited zircon ages include the Palaeoarchaean–Neoarchaean (average 2938 ± 27 Ma, n = 8 ages), Lüliang (2254 ± 38 Ma, n = 7), Changcheng–Jixianian (1274 ± 47 Ma, n = 33), Qinbaikou (963 ± 29 Ma, n = 7), Nanhua (787 ± 24 Ma, n = 7), Sinian (595.4 ± 12.2 Ma, n = 14), Qilian (452.2 ± 8.7 Ma, n = 24) and Tienshan (358.9 ± 12.4 Ma, n = 5). The presence of these ages decrease from the batholith’s central portion (>50% ages) to eastern perimeter (2–16% ages), as the rocks appear progressively metamorphosed. The distribution of U/Th ratio suggests inherited zircons are Carboniferous (317.6 ± 5.7 Ma) and older and crystallization ages span the Permian to Early Jurassic. The average and youngest zircon age per sample decreases from the centre of the batholith to its eastern perimeter, from 226.8 ± 8.8 and 210.7 ± 3.3 to 211.8 ± 5.7 and 171.0 ± 5.4 Ma, respectively. If recorded by syntectonic zircon crystallization, collision and closure of a branch of the Palaeo-Tethyan Ocean occurred here over an ~100 million years time period from the Permian (281.0 ± 13.0 Ma) to Jurassic (171.5 ± 5.4 Ma).  相似文献   

5.
《Gondwana Research》2001,4(3):421-426
The Rio Bonito Formation in southern Paraná basin contains a set of tonsteins interbedded with coal-seams. These tonsteins are composed mainly of kaolinite with zircon, apatite and beta-quartz paramorphs as accessory minerals, and were interpreted as volcanic ashes deposited by ash falls over pits protected by barrier islands in a barrier-lagoon system. A U-Pb dating of zircons in the tonstein A, which furnished an age of 267.1 ± 3.4 Ma (Early Permian) confirming previous age-dates based on palynology and correlating them with one of the main periods of volcanic activity in the Gondwana.The source of the pyroclastic material was attributed to the early Permian Choiyoi magmatic arc in Argentina, developed during the Sanrafaelic orogeny, and with a main peak of volcanic activity between 260 and 272 Ma.  相似文献   

6.
INTRODUCTIONPethenreefsarewidelydistributedinSouthetna,espeCiallyinsouthernGulzhouandnorth~ternGUanghProvince,wherenamusreefsoccurandareWellexposed.TheUpperPenmanreefinZiyUnChamy,southernG~uisoneofthehotdevelopedandexposedhairierreefsinthearea(WangandFan,1994).DuetoitSspedaltectonic--geographicpositionandcompletefactesbeltd~iation,thebatherreefshavearousedagreatinterestamonggeologistS.SpstelnaticinvestigationandstudyonthebarrierreefshaveaammadebymanygeologistSsince197ds(LiuandGao,…  相似文献   

7.
Meishan Section D in Changxing County, Zhejiang Province, China has been selected as the global stratotype of the Permian-Triassic boundary and various studies hav been done at the boundary but the gas chromatographic-mass spectrographic analysis of alkane biomarkers has not been investigated. This paper presents of results of a study of the biomarkers analyzed in a series of samples across the permian-Triassic boundary at both Meishan Section A and Section D. The results show that the overall concentration of alkane biomarkers in the Permian-Triassic boundary strata is high in Bed 26 while it is low in Bed 27. A variety of biomarker parameters demonstrate that the main sources of organic matter in the sediment are algae and bacteria and that the depositional enviroment varied from weakly oxidizing to reducing during the studied interval.  相似文献   

8.
Nitrogen isotopic compositions of upper Permian to lowermost Triassic rocks were analyzed at Chaotian in northern Sichuan, South China, in order to clarify changes in the oceanic nitrogen cycle around the Permian–Triassic boundary (P–TB) including the entire Changhsingian (Late Late Permian) prior to the extinction. The analyzed ca. 40 m thick interval across the P–TB at Chaotian consists of three stratigraphic units: the upper Wujiaping Formation, the Dalong Formation, and the lowermost Feixianguan Formation, in ascending order. The upper Wujiaping Formation, ca. 10 m thick, is mainly composed of dark gray limestone with diverse shallow-marine fossils such as calcareous algae and brachiopods, deposited on the shallow shelf. In contrast, the overlying Dalong Formation, ca. 25 m thick, is mainly composed of thinly bedded black mudstone and siliceous mudstone containing abundant radiolarians, deposited on the relatively deep slope/basin. Absence of bioturbation, substantially high total organic carbon contents (up to 15%), and abundant occurrence of pyrite framboids in the main part of the Dalong Formation indicate deposition under anoxic condition. The lowermost Feixianguan Formation, ca. 5 m thick, is composed of thinly bedded gray marl and micritic limestone with minor fossils such as ammonoids and conodonts, deposited on the relatively shallow slope. δ15NTN values are in positive values around +1 to +2‰ in the upper Wujiaping Formation implying denitrification and/or anammox in the ocean. δ15NTN values gradually decrease to −1‰ in the lower Dalong Formation and are consistently low (around 0‰) in the middle Dalong to lowermost Feixianguan Formation. No clear δ15NTN shift is recognized across the extinction horizon. The consistently low δ15NTN values suggest the enhanced nitrogen fixation in the ocean during the Changhsingian at Chaotian. Composite profiles based on previous and the present studies demonstrate the substantial δ15N variation on a global scale in the late Permian to earliest Triassic; a systematic δ15N difference by low and high latitudes is particularly clarified. Although the enhanced nitrogen fixation throughout the Changhsingian at Chaotian was likely a regional event in northwestern South China, the composite δ15N profiles imply that the sea area in which fixed nitrogen is depleted has gradually developed worldwide in the Changhsingian, possibly acting as a prolonged stress to shallow-marine biota.  相似文献   

9.
Late Paleozoic or Permo-Carboniferous Gondwana successions world-wide are marked by widespread and lengthy glaciation (~ 67 Ma), and multiple transitions from Icehouse to Greenhouse state. Mineralogical and compositional changes in sandstones and mudstones of the Gondwana succession in drill hole GDH-45 from the Khalaspir basin of Bangladesh are interpreted in a climatic framework, using the proxies of the Mineralogical Index of Alteration (MIA) and the Chemical Index of Alteration (CIA). Low MIA (< 75) and CIA (< 70) values in the lowermost unit (Unit 1) of the Khalaspir Gondwana sequence indicates minimal chemical weathering of the source and imply cold and dry glacial climatic conditions. Values increase progressively in the overlying Unit 2, suggesting warming and deglaciation. Very high MIA (80–100) and CIA (90–100) values in Unit 3 indicate intense chemical weathering associated with warm and humid climatic conditions in a post-glacial setting. These changes are recorded in both sandstones and mudstones, illustrating the value of acquiring data for a variety of size grades. The stratigraphic changes are also well recorded by progressively decreasing K2O/Al2O3 and increasing Ga/Rb ratios, the combination of which may comprise a new geochemical proxy of climate and weathering. Upward increase in the modal Q / (F + L) and Qp / (F + L) ratios are also consistent with change from cool to warm and humid climate in the source region. The change in climatic conditions within the Khalaspir sequence is also well correlated with the Gondwana successions of other continental blocks, and records the climatic fluctuations and extent of climatic impact in Gondwanaland during the Permo-Carboniferous.  相似文献   

10.
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11.
正Late Paleozoic igneous rocks are extensively developed in Qiangtang terrene,including west Qiangtang(WQT),east Qiangtang(EQT)and the central Qiangtang(CQT)metamorphic belt.The igneous rocks distributed in WQT  相似文献   

12.
The Permian foraminifer Shanita is a genus of special paleobiogeographic importance. Current data indicate that this genus occurs in peninsular Thailand, Shan States of Burma, western Yunnan and northwestern Tibet of China, south Pamir of Tajikistan, South Afghanistan, Kuh-e Gahkum area of lran, Transcaucasus, Pinarbasi area of Turkey, and the Saiq Plateau of Oman. Studies also show that several species of Hemigordius usually coexist with Shanita, and form a peculiar Shanita-Hemigordius fauna. Localities of the Shanita-Hemigordius fauna that have been found hitherto are confined on Gondwanaderived blocks, which constitute a strip starting from peninsular Thailand and extending northwestwards and westwards to Turkey. This fauna is considered as another Permian palaeontological marker of marginal Gondwana environment.  相似文献   

13.
The late Carboniferous to Triassic tectonic history of eastern Australia includes important periods of regional-scale crustal extension and contraction. Evidence for these periods of tectonism is recorded by the extensive Pennsylvanian (late Carboniferous) to Triassic basin system of eastern Australia. In this study, we investigate the use of U–Pb dating of detrital zircons in reconstructing the tectonic development of one of these basins, the eastern Galilee Basin of Queensland. U–Pb detrital zircon ages were obtained from samples of stratigraphically well-constrained Cisuralian and Lopingian (early and late Permian, respectively) sandstone in the Galilee Basin. Detrital zircons in these sandstones are dominated by a population with ages in the range of 300–250 Ma, and ages from the youngest detrital zircons closely approximate depositional ages. We attribute these two fundamental findings to (1) appreciable derivation of detrital zircons in the Galilee Basin from the New England Orogen of easternmost Australia and (2) syndepositional magmatism. Furthermore, Cisuralian sandstone of the Galilee Basin contains significantly more >300 Ma detrital zircons than Lopingian sandstone. The transition in detrital zircon population, which is bracketed between 296 and 252 Ma based on previous high-precision U–Pb zircon ages from Permian ash beds in the Galilee Basin, corresponds with the Hunter–Bowen Orogeny and reflects a change in the Galilee Basin from an earlier extensional setting to a later foreland basin environment. During the Lopingian foreland basin phase, the individual depocentres of the Galilee and Bowen basins were linked to form a single and enormous foreland basin that covered >300 000 km2 in central and eastern Queensland.  相似文献   

14.
This study recovered the Guadalupian conodont faunas from Shangsi (上寺) Section in Northeast Sichuan (四川). Four genera and nine species were identified, and three conodont zones were recognized and established; they include Jinogondolella nankingensis Zone, J. aserrata Zone, and J. postserrata Zone. The Roadian and Wordian boundary is set in the interval 5 m from the top of Bed 86 by the first appearance of the conodont J. aserrata. The Wordian and Capitanian boundary is set in the interval 2.3 m from the top of the Bed 95 by the first appearance of J. postserrata. Most of the specimens demonstrated low color alteration index (CAI) as 1.5-3, indicating that most part of the Maokou (茅口) Formation may have the suitable thermal conditions for the formation of oil source rocks.  相似文献   

15.
The Zhejue Section is an excellent terrestrial permian-Triassic boundary (TPTB) section not only for its convenient accessibility and good outcrop, but also for its abundant fossils. In addition, there are two claystone beds that were formed by events across the Permian-Triassic boundary (PTB) at this section. The claystones provide a bridge for high-resolution correlation between marine and terrestrial PTBs. Another advantage is that the PTB at the Zhejue Section can be correlated with that of littoral and neritic facies by tracing estwards. Synthesized stratigraphic studies, including biostratigraphy, eventostratigraphy )susceptibilities and carbon isotopes across the TPTB, and microspherules found in the boundary claystones) and sequence stratigraphy, are carried out at this section.  相似文献   

16.
In an attempt to elucidate their ages, the often incomplete and poorly known early Permian marine faunas and sequences of India, Tibet, Pakistan, Afghanistan, Iran and Oman are compared with those of the Perth, Carnarvon and Canning Basins of Western Australia, where faunas are documented and in sequence, and stratigraphic relationships between units are clear. This comparison indicates that the faunas discussed are Latest Asselian or younger in age, and that most of the underlying glacial beds are probably Early Permian (Asselian) in age. By implication, the Permo‐Carboniferous boundary for Gondwana is considered to lie at or near the base of Unit II/Stage 2 and equivalent palynomorph zones throughout Gondwana.  相似文献   

17.
The Late Permian–early Middle Triassic strata of the northern West Qinling area, northeastern Tibetan Plateau, are composed of sediment gravity flow deposits. Detailed sedimentary facies analysis indicates these strata were deposited in three successive deep-marine environments. The Late Permian–early Early Triassic strata of the Maomaolong Formation and the lowest part of the Longwuhe Formation define a NW–SE trending proximal slope environment. Facies of the Early Triassic strata composing the middle and upper Longwuhe Formation are consistent with deposition in a base-of-slope apron environment, whereas facies of the Middle Triassic Anisian age Gulangdi Formation are more closely associated with a base-of-slope fan depositional environment. The lithofacies and the spatial–temporal changes in paleocurrent data from these strata suggest the opening of a continental margin back-arc basin system during Late Permian to early Middle Triassic time in the northern West Qinling. U–Pb zircon ages for geochemically varied igneous rocks with diabasic through granitic compositions intruded into these deep-marine strata range from 250 to 234 Ma. These observations are consistent with extensional back-arc basin development and rifting between the Permian–Triassic Eastern Kunlun arc and North China block during the continent–continent collision and underthrusting of the South China block northward beneath the Qinling terrane of the North China block. Deep-marine sedimentation ended in the northern West Qinling by the Middle Triassic Ladinian age, but started in the southern West Qinling and Songpan-Ganzi to the south. We attribute these observations to southward directed rollback of Paleo-Tethys oceanic lithosphere, continued attenuation of the West Qinling on the upper plate, local post-rift isostatic compensation in the northern West Qinling area, and continued opening of a back-arc basin in the southern West Qinling and Songpan-Ganzi. Rollback and back-arc basin development during Late Permian to early Middle Triassic time in the West Qinling area explains: the truncated map pattern of the Eastern Kunlun arc, the age difference of deep-marine sediment gravity flow deposits between the Late Permian–early Middle Triassic northern West Qinling and the late Middle Triassic–Late Triassic southern West Qinling and Songpan-Ganzi, and the discontinuous trace of ophiolitic rocks associated with the Anyemaqen-Kunlun suture.  相似文献   

18.
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19.
The marine primary producers assimilate the atmospheric CO2 to form the organic carbon in surface water. The organic carbon then settles down through the water column and is removed from the oceans by final preservation in sediments in the form of petroleum or nature gases. The reconstruction of paleoproductlvity will thus improve our understanding of the biological processes in the formation of fossil energy resource and help to locate new sites for future exploration. In this study, biorelated elements P, Cd, Al, Ba, as well as redox sensitive element Mo, were analyzed in the 448 rock samples collected from Permian strata at the Shangsi (上寺) Section, Guangyuan (广元), Northeast Sichuan (四川) in China. On the basis of the Ti content, the nondetrital contents of P, Ca, and Al, denoted as Pxs, Cdxs, and Alxs, were calculated and found to coincide with the TOC content throughout the whole section, with some enrichment intervals being found in the middle part of Chihsia Formation, topmost Maokou (茅口) Formation, and Dalong (大隆) Formation. This suggests that the biorelated elements could be used as proxies for the paleoproductivity here in this section. Baxs, a paleoproductivity indicator widely used in the paleoceanography, shows insignificant correlation with TOC, Pxs, Cdxs, and Alxs, probably arising from the loss of biological barium in anoxic conditions. Compiled with the data of TOC content and Pxs Cdxs, and Alxs, three episodes of enhanced paleoproductivity were identified in Permian strata including the middle part of Chihsla Formation, topmost Maokou Formation, and Dalong Formation.  相似文献   

20.
1IntroductionThe formation of the Junggar,Turpan and Ili ba-sins is ascribed to Hercynian orogeny between theJunggar and Tianshan Mountains during the MiddlePermian.The rock assemblage of thick and stable sedi-mentary dark muddy shales interbedded with th…  相似文献   

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