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1.
Foraminiferal and conodont faunas at the Devonian–Carboniferous (D–C) boundary in the southern part of the Moravian Karst (Czech Republic) were studied in different facies of the basin slope. The joint presence of foraminifers and conodonts in calciturbidites along with a positive δ13C excursion of the Hangenberg anoxic event enabled the high‐resolution calibration of the late Famennian–early Tournaisian interval (Upper expansa–crenulata conodont zones). The conodont stratigraphic and biofacies succession reveals a strong correlation with other European areas. The Siphonodella sulcata morphotype (close to Group 1 sensu Kaiser and Corradini and “nov. gen. nov. sp. 1” sensu Tragelehn) enters prior to the Hangenberg Event, which resembles Upper and Uppermost Famennian conodont successions from Franconia, Bavaria and Morocco. The diversification of the early siphonodellids takes place after the Hangenberg Event and after the protognathodid radiation. In terms of foraminiferal biostratigraphy, the D–C boundary interval is characterized by the first appearance datum (FAD) of Tournayellina pseudobeata close below the D–C boundary followed by a sequence of Tournaisian bioevents, where apart from the last appearance datums (LADs) of quasiendothyrs, the FADs of the Neoseptaglomospiranella species and chernyshinellids play an important role in a similar manner as in Eastern Europe. The correlation of these bioevents elsewhere is often hindered by glacioeustatically‐driven unconformities and widespread occurrences of unfavourable facies for plurilocular foraminifers (Malevka beds and Bisphaera beds). Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
9172 Conodonts have been recovered from the uppermost Hunghuayuan Formation and the Zitai Formation at two sections in Shitai County, southern Anhui Province, South China, which was situated close to the margin of the Lower Yangtze Platform during the Early to Middle Ordovician. Systematic and multivariate statistical studies on these conodonts permit recognition of seven conodont biofacies: Tropodus biofacies, Diaphorodus biofacies, Oepikodus biofacies, Baltoniodus biofacies, Paroistodus biofacies, Periodon biofacies and Protopanderodus biofacies. Each biofacies is restricted to a particular lithofacies and stratal position and shows a consistent order and/or position within the succession. Turnover of these conodont biofacies is related to sea-level changes. The transgressive–regressive patterns demonstrated by the conodont biofacies compare closely to published sea level curves for South China, and highlight the utility of conodont biofacies as a means of confirming sedimentological evidence of relative sea-level change.  相似文献   

3.
云南保山地区的下石炭统   总被引：4，自引：1，他引：4  
王向东  朱夔玉 《地层学杂志》1993,17(4):241-255,T002
<正> 云南保山地区下石炭统及其生物群曾引起许多学者的兴趣(Reed l927;王鸿桢,1945;段丽兰,1973,1985;宋学良,1982;金玉玕、方润森,1983;杨宗仁,1983;陈重泰,1984;陈根保,1984;金苏华,1992),其主要原因在于丰富而特殊的生物类群,悬而未决的地层问题以及独特的生物地理位置。本文以4条剖面(图1)为基础,依据多门类的生物化石对诸如本区杜内/维宪阶界线、Siphonophyllia-Keyserlingophyllum(Humboldtia)动物群的时代、冷水(凉水)珊瑚动物群、岩石地层单位等问题进行讨论。  相似文献   

4.
Abstract On the basis of existing conodont data, the authors have studied the Late Permian-Early Triassic cohodonts of different farms and biofacies in detail Five conodont biofacies are recognised, from shallow to deep water: 1. Hindeodus conodont biofacies 2. Pachycladina-Parachi rognathus conodont biofacies, 3. Gondolella-Hindeodus Conodont biofacies, 4. Gondolella - Neospathodus conodont biofacies, and 5. Xaniognathus cohodont biofacies. Considering the temporal and spatial changes of these conodont biofacies, 3 conodont bioprovinces have been divided. In light of the biofacies changes of each bioprovince, the authors also discuss, in this paper, the regularity of transgression-regression cycles of eastern Tethys and their possible relation to the mass biotic alternation.  相似文献   

5.
一、绪言保山地区是滇西泥盆系和下石炭统出露的主要地区之一,以前已有不少报道。近年来,由于该地区特殊的大地构造位置,引起了国内外广大地质工作者的密切注意,因而对泥盆石炭纪地层及其古生物的研究也更加深入。保山地区的上泥盆统目前暂分为何元寨组和整合其上的大寨门组,前者底部尚属中泥盆统(龚大明等,待刊)。下石炭统下部称鱼洞组。何元寨组在其命名剖面施甸何元寨主要是一套中层灰岩和泥灰岩,厚约220m,腕足、珊瑚、层孔及苔藓动物丰富,向东北至大寨门、由  相似文献   

6.
Devonian sediments of the Malaguide Complex potentially could include the Frasnian–Famennian boundary, one of the five greatest Phanerozoic biotic crises. Conodont biofacies and microfacies of carbonate clasts from a pebbly mudstone underlying Tournaisian radiolarites allows identification, for the first time in the Malaguide Complex, of Devonian shallow marine environments laterally grading to deeper realms. The clasts yielded Frasnian conodont associations of the falsiovalis to rhenana biozones, with six biofacies that reveal different environmental conditions in their source areas. Source sediments were dismantled and redeposited within the pebbly mudstone, whose origin is tentatively related to one of the events that are associated worldwide with the Frasnian–Famennian crisis. The latter is recorded, in two equivalent Malaguide pelagic successions, by stratigraphic discontinuities, and it was, probably, tectonically and/or eustatically controlled, as in other Alpine‐Mediterranean Paleotethyan margins.  相似文献   

7.
保山西邑铅锌矿区香山组一段灰岩牙形石丰富,包括5属7种1个相似种及2个未定种,分别为:Ancyrodella curvata,A.nodosa,A.spp.,Ancyrognathus triangularis,Icriodus alternatus alternatus,I.sp.,Palmatolepis hassi,Pa.simpla,Polygnathus webbi,Po.cf.tenellus和Po.sp.。该牙形石组合面貌可与上泥盆统Late Palmatolepis rhenana带对比,表明研究区内香山组一段的时代为晚泥盆世弗拉斯期晚期,并非早石炭世。  相似文献   

8.
Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected: Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus inornatus-Monocostodus sevierensis-Semiacontiodus lavadamensis zones, in ascending order. More confident biozones are recognized in the Sesong Slate and lower Hwajeol Formation in the Makgol section, a part of the southern limb of the Baekunsan syncline, Taebaeksan Basin, Korea, especially focusing on the conodont biostratigraphic boundary of two units, and the subdivision potential of the previous "Proconodontus Zone", lowermost biozone of the Hwajeol Formation. Similarly, only a few conodont elements recovered from upper 14.5 m interval, namely the Furongian portion of the Sesong Slate, in the Makgol section did not allow erection of a biozone. Nevertheless, this part of the unit plus the basal 2.5 m interval of the Hwajeol Formation is characterized by the occurrence of Prooneotodus rotundatus(Druce and Jones), Teridontus nakamurai(Nogami), Phakelodus elongatus(An) and Phakelodus tenuis Müller. This interval marks the early Furongian "Prooneotodus rotundatus Zone". The rest of the measured section yielded relatively abundant conodonts, so three conodont biozones are proposed, based on the successive appearance of key species: Proconodontus tenuiserratus, Proconodontus posterocostatus, and Proconodontus muelleri zones, in ascending order, and thus allowing subdivision of the previous "Proconodontus Zone". The four conodont biozones are correlated with the relevant biozones of North and South China, and North America.  相似文献   

9.
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   

10.
广西六景泥盆系剖面是中国泥盆系标准剖面之一,通过对其弗拉斯阶-法门阶(F-F)界线附近地层进行详细的牙形石生物地层研究,自下而上识别出3个牙形石带:晚rhenana带、linguiformis带和triangularis带。F-F界线位于融县组下部(第7号层与第8号层之间),在谷闭组顶界之上3.32,m处。碳同位素的分析结果表明,F-F之交δ13C具有显著正偏移,增幅为2.0‰,与湖南老江冲、广西垌村和杨堤以及欧洲、美洲、非洲和澳洲等地的F-F界线附近的碳同位素记录一致,且具有相近的变化幅度。δ13C正异常与F-F界线上的生物灭绝有关,由于食微生物的高等生物灭绝,微生物大量繁盛,诱导海水缺氧,导致海洋有机碳埋藏速率增加,从而形成δ13C的正偏。F-F界线层发育一套以碎屑灰岩为特色的事件沉积,该事件沉积在广西乃至全球具有等时性,可能与小行星碰撞地球引起的全球性海啸有关。  相似文献   

11.
Secular variations in stable carbon‐isotope values of marine carbonates are used widely to correlate successions that lack high‐resolution index fossils. Various environmental processes, however, commonly may affect and alter the primary marine carbon‐isotope signal in shallow epicratonic basins. This study focuses on the marine carbon‐isotope record from the carbonate–evaporite succession of the upper Katian (Upper Ordovician) Red River Formation of the shallow epicratonic Williston Basin, USA. It documents the carbon‐isotope signal between the two major Ordovician positive shifts in δ13C, the early Katian Guttenberg and the Hirnantian excursions. Eight δ13C stages are identified based on positive excursions, shifts from positive to negative values and relatively uniform δ13Ccarb values. A correlation between carbon‐isotope trends and the relative sea‐level changes based on gross facies stacking patterns shows no clear relation. Based on the available biostratigraphy and δ13C trends, the studied Williston Basin curves are tied to the isotope curves from the North American Midcontinent, Québec (Anticosti Island) and Estonia, which confirm the Late Katian age (Aphelognathus divergens Conodont Zone) of the upper Red River Formation. The differences in the δ13C overall trend and absolute values, coupled with the petrographic and cathodoluminescence evidence, suggest that the carbon‐isotope record has been affected by the syndepositional environmental processes in the shallow and periodically isolated Williston Basin, and stabilized by later burial diagenesis under reducing conditions and the presence of isotopically more negative fluids.  相似文献   

12.
On the basis of existing conodont data, the authors have studied the Late Permian-Early Triassic conodonts of different forms and biofacies in detail. Five conodont biofacies are recognized, from shallow to deep waters 1. Hindeodus conodont biofacies, 2. Pachycladina-Parachi rognathus conodont biofacies, 3. Gondolella -Hindeodus conodont biofacies, 4. Gondolella-Neospathodus conodont biofacies, and 5. Xaniognathus conodont biofacies. Considering the temporal and spatial changes of these conodont biofacies, 3 conodont bloprovinces have been divided. In light of the biofacies changes of each bioprovince, the authors also discuss, in this paper, the regularity of transgression-regression cycles of eastern Tethys and their possible relation to the mass biotic alternation.  相似文献   

13.
阎春波  张保民  杨博 《地质通报》2019,38(6):922-929
针对保山地层区熊洞剖面原属栗柴坝组的灰岩进行了牙形石样品分析,总计建立了5个牙形石带,分别为Pterospathodus pennatus procerus带、Kockelella walliseri带、Ancoradella ploeckensis带、Polygnathoides siluricus带和Polygnathus nothoperbonus带。该剖面第8层原属栗柴坝组,Polygnathus nothoperbonus分子的出现证实其为下泥盆统埃姆斯阶的地层,应归为向阳寺组。剖面总体对应志留系温洛克统底部到下泥盆统埃姆斯阶中部,中间缺失志留系罗德洛统卢德福特阶—下泥盆统埃姆斯阶之间的8～10个标准牙形石带,说明该地区后期可能受构造作用影响,志留系和泥盆系界线为断层接触。该剖面牙形石序列的建立一定程度上完善了滇西保山地层区志留系生物地层的研究程度,为下一步该区生物地层格架的建立奠定了基础。  相似文献   

14.
The Penglaitan section, as the Global Stratotype Section for the Guadalupian–Lopingian boundary (GLB), displays continuous deposition with a complete succession of pelagic conodont zones across the GLB. However, there is no reliable radiometric age from the Penglaitan section itself to constrain the GLB. Here, we report SIMS zircon U‐Pb ages from two bentonite layers (Bed 7c) in the Penglaitan Global Stratotype Section near the GLB. The sample PL‐62‐1 yields a weighted mean 238U/206Pb age of 257.1 ± 2.2 Ma, and the sample PL‐62‐2 yields a weighted mean 206Pb/238U age of 257.0 ± 4.2 Ma. Therefore, we consider 257.0–257.1 Ma as the age of deposition of Bed 7c (the end of the C. postbitteri postbitteri conodont Zone, ca. 86 cm above the GLB), and, considering the depositional rate of chert, we suggest 258.6 Ma as the age of the GLB. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

15.
The demarcation of the Lower–Middle Triassic boundary is a disputed problem in global stratigraphic research. Lower–Middle Triassic strata of different types, from platform to basin facies, are well developed in Southwest China. This is favorable for the study of the Olenekian–Anisian boundary and establishing a stratotype for the Qingyan Stage. Based on research at the Ganheqiao section in Wangmo county and the Qingyan section in Guiyang city, Guizhou province, six conodont zones have been recognized, which can be correlated with those in other regions, in ascending order as follows: 1, Neospathodus cristagalli Interval-Zone; 2, Neospathodus pakistanensis Interval-Zone; 3, Neospathodus waageni Interval-Zone; 4, Neospathodus homeri-N. triangularis Assemblage-Zone; 5, Chiosella timorensis Interval-Zone; and 6, Neogongdolella regalis Range-Zone. An evolutionary series of the Early–Middle Triassic conodont genera Neospathodus-Chiosella-Neogongdolella discovered in the Ganheqiao and Qingyan sections has an intermediate type named Neospathodus qingyanensis that appears between Neospathodus homeri and Chiosella timorensis in the upper part of the Neospathodus homeri-N. triangularis Zone, showing an excellent evolutionary relationship of conodonts near the Lower–Middle Triassic boundary. The Lower–Middle Triassic boundary is located at 1.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Qingyan section, whereas this boundary is located 0.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Ganheqiao section. There exists one nearly 6-m thick vitric tuff bed at the bottom of the Xinyuan Formation in the Ganheqiao section, which is usually regarded as a lithologic symbol of the Lower–Middle Triassic boundary in South China. Based on the analysis of high-precision and high-sensitivity Secondary Ion Mass Spectrum data, the zircon age of this tuff has a weighted mean 206Pb/238U age of 239.0±2.9Ma (2s), which is a directly measured zircon U-Pb age of the Lower–Middle Triassic boundary. The Ganheqiao section in Wangmo county can therefore provide an excellent section through the Lower–Middle Triassic because it is continuous, the evolution of the conodonts is distinctive and the regionally stable distributed vitric tuff near the Lower–Middle Triassic boundary can be regarded as a regional key isochronal layer. This section can be regarded not only as a standard section for the establishment of the Qingyan Stage in China, but also as a reference section for the GSSP of the Lower–Middle Triassic boundary.  相似文献   

16.
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   

17.
Evidence is presented from the upper Aeronian, lower Sheinwoodian and middle Homerian demonstrating that positive δ13C excursions in the lower Silurian are the result of increased carbonate weathering and probably also enhanced burial of organic carbon coincident with sea‐level falls resulting from growth of ice sheets on the South American part of Gondwana. Graptolite extinctions are coincident with the δ13C excursions, whereas major conodont extinction events (Ireviken and Mulde) are not, but conversely, occur at times of high sea level. This suggests very different controls on graptolite and conodont global diversity patterns. Palynological studies suggest that netromorph acritarchs may have been opportunists that flourished during positive δ13C excursion intervals. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

18.
During the Ordovician, huge biological revolutions and environmental changes happened in Earth’s history, including the Great Ordovician Biodiversification Event, global cooling and so on, but the cause of these events remains controversial. Herein, we conducted a paired carbon isotopic analysis of carbonate (δ13Ccarb) and organic matter (δ13Corg) through the Ordovician in the Qiliao section on the Yangtze platform of South China. Our results showed that the δ13Ccarb trend of the Qiliao section can be correlated with local and global curves. The δ13Corg trend seems is less clear than the δ13Ccarb trend for stratigraphic correlations, but some δ13Corg positive excursions in the Middle and Upper Ordovician may be used for correlation studies. These carbon isotopic records may have global significance rather than local significance, revealing several fluctuations to the global carbon cycle during the Ordovician. Several known δ13Ccarb and δ13Corg negative and positive excursions have been recognised in this study, including the early Floian Negative Inorganic Carbon (δ13Ccarb) Excursion (EFNICE), as well as the early Floian Positive Organic Carbon (δ13Ccarb) Excursion, the mid-Darriwilian Inorganic Carbon (δ13Ccarb and δ13Corg) Excursion (MDICE), and the early Katian Guttenberg Inorganic Carbon (δ13Ccarb and δ13Corg) Excursion (GICE). These positive excursions and a smooth decline trend of δ13Corg values during the early to mid-Floian may imply multiple episodes of enhanced organic carbon burial that began at the early Floian stage, probably resulting in further decline in atmospheric pCO2 and then global cooling.  相似文献   

19.
Ninety species of conodont are recorded from rocks of Frasnian age in the Bugle Gap area in the Canning Basin of Western Australia: 56 of these species are reported for the first time from the Canning Basin. One new subspecies is described. Two parallel but disparate conodont sequences are present, which are presumed to represent different environments: one, the Palmatolepis sequence of the standard zonation is present in the uppermost beds of the Sadler Limestone at Sadler Ridge, the Gogo Formation, and much but not all of the Virgin Hills Formation, and presumably represents an inter‐reef faunal succession; the other consists of a sequence of Icriodus assemblages which is present in the Sadler Limestone and a part of the Virgin Hills Formation at Lawford Range. An Icriodus zonation is proposed for this sequence. No conodonts were recovered from many samples of the Pillara Limestone (back‐reef facies) in the Bugle Gap area. Conodont data presented here suggest that the Gogo Formation in this area is restricted to the Lower and Middle asymmetricus Zones (to Iα); the upper part of the Sadler Limestone at Sadler Ridge may also be assigned to the Lower and Middle asymmetricus Zones ((to Iα); the Sadler Limestone of the Lawford Range extends through the Lower, Middle and Upper asymmetricus Zones (to Ia — to Iß); and the Virgin Hills Formation extends from the base of the Ancyrognathus triangularis Zone, or just below it (to Iß/γ) through to the velifer Zone (to III). No assumption is made about the applicability of these determinations to outcrops other than those sampled in this study.  相似文献   

20.
The Middle Ordovician Rosroe Formation consists of some 1350 m of coarse, mainly siliciclastic to volcaniclastic sedimentary rocks, deposited in a submarine fan environment, and is restricted to the southern limb of the South Mayo Trough, western Ireland. Discrete allochthonous blocks, reaching 5 m in size, are present in the formation at several localities. Conodonts recovered from these blocks, collected from two separate locations, are of late Early and mid Mid Ordovician age. The conodonts have high conodont‐alteration indices (CAI 5) indicative of temperatures as high as 300o to max. 480 °C; some found in the Lough Nafooey area have abnormally high indices (CAI 6), which correspond to temperatures of about 360o to max. 550 °C. The oldest fauna is dominated by Periodon aff. aculeatus and characterized by Oepikodus evae typical of the Oepikodus evae Zone (Floian Stage; Stage Slices Fl2–3, Lower Ordovician). The younger conodont assemblage, characterized by Periodon macrodentatus associated with Oistodella pulchra, is referred to the P. macrodentatus conodont Biozone (lower Darriwilian; Stage Slices Dw1–2). The Rosroe conodont assemblages are of Laurentian affinity; comparable faunas are well known from several locations along the east to south‐eastern platform margin of Laurentia and the Notre Dame subzone of central Newfoundland, Canada. The faunal composition from the limestone blocks suggests a shelf edge to slope (or fringing carbonate) setting. The faunal assemblages are coeval with, respectively, the Tourmakeady Formation (Floian–Dapingian) and Srah Formation (Darriwilian) in the Tourmakeady Volcanic Group in the eastern part of the South Mayo Trough and probably are derived from the same or similar laterally equivalent short‐lived carbonate successions that accumulated at offshore ‘peri‐Laurentian’ islands, close to and along the Laurentian margin. During collapse of the carbonate system in the late Mid Ordovician, the blocks were transported down a steep slope and into deep‐water by debris flows, mixing with other rock types now found in the coarse polymict clastics of the Rosroe Formation. The faunas fill the stratigraphical ‘gap’ between the Lower Ordovician Lough Nafooey Volcanic Group and the upper Middle Ordovician Rosroe Formation in the South Mayo Trough and represent a brief interval conducive to carbonate accumulation in an otherwise siliciclastic‐ and volcaniclastic‐dominated sedimentary environment. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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