A Potential Candidate For the Middle-Upper Cambrian Boundary Stratotype——An Introduction to the Paibi Section in Huayuan,Hunan

The Middle-Upper Cambrian boundary is one of the current stratigraphical problems which remain openin the geological world, since there have been no universally acknowledged delimiting standard and stratotype.Acting on the instruction of Profs. Lu Yanhao and An Taixiang the author studied in details the Paibi Section,which is well exposed as a continuous sequence at an easily accessible locality. The Middle-Upper Cambrianboundary strata are composed of biocalcimicrosparite, indicating the sedimentary environment of anunderwater upheaval on the gentle slope along the frontal margin of the Yangtze carbonate platform. For the upper Middle and lower Upper Cambrian agnostid trilobite zones and conodont zones are erected,and a more accurate correlation between the trilobite and conodont sequences is established. Based on these,the Middle-Upper Cambrian boundary is drawn more reasonably and precisely than what was done before. Inshort, the section studied is superior to other known sections of Middle-Upper Cambrian. and it will probablybe an ideal candidate for the Middle-Upper Cambrian boundary stratotype.     

A Comprehensive Evaluation on the Devonian-Carboniferous Boundary Stratotype Candidate Section in Nanbiancun, Guilin, Guangxi

This paper presents a comprehensive evaluation on the Devonian-Carboniferous Boundary (DCB) sectionin Nanbiancun. Guilin. Guangxi on the basis of Palaeontological, biostratigraphical and sedimentarypetrological studies as well as microfacies analysis. REE and trace element analysis and isotopic dating. The DCB at this section conforms to the definition of this boundary and essentially measure up the criteriaand conditions for selection of the boundary stratotype. Up to 14 fossil groups are contained in the section. Thesection presents a general biostratigraphical framework with multispecies fossils zones, assemblage zones andmultiple groups of fossils and has latent preponderant conditions for magnetostratigraphic andchronostratigraphic studies. The boundary and point occur in a persistent and continuous monofacialcarbonate succession. and the section is located in a tourist city with convenient communication, where variousfacies of DCB sections are developed. allowing the correlation within a small area. So it is an ideal candidateboundary stratotype.     

Palaeomagnetic Study on the Precambrian-Cambrian Boundary Candidate Stratotype Section at Meishucun, Yunnan

The Meishucun secton has been recommended as an international candidate stratotype secton of thePrecambrian-Cambrian boundary. The paper deals with the palaeomagnetic study on the section. A total of159 palaeomagnetic samples were successively collected from the platform-facies sequence of carbonates andphosphates at the section. Thermal demagnetization results indicate a great majority of the rocks at the sectionhave been strongly overprinted by recent magnetic field, but 57 samples have preserved remanentmagnetization with antipodal directions (mean D/I=4.2°/ 7.1°, K=9, α_(95) = 6.6°). Baaed on calculation,the location of the palaeomagnetic pole was at 68.8°N and 270.7°E, which is different from any palaeopolesobtained from younger Phanerozoic rocks in South China. The results reveal a polarity zonation which in-cludes at least 9 reversal events. A comparison of China's magnetostratigraphic records with those fromSiberia, Australia and the western U.S.A. shows that all the sections are characterized by frequent polarity re-versals.     

Study on a Terrestrial Permian—Triassic Boundary Section—Zhejue Section, Weining County,Guizhou Province, China

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.     

The Global Boundary Stratotype Section and Point （GSSP） for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France

Following the unanimous recommendation of the International Commission on Stratigraphy, the Global boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage is defined at a level 36 metres below the top of the Marnes Bleues Formation, a level that corresponds to the the first appearance of the planktonic foraminiferan Rotalipora globotruncanoides Sigal, 1948, on the south side of Mont Risou, east of Rosans, Haute-Alpes, France, where it can be placed in the context of a series of secondary marker levels based on nannofossils, planktonic foraminifera, ammonites,and an ornate δ^13C curve.     

Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City,Guizhou Province

The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe^2 and Mn^2 ,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe^2 increased later and decreased earlier than that of Mn^2 .Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe^2 ,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system.     

Aproposed Area for Study of Accessory Section and Point of Terrestrial Permian—Triassic Boundary

After the establishment of the global stratotype section and point (GSSP) of the Permian-Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian-Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcoming:(1) the exact TPTB horizon is difficult to define paleontologically with high-resolution, and (2) accurate correlation between marine and terrestrial PTBs in hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic-Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well-developed, allowing bed-to-bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high-resolution demarcation of the TPTB. These features fund in estern Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.     

A Comprehensive Evaluation on the Devonian-Carboniferous Boundary Stratotype Candidate Section in Nanbiancun,Guilin, Guangxi1

Abstract This paper presents a comprehensive evaluation on the Devonian-Carboniferous Boundary (DCB) section in Nanbiancun, Guilin, Guangxi on the basis of Palaeontological, biostratigraphical and sedimentary petrological studies as well as microfacies analysis, REE and trace element analysis and isotopic dating. The DCB at this section conforms to the definition of this boundary and essentially measure up the criteria and conditions for selection of the boundary stratotype. Up to 14 fossil groups are contained in the section. The section presents a general biostratigraphical framework with multispecies fossils zones, assemblage zones and multiple groups of fossils and has latent preponderant conditions for magnetostratigraphic and chronostratigraphic studies. The boundary and point occur in a persistent and continuous monofacial carbonate succession, and the section is located in a tourist city with convenient communication, where various facies of DCB sections are developed, allowing the correlation within a small area. So it is an ideal candidate boundary stratotype.     

关于奥陶系最上部赫南特(Hirnantian)亚阶全球层型的建议

在对鄂西宜昌王家湾和分乡、黔北桐梓红花园、黔东北松桃陆地坪 4条剖面的相关地层和主要门类化石做了新的无间断采集和重新鉴定笔石和腕足动物这两个重要化石门类的基础上 ,发现奥陶纪最末期—志留纪最早期的完整笔石序列与腕足动物等新的化石材料 ,初步了解奥陶纪末集群灭绝后生物幸存的基本特征。经过选择 ,特推荐宜昌王家湾公路旁穿越奥陶 -志留纪界线地层剖面作为建立国际赫南特亚阶的首位候选 (leading candidate)层型 ,并推荐桐梓红花园相关剖面作为辅助候选 (auxiliary candidate)层型。对建立全球赫南特亚阶界线层型的基本条件和国外相关剖面的优缺点作了分析。本文所识别的赫南特亚阶相当于两个笔石带 :下部 N ormalograptus ex-traordinarius- N.ojsuensis带和上部 N.persculptus带。典型的 H irnantia动物群的整体地质历程为奥陶纪最末期 ,相当于 N ormalograptus extraordinarius- N.ojsuensis带和 N.persculptus带的一部分。     

石炭纪维宪阶全球界线层型剖面和点位补遗

经国际地质科学联合会批准,我国广西柳州北岸乡碰冲剖面为石炭纪维宪阶全球界线层型剖面和点位.层型剖面位于柳州市东北15 km之碰冲村南小溪(24°26'N,109°27'E).层型点位在剖面83层之底,与底栖有孔虫"E.ovalis种群"至Eoparastaffella simplex谱系中Eoparastaffella simplex的首次出现吻合.辅助标志是点位之上近5m处,牙形石Gnathodus homopunctatus首现,其下约30 m为Scaliognathus anchoralis europensis的最高出现.本文补充介绍了层型点位的岩石特征和区域上的对比.     

吉林大阳岔寒武系-奥陶系界线层型候选剖面再描述

吉林大阳岔剖面是目前国际寒武系-奥陶系界线工作组(ICOBWG)所确认的全球唯一的寒武系-奥陶系界线层型候选剖面。运用坐标系统对大阳岔界线剖面进行重新测量、详细描述Cambrooistodus 带至 Cordylodus lindstromi 带45.9m 厚的地层序列,将不同学者在大阳岔剖面所采用的样品采集系统相应地标在新的坐标剖面上,以统一它们在新坐标剖面上的坐标位,置点。新的坐标剖面将为国际寒武系-奥陶系界线工作组在确定全球界线层型剖面和点位(GSSP)时提供一个共同的参照标准。     

南雄盆地武台岗白垩系与古近系界线剖面研究进展

上湖洞、武台岗一带是上湖组命名的典型地区,富产哺乳动物化石,又是古新世早、中期哺乳动物群研究最早最详细的地区,但微体化石面貌不清,近年来在武台岗剖面浈水组上部至上湖组下部发现丰富的介形虫、腹足类和轮藻化石,介形虫属于扣星介动物群,可以划分出Porpocypris orbiculata带和P.sphaeroidalis带,并且P.sphaeroidalis与Bemalambda的始现点几乎一致,与大塘E/K界线剖面所见相同.建议以介形虫P.sphaeroidalis始现点来限定古近系的底界,把E/K界线划在     

A Middle–Upper Devonian Boundary Section in the Open Platform,Platform Margin Facies of Guilin, South China

Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common–rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 “standard” conodont zones are recognized across the Givetian–Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni–cristatus Zone, the Lower hermanni–cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle–Upper Devonian (Givetian–Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.     

渭北煤田洛河剖面石炭系上限的确立

华北地区山西组与太原组的分界,以太原西山地区研究最详。自1922年以来,中外学者曾相继发表过许多论著。在1959年全国地层会议上,也曾依据充足的地层古生物资料,将上石炭统太原组顶界确立在东大窑灰岩之顶（即北岔沟砂岩之底）。1975年华北区二叠系专题会议期间,重新作了实地观察与讨论,仍将石炭系顶界定于东大窑灰岩（或海相层）之顶。     

A Middle-Upper Devonian Boundary Section in the Open Platform,Platform Margin Facies of Guilin,South China

The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin.It hosts relatively abundant benthic and common-rare pelagic fossils,including brachiopods,corals,tentaculites,and conodonts,which may serve as a better suitable section for pelagic and neritic stratigraphic correlation.In this section,10"standard"conodont zones are recognized across the Givetian-Frasnian boundary,including,in descending order,the Lower hassi Zone,punctata Zone,transitans Zone,the U...