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.     

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.     

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.     

The Global Boundary Stratotype Section and Point for the base of the Turonian Stage of the Cretaceous： Pueblo, Colorado, U.S.A.

Following the recommendation of the International Commission on Stratigraphy (16 votes Yes [94%], 1 abstention, 2 votes not received), the Global boundary Stratotype Section and Point (GSSP) for the base of the Turonian Stage of the Cretaceous System is defined as the base of bed 86 of the Bridge Creek Limestone Member of the Greenhorn Limestone Formation at the western end of the Denver and Rio Grande Railroad cut near the north boundary of the Pueblo Reservoir State Park Recreation Area, west of Pueblo, Colorado, USA. This GSSP horizon is also exposed and protected in the adjacent state recreation area. It coincides with the first occurrence of the ammonite Watinoceras devonense, is in the middle of a global positive excursion in Carbon-13 isotopes, and is bracketed by widespread bentonites that have yield edages of 93 to 93.5 Ma.     

The Global boundary Stratotype Section and Point （GSSP） of the Tortonian Stage （Upper Miocene） at Monte Dei Corvi

The GSSP of the Tortonian Stage, which per definition marks the base of the Tortonian and, hence, the boundary between the Serravallian and Tortonian Stages of the Middle and Upper Miocene Subseries, has recently been defined and ratified by the IUGS. The boundary stratotype-section is Monte dei Corvi (Italy) where the Tortonian GSSP is now formally at the mid-point of the sapropel of small-scale sedimentary cycle no. 76, close to the last common occurrences (LCOs) of the calcareous nannofossil Discoaster kugleri and the planktonic foraminifer Globigerinoides subquadratus and associated with the short normal subchron C5r.2n. The GSSP level coincides closely with oxygen isotope event Mi-5 and the associated glacio-eustatic sea-level low-stand of supercycle T3.1 and concurrent deep-sea hiatus NH4,and is dated astronomically at 11.608 Ma. The Monte Gibliscemi section is accepted as an auxiliary boundary stratotype because the better preservation of the calcareous microfossils in this section enables quantitative analyses and the construction of a stable isotope record.     

A proposed Global Stratotype Section and Point （GSSP） for the base of the Upper （Late） Pleistocene Subseries （Quaternary System/Period）

Following the precedence already established during the INQUA Congress in 1932, the Middle/Upper （Late） Pleistocene boundary is defined at the base of the Last Interglacial, the Eemian Stage. It is proposed that a high-resolution core sequence from the Amsterdam Terminal （the Eemian Stage parastratotype） should constitute the Global Stratotype Section and Point （GSSP） for the base of the Upper （Late） Pleistocene Subseries （Quaternary System/Period）.     

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.     

New Advances in the Study of the Devonian-Carboniferous Boundary Stratotype in Muhua,Changshun,Guizhou——An Introduction to the Daposhang Devonian-Carboniferous Boundary Section

The Daposhang section at Muhua, Changshun. Guizhou. is an excellent and attractive DevonianCarboniferous boundary section. The transitional beds between the Devonian and Carboniferous of the sectionare continuous and well exposed. belonging to the deep-water basin facies Abundant fossil groups have beendiscovered from this section: conodonts. ammonoids. trilobites. ostracods. vertebrate microfossils and so on.So far as known. it has the most continuous and complete conodont zonation for the Devonian-Carboniferousboundary beds in the world. It is especially worth pointing out that both typical Siponodella pracsulcata andthe transitional forms between S. praesulcata and S. sulcata have been found from the upper pracsulcata Zoneof the Daposhang section. Evidently. we can not only prove the actual existence of the evolutionary lineagefrom S. praesulcata to S. sulcata, but also exactly define the level of the Devonian-Carboniferous boundary. Inthis paper. the development of the Devonian-Carboniferous boundary beds at the Daposhang section is dealtwith and the section is compared with the Muhua section and the Nanbiancun section which are the candidatesfor the Devonian-Carboniferous boundary stratotype. In the authous opinion the Daposhang section is obvi-ously better than the Muhua and the Nanbiancun sections. hence it can be recommended as one of the candi-dates for the international Devonian-Carboniferous boundary stratotype.     

Carbon Isotope Features of the Sugetbrak Section in the Aksu?Wushi Area, Northwest China: Implications for the Precambrian/Cambrian Stratigraphic Correlations

The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi area. Negative δ13C excursion above the Yurtus Fm/ Qigeblaq Fm boundary was determined in this study. The pronounced negative carbon isotope excursion occurs in the phosphatic chert layers at the bottom of the Cambrian Yurtus Fm, below which the first appearance of the Asteridium- Heh＇osphaeridium-Comasphaeridium （AHC） acritarch assemblage zone. The δ13C curve of the lower part of the Yurtus Fm in the Aksu-Wushi area was found to be correlated with the early Cambrian δ13C curves of the Zhujiaqing Fm （Daibu Member）, the lower part of the Yanjiahe Fm on the Yangtze Platform in China, the lower Tal Fm in India, the Sukharikha Fm in Siberia, and the upper part of the Tsagaan Oloom Fm in Mongolia through biostigraphy. The lower part of the Yurtus Fm in the Tarim Basin is at the Nemakit-Daldynian stage, and the Precambrian/Cambrian boundary of the Aksu-Wushi area may be located in the phosphatic chert unit which just below the first appearance AHC acritarch assemblage zone. The negative δ13C excursion （N1） across the Precambrian/Cambrian boundary in the studied section may have resulted from oceanic overturning and sea level rise.     

Integrated stratigraphy across the Aptian/Albian boundary at Col de Pré-Guittard (southeast France): A candidate Global Boundary Stratotype Section

The outcrop of the Marnes Bleues at the Col de Pré-Guittard, 11 km north of the village of Rémuzat in the Départment of Drôme in southeastern France is probably the most intensively studied succession spanning the Aptian/Albian boundary interval. Following the rejection of the proposed GSSP for the base of the Albian Stage (based on the first occurrence of the ammonite Leymeriellla tardefurcata in the section at Le Pillart, Tartonne, Alpes-de-Haute Provence), we re-visit the Pré-Guittard section. A new candidate GSSP defined by the first occurrence of the planktonic foraminifera Microhedbergella renilaevis Huber and Leckie, 2011 is here proposed. This first occurrence is placed in a 100 m section with 28 secondary markers, including calcareous nannofossils, planktonic foraminifera, palynomorphs, an inoceramid bivalve, ammonites, stable carbon isotopes, and local marker beds. The outcrop fulfils most of the physical criteria required of a Global Stratotype Section and Point.