Nomenclature of Cambrian epochs and series based on GSSPs Comments on an alternative proposal by Rowland and Hicks

In this issue, Rowland ＆ Hicks advocate a nomenclature for the four epochs of the Cambrian Period that carries over the terms Early, Middle, and Late Cambrian from previous usage （but with new definitions） and introduces a non-geographically-based term, Ichnocambrian, for the earliest Cambrian epoch. The terms Lower/Early, Middle, and Late/Upper Cambrian are confusing because they connote the second, third, and fourth epochs/series of the period/system, and because each is defined in a way that is different from traditional definitions of those intervals. The use of these terms will ultimately lead to confusion between older concepts of Early, Middle, and Late Cambrian and newer, refined concepts of the epochs. The philosophy of the International Subcommission on Cambrian Stratigraphy for establishing a clear subdivision of the Cambrian on a global scale is unambiguous： stratigraphic terms previously in use lack global applicability and should not be adopted as chronostratigraphic/geochronologic units in the developing global stratigraphic chart of the Cambrian. Moreover, all series and stage names should be GSSP （stratotype section）-based.

全球已批准的和潜在的层型剖面和点位(GSSPs)

自 1978年确立全球泥盆系底界层型和点位以来 ,国际地层委员会动员全球许多领域的地层学家为地质历史各个断代 (包括界、系、统、阶 )确立底界层型和点位 (俗称“金钉子”)。这在国际地层学发展史上 ,是一个重要的里程碑。尽管在实施原理和方法上还有不同的意见、工作中也出现一些不尽如人意的地方 ,但其功绩 ,特别是在为寻求全球地质学基础的共同语言中所建立的功勋 ,将永载史册。然而 ,当前国际地层委员会已认识到这项工作并不是、也不能代表地层学的全部。从目前情况看 ,在显生宙 13个系内约 10 0个层型剖面和点位中 ,已有 45个被批准确立 ,18个或条件已经成熟或接近完成 ,预计2 0 0 3年将被提出并批准 ;还有约 37个的研究正在进行之中。新生代的大部分完成了 ;中生代 (特别是白垩系和三叠系 )的还有一大半没有定 ,任务不轻 ;古生代的以志留系和泥盆系的确立最早 ,但前者还存在一些问题 ,奥陶系的虽起步不晚 ,但由于种种原因 ,进展稍慢 ,正在加紧进行 ,石炭系和寒武系的也在努力之中。国际地层委员会已经决定这项工作必须在 2 0 0 8年全部完成 ,以利于尽早转入下一个阶段更加深入的、全球地层学各领域的协同研究。

全球中、下寒武统界线研究现状及展望

美国、中国、摩洛哥、俄罗斯、西班牙等国的地层古生物学者均在进行中、下寒武统界线层型剖面及标准点 (GSSP)的研究 ,并相继提出潜在的中寒武统FAD分子如Oryctocephalusindi cus,Ovatoryctocara granulata ,Acadoparadoxidesmureroensis ,Hupeolenus和Arthricocephaluschauveaui及潜在中、下寒武统界线层型剖面 .早及中寒武世之交 ,广泛分布的三叶虫极少 ,能够作全球完美的中寒武统FAD分子至今几乎没有 .Oryctocephalusindicus分布比较广泛 ,三大生物区均有产出 ,特征明显 .首现点正好是三叶虫大量灭绝、新的三叶虫大量出现的演化点 ,是一个相对最佳的中寒武统FAD分子 .而中国台江八郎乌溜剖面岩性单一且连续 ,底栖及游泳的三叶虫非常丰富 .Oryctocephalusindicus首现点距Redlichia、Bathynotus灭绝点分别是 0 .8及 1.2m ,处于三叶虫的重要演化阶段 .疑源类的演化及微量元素、碳同位素变化特征和中、下寒武统界线划分一致或基本一致 .界线之上为著名的中寒武世凯里生物群 ,剖面点距 32 0国道仅 5km ,是一个潜在的、好的中、下寒武统界线层型剖面 .

推荐一条GSSP的辅助剖面

该文赞同以Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ的首次出现作为划分二叠－三叠系界线的生物标志．笔者强调只有以正模及其描述为准所厘订的Ｈ．ｐａｒｖｕｓ，且以主齿、细齿均保存完美、距界线粘土层顶面位置最低以及其顶面至界线生物面之上均为单一岩相的Ｈ．ｐａｒｖｕｓ的首次出现点位，才有可能成为二叠－三叠系全球界线层型剖面点的位置．东岭剖面可以它典型的Ｈ．ｐａｒｖｕｓ距界线粘土层顶面仅高出１３ｃｍ，化石保存完好以及界线粘土层至Ｐ／Ｔ界线附近均为单一的灰泥岩三特点弥补煤山剖面之不足．为使作为二叠－三叠系全球界线层型剖面点（ＧＳＳＰ）的候选剖面的浙江长兴煤山剖面更臻完善。

全球标准层型剖面和点位(“金钉子”)和中国的“金钉子”研究

《国际年代地层表》中显生宇所有的年代地层(地质年代)单位和元古宇的部分年代地层(地质年代)单位都已经或将要由全球标准层型剖面和点位("金钉子")定义。这是研发一个完全连续的、既无重复也无间断的年代地层(地质年代)等级系统的唯一途径。文中回顾了过去近50年在国际地层委员会倡导和推行下"金钉子"概念形成和发展过程,简介了"金钉子"概念和由国际地层委员会制定建立"金钉子"的程序;同时简要回顾了中国科学家研究"金钉子"的历史和卓越成就,包括竞争"金钉子"中的失利和收获10枚确立在我国的"金钉子"。

The Golden Spike Still Glitters:The(Re)construction of a Global Chronostratigraphy

1 Introduction Stratigraphy,placing the sequence of events in Earth history into order,is a fundamental part of the geosciences.Traditionally the starting point is a regional stratigraphy,based on lithological,mappable units,correlated by fossils with local,regional and global chronostratigraphical schemes.Chronostratigraphic units were traditionally defined on their fossil content,as essentially unit stratotypes.But,commonly there were no clear boundaries.

The Global Boundary Stratotype Section and Point （GSSP） for the base of the Hirnantian Stage （the uppermost of the Ordovician System）

The Global boundary Stratotype Section and Point （GSSP） for the base of the Hirnantian Stage （the uppermost of the Ordovician System） is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section. The section is located near Wangjiawan village, 42 km north of Yichang city （western Hubei, China）, at 30° 58′56″N and 111° 25′10″E. The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius （Sobolevskaya）. Secondary markers include the onset of a positive carbon-isotope excursion, and a slightly earlier first appearance of Normalograptus ojsuensis （ Koren and Mikhailova ）. The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures, abundant and well-preserved graptolites and shelly fossils, i. e. the Hirnantia- Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage. The Wangjiawan North, South and Riverside sections possess favorable facies and widespread correlation potential, are free from structure complication, metamorphism and other alteration, and have good accessibility. The Riverside section in particular possesses amenability to isotopic age determination. The beginning of the Hirnantian was followed by a global episode of a major extinction event, which happened in the Diceratograptus mirus Subzone. The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October, 2004, approved by the International Commission on Stratigraphy in February, 2006, and ratified by the International Union of Geological Sciences in May, 2006.

A proposed GSSP for the base of the Middle Ordovician Series： the Huanghuachang section,Yichang, China

The Huanghuachang section near Yichang, southern China meets the requirements of Global Stratotype Section and Point (GSSP) for the base of the Middle Ordovician Series and the yet-to-be-named third stage of the Ordovician System (or lower stage of Middle Ordovician Series). The conodont succession at the section is complete across the Lower to Middle Ordovician series boundary and several excellent phylogenetic lineages of Baltoniodus, Trapezognathus, Periodon, and Microzarkodina are represented. The definition of the base of the Middle Ordovician is proposed to be the first appearance datum (FAD) of Baltoniodus? triangularis in the section. It is followed closely by the FAD of Microzarkodina flabellum, which is taken as a reasonable proxy for the boundary. This level approximates the boundary between the lower and upper intervals of the Azygograptus suecicus graptolite Biozone, and nearly coincides with the base of the Belonechitina henryi chitinozoan Biozone.The proposed GSSP for the base of the international Middle Ordovician Series is located in a roadside exposure at the base of Bed (SHod) 16, 10.57 m above the base of the Dawan Formation in the measured Huanghuachang section near Yichang City, southern China. The same faunal succession is also recorded from the Chenjiahe (formerly Daping) section, 5 km to the north of the Huanghuachang section. The proposed boundary horizon can be recognized and correlated globally with high precision in both relatively shallow-water carbonate facies as well as in deep-water graptolite facies.

The Global boundary Stratotype Section and Point （GSSP） of the Ladinian Stage （Middle Triassic） at Bagolino （Southern Alps, Northern Italy） and its implications for the Triassic time scale

The Global boundary Stratotype Section and Point （GSSP） for the base of the Ladinian Stage （Middle Triassic） is defined in the Caffaro river bed （45°49＇09.5＂N, 10°28＇15.5＂E）, south of the village of Bagolino （Province of Brescia, northern Italy）, at the base of a 15-20-cm-thick limestone bed overlying a distinct groove （＂Chiesense groove ＂） of limestone nodules in a shaly matrix, located about 5 m above the base of the Buchenstein Formation. The lower surface of the thick limestone bed has the lowest occurrence of the ammonoid Eoprotrachyceras curionii （base of the E. curionii Zone; onset of the Trachyceratidae ammonoid family）. Secondary global markers in the uppermost Anisian include the lowest occurrence of conodont Neogondolella praehungafica and a brief normal-polarity magnetic zone recognized in closely correlated sections including the principal auxiliary section at Seceda in the Dolomites. The GSSP-level is bracketed by U-Pb single zircon age data from volcaniclastic horizons, indicating a boundary age of ca 241 Ma.

The GSSP of the Second （Upper） Stage of the Lower Ordovician Series： Diabasbrottet at Hunneberg, Province of Vaeistergoetland, Southwestern Sweden

Diabasbrottet, selected by the International Subcommisson on Ordovician Stratigraphy and in 2002 ratified by the International Commission on Stratigraphy as the GSSP of the Second (Upper) Stage of the Lower Ordovician, is located on the Hunneberg Mountain in southwestern Sweden. The stratigraphic succession represents an outer shelf environment near the Baltic Shield margin. The shale-dominated, biostratigraphically complete, richly fossiliferous boundary interval is completely exposed in a disused quarry. The GSSP is in the lower TФyen Shale 2.1 m above the top of the Cambrian and is marked by the first appearance of the graptolite Tetragraptus approximatus Nicholson. The boundary interval contains a diverse graptolite fauna and biostratigraphically diagnostic conodonts and trilobites that make it possible to define the boundary in terms of zone schemes based on these groups. In this respect, the Diabasbrottet and nearby sections are unique in the world among described localities having this boundary interval. Based on the appearance of T. approximatus, the base of the Second Stage can be identified in many graptolitiferous successions round the world but this level is currently more difficult to recognize precisely in some carbonate sequences outside Baltoscandia. We propose the Second Stage be called the Floan Stage. It is named for the Village of Flo, which is situated about 5 km southeast of the GSSP.

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 Boundary Stratotype Section and Point for the base of the Middle Ordovician Series： The Niquivil section, Precordillera of San Juan, Argentina

The Niquivil section, Argentine Precordillera, fulfills most of the requirements for a Global Stratotype Section and Point （GSSP） for the base of the Middle Ordovician Series. It has excellent conodont biostratigraphy in a continuous succession of uniform lithology, is readily accessible, and the critical interval is not tectonically affected. The position of the Lower/Middle Ordovician Series boundary in the Central Precordillera is placed at the middle part of the San Juan Formation, an open-platform carbonate unit. The Niquivil section is proposed as a GSSP for the base of the Middle Ordovician, which is marked by the FAD of the conodont Cooperignathus aranda （Cooper）. It occurs in level NCA, at the upper part of the Oepikodus evae Zone （overlapping uppermost records of O. evae in association with other guide species）; i.e., 100.15 m above the base of the reference section. The auxiliary Pena Sombria section from northern Precordillera records graptolites of the lower （but not lowest） Middle Ordovician in the Isograptus victoriae maximus Zone, few meters above the proposed boundary biohorizon. The range of C. aranda can be correlated with the I. victoriae lunatus Zone up to the lower part of the Undulograptus austrodentatus Zone in diverse sections of the world. C. aranda presents cosmopolitan distribution and occurs in virtually all environments. The proposed GSSP preserves a carbon-isotope record that provides an auxiliary marker of potential global application. Radiometric dating of K-bentonite samples, interbedded with carbonate strata yielding lower records of C. aranda, were recovered from the auxiliary Talacasto section in Central Precordillera （469.8 ±2.3 Ma, U-Pb SHRIMP dating）.

Suggestion of Meishan Section as GlobalStratotype Section and Point （GSSP） of Permian－Triassic Boundary

The Meishan Section of Changxing County, Zhejiang Province, China and the base of its Bed 27c,in which Hindeodus parvus first occurs, are recommended as the GSSP of Permian-Triassic boundary (PTB).The present paper introduces a description of the section. Biostratigraphic correlation with other famous sections shows the completeness of this section and justifies choice of H. Parvus as the index fossil. Chemostratigraphic investigation provides the δ￣13C excursion and the moderate but inconsistent Ir spike as auxiliary symbols for the PTB. This boundary is closely related to transgression,anoxia,volcanism,mass extinction and possible impact events which can be correlated with those in South China and other parts of the world .

The Global Boundary Stratotype Section and Point （GSSP） for the base of the Pliensbachian Stage （Lower Jurassic）, Wine Haven, Yorkshire, UK

Following votes by the Pliensbachian Working Group, the Jurassic Subcommission and the International Commission on Stratigraphy, lUGS ratified the proposed Global Boundary Stratotype Section and Point （GSSP） for the base of the Pliensbachian Stage （Lower Jurassic） at the base of bed 73b in the Wine Haven section, Robin Hood＇s Bay, Yorkshire Coast, UK. This level contains the characteristic ammonite association Bifericeras donovani Dommergues and Meister and Apoderoceras sp. Complementary data include： a） Strontium-isotope stratigraphy, based on analysis of belemnites which yield a calcite 87Sr/^86Sr ratio for the boundary level of 0. 707425 and data supporting interpretation of continuous sedimentation; b） Belemnite oxygen-isotope data indicate a significant temperature drop （-5 ℃） across the boundary at this locality; c） A Transgressive Systems Tract （TST） initiated in the Aplanaturn Subzone （uppermost Sinemurian） continues into the Lowermost Pliensbachian （Taylori Subzone）; it forms part of a transgressive facies cycle sensu Graciansky et al. （1998）; d） The Upper Sinemurian to lowermost Plensbachian at Wine Haven section has a predominantly norreal magnetic polarity, but two discrete reversed polarity magnetozones are present. The first spans much of the latest Sinemurian Aplanatum Subzone. It terminates 〈0.5m below the Sinemurian-Pliensbachian boundary and may prove a valuable chronostratigraphic marker The second extends from the latest Oxynotum Subzone probably through to the lower part of the Raricostatum Subzone.

Sequence Boundary:Its Significance in Stratigraphic Subdivision,Correlation and Classification

Sequence boundary is studied in detail in reference to the Permian Guadalupian Lopingian boundary, based on high resolution correlation of conodont zones. A conceptual synchronous stratigraphic boundary, corresponding to the age of the sequence boundary dated in the conformable portion of the sequence boundary, is defined as the sequence chronostratigraphic boundary (SCB). The sequence boundary is proved to be dual in nature in regards to tin-synchrony and diachroneity of stratigraphic boundaries. The merits of the sequence boundary in stratigraphic subdivision, correlation and classification are elucidated in comparison with the lithostratigraphic boundary, the biostratigraphic boundary and the traditional approach of the global stratotype section and point (GSSP ). By integrating the virtues of the sequence boundary and the GSSP, it is proposed that the GSSP should be established in the conformable portion of the related sequence boundary. The boundary established in light of this approach is defined as the best natural boundary. The analysis of the sequence boundary leads to the conclusion that sequence stratigraphy is a regional and transitional stratigraphic system between local lithostratigraphy and global chronostratigraphy. Therefore, a new tripartite stratigraphic classification scheme is tentatively proposed.

Problems of Sequence Stratigraphy in China

A comprehensive study of outcrop sequence stratigraphy in China began in the early 1990s. The investigated strata range from Mesoproterozoic to Quaternary and the studied areas cover the three platforms and margins, the Southern Himalayas and the East China and South China seas. Problems of general concern in the sequence stratigraphy of China are discussed. These are: the hierarchy for sequence stratigraphy, the third order Sequence and eustasy, the chronostratigraphic boundaries and GSSP, and the International Stratigraphic Chart and the sequence chronostratigraphy of China. The average time interval of Mesosequence (25-40 Ma) and of the Sequence (2-5 Ma) is suggested and the minor sequences below the Sequence are discussed. The time interval of the Sequence shows no evident decrease with time, but several epochs with remarkable short intervals occur in the Phanerozoic, which may represent a planetary behavior denoting the special development stages in earth’s evolution. Sea level change curves are given separately for the three platforms and the different regions. The Global Stratotype Section and Point (GSSP) concept and practice are discussed, and a comparison between the first appearance point of biozone and the first flooding surface in the Sequence is made for designation of the chronostratigraphic boundary. It is suggested that the chronostratigraphic boundaries might be set at the first flooding surface in the Sequence for easy recognition. The idea of sequence chronostratigraphy is recommended, and a comparison between the International Stratigraphic Chart and the sequence chronostratigraphy of China is made. The close relation between chronostratigraphy and sequence stratigraphy makes it possible for sequence stratigraphy to improve chronostratigraphic research. It is pointed out that multidisciplinary study in chronostratigraphy is necessary and should be promising and profitable.

The Best Natural Boundary:a New Concept Developed by Combining the Sequence Boundary with the GSSP

Through a detailed study of sequence boundaries, it is concluded that sequence stratigraphy is an independent regional and transitional stratigraphic system between local lithostratigraphy and global chronostratigraphy. Therefore, a new tripartite stratigraphic classification scheme has been proposed. By combining organically the concept of sequence boundaries with the GSSP, it is suggested that the GSSP should be chosen in a conformale portion of a related sequence boundary, and the boundary established in light of this concept is defined as the Best Natural Boundary (BNB). The definition of the BNB points out the working area and stratigraphic level for the GSSP. By referring to a case study of the Permian Guadalupian/Lopingian boundary, the concept of the BNB has been elaborated in detail, and it is proposed that the BNB of the Guadalupian and the Lopingian lies between the Mesogondolella granti Zone and the Ctarkina postbitteri Zone, which is also the sequence chronostratigraphic boundary between the Transpecos composite sequence (chronozone)and the UAA- 1 composite sequence (chronozone).

Multiobjective scheduling optimization of bearing production workshop for green manufacturing

Aiming at the machining process of high-performance bearing parts,the green shop scheduling problem of bearing parts processing was studied herein,with the maximum completion time,minimum machine carbon emission,and minimum grinding fluid usage as the optimization objectives.The manufacturing process is divided into six technological processes:startup,clamping,machining,unloading,standby,and shutdown.The multiobjective green shop scheduling mathematical model is established.Then,an improved multiobjective genetic algorithm is proposed,adopting a segmented coding method that integrates the process and machine selections and improves the steps of crossover and mutation,all of which improve the algorithm s convergence.Finally,the bearing parts processing of a bearing company is taken as a case study,and large-scale data tests and analyses are constructed.The result shows that the proposed model can obtain lower completion time,carbon emission,and grinding fluid consumption,which verifies the scientificity and effectiveness of the proposed model.