层序地层与地层界线优化

以扬子地台、华北地台和塔里木地台早古生代层序地层研究成果和典型范例为基础 ,讨论了层序地层与年代地层和岩石地层单位及其界线之间的相互关系。在年代地层方面 ,进一步强调以初始海泛面 ( FFS)作为优化年代地层“阶”的标准。从自然界线的观点 ,建议将全球界线层型剖面和点 ( GSSP)在层序地层序列中的位置优化至初始海泛面 ( FFS)。探讨了三级层序结构与生物宏演化阶段之间的可能关系。在岩石地层方面 ,强调以层序地层的关键界面 (层序界面、初始海泛面、最大海泛面 )优化组、段界线。     

中国南方海、陆相侏罗系的划分与对比

对自21世纪以来中国南方海、陆相侏罗系的研究进展进行了总结,依据地层发育的总体特征,将中国南方侏罗系划分为4个地层区和14个地层分区,文中着重介绍了中国南方海、陆相侏罗纪年代地层划分、底界界线层型及各统之间的界线生物标志和与全球年代地层的对比关系。此外,对全球年代与生物地层的研究进展也作了扼要介绍。     

Problems of Sequence Stratigraphy in China

Sequence stratigraphy is the study of rock relationshipwithin a chronostratigraphic fram ework of the genetically re-lated strata bounded by unconform ities and its correlative con-formities(Van Wagoner,1995 ) .As a subdiscipline of stratig-raphy,sequence stratigraphy evolved in the late 1980 s fromseismic stratigraphy which was established in the late 1970 s(Mitchum,1977;Mitchum et al.,1977;Vail et al.,1977) .Although the history of sequence stratigraphy as a subdisci-pline is very brief,th…     

层序地层研究产生的地层学新观点、新概念和新方法——兼论建立新一代年代地层表

层序地层学在地层划分、对比、分类和级别体系等地层学根本理论问题上给地层学带来了新认识、新概念和新方法。全球层型剖面和点(GSSP)可建在层序界面的整合部位,从而将传统的自然界线(或不整合面)、层序界面和GSSP三者有机结合起来,使得年代地层界线成为可在野外识别和追索的界线。论证了层序地层是独立存在于岩石地层和年代地层之间的地层类别和包含这三个基本地层类别的新的三重地层分类方案。阐述用层序地层界线优化各类原有年代地层和岩石地层界线的原理和方法,探讨和阐述了新的地层学体系和建立新一代年代地层表的途径和方法。     

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 th     

Paleomagnetic stratigraphy and biostratigraphy of the Plio-Pleistocene in the Kinki district, Japan

The magnetostratigraphic subdivision of the Plio-Pleistocene series in the Kinki district around Osaka in southwest Japan, based on NRM measurements of volcanic ash beds, is correlated with biostratigraphic and paleoclimatic marker beds as well as past sea level oscillations. At least 10 high sea level stands occurred in the study area between about 1.5 and 0.27 million years ago, all associated with relative warming. A significant change in the composition of flora, from Metasequoia to Fagus dominated assemblages, was observed around the Jaramillo event.     

火山灰锆石U-Pb定年在沉积岩定年上的应用

本文系统总结了沉积岩定年的意义和常用的定年手段,详细介绍了火山灰锆石U-Pb定年在沉积岩定年上的应用。从火山事件层的分布、火山灰夹层的识别、火山灰锆石的区分、应用实例等方面对前人的研究进行概述,旨在为科研工作者运用火山灰锆石U-Pb定年提供借鉴经验。与传统的成岩矿物K-Ar/Ar-Ar和Rb-Sr定年技术相比,火山灰锆石U-Pb定年在沉积岩定年上具有显著的优势。火山灰夹层具有广泛性和等时性,且锆石U-Pb同位素体系不容易受到扰动,因此火山灰锆石U-Pb定年是高精度沉积岩定年的首选方案。沉积岩定年涉及到野外观察、样品采集、室内岩相学观察及地质年代学分析和年龄解释等多个环节。在这些环节中,识别火山灰夹层是最关键的一点,也是一大难点。这需要明确火山灰夹层的岩石类型并了解火山事件沉积层的分布,在此基础上通过野外观察和室内研究进一步判别,这样可以更加准确地识别出火山灰夹层。此外,火山灰锆石定年需要区分火山灰锆石、碎屑锆石、继承/捕获锆石,可以通过矿物形态学和矿物化学特征来加以区分。     

The Jiangnan orogenic belt between the Yangtze and Cathaysia blocks for Neoproterozoic context

In recent years, more high quality zircon U-Pb ages have been obtained from Neoproterozoic strata in the South China continental block. A refined chronostratigraphic framework is being set up on these data. A basis of the high quality chronostratigraphic system is fundamental for global Precambrian study and strata correlation. Our recent geological studies focus on systematic SHRIMP zircon dating. We will refine the chronostratigraphic framework of the Neoproterozoic and the start time of the cover beds of the Shuangqiaoshan Group basing on the new SHRIMP zircon ages from the volcanic ash beds in the Hengyong and Anlelin formations. Accordingly, we will also discuss Neoproterozoic tectonostratigraphy in South China     

The role of dispersed ash in orbital-scale time-series studies of explosive arc volcanism: insights from IODP Hole U1437B,Northwest Pacific Ocean

ABSTRACT

Tephra fallout beds in marine sediments provide chronologically precise and highly resolved records of volcanism at time scales relevant to Quaternary climate cycles. While the record of discrete (visible) thin tephra beds is readily accessible, the significance of the dispersed (invisible) tephra record remains unclear. Here we evaluate the role of dispersed tephra for orbital-scale volcanic time variations in the Quaternary (<1.2 Ma) carbonate mud of IODP Hole U1437B (Northwest Pacific). The carbonate mud contains cyclic series of discrete fallout tephra beds from the oceanic Izu Bonin (~85% of tephra beds) and the continental Japan (~15%) volcanic arcs, respectively. Our results show the inorganic aluminosilicate (lithogenic) fraction is a mixture of dispersed Izu Bonin and Japan ash, and Asian dust. The time distribution of the Izu Bonin ash with its distinct composition appears to confirm and enhance the cyclic time variation of the discrete ash beds at Hole U1437B. Dispersed Japan ash resembles Asian dust in trace elements and is only distinguishable in Sr-Nd isotope space. Collectively, our results confirm the existence of periodic, orbital-scale fluctuations of arc volcanic frequency. Orbital-scale time variations of marine ash may be best established by series of discrete marine ash beds, yet the concomitant dispersed ash flux must also be recorded in order to understand the total flux of arc volcanic ash into the ocean basins and thus the role of the volcanism-climate link.     

Facies analyses and volcanic setting of the giant Neves Corvo massive sulfide deposit,Iberian Pyrite Belt,Portugal

In the Iberian Pyrite Belt, volcanic rocks are relatively scarce, accounting for approximately only 25% of the geologic record, with the remaining 75% consisting of sedimentary units. This association is very clear in the host succession to the Neves Corvo massive sulfide deposit in Portugal. The Neves Corvo host succession comprises the products of explosive and effusive rhyolitic eruptions intercalated with mudstone that records a submarine below-wave-base environment and provides precise biostratigraphic age constraints. The first and second volcanic events involved eruptions at local intrabasinal vents. The first event generated thick beds of fiamme breccia that are late Famennian in age. The fiamme were originally pumice clasts produced by explosive eruptions and were subsequently compacted. The second event was the late Strunian (latest Famennian) effusion of rhyolitic lava that was pervasively quench-fragmented. The third and final event is younger than the massive sulfide deposits poorly represented in the mine area and minor compared with the two other events. The integration of biostratigraphic data with the volcanic facies architecture indicates that the Neves Corvo ore deposits are similar in age to the late Strunian rhyolitic lava. Although regionally the Iberian Pyrite Belt is essentially a sedimentary succession, ore formation at Neves Corvo can be closely linked to discrete volcanic events that produced a relatively narrow range of volcanic facies.     

试论地层学的新体系与建立新一代年代地层表

全球层型剖面和点（ＧＳＳＰ）应尽可能在层序界面的整合部位,从而将地层的自然界线、层 ＧＳＳＰ有机地结合起来,使年代地层界线可在野外识别和追索,层序地层可以做为岩石地层和年代地层的而独立存在,构成新的三重地层分类,地层界线的优化应尽可能与层序界面相结合,以使其具有更强的可损伤性,随着层序地层学的发展及其在地层学和概念上取得了的创新和突破,有在新的地层学体系指导下建立新一代年代地层表,从而更加客观地反     

华南二叠－三叠系的事件地层与生物地层界线

华南二叠－三叠系界线研究应严格区分事件地层界线与生物地层界线。“界线粘土”层的底界即为事件地层界线。生物地层界线定义不能与“混生层”或“过渡层”的概念连在一起。长兴煤山忠心大队剖面是最好的二叠－三叠系全球界线层型剖面点（ＧＳＳＰ）。二叠－三叠系生物地层界线定义为ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,其位置就在长兴剖面界线层（混生层）２的内部,比事件地层界线高１５ｃｍ。ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,即为长兴阶的顶界。     

华南二叠－三叠系的事件地层与生物地层界线

华南二叠－三叠系界线研究应严格区分事件地层界线与生物地层界线。“界线粘土”层的底界即为事件地层界线。生物地层界线定义不能与“混生层”或“过渡层”的概念连在一起。长兴煤山忠心大队剖面是最好的二叠－三叠系全球界线层型剖面点（ＧＳＳＰ）。二叠－三叠系生物地层界线定义为ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,其位置就在长兴剖面界线层（混生层）２的内部,比事件地层界线高１５ｃｍ。ＨｉｎｄｅｏｄｕｓｐａｒｖｕｓＭｏｒｐｈｏｔｙｐｅ１的首次出现,即为长兴阶的顶界。     

New Early Triassic ammonoid faunas from the Dienerian/Smithian boundary beds at the Induan/Olenekian GSSP candidate at Mud (Spiti,Northern India)

New collections at the Induan/Olenekian boundary GSSP candidate at Mud (Himachal Pradesh, Northern India) lead to the recognition of several well preserved ammonoid faunas that significantly improve the biostratigraphic resolution in the beds underlying the proposed GSSP level. In ascending order, the new biostratigraphical sequence comprises: the Ambites lilangense beds, the Fuchsites markhami beds, the Kingites lens beds, the Prionolobus rotundatus beds, the Flemingites bhargavai beds, the Kashmiritidae gen. nov. A beds and the Vercherites cf. pulchrum beds. The faunas from Bed 10, located about 1 m below the proposed GSSP level, contain certain ammonoids with typical early Smithian affinity (Flemingitidae, Kashmiritidae) and thus reflect the beginning of the early Smithian evolutionary radiation. Seen from an evolutionary point of view, the Dienerian/Smithian boundary can therefore be placed just below Bed 10. Ideally, the stage boundary should also be intercalibrated with other biological, chemical or physical proxies as additional tools for world-wide correlations.Four new species (Flemingites bhargavai, Kingites korni, ?Kingites parkashi and Xenodiscoides variocostatus) and two new genera (Mudiceras, Vercherites) are described.     

羌塘地块南部晚白垩世火山岩离子探针测年及其对红层时代的约束

羌塘地块南部广泛出露陆相红层,1:25万区域地质调查将大部分红层划归为中新统康托组,但缺乏可靠的年代学依据。野外观测发现火山岩与红层之间存在喷发不整合接触关系,室内从火山岩选出很多岩浆锆石;应用离子探针U-Pb同位素测年方法精确测定岩浆锆石年龄,能够为研究火山喷发期次和红层形成时代提供重要依据。对羌塘地块南部红层内部粗面安山岩夹层—比洛错火山岩和扎加藏布北侧红层上覆安山岩,挑选岩浆锆石进行高精度的离子探针U-Pb同位素测年,发现比洛错粗面安山岩锆石206Pb/238U同位素年龄为(83.3±1.3)Ma,扎加藏布北侧安山岩锆石206Pb/238U同位素年龄为(75.65±0.82)Ma。这些年龄良好地揭示了晚白垩世不同期次的火山喷发时代,同时为红层形成时代和红层盆地演化提供了重要的年代学约束。根据比洛错和扎加藏布北侧火山岩的锆石U-Pb同位素测年资料,将羌塘盆地南部红层时代归属上白垩统阿布山组,这对分析羌塘地块南部油气地质构造保存条件和构造地貌演化具有重要意义。     

三叠纪年代地层与生物复苏

二叠纪末大灭绝之后，三叠纪初残存期和复苏期生态系研究成为当今热点。这也是2005年5月在安徽巢湖召开的“三叠纪年代地层与生物复苏国际学术会议”上的主导论题。逐一介绍了会议学术报告的主题内容，以期提炼相关领域的学术关键和学科发展趋向。学术主题之一是早三叠世年代地层格架，尤其是印度阶―奥伦尼克阶界线层型；第二是二叠纪―三叠纪之交灭绝和环境事件的表现形式和过程；第三是二叠纪―三叠纪之交及早三叠世微生物岩及其代表的特殊生态系；第四是灭绝事件后三叠纪初一些关键生物类别的演变历程；第五是中生代初生态系复苏过程和型式；第六是早三叠世生物迟滞复苏的原因。     

40Ar/39Ar ages and geochemical characterization of Cretaceous bentonites in the Nanushuk,Seabee, Tuluvak,and Schrader Bluff formations,North Slope,Alaska

Diagenetically altered volcanic ash deposits (bentonites) found in Cretaceous terrestrial and marine foreland basin sediments have the potential to be used for chronostratigraphy and subsurface correlation across Alaska's North Slope. Detailed age and geochemical studies of these volcanogenic deposits may also shed light on the tectonic evolution of the Arctic. Though these bentonites have been previously studied, there are few published results for regional bentonite ages and geochemistry due to challenges of dating weathered volcanic ash. We analyzed mineral separates from cored bentonites recovered from wells in the National Petroleum Reserve Alaska. The analyses confirm that an intense period of volcanic ash deposition on Alaska's North Slope began by the late Albian and persisted throughout the Cenomanian, an interval of rapid progradation and aggradation in the Colville basin. These results also add to a sparse record of radioisotopic ages from the Nanushuk Formation. A bentonite preserved in delta plain sediments in the upper Nanushuk Formation dates to 102.6 ± 1.5 Ma (late Albian), while a bentonite near the base of the overlying Seabee Formation was deposited at 98.2 ± 0.8 Ma, in the early Cenomanian. The two ages bracket a major flooding surface at the base of the Seabee Formation near Umiat, Alaska, placing it near the Albian-Cenomanian boundary (100.5 Ma). Several hundred feet up-section, the non-marine Tuluvak Formation contains bentonites with ⁴⁰Ar/³⁹Ar ages of 96.7 ± 0.7 to 94.2 ± 0.9 Ma (Cenomanian), several million years older than previously published K–Ar ages and biostratigraphic constraints suggest.Major and trace element geochemistry of a sub-sample of six bentonites from petroleum exploration wells at Umiat show a range in composition from andesite to rhyolite, with a continental arc source. The bentonites become more felsic from the late Albian (∼102 Ma) to late Cenomanian (∼94 Ma). A likely source for the bentonites is the Okhotsk-Chukotka Volcanic Belt (OCVB) of eastern Siberia, a continental arc which became active in the Albian and experienced episodes of effusivity throughout the Late Cretaceous. Chronostratigraphically anomalous ⁴⁰Ar/³⁹Ar ages coincide with peaks of magmatic activity in the OCVB, suggesting that these anomalously old ages may be due to magmatic contribution of xenocrysts or recycling of detrital minerals from older volcanic events. An alternative explanation for the chronostratigraphically anomalous ages is mixing of bentonites with detrital sediment derived from unroofing and erosion of metamorphic rocks in the Brooks Range, Herald Arch, and Chukotka throughout the mid to Late Cretaceous.     

内蒙古东部霍林河盆地霍林河组的年龄:来自锆石U-Pb测年和孢粉组合的证据

内蒙古东部霍林河盆地霍林河组是我国最重要的下白垩统含煤地层之一.该组产出大量不同种类且保存完好的植物化石,但因为缺乏海相沉积和火山岩夹层,我们对这套地层的精确年龄认知不足.我们最近在扎鲁特旗扎哈淖尔露天煤矿霍林河组发现了火山灰层,基于钻孔数据的地层分析显示该火山灰层位于霍林河组下含煤段的底部.二次离子质谱(SIMS)锆...     

第三纪年代地层研究和中国第三纪年代地层表

主要介绍国际上第三纪年代地层和年代学研究最新简况 ,显示几个重要的年代地层表或年代表 ,并报道全国地层委员会 1999年 12月断代专业组工作会议关于建立中国年代地层表中第三纪年代地层构架讨论的初步方案。     

安徽巢湖地区下三叠统牙形石生物地层分带及其全球对比

安徽巢湖地区早三叠世处于下扬子碳酸盐岩缓坡较深水区域,地层序列完整、清晰,各类化石是区域乃至全球最为丰富、序列最为完整的,是研究国际早三叠世年代地层最经典地区之一．对安徽巢湖平顶山西坡剖面、平顶山北坡剖面、马家山南剖面系统采样和精细的牙形石生物地层研究结果表明,下三叠统至少可以划分为8个牙形石带,建立了在华南具有代表性的下三叠统牙形石生物地层序列,自下而上为（1）Hindeodus typicalis带;（2）Neogondolella krystyni-Neogondolella planata带;（3）Neospathodus kummeli带;（4）Neospathodus dieneri带;（5）Neospathodus iaageni带;（6）Neospathodus pingdingshanensis带;（7）Neospathodus homeri带;（8）Neospathodus anhuinensis带．并与世界其他地区同期地层进行精确对比,为建立下三叠统印度阶与奥伦尼克阶界线的全球层型（GSSP）提供可靠依据．