国际泥盆-石炭系界线研究介绍

泥盆—石炭系界线问题的争论旷日持久,问题复杂。究其根源在于泥盆系(Murchison ＆ Sedgwick,1842)和石炭系(Congbeare ＆ Phillips,1842)最初确立在英国的不同地区。由于英国地层出露较差,结果导致在法、比海西褶皱带建立了两个系的各个阶,并且又一次将法门阶和杜内阶确定在不同的地区。从1927年第一届国际石炭系会议至今,石炭系之下界问题仍未圆满解决,下界的定义已经多次修订。本文仅择其讨论要点作一概略介绍。     

海南岛泥盆—石炭系界线研究

通过对新建立的海南岛上泥盆统昌江组及其下石炭统南好组多重地层的综合研究,并以首次发现的南好组底部的河流相砾岩和砂砾岩为标志,指出海南岛在泥盆纪末期曾发生大规模海退事件,这恰好与泥盆纪—石炭纪之交的全球海平面下降事件完全一致。不仅确认了昌江组与南好组为平行不整合接触关系,而且两者以Ⅰ型层序界面相隔分别构成2个三级层序,因而认为海南岛泥盆—石炭纪年代地层界线已与层序界面重合为一个共同的分界面——平行不整合面。     

中国南方泥盆—石炭系界线年龄

以贵州大坡上剖面和广西南边村剖面为基础,介绍了我国泥盆—石炭系界线年龄研究现状。桂林南边村剖面属于斜坡相重力流沉积,牙形类的演化序列有些混乱。虽然前人将泥盆—石炭系界线定在‘56层’与‘57层’之间,但这些 ‘层’号实际上是牙形类采样号。‘55层’—‘58层’是一层介壳灰岩,采集了4个牙形类样品。研究认为,将泥盆—石炭系界线置于该层介壳灰岩内不正确,在理论上也不科学,不能将介壳灰岩中的腕足类化石一分为二,即个体的下部属于晚泥盆世,上部属于早石炭世。用于测年的样品采自‘58层’和‘66层’,明显高于剖面中牙形类Siphonodella sulcata出现的层位,很显然,获得的（361.0±4.1）Ma界线年龄值不可信。贵州大坡上剖面属于深水盆地相沉积,也是我国唯一既产出Wocklumeria动物群又产出Gattendorfia动物群的剖面。刘永清等（2012）在王佑组底部2～4 cm厚的含凝灰岩黑色页岩中采集了1件凝灰岩测年样品,获得了1个锆石U-Pb测定年龄（359.6±1.9）Ma,该年龄值非常接近但又老于国际地层委员会2020年公布的（358.9±0.4）Ma的界线年龄值,表面看来,该年龄值基本可信,也是可接受的,但其误差较大、精度较差,需再次采样加以验证。研究认为,国际地层委员会公布的界线年龄值（358.9±0.4）Ma是可以接受的,而且泥盆纪末期事件层的年龄值在360.0～361.0 Ma区间同样也是可接受的。     

桂林不同沉积相泥盆—石炭系界线

桂林地区海相泥盆—石炭系发育,剖面露头连续,具有不同沉积相和不同生物群的泥盆—石炭系界线剖面,可与国内外同类剖面对比.本文对国际泥盆—石炭系界线辅助层型——桂林南边村剖面等作了介绍,依据牙形刺、菊石、有孔虫、介形类、腕足类、珊瑚等多门类化石的地质分布,以及生物事件、岩石（沉积）事件,对泥盆—石炭系界线作了探讨,为不同沉积相和生物群的泥盆—石炭系界线的划分和对比提供了较丰富的资料。     

黔南早石炭世牙形石及泥盆－石炭系界线

本文根据早石炭世牙形石、珊瑚、腕足等化石的对比研究,认为贵州独山及睦化一带的泥盆－石炭系界线应划在革老河组底部,主要依据如下：（１）者王组的牙形石Ｂｉｓｐａｔｈｏｄｕｓａｃｕｌｅａｔｕｓ,Ｂ．ａｎｔｅｐｏｓｉｃｏｒｎｉｓ,最早出现在晚泥盆末期的Ｗｏｃｋｌｕｍｅｒｉａ带内;（２）者王组中Ａｃｔｉｎｏｓｔｒｏｍａ,Ｐｓｅｕｄｏｌｅｂｅｃｈｉａ,Ｓｔｒｏｍａｔｏｅｅｒｉｕｍ等层孔虫的一些属种,与西欧晚泥盆世艾特隆层的分子极为相近;（３）革老河组产腕足,珊瑚、牙形石等,与上覆汤耙组的一些属种,具有密切的演化关系,但与其下伏者王组的属种却存在很大差异。因此,作者提出将泥盆－石炭系的分界线,置于革老河组Ｃｙｓｔｏｐｈｒｅｎｔｉｓ－ｃｏｍｐｓｉｔｅ－Ｓｈｕｃｈｅｒｔｅｌｌａ组合带之底部。     

黔南早石炭世牙形石及泥盆—石炭系界线

本文根据早石炭世牙形石，珊瑚，腕足等化石的对比研究，认为贵州独山及睦化一带的泥盆－石炭系界线应划在革老河组底部，主要依据如下：（１）者王组的牙形石Ｂｉｓｐａｔｈｏｄｕｓ ａｃｕｌｅａｔｕｓ，Ｂ．ａｎｔｅｐｏｓｉｃｏｒｎｉｓ，最早出现在晚泥盆示＝期的Ｗｏｃｋｌｕｍｅｒｉａ带内；（２）者王组中Ａｃｔｉｎｏｓｔｒｏｍａ，Ｐｓｅｕｄｏｌｅｂｅｃｈｉａ，Ｓｔｒｏｍａｔｏｅｅｒｉｕｍ等层孔虫的一些属种，与西欧     

西准噶尔洪古勒楞组及泥盆-石炭系界线

<正> 新疆西准噶尔和布克赛尔蒙古自治县的沙尔布尔提山一带,上泥盆统发育,其下部称朱鲁木特组,为陆相地层,上部为洪古勒楞组,下石炭统称为黑山头组。洪古勒楞组建于1979年(曾亚参、肖世禄1979,侯鸿飞等1979)。1985年笔者重测洪古勒楞组的命名剖面,发现它可能位于向斜构造上,地层有重复,缺失与石炭系接触的上部地层;此外发现三个泥盆—石炭系的连续剖面。     

贵州长顺睦化泥盆—石炭系界线研究取得重大突破——介绍大坡上泥盆—石炭系界线剖面

自1979年以来,我国先后有两条剖面被列为国际泥盆—石炭系界线层型侯选剖面,这就是贵州长顺睦化剖面和广西桂林南边村剖面。在1987年北京召开的第十一届国际石炭纪地层和地质大会期间,国际泥盆—石炭系界线工作组主席Eva paproth代表工作组分别对我国的两条侯选剖面作了评论。她说,睦化剖面是一条十分重要的剖面,沉积连续,化石丰富,不仅具有世界上最为完整     

据珊瑚化石讨论华南泥盆,石炭系界线

华南岩关阶Ceriphyllum-Caninophyllum patulum组合带、Cystophyentis延限带和Pseudouralinia延限带代表3个不同层位的珊瑚动物群特征。本文据珊瑚及其与共生牙形石的关系,并结合与欧、美有关地层对比,我们主张前一组合带或邵东组划归下石炭统。     

华南泥盆系－石炭系界线附近的珊瑚、有孔虫和牙形类及其地层意义

华南地区岩关阶依皱纹珊瑚可分为Ｃｅｒｉｐｈｙｌｌｕｍ－Ｃａｎｉｎｏｐｈｙｌｌｕｍｐａｔｕｌｕｍ（Ｇ－Ｃ）组合带、Ｃｙｓｔｏｐｈｙｒｅｎｔｉｓ（Ｃ）延限带和Ｐｓｅｕｄｏｕｒａｌｉｎｉａ（Ｐ）延限带及相应的有孔虫带和牙形类带（表１）。与法国一比利时盆地、英国和俄罗斯奥莫朗地区有关生物地层相比,Ｃ－Ｃ组合带与法一比盆地的ＲＣ１间隔带下部和英国的Ｋｍ－Ｋ１亚带大致相当;Ｃ延限带与ＲＣ１间隔带上部至ＲＣ２间隔带下部和英国的Ｋ２－Ｚ１亚带对比;Ｐ延限带与ＲＣ２间隔带上部至ＲＣ３奥佩尔带和英国的Ｚ方亚带至γ层对比。若以Ｐ延限带或所谓的＂Ｃ－Ｐ间隔带＂做为中国石炭系与泥盆系的分界标志,则石炭系的底界过于偏高。笔者认为Ｃ－Ｃ组合带或邵东组属于早石炭世地层。     

The Huohua Section: a new Devonian-Carboniferous boundary section The Huohua section: a new Devonian-Carboniferous boundary section of deep-water facies in Ziyun County, Guizhou Province, China

This paper introduces a new section of the Devonian-Carboniferous boundary in Huohua area, Ziyun County, Guizhou Province, South China. The Huohua section of Upper Devonian and Lower Carboniferous is well-outcropped along a new countryside road. In this section, the D-C boundary beds can be grouped into three litho-units: the Daihua Formation, the Changshun Shale and the "Wangyou Formation", from which more than 30 conodont samples were collected and processed. According to our current study, some important conodonts in the Daihua Formation and the Changshun Shale have been recognized, such as Palmatolepis tenuipunctata, Pa. glabra, Pa. marginifera, Pa. gracilis, Polygnathus vogesi and Polygnathus purus purus. A few conodonts have been found from the Wangyou Formation, such as Polygnathus communis and Hindeodella subtilis. Based on the comparison with the Muhua section in Changshun county and the Hasselbachtal section in Germany in lithology, sedimentology and conodont biostratigraphy, the D-C boundary could be temporarily placed between Bed 25 and Bed 26, namely between the Changshun Shale and the Wangyou Formation.     

The Jurassic/Cretaceous boundary in northern Siberia and Boreal-Tethyan correlation of the boundary beds

There is no international consensus regarding the GSSP for the Berriasian, the basal stage of the Cretaceous System. Any of the events discussed by the international expert community can be regarded as a marker of the Jurassic/Cretaceous boundary: a phylogenetic change of taxa, paleomagnetic reversal, or isotopic excursion. However, the problem of identification of this level in Boreal sections can be solved only using a combination of data obtained by paleontological and nonpaleontological methods of stratigraphy (bio-, chemo-, magnetostratigraphy, etc.). With any of the accepted markers, the Jurassic/Cretaceous boundary in Siberian sections will be within the upper part of the regional Bazhenovo Horizon. The least interval of the uncertainty of the position of this boundary in Siberian sections will be ensured by the selection of one of two markers: biostratigraphic (base of the Pseudosubplanites grandis Subzone) or magnetostratigraphic (base of the M18r magnetozone).     

Biotic characteristics of the Sinian-Cambrian boundary beds in China and the boundary problems

There is general agreement that the first appearance of various small shelly fossils should be used to help delineate the beginning of the Cambrian Period. The history of research on this stratigraphic topic in China is briefly outlined and leads on to a discussion of the boundary problem in the light of information available both inside and outside China.The sections across the Precambrian—Cambrian (Sinian—Cambrian) boundary are described with notes on fossils in: (1) Tianzhushan section, Yichang, Hubei; (2) Maidiping section, Emli, Sichuan; (3) Wangjiawan section, Jinning County, Yunnan; and (4) Kunyang section, Yunnan.This is followed by a consideration of the biotic characteristics of Sinian—Cambrian Period. The history of research on this stratigraphic topic in China is briefly outlined and leads on to a discussion of the boundary problem in the light of information available both inside and outside China. This is followed by a consideration of the biotic characteristics of Sinian—Cambrian boundary beds, with respect to stratigraphy as well as organic evolution. The Precambrian—Cambrian boundary in China is estimated to have an age of 615 ± 20 Ma.It is commented that the above sections are qualified to be important candidates for the selection of the Sinian—Cambrian boundary stratotype and are also important working reference sections for the international Precambrian—Cambrian boundary stratotype.     

The Upper Devonian Kellwasser event recorded in a regressive sequence from inner shelf to lagoonal pond,Catalan Coastal Ranges,Spain

This study, conducted in the Catalan Coastal Ranges, north‐east Spain, describes the Upper Devonian Kellwasser event in a shallowing‐upward sequence of black shales, siltstones and quartz arenites. This sequence was deposited in a progradational and regressive coastal system where the sedimentary environment evolved from the inner shelf to a lagoonal pond located landward of the shoreline. Three anomalous succeeding steps have been identified by geochemical analysis. The first one, detected on the inner shelf, was characterized by oxygen depletion and high organic productivity. The second, detected in the nearshore, was caused by hydrothermal activity occurring under normal oxic conditions. The third and most intense step was identified in the muds of the lagoonal pond and has been linked to strong anoxic conditions, elevated clastic input derived from changes in the weathering regime at the source area and moderate hydrothermal activity. The Kellwasser event is thus defined in the study area as stepwise and multi‐causal. This is the first time that the Kellwasser event has been identified in a sedimentary environment behind the shoreline. It is also the first time that it has been reported in the Catalan Coastal Ranges.     

Metallogenesis of Devonian—Carboniferous Strata—bound Carbonate—type Uranium Deposits in South China

This paper deais with the geological conditions.mineralization characteristics,genetic types and space-time distribution of the Devonian-Carboniferous strata-bound carbonate-type uranium deposits in South China.These ore deposits are genetically classified as the leaching type and the leaching-hydrothermal superimposed type,These ore deposits are confined mainly to the strata (D2-3,C1)of platform-lagoon carbonate facies.Unique tectonic settings are a vital factor leading to the formation of these uranium deposits.A metallogenetic model for these uranium deposits has been proposed.     

Facies changes and diagenetic processes across the Permian–Triassic boundary event horizon, Great Bank of Guizhou, South China: a controversy of erosion and dissolution

The Permian–Triassic boundary interval in shallow shelf seas of South China shows Upper Permian limestones overlain by lowermost Triassic microbialites. Global sea‐level rose across the Permian–Triassic boundary, but an irregular top‐Permian erosion surface across a 10 km north–south transect of the Great Bank of Guizhou contains evidence of sea‐level fluctuation. The surface represents the ‘event horizon’ of mass extinction, below the biostratigraphic Permian–Triassic boundary defined by first appearance datum of conodont Hindeodus parvus. An Upper Permian foraminiferal grainstone beneath this surface contains geopetal sediments, etched grains, and pendent and meniscus cements interpreted here as vadose. However, these latter diagenetic processes occurred before the event horizon and were followed by erosion of the final Permian surface. This erosion cuts previous fabrics but lacks evidence of weathering or bioerosion. A few centimetres below is an earlier grainstone that was also eroded but lacks proof of sub‐aerial processes. Samples therefore reveal one, or possibly two, small‐scale relative sea‐level changes before the Triassic transgression in this area, and these may relate to local tectonics. The final Permian surface is subject to at least four interpretations: (i) sub‐aerial physical erosion and dissolution by carbon dioxide‐enriched fresh water or carbon dioxide‐enriched mixed water, prior to Triassic transgression; (ii) sub‐aerial physical erosion overprinted by dissolution related to carbon dioxide‐enriched sea water in the Early Triassic transgression; (iii) submarine dissolution affected by acidified sea water due to rapid increase in volcanically‐derived carbon dioxide and oxidized methane released from marine clathrates; (iv) submarine dissolution due to acid anoxic waters rising across the continental shelf, unrelated to atmospheric carbon dioxide or oxidized methane. Field and petrographic evidence suggests that (i) is the simplest option; and it is possible that (ii) and (iii) occurred, but none are proved. Option (iv) is unlikely given the evidence and modelling of supersaturation of upwelled waters with respect to bicarbonate.     

南海礼乐盆地新生代构造层序界面特征及油气地质意义

礼乐盆地是中国南海深水领域一个重要的含油气盆地,具有较好的油气资源前景。应用沉积学和层序地层学的原理和方法,结合区域构造演化特征,详细研究了礼乐盆地新生代沉积充填过程中关键构造层序界面（S100、S70、S50）在钻井岩性、测井曲线、古生物及地震剖面上的特征。结果表明,构造层序界面为岩性、电性的突变面,在构造层序界面附近,古生物演化过程中存在标志生物种属和数量的突变。在地震剖面上,构造层序界面是区域性的不整合界面,表现为明显的上超、下超或削截特征。进而详细论述了这3个构造层序界面形成的油气地质意义,具体表现为：（1）反映了关键时期礼乐盆地性质的转化;（2）有利于形成优质储集空间;（3）层序不整合面既是油气横向长距离运移的重要通道,也是礼乐盆地油气藏成藏的关键。