中国二叠系[竹蜓]的属带与国际二叠系的阶

中国已建立的二叠系各阶的[竹蜓]的属带．对中国二叠系生物地层的研究曾起到重要的作用。由于二叠系的[竹蜓]的属带时限都很长,定义不明确和地方性较强,中国二叠系的阶不宜再用[竹蜓]的属带来确定。国际二叠系的主导化石门类是牙形刺,二叠系的3统9阶都是用牙形刺来确定的,而不是用[竹蜓],更不是用[竹蜓]的属带。进一步研究[竹蜓]类各属内的种一级的谱系演化关系,参照牙形刺带确认[竹蜓]的属种的时限,进行不同相区的对比,是今后二叠纪生物地层研究的重要任务。     

再论石炭-二叠系界线及古地磁学的证据

滇东南八宝附近的安乐剖面,是石炭-二叠系界线地层的典型剖面,沉积连续、单相、富含牙形刺、类、四射珊瑚和腕足类化石,以牙形刺Streptognathodus elongatus带之底作为二叠系的开始,Pseudoschwagerina uddeni带稍高于这一界线。我们建议石炭-二叠系界线必须建立在沉积连续、单相,化石类型多样、丰富的剖面上,为了尽可能接近假希瓦格亚科分子的始现界线,以牙形刺Streptognathldus elegantulus到St.elongatus演化系列中St.elongarus始现作为界线,这一界线大致相当于前苏联阿舍林阶的底界。古地磁学研究表明,该剖面的第3层底部,在长期的基亚曼极性段中存在着一个短暂的正极性亚带,它具有广泛的代表性,而且它与Streptognathodus elongatus的始现相一致,强烈支持上述生物界线作为石炭-二叠系界线。     

广东连阳煤田二叠纪牙形刺的发现及其意义

在广东连县－阳山煤田的二叠纪地层中首次采集到牙形刺化石计11属20种和3个未定种。通过与中国南方相应标准剖面对比，建立了4个组合带；茅口阶Neogondolella serrata-N.postserrata组合带，吴家坪阶中、下部Neogondolella liangshanensis组合带、吴家坪阶上部Neogondolella orientalis组合带，长兴阶Neogondalella changxingensis-N.subcarinada组合带。同时讨论了上统与下统、长兴阶与吴家坪阶、下三叠统与上二叠统的地层界线。     

扬子地台西缘志留系牙形刺研究新进展

笔者详细研究了扬子地台西缘宁蒗－盐边地区志留系岩石地层和牙形刺生物地层的特征，该岩系自下而上可建立3个牙形刺组合带：①Panderodus gracilis-Panderodus simplex组合带；②Pterospathodus celloni Walliser组合带；③Pterospathodus amorphognathoides Walliser组合带；从生物层学、沉积学和区域对比的角度对地层进行了重新划分，分析了Puetospathodus cellini Wal-liser带和Pterospathodus amorphognathoides Walliser带之间的相互重叠关系，并认为其相互关系为渐变演化关系，而不是突变关系；并对部健重要属种进行了措施。     

南非陆相二叠系-三叠系界线研究进展

从岩石地层研究着手,介绍了南非卡鲁盆地内综合地层研究的相关成果.在生物地层方面,脊椎动物和植物化石的研究在该区具有传统优势,孢粉化石的研究则是在最近几年才取得较大进展,在陆相界线地层研究中菌孢化石在二叠系-三叠系界线处约1 m厚的地层内的富集事件属首次报道.在地球化学地层方面,南非有机碳同位素在二叠系-三叠系界线附近的变化趋势与海相二叠系-三叠系界线地层存在相似的对应关系,可以作为海、陆相界线地层对比的辅助标志.在磁性地层方面,南非卡鲁盆地内的磁极性存在从反向到正向然后再反转(R-N-R)的变化,二叠系-三叠系界线则位于第一反向极性带的顶部.同时,结合目前全球陆相二叠系-三叠系界线的研究现状及特点,分析了陆相界线地层研究中存在的基本问题,指出华南地区可能为突破传统观念的研究地区,陆地事件地层研究意义重大.     

亚洲奥陶系牙形刺生物地层研究进展

牙形刺是奥陶纪地层划分的主导化石门类,目前已建立了可以全球对比的牙形刺生物化石带,但还缺乏对洲际尺度牙形刺生物带对比资料,特别缺乏精细年代控制的牙形刺生物地层资料。以研究程度较高的亚洲地区为例,梳理了亚洲内部奥陶纪牙形刺生物地层研究资料,初步建立了亚洲地区牙形刺生物地层对比格架,结合国际地质年表研究进展,提出了亚洲地区奥陶纪牙形刺研究需要解决的问题,即以目前执行的IGCP 652项目中国工作组研究任务为依托,开展我国鄂尔多斯西南缘奥陶系多重地层研究,有望获得高精度年代控制的奥陶纪牙形刺生物地层资料。     

下扬子区二叠系层序地层格架

针对研究区钻及二叠系的井甚少,现有的几条地震剖面质量欠佳的状况,采用露头层序地层学的方法在８条主干剖面、数十条辅助剖面详细研究的基础上将研究区二叠系划分为１１个Ⅲ级层序（栖霞阶为３个层序,茅口阶为３个层序,吴家坪阶为３个层序和长兴阶为２个层序）。以具区域性分布的生物化石带为主,辅以岩性组合、岩相特征、垂向相序特点及地质事件,对研究区二叠系进行详细区域层序对比,总结了二叠系层序特点。     

中国三叠纪牙形刺生物地层

<正> 三叠纪是牙形动物最后一个繁盛期,国际三叠纪牙形刺一般划分为22带(Sweet,1971),按Kozur(1980)将瑞替克阶划为2牙形刺带和 Orchard(1983)将诺利期的牙形刺划分为8带的方案,三叠纪牙形刺分带可达29带。国外三叠纪牙形刺以巴基斯坦盐岭地区、北美内华达、地中海沿岸、德国和澳大利亚等地研究的为好。下三叠统下部6     

湖北黄石二门二叠系/三叠系界线剖面长兴阶牙形刺分带及有机碳同位素的变化

湖北黄石二门二叠系/三叠系界线剖面出露完好,原始沉积连续,由乐平统龙潭组保安段灰黑色硅质岩、大隆组黑色硅质岩—硅质泥岩和下三叠统大冶组黑灰色泥岩以及泥岩夹灰岩组成,为介于典型浅水碳酸盐岩型与深海硅质岩型二叠系/三叠系界线剖面之间的半深海剖面。长兴阶可划分为Clarkinasubcarinata—Clarkinawangi及Clarkinachangxingensis两个牙形刺带。后者又可划分为3个亚带,自下而上依次为Clarkinachangxingensischangxingensis—Clarkinadeflecta亚带、Clarkinameishanensis亚带及Waning—Clarkina亚带,完全可以与二叠系/三叠系界线的全球层型剖面与点进行对比。另外,二叠纪末牙形刺的生态演化呈阶段性绝灭模式;有机碳同位素值在二叠纪/三叠系界线处出现明显的负偏移,指示了二叠纪/三叠纪之交生物绝灭后海水表层水原始产率的降低以及大气和海水中CO2含量的增加。     

三叠系的阶与牙形刺生物地层

三叠纪的3统7阶时限相差极大,晚三叠世的时限最长。牙形刺是三叠纪生物地层的主导化石门类,在生物地层划分中的作用越来越重要。中国三叠纪牙形刺生物地层的牙形刺带已达50带,还会增加,特别是在晚三叠世。阶是全球的地质年代单位,应全球统一,使用共同的名称和定义。不要按国别建阶,更不能按岩相或生物群建阶。陆相地层不适宜建阶,陆相地层的阶名也不宜再使用。     

Permian

Summary Late in the Carboniferous Period or early in the Permian ice covered much of Tasmania (Fig. 30b). The sub‐Permian surface had a relief of several thousand feet with particularly low areas near Wynyard and Point Hibbs and high areas near Cradle Mountain, Devonport, Deloraine, Wylds Crag and Ida Bay and a peninsula in eastern Tasmania (Fig. 30a).

The glaciers from an ice centre north‐west of Zeehan diverged about a higher area near Cradle Mountain. One tongue occupied a deep valley near Wynyard and a lobe fanned out south of the high area to occupy parts of northern and central Tasmania and to override some parts of the east coast peninsula.

West of Maydena the ice scoured shell beds and dumped the shell fragments in the till on the Styx Range. Thus the base of the ice may well have been below sea‐level. Carey and Ahmad (1961) suggested that the Wynyard Tillite was deposited below a “wet‐base” glacier. David (1908, p. 278) suggested deposition from “land ice in the form of a piedmont or of an ice‐sheet” but that near Wynyard the ice came down very close to, if not actually to, sea‐level. The extent of the glaciation and the distribution of erratics of western Tasmanian origin in eastern Tasmania make it seem likely that either a piedmont glacier or an ice‐sheet rather than mountain glaciation was involved.

Following retreat of the glaciers the sea covered the till, probably to a considerable depth, eustatic rise of sea‐level being much more rapid than isostatic readjustment.

The Quamby Group is underlain by or passes laterally into thin conglomerates and sandstones in a number of places, but most of the group appears to be of deep water, partially barred basin origin. Marine oil shales accumulated close to islands. Shallowing of the sea during deposition of the upper part of the Quamby Group seems to be indicated by the fauna and increasing sandiness in marginal areas. Instability in the source areas is shown by the presence of turbidity current deposits in the higher parts of the group. The Golden Valley Group, of Upper Sakmarian and perhaps Lower Artinskian age, was deposited in a shallower sea than the Quamby Group but the deposits are more extensive along the east coast peninsula and on the flanks of the Cradle Mountain island. This anomaly may be explained if the rate of deposition exceeded the rate of rise of sea‐level. The sediments of the Golden Valley Group became finer‐grained upwards in most parts of Tasmania probably indicating reduction in relief of the source area. Some instability is indicated by turbidity current deposits. Uplift of source areas in north‐western Tasmania early in Artinskian time resulted in the spreading of sand over the shallow silts of the Golden Valley Group onto the east coast peninsula and over the Cradle Mountain area. The sand formed a wide coastal plain containing lakes and swamps and the sea was restricted to a small gulf in southern Tasmania during the deposition of the lower part of the Mersey Group. During deposition of this group the sea rose once to form a long, narrow gulf extending as far north as Port Sorell and then retreated. This inundation resulted in the development of two cyclothems in many parts of Tasmania.

A little later in Lower Artinskian time the sea rose and covered most of Tasmania except perhaps the far north‐west. This wide transgression probably resulted from down‐warping as an eustatic rise in sea‐level would be expected to produce thickest deposition over the old gulf in southern Tasmania and along the axis of Mersey Group inundation but the zone of thickest Cascades Group crosses these at a high angle. During deposition of the Cascades Group marine life became very abundant in the shallow sea over which a few icebergs floated. During the Artinskian tectonic instability increased as shown by the increasing number of turbidites in the upper part of the Grange Mudstone and the lower part of the Malbina Formation. The sea became less extensive and the source areas in north‐western and north‐eastern Tasmania were uplifted. The zone of thickest deposition of the Malbina Formation trended north‐north‐westerly. The rapid succession of turbidity currents killed the benthonic fauna and it was only during deposition of the upper part of the formation possibly in Lower Kungurian time that life became abundant again in the Hobart area. The sea spread a little over the east coast peninsula and further instability is recorded in the Risdon Sandstone. The resulting turbidity currents killed the benthonic fauna and it never became properly established again in any part of Tasmania during the Permian. A wide shallow sea covered much of Tasmania and was bordered by low source areas during deposition of the Ferntree Group. The axis of greatest thickness had an almost meridional trend and lay west of that of the Malbina Formation. Late in the Permian, probably in the Tartarian, rejuvenation of the source areas, particularly in western Tasmania, and withdrawal of the sea, resulted in deposition of sands and carbonaceous silts of the Cygnet Coal Measures. The zone of greatest thickness was almost parallel to but west of that of the Ferntree Group.

The thickness of the Permian System and the sheet‐like character of many of the members and formations suggest shelf rather than geosynclinal deposition. The average rate of deposition was of the order of 1 ft. in ten thousand years (about 0–003 mm./annum). However, the sediments differ markedly from those on stable shelves in that many of them are poorly‐sorted. Some of the poor sorting may be attributed to deposition from drifting icebergs but some is due to tectonic instability.

Uplift and downwarping and movement of zones of maximum thickness have been deduced above and it is probable that the tectonic instability started as early as Lower Artinskian and it may have started during Sakmarian (upper part of Quamby Group). Maximum instability seems to have occurred in Middle or Upper Artinskian time (Malbina Formation) and it is probably significant that this was a time of considerable orogenic movement in New South Wales (part of the Hunter‐Bowen Orogeny, Osborne, 1950). Progressive westward movement of zones of maximum thickness of units in Upper Permian time seems to have occurred and this again is reminiscent of the situation at the time in New South Wales (Voisey, 1959, p. 201) but seems to have started later. Uplift and development of a major synclinal structure with a trend approximately north‐north‐westerly occurred late in Permian time.     

New Late Permian Therocephalian

A new primitive whaitsiid therocephalian, Moschowhaitsia vjuschkovi, is described from the Vyaznika deposits (Upper Tatarian, Upper Permian), Vladimir Province, U.S. S. R. Moschowhaitsia is distinguished from other members of the family Whaitsiidae by the retention of a large number of cheek teeth. In its palate the, new genus embodies a nice combination of the characteristics ordinarily used to distinguish between the whaitslid subfamilies Whaitsiinae and Moschorhininae, and is therefore assigned to a new subfamily, Moschowhaitsiinae, annectent between the two previously described subfamilies. The well-preserved, acid-prepared skull reveals a number of features unexpected in a theriodont of otherwise generally primitive aspect. There is a well-developed secondary palate, a large parapineal body but no parietal foramen, evidence of turbinate bones in the nasal passage, and evidence of an expanded cerebral region in the rhinencephalon. The snout contains numerous passages for blood-vessels and nerves, and superficial pits that are interpreted as skin glands. These features are discussed briefly in terms of early evolution of a constant temperature physiology.—N. Hotton, III.     

Revision of the stratigraphy of Permian and supposed Permian rocks of Southern Scotland

The formal stratigraphy of the Permian basins of southern Scotland is described for the first time. These rocks consist of piedmont breccias and lavas, overlain by wadi-fan and dune complexes, and alluvial fan and floodplain sediments. The sequences are inferred to be Stephanian to Lower Permian in age and correlatable with similar continental sediments in England and with the Lower Rotliegendes of Germany and the North Sea.

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Zusammenfassung Erstmals wird hier eine stratigraphische Gliederung der permischen Beckensedimente im südlichen Schottland gegeben. Diese Gesteine bestehen aus Piedmont-Brekzien und Laven, die von Fanglomeraten und Dünenkomplexen überlagert werden. Alluviale Fächer und Schwemmflächen-Sedimente gehören hierzu. Diese Serien sollen ein Alter von Stephan bis Unter-Perm aufweisen und vergleichbar mit ähnlichen kontinentalen Sedimentfolgen in England und im Unter-Rotliegenden von Mitteleuropa sein.

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Résumé La stratigraphie des formations des bassins permiens du Sud de l'Ecosse est ici décrite pour la première fois. Ces roches sont des brèches de piedmont et des laves, surmontées par un complexe de dépôts d'épandage et de dunes, et par des cones et des dépôts alluviaux. Les couches seraient à rapporter au Stéphanien et au Permien inférieur, et à correler avec des sédiments continentaux semblables en Angleterre et avec le Rothliegend inférieur d'Allemagne et de la Mer du Nord.

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. Piedmont , . . - ; .

     

晚二叠世末的生物礁出露及其意义

贵州紫云长兴期生物礁礁前礁后和礁核的顶部都有白云岩。如下证据说明这种白云岩是潮上萨勃哈环境蒸发交代成因的：①这种白云岩的氧同位素值都比其灰岩原岩明显高得多，②其微量元素Sr、Fe的含量范围与陕甘宁盆地奥陶纪马家沟组马五段蒸发交代成因的泥晶白云岩的很相似，③白云石的晶体都是泥粉晶大小的自形—半自形晶体，④出现在礁体的顶部，⑤含有藻纹层、鸟眼构造、干裂缝等典型的潮坪环境构造。该礁的出露可能是海平面下降造成的。意大利的Dolomites盆地在二叠纪末由中陆架环境变浅到鲕粒滩环境，再到大气水环境。我国下扬子盆地在二叠纪末由碳酸盐补偿面以下的深水盆地变浅到碳酸盐补偿面以上的深水盆地。这些事实都说明，二叠纪末曾经发生全球性的海平面下降。这种大规模的海平面下降可能是引起二叠纪末生物礁集群绝灭的机制的表现之一。     

Permian ammonoids from Eastern Australia

Umbrella‐shaped objects, presumably fossils, were collected from the Lower Proterozoic Noltenius Formation at two localities about 80 miles south of Darwin. Radial and concentric forms are described morphologically, and their probable mode of origin is discussed.     

国际二叠纪年代地层划分新方案

国际二叠纪地层分会已就二叠系的统和阶的划分,命名及下界的层位达成统一意见,提出新的二叠系年代地层表,该表由３个最佳的区域性地层序列组成,即代表下二叠统的俄罗斯和哈萨克坦乌拉尔地区的乌拉尔统（ＣｉｓｕｒａｌｉａｎＳｅｒｉｅｓ）上二叠下部和上部的美国西南部的瓜德鲁普统（ＧｕａｄａｌｕｐｉａｎＳｅｒｉｅｓ）和中国华南地区的乐平统（ＬｏｐｉｎｇｉａｎＳｅｒｉｅｓ）。新表为建立二叠系内部界线的全球层型及点位     

二叠纪地层研究述评

近二十年来 ,全球和中国的二叠纪年代地层方案基本形成。层序地层、同位素年龄和磁性极性地层也获得系统的资料 ,所以国际二叠系对比的精度大为提高。不过年代地层单位的界线层型犹待厘定 ,还存在若干重要的对比问题。