西准噶尔克拉赛勒克山和布克河组晚泥盆世化石的发现及其地层归属

西准噶尔地区广泛分布的和布克河组已被证明是洪古勒楞组的晚出异名,本文在西准噶尔克拉赛勒克山原划为下石炭统"和布克河组"的碎屑岩地层中发现了丰富的动、植物化石,包括:三叶虫Phacops sp.,菊石Manticoceras sp.,腕足类Tylothyris sp.,Aulacella sp.,"Mucrospirifer"sp.,Cyrtospirifer sp.,植物Leptophloeum rhombicum,Syringodendron sp.,Knorria sp.,其时代显示为晚泥盆世。根据岩性组合特征将其厘定为上泥盆统铁列克提组,而非"和布克河组"的替代名称洪古勒楞组。通过区域地质调查工作,证明了西准噶尔玛依力山地层小区内没有洪古勒楞组的分布,其晚泥盆世地层仅由铁列克提组组成,洪古勒楞组只分布在沙尔布尔提山地层小区,两个地层小区的界线为孟布拉克北侧至谢米斯台山南坡的深大断裂。晚泥盆世两个地层小区沉积分异明显,直到早石炭世早期才进入统一的盆地演化阶段,地层小区的分区性也随之消失。     

New Devonian fossil localities in Bolivia

An examination of Palaeozoic sections west of Cochabamba, and west of Lake Poopó, in western Bolivia, was conducted during a field expedition in 1991. The Río Iglesiani valley, west of Cochabamba, surprisingly yielded a Middle Devonian age to all the visited sites, originally supposed to be Ordovician. This result is based on spores, shelly faunas (brachiopods and bivalves), and trilobites. The Copacabana de Andamarca section, west of Lake Poopó, is also dated as Middle Devonian on account of its rather rich fauna (bryozoans, corals, brachiopods, conulariids, hyolithids, tentaculitids, ostracodes, trilobites, crinoids, vertebrates). Both localities correlate to the Icla and/or Huamampampa Formation of the Tarabuco area and Subandean belt, and to the Belén and/or Sica Sica Formation of the northern Altiplano.     

贵州平塘甘寨剖面二叠系茅口组沉积特征与层序地层

本文应用沉积学手段对贵州平塘甘寨剖面中二叠统茅口组进行详细的沉积特征和层序地层的研究。研究结果显示,茅口组主要的岩石类型有亮晶-微晶生屑灰岩、生物灰岩、微晶灰岩、亮晶内碎屑灰岩、硅质岩、瘤状灰岩和含燧石灰岩等,茅口组生物种类有介形虫、腹足、腕足、三叶虫、藻类、棘屑、蜒、珊瑚、海百合茎等。岩石学特征和生物组合指示,平塘甘寨地区中二叠统茅口组为开阔碳酸盐台地沉积环境,包括台内滩和滩间两个亚相。茅口组可划分出3个Ⅲ级层序PSQ1、PSQ2和PSQ3,均由海侵体系域（TST）与高水位体系域（HST）两部分组成。层序发育受到了海平面升降变化控制,层序之间的界面P2q/PSQ1、PSQ1/PSQ2、PSQ2/PSQ3皆为岩性-岩相转换面,层序界面P3l/PSQ3在茅口末期受到东吴运动的影响,为构造不整合面。     

Climate instability and tipping points in the Late Devonian: Detection of the Hangenberg Event in an open oceanic island arc in the Central Asian Orogenic Belt

Sedimentary petrology and trace element geochemistry indicate that the Late Devonian to Early Carboniferous Heishantou Formation near Boulongour Reservoir (NW Xinjiang, China) was deposited on a steep slope, mid-latitude accreting island arc complex in an open oceanic system. Bulk ⁸⁷Sr/⁸⁶Sr ratios show excursion patterns that are consistent with excursions at the Devonian–Carboniferous (D–C) boundary in epicontinental margin sediments. Sedimentation rates for the Boulongour Reservoir sediments show highly variable rates that range from 0.5 cm/ky to 10 cm/ky, consistent with other Late Devonian sections and modern arc environments. Multiple whole rock geochemical proxies for anoxia and the size and distribution of pyrite framboids suggest the presence of the Hangenberg Event in the sediments associated with the D–C boundary, despite the lack of visible black shale. The presence of anoxia in an open ocean, island arc environment cannot be explained by upwelling of anoxic bottom waters at this paleolatitude, but can be explained by the global infliction of oceanic shallow water eutrophication on to a climate system in distress.     

Trilobites,scolecodonts and fish remains occurrence and the depositional paleoenvironment of the upper Monte Alegre and lower Itaituba formations,Lower – Middle Pennsylvanian of the Amazonas Basin,Brazil

This study aims to characterize the scolecodonts, trilobite pygidium fragments and fish remains of an outcropped region in the southern Amazonas Basin, comprising the uppermost section of the Monte Alegre Formation and the basal section of the Itaituba Formation. These, correspond to part of the marine portion of the Tapajós Group, related to an intracratonic carbonate platform. The Monte Alegre Formation includes a deposition of fluvial-deltaic and aeolian sandstones, siltstones and shales of interdunes and lakes, intercalated with transgressive carbonates of a shallow restrict nearshore marine environment. The Itaituba Formation comprises a thickest deposit of marine carbonates, representing the establishment of widespread marine conditions, and is the richest interval containing organisms of shallow marine environment in the Pennsylvanian of the Amazonas Basin. The associated fauna includes brachiopods, bivalves, gastropods, crinoids, echinoids, bryozoans, corals, foraminifers, sponges, ostracods, trilobites, scolecodonts, fish remains and conodonts, mainly in the packstones, and subordinately in the wackestones and mudstones. Conodonts Neognathodus atokaensis, Diplognathodus orphanus, Idiognathodus incurvus, and foraminifers Millerella extensa, Millerella pressa, Millerella marblensis, Eostaffella ampla, Eostaffella pinguis and Eostaffella advena characterizes a predominant Atokan age to the analyzed profile. The fossil association herein presented is taxonomically diversified and biologically interesting, comprising an important and well preserved, for the first time occurrence of two molds and two fragments of Proetida trilobites. Well preserved Eunicida and Phyllodocida scolecodonts and paleonisciform fish remains. These fossils help in the paleoenvironmental establishment of the studied interval in the Amazonas Basin and as a potential biostratigraphic and paleoecological tool to correlate regionally and globally the Pennsylvanian.     

南秦岭淅川地区上石炭统周营组生物群特征

南秦岭淅川地区上石炭统周营组有多门类化石共生 ,类为晚石炭世的标准分子 ,菊石、腕足、珊瑚、双壳、腹足类多具泥盆纪生物群特征。岩石组合、岩性特征、层序特征、沉积环境演变及构造古地理、生态的综合研究表明 ,周营组为晚石炭世沉积地层 ,其内的晚石炭世、中晚泥盆世古生物组合是在有障壁的局限滞留盆地这一特殊的古地理和生态环境下形成和发展起来的 ,是南秦岭淅川地区特有的组合 ,不具有搬运再沉积的物质条件 ,不是搬运再沉积的结果。每一次海侵 ,海水的加深和有机质的富集 ,是周营组生物群得以发生和发展的有利条件。海水的退出、咸化和相对闭塞环境下食物的缺乏 ,是生物群绝灭 ,并很好保存埋藏的主要原因。     

Paleomagnetism of the late Cryogenian Nantuo Formation and paleogeographic implications for the South China Block

A new paleomagnetic pole position is obtained from the well-dated (636.3 ± 4.9 Ma) Nantuo Formation in the Guzhang section, western Hunan Province, and the correlative Long’e section in eastern Guizhou Province, South China. Remagnetization of the recent geomagnetic field was identified and removed for both sections. The hard dual-polarity, interpreted as primary, component of the Nantuo Formation, directs east–westward with medium inclinations, yielding an average pole of 9.3°N, 165°E, A₉₅ = 4.3° that, for the first time, passed a strata-bound reversals test. The new data are consistent with previously published paleomagnetic data of the Nantuo Formation from Malong county, central Yunnan Province, which passed a positive syn-sedimentary fold test. Together, these sites represent shallow- to deep-water sections across a shelf-to-basin transect centered at ∼33° paleolatitude. The sedimentary basin may have faced an expansive ocean toward the paleo-East. In the ∼750 Ma and ∼635 Ma global reconstructions, the South China Block (SCB) was best fitted in the northern hemisphere close to northwestern Australia. However, a direct SCB-northwestern Australia connection, inferred to have existed during the Early Cambrian–Early Devonian, had not formed by the time of ∼635 Ma.     

华南栖霞组灰岩-泥灰岩韵律层的成因

华南中二叠统栖霞组沉积了一套特殊的碳酸盐岩地层, 该套地层富含有机质和硅质结核, 是中国南方四套区域性海相烃源岩之一.在野外露头上, 灰岩-泥灰岩韵律层因为其抗风化能力不同而受到广泛关注, 其在整个华南栖霞组分布广泛.其中, 灰岩层富含各种生物碎屑, 主要包括钙藻、有孔虫和腹足, 其次还有腕足, 棘皮类和介形虫, 偶尔见苔藓虫和三叶虫.灰岩层中较好的保存了易碎的钙质藻类, 说明灰岩的胶结作用发生在成岩早期, 没有明显压实作用的痕迹.泥灰岩以粒泥生物碎屑灰岩和黑色钙质泥岩为主, 主要的生物碎屑以腕足和介形虫为主.生物碎屑都非常破碎, 壳体大都平行层面, 颗粒之间发育大量压溶缝, 说明泥灰岩层经历过强烈的成岩压实作用.基于对灰岩-泥灰岩韵律层的生屑类型和成岩现象的分析, 提出差异成岩作用来解释该套地层的形成过程: 泥灰岩层中不稳定的文石在早期成岩过程中溶蚀, 然后迁移到灰岩层中形成方解石胶结灰岩层; 随后机械压实作用和化学压实作用主要发生在泥灰岩层中; 最终灰岩-泥灰岩层由于差异成岩作用导致其抗风化能力不同而形成不同的露头特征.其中文石溶蚀发生在海水埋藏环境, 有机质的分解为其提供了动力来源, 这与栖霞期较高的原始生产力相符合.      

四川盆地东部涪陵地区上二叠统长兴组顶部风化壳特征及地质意义

四川盆地东部(文中简称“川东”)上二叠统长兴组近顶部非礁相地层尚未见暴露剥蚀现象的报道。文中以川东涪陵地区二龙口长兴组顶部非礁相地层剖面为例,综合宏微观特征、矿物学特征及地球化学特征等分析发现,在长兴组顶部存在厚3～7cm、垂向分带特征清晰的风化壳,自下而上可分为4层:泥晶生屑灰岩构成的基岩、微风化层、以富硅脱钙为特征的半风化层(由下至上分为3个微层:致密的半风化层、具晕圈的铁质夹层和疏松多孔的半风化层)和以富铁为特征的全风化层(由下至上分为3个微层:橙红色富铁质层、杂色纹层状黏土层、红色富铁质表层)。风化壳中黏土矿物几乎全是伊利石,未见到强风化阶段的次生矿物如高岭石、三水铝石,氧化铁矿物富集,总体体现出中等风化的特征,对应于风化壳演化的富铁锰阶段。进一步分析发现,该风化壳之上的飞仙关组底部存在厚约80cm的泥页岩与灰岩韵律地层,并富含珊瑚、腕足类(欧姆贝)、苔藓虫及三叶虫等原位埋藏的典型二叠系宏体生物化石,反映了研究区在二叠纪末期曾发生抬升暴露;同时研究区长兴组野外露头和钻井岩心均发育较多垂直溶沟、溶洞等岩溶组构,并为离解的碳酸盐岩砂、角砾和碳质泥等混合充填,说明川东地区长兴组非礁相地层受到了表生岩溶的改造。川东地区二叠纪末期的海退事件不仅使台地区海水变浅,甚至长时间的大面积暴露,而且使长兴组碳酸盐岩普遍受到表生岩溶改造,甚至非礁相地层也可能被改造成为岩溶型储集层。这一结果不仅对二叠纪晚期海平面升降事件研究具有借鉴意义,而且指出了台地内受到表生岩溶改造的非礁相地层也可作为勘探有利区带,因而具有重要的勘探实践意义。     

The status and local stratigraphical context of the Hampen Formation type section (Bathonian,Middle Jurassic)

The type section of the Hampen Formation, as currently defined, is located near Salperton (Gloucestershire); it comprises beds of Middle Jurassic (Bathonian) age. Its validity as a type section is questioned; only the uppermost 2.3 m are herein considered truly to represent the Hampen Formation. The underlying 7.4 m are re-defined as a facies variant of the Througham Formation, for which the name Daglingworth Member is proposed. A review of the local stratigraphical context clarifies the relationship of the Hampen Formation, as newly defined, and of the Daglingworth Member, to contiguous stratigraphical units.     

Isotopic analysis of belemnites and brachiopods from the Cretaceous (Albian) Hunstanton Red Chalk Formation (Hunstanton,Norfolk, UK)

Cretaceous brachiopods (Moutonithyris dutempleana) and belemnites (Neohibolites minimus) from the (Albian) Hunstanton Red Chalk Formation (Hunstanton, UK) were isotopically analysed with the aim of identifying palaeoecological and palaeotemperature trends. Shell preservation was assessed via thin section petrography and geochemical analyses. Oxygen isotopic compositions (and corresponding temperature interpretations) of well-preserved belemnites are similar in comparison to the brachiopod shells. Assuming calcite precipitation in isotopic equilibrium, they are interpreted to have occupied the same or similar warm (15–19 °C) shallow marine environment. Further, these findings indicate that the belemnites mineralised in relatively warm waters and not in deep and cool waters as suggested for some belemnite species. The isotope data are thus inconsistent with the belemnites being associated with a cool water pulse, contrasting with events associated with the Cenomanian chalks. A difference δ¹³C between the belemnites and brachiopods is interpreted to originate from differences in metabolic rates.     

Biogenic and abiogenic low-Mg calcite (bLMC and aLMC): Evaluation of seawater-REE composition,water masses and carbonate diagenesis

The ΣREE and shale-normalized (PAAS) REE_SN values of modern brachiopods (biogenic low-Mg calcite: bLMC) represented by several species from high- to low latitudes, from shallow- to deep waters and from warm- and cold-water environments, define three distinct average ‘seawater’ trends. The warm- and cold-water brachiopods define two indistinguishable (p < 0.050) groups that mimic open-ocean seawater REE chemistry, exhibiting the typical LREE enrichment with a slightly positive to negative Ce anomaly followed by an otherwise invariant series. Other recent brachiopods from an essentially siliciclastic seabed environment are distinct in both ΣREE and REE_SN trends from the previous two populations, showing a slight enrichment in the MREEs and an increasing trend in the HREEs. Other groups of modern brachiopods are characterized by elevated REE_SN trends relative to the ‘normal’ groups as well as by complexity of the series trends. The most characteristic feature is the decrease in the HREEs in these brachiopods from areas of unusual productivity (i.e., such as upwelling currents, fluvial input and aerosol dust deposition). Preserved brachiopods from the Eocene and Silurian exhibit REE_SN trends and Ce anomalies similar to that of the ‘open-ocean’ modern brachiopods, although, their enriched ΣREE concentrations suggest precipitation of bLMC influenced by extrinsic environmental conditions.Preservation of the bLMC was tested by comparing the ΣREE and REE_SN trends of preserved Eocene brachiopods to those of Oligocene brachiopods that were altered in an open diagenetic system in the presence of phreatic meteoric-water. The altered bLMC is enriched by approximately one order of magnitude in both ΣREE and REE_SN trends relative to that in bLMC of their preserved counterparts. Similarly, the ΣREE and REE_SN of preserved Silurian brachiopod bLMC were compared to those of their enclosing altered lime mudstone, which exhibits features of partly closed system, phreatic meteoric-water diagenesis. Despite these differences in the diagenetic alteration systems and processes, the ΣREEs and REE_SN trends of the bLMC of altered brachiopods and of originally mixed mineralogy lime mudstones (now diagenetic low-Mg calcite) are enriched by about one order of magnitude relative to those observed in the coeval and preserved bLMC.In contrast to the changes in ΣREE and REE_SN of carbonates exposed to phreatic meteoric-water diagenesis, are the REE compositions of late burial calcite cements precipitated in diagenetically open systems from burial fluids. The ΣREE and REE_SN trends of the burial cements mimic those of their host lime mudstone, with all showing slight LREE enrichment and slight HREE depletion, exhibiting a ‘chevron’ pattern of the REE_SN trends. The overall enrichment or depletion of the cement REE_SN trends relative to that of their respective host rock material reflects not only the openness of the diagenetic system, but also strong differences in the elemental and REE compositions of the burial fluids. Evaluation of the (Ce/Ce*)_SN and La = (Pr/Pr*)_SN anomalies suggests precipitation of the burial calcite cements essentially in equilibrium with their source fluids.     

西准噶尔俄姆哈剖面泥盆纪-石炭纪之交介形类的发现及其意义

为进一步丰富新疆西准噶尔地区泥盆纪-石炭纪(D-C)之交古生物地层资料,为研究区泥盆和石炭系划分、古环境重建提供新的证据,经野外采样、室内处理等工作,首次报道了西准噶尔俄姆哈地区D-C之交介形类9属12种(包括1新种):Cavellina sublatiovata, C.cf.obesa, C.sp., Glyptopleura sp., Healdianella renalata, H.sp., Bairdiocypris vafra, Bairdia sp., Rectobairdia sp., Fabalicypris sp., Youngiella calvata, Coelonella xizhunensis sp.nov..根据介形类生物地层,并参照共生的其他门类化石,认为西准噶尔俄姆哈剖面至少在第3层就进入了早石炭世,进一步证明了洪古勒楞组的时代应该是晚泥盆世-早石炭世.介形类的古生态研究表明,西准噶尔俄姆哈地区是火山岛弧区在火山间歇期的近岸浅水沉积环境.      

鄂西—湘西北地区二叠纪栖霞期岩相古地理

对鄂西—湘西北地区多个沉积剖面的地层及沉积相进行了详细分析,结果表明,该区二叠纪栖霞期至茅口初期主要为内克拉通碳酸盐岩缓坡环境,发育内缓坡相、中缓坡相、外缓坡相和盆地相.内缓坡相以厚层至块状生物碎屑石灰岩为主,生物颗粒以绿藻和底栖有孔虫为主,缺乏高能沉积的生物颗粒.中缓坡相以中厚层含生物碎屑颗粒石灰岩以及厚层灰泥石灰岩...     

滇西亲冈瓦纳相生物群特征及地层时代的重新厘定

滇西保山地区丁家寨组及其上覆卧牛寺组,前人根据其中(虫筳)类化石定为上石炭统(马平阶),沿用至今。笔者在该区多门类化石中,见到不同时代的化石混积在一起,包括异地再沉积的早石炭世腕足类Syringothyris,石炭纪的(虫筳)类、珊瑚等。原地埋藏的腕足类有Steriochia litostyla等,并保存有完好的壳刺。厘定后的时代为Sakmarian晚期至Artinskian,它可与西藏的冈瓦纳相地层及生物群进行对比。 滇西腾冲地区空树河组及其上覆的岩子坡组,前人因其含(虫筳)Triticites,Quasifusulina等也定为上石炭统。实际上,空树河组中、上部的多门类化石(包括腕足类、苔藓虫、单体珊瑚和微古植物等),与丁家寨组相似,具有强烈的二叠纪面貌,与冈瓦纳相更为接近。厘定空树河组时代为Sakmarian—Chihsian,它与西藏的相应地层可以很好地进行对比。     

西藏北部永珠地区石炭系永珠组岩石地层和古生物特征

永珠地区位于申扎古生代盆地,区内发育连续的早奥陶世—中二叠世海相沉积序列。石炭系永珠组岩石组合特征为细粒石英砂岩、页岩、粉砂岩,夹多层生物碎屑灰岩,含丰富的生物化石,主要有腕足类、双壳类、牙形刺、珊瑚、苔藓虫、菊石、三叶虫。牙形刺Gnathodusgirtyi—Gnathodustexanus为早石炭世晚期组合;腕足类Productus—Rhipidomellatibetena为早石炭世晚期组合,Choristites—Spirigerella为晚石炭世早期下部组合,Trigonatretacf.paucicostulata—Elivellabaschkirica为晚石炭世早期上部组合。Uncinunellina是典型的冷水习性腕足类,Cyathaxonia是典型的冷水习性珊瑚,表明了全球石炭纪冰期已影响到本区。确定了永珠组的时代为早石炭世晚期—晚石炭世早期,且早石炭世与晚石炭世分界线在第11层与第12层之间。     

New Precambrian palaeomagnetic constraints on the position of the North China Block in Rodinia

We report new palaeomagnetic results from a ca. 1300 to 800 Ma continental shelf succession on the southern margin of the North China Block. A total of 386 oriented core samples were subjected to stepwise demagnetisation. Two overprint components (‘A’ and ‘B’) were identified, with ‘A’ being a Recent geomagnetic field component and ‘B’ a likely Mesozoic remagnetisation related to collision of the North and South China Blocks. An interpreted primary remanence was isolated from six rock units. The most reliable results are as follow, in the order of stratigraphic ascendance. (1) Purple mudstone, muddy sandstone and andesite of the lower Yunmenshan Formation (Rb–Sr age ca. 1270 Ma) yields a high-temperature component that passes both reversal and fold tests and gives a palaeopole at (60.6°S, 87.0°E, A₉₅ = 3.7°). (2) Mudstone in the overlying Baicaoping Formation yields a high-temperature component with a palaeopole at (43.0°S, 143.8°E, A₉₅ = 11.1°). (3) Purple sandstone of the earliest Neoproterozoic Cuizhuang and Sanjiaotang Formations exhibits a high-temperature component that provides a palaeopole at (41.0°S, 44.8°E, A₉₅ = 11.3°). Based on both our new results and a critical selection of available palaeomagnetic data, we construct a preliminary apparent polar wander path (APWP) for the North China Block between 1300 and 510 Ma. Regardless of alternative polarity options applicable to these poles, North China was located within equatorial latitudes for much of this interval. Comparing the North China poles with coeval poles from Laurentia suggests that the two continents were situated on the same plate between 1200 and 700 Ma. North China was thus likely part of the supercontinent Rodinia. Separation of North China and Laurentia occurred between 650 and 615 Ma.     

黔南坳陷平塘甘寨二叠系茅口组沉积相与储层特征分析

通过铸体薄片、物性测试、扫描电镜等资料,对黔南坳陷平塘甘寨二叠系茅口组沉积相与储层特征进行深入分析,认为贵州平塘甘寨茅口组主要的岩石类型为亮晶-微晶生屑灰岩、生物灰岩、微晶灰岩、内碎屑亮晶灰岩、硅质岩、瘤状灰岩和含燧石灰岩等。茅口组生物种类较多,有介形虫、腹足、腕足、三叶虫、藻类、棘屑、蜒、珊瑚、海百合茎等。上述岩石学特征和生物组合指示平塘甘寨地区中二叠统茅口组为开阔碳酸盐台地沉积环境,包括台内滩和滩间两个亚相。储层特征分析结果表明,茅口组储集空间以晶间溶孔和晶间孔为主,具有明显的低孔低渗特征。局部溶蚀孔、构造裂缝相对较发育,对改造储层的孔渗性有重要的贡献。储层类型为碳酸盐岩裂缝-孔隙型储层,储层质量及发育部位受沉积相、成岩作用和构造活动多因素的控制。     

Permian (Leonardian) brachiopods from Paso Hondo Formation,Chiapas, southern Mexico. Paleobiogeographical implications

One of the most important marine sequences of calcareous rocks from the Paleozoic of Mexico outcrops in southern Chiapas. It is composed by different units from Early Permian, being the Paso Hondo Formation the youngest with a Leonardian age. Different groups of marine invertebrates as corals, bivalves, gastropods, bryozoans, brachiopods and crinoids have been previously reported of this unit. Five brachiopod species of the orders Productida, Athyridida, Spiriferida and Spiriferinida from the Barrio Allende section of this unit are herein described. The new species Dyoros (Lissosia) maya and Hustedia shumardi are proposed. Sedimentology and paleoecology of the Paso Hondo Formation, suggest a well-lighted shallow lagoon environment with continuous terrigenous input. The subgenus Dyoros (Lissosia), the genus Paucispinifera and the species Hustedia shumardi, Spiriferella propria and Spiriferellina tricosa are typical taxa from Permian localities of Texas, New Mexico and Coahuila. Their presence in the studied area suggests that during Early Permian there was a geographic connection between the different localities of the biotic Grandian Province (southern USA, northern Mexico and Venezuela) and southeastern Chiapas.