燕山西段前寒武系雾迷山组叠层石的环境意义

叠层石广泛见于燕山西段前寒武系雾迷山组,文中将其分为六种类型:核形石、凝块石、层状叠层石、波状叠层石、锥状叠层石和柱状叠层石。叠层石形态的变化由前向后代表由低能向高能的环境转变,其中以层状叠层石在雾迷山组最为丰富。研究表明,在当时无捕食动物与钻孔动物存在的情况下,大多数叠层石发育于潮下带环境。层状和波状叠层石主要出现在潮下高能带的下部,少量见于受保护的潮间环境。潮下层状和波状叠层石以其色深、纹层密集、缺乏干裂收缩缝和窗格状组构区别于潮间带。锥柱状叠层石出现于潮间带和潮下高能带的上部;潮间带的锥柱状叠层石可能因暴露干裂而继承性地有壁,但潮下带的却可能没有。核形石和凝块石占据着泻湖和水下凹地(生物丘之间的低洼地或废弃潮汐沟道)等低能环境。燕山西段的叠层石罕见于潮上带和波基面之下的潮下低能带。     

The role of microbes in accretion, lamination and early lithification of modern marine stromatolites

For three billion years, before the Cambrian diversification of life, laminated carbonate build-ups called stromatolites were widespread in shallow marine seas. These ancient structures are generally thought to be microbial in origin and potentially preserve evidence of the Earth's earliest biosphere. Despite their evolutionary significance, little is known about stromatolite formation, especially the relative roles of microbial and environmental factors in stromatolite accretion. Here we show that growth of modern marine stromatolites represents a dynamic balance between sedimentation and intermittent lithification of cyanobacterial mats. Periods of rapid sediment accretion, during which stromatolite surfaces are dominated by pioneer communities of gliding filamentous cyanobacteria, alternate with hiatal intervals. These discontinuities in sedimentation are characterized by development of surface films of exopolymer and subsequent heterotrophic bacterial decomposition, forming thin crusts of microcrystalline carbonate. During prolonged hiatal periods, climax communities develop, which include endolithic coccoid cyanobacteria. These coccoids modify the sediment, forming thicker lithified laminae. Preservation of lithified layers at depth creates millimetre-scale lamination. This simple model of modern marine stromatolite growth may be applicable to ancient stromatolites.     

Using the fossil record to estimate the age of the last common ancestor of extant primates

Divergence times estimated from molecular data often considerably predate the earliest known fossil representatives of the groups studied. For the order Primates, molecular data calibrated with various external fossil dates uniformly suggest a mid-Cretaceous divergence from other placental mammals, some 90 million years (Myr) ago, whereas the oldest known fossil primates are from the basal Eocene epoch (54-55 Myr ago). The common ancestor of primates should be earlier than the oldest known fossils, but adequate quantification is needed to interpret possible discrepancies between molecular and palaeontological estimates. Here we present a new statistical method, based on an estimate of species preservation derived from a model of the diversification pattern, that suggests a Cretaceous last common ancestor of primates, approximately 81.5 Myr ago, close to the initial divergence time inferred from molecular data. It also suggests that no more than 7% of all primate species that have ever existed are known from fossils. The approach unites all the available palaeontological methods of timing evolutionary events: the fossil record, extant species and clade diversification models.     

淮南地区新元古代刘老碑组叠层石消失原因初探

安徽淮南地区新元古代刘老碑组主要由页岩和中薄层泥质、粉砂质灰岩组成。在该组上部中薄层砂质灰岩中产有该地区新元古代最古老的叠层石Baicalia和?Linella。大量的臼齿碳酸盐脉体穿插在该组叠层石的基本层中的现象较为独特,该组上部发育的滑塌构造和臼齿碳酸盐岩脉体的特征表明该沉积时期发生过强烈的地震活动;此外,在叠层石礁体周围还有大量的风暴沉积产出。这些现象表明,该组叠层石发育于风暴活动和地震活动交织的环境之中,地震活动是导致该组叠层石消失的主要原因。     

Stratigraphic,chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash,Ethiopia

Clarifying the geographic, environmental and behavioural contexts in which the emergence of anatomically modern Homo sapiens occurred has proved difficult, particularly because Africa lacked adequate geochronological, palaeontological and archaeological evidence. The discovery of anatomically modern Homo sapiens fossils at Herto, Ethiopia, changes this. Here we report on stratigraphically associated Late Middle Pleistocene artefacts and fossils from fluvial and lake margin sandstones of the Upper Herto Member of the Bouri Formation, Middle Awash, Afar Rift, Ethiopia. The fossils and artefacts are dated between 160,000 and 154,000 years ago by precise age determinations using the 40Ar/39Ar method. The archaeological assemblages contain elements of both Acheulean and Middle Stone Age technocomplexes. Associated faunal remains indicate repeated, systematic butchery of hippopotamus carcasses. Contemporary adult and juvenile Homo sapiens fossil crania manifest bone modifications indicative of deliberate mortuary practices.     

银根—额济纳旗盆地白垩纪地层、古生物群和古环境研究

利用盆地周缘露头、盆内钻井资料系统总结了银根—额济纳旗盆地白垩纪的地层、古生物特征,探讨了白垩纪的古环境.白垩系划分为下统巴音戈壁组、苏红图组及银根组,上统乌兰苏海组.地层特征盆地各区差异明显,巴音戈壁组北、东部以含烃源岩,西南部以不含烃源岩为特征;苏红图组西部以不含火山岩系和含煤层,东部以含火山岩系为特征.白垩系地层中发育介形类、双壳类、叶肢介、轮藻、藻类、腹足类、鱼类、昆虫、古植物和孢粉等多门类古生物化石.白垩纪可分为早白垩世的暖温带—亚热带干湿交替过渡性气候和晚白垩世的亚热带—热带半干旱—干旱气候.     

Post-Jurassic mammal-like reptile from the Palaeocene.

Mammal-like reptiles of the order Therapsida document the emergence of mammals from more primitive synapsids and are of unique zoological and palaeontological interest on that account. Therapsids, first appearing in the Early Permian, were thought to become extinct in the Middle Jurassic, soon after the Late Triassic origin of mammals. Here, however, we report the discovery of a therapsid from the late Palaeocene, 100 million years younger than the youngest previous occurrence of the order. This discovery nearly doubles the stratigraphic range of therapsids and furnishes their first record from the Cenozoic. The documenting fossils, an incomplete dentary containing three teeth, and four isolated teeth from other, conspecific individuals (Fig. 1), are from the Paskapoo Formation, at Cochrane, Alberta, Canada, from beds yielding a diverse mammalian fauna of early Tiffanian age. These specimens are catalogued in the collections of the University of Alberta Laboratory for Vertebrate Paleontology (UALVP) and provide the basis for a new taxon, as named and described below: (see text)     

Model of carbon fixation in microbial mats from 3,500 Myr ago to the present

Biological carbon fixation is an important part of global carbon cycling and ecology. Fixation that took place 3,500 million years ago is recorded in the laminated sedimentary rock structures known as stromatolites, which are fossilized remains of microbial mat communities. Stromatolites are the most abundant type of fossil found in the Proterozoic (2,500 to 590 Myr ago), but they then declined, possibly because of predation and competition. Using modern microbial mats as analogues for ancient stromatolites, we show that the rate of carbon fixation is higher at the greater levels of atmospheric CO2 that were probably present in the past. We suggest that carbon fixation in microbial mats was not carbon-limited during the early Precambrian, but became carbon-limited as the supply of inorganic carbon decreased. Carbon limitation led to a lower rate of carbon fixation, especially towards the end of the Precambrian. Thus, another reason for the decline of the stromatolites could have been a decrease in available CO2.     

湖北兴山中寒武统覃家庙群微生物岩及其古环境意义

通过野外考察及对岩石光面的观察,发现湖北兴山古洞口剖面中寒武统覃家庙群微生物岩的类型主要为波状-半球状叠层石,少量为凝块石。显微镜下观察发现叠层石及凝块石中保存有蓝绿菌类丝状微生物Girvanella,依据Girvanella丝状体在微生物岩中的赋存状态,认为覃家庙群的微生物岩是由底栖微生物群落的钙化和粘结、捕获等共同作用形成的。此外,古洞口剖面中寒武统微生物岩的宏观形态和巨型构造及其伴生的碳酸岩沉积相,指示其形成环境位于深潮下带和浅潮下带。通过对比研究,发现扬子地块表现出的中寒武世微生物岩再繁盛现象具有全球性,推测后生动物的匮乏或衰退是其主要控制因子,反映了生物礁结构由元古代的叠层石礁演变为显生宙的后生生物礁的重要转折。     

Virtual three dimensions reconstruction and isoline analysis of human marks on the surface of animal fossils

Animal fossils in archaeological sites are closely related to human activities. The environment and human activities, such as hunting-selection, cook process, traditional culture and habits can be partly inferred from the variety of fauna, fragmentation of the bones, and the human marks on bones’ sur-faces. So far, researches about marks on fossils are few in China, and are mainly observed directly by eyes. Light Microscopes and Scanning Electron Microscopes are also applied to the observation abroad. These...     

Silurian brachiopods with soft-tissue preservation

'Articulated' rhynchonelliformean brachiopods are abundant shelly fossils, but the direct fossil record of their soft parts was hitherto confined to a single pyritized trace possibly representing a lophophore. Anatomical knowledge of extinct rhynchonelliformeans relies heavily on analogies to extant species; these analogies are untested for stem-group clades. The Silurian Herefordshire (UK) Konservat-Lagerst?tte (about 425 Myr bp) yields exceptionally preserved three-dimensional fossils that provide unrivalled insights into the palaeobiology of a variety of invertebrates. The fossils are preserved as calcitic void in-fills in carbonate concretions within a volcaniclastic horizon, and are reconstructed digitally. Here we describe a stem-group rhynchonelliformean specimen from this deposit; it most probably belongs in the order Orthida. A robust ridged pedicle with distal rootlets is preserved, together with a lophophore and other soft-tissue structures. The pedicle morphology is novel, urging caution in inferring stem-group rhynchonelliformean anatomy from that of crown-group species. Smaller brachiopods are attached to the specimen; these include a probable atrypide, with pedicle and marginal setae preserved.     

Modern freshwater microbialite analogues for ancient dendritic reef structures

Microbialites are organosedimentary structures that can be constructed by a variety of metabolically distinct taxa. Consequently, microbialite structures abound in the fossil record, although the exact nature of the biogeochemical processes that produced them is often unknown. One such class of ancient calcareous structures, Epiphyton and Girvanella, appear in great abundance during the Early Cambrian. Together with Archeocyathids, stromatolites and thrombolites, they formed major Cambrian reef belts. To a large extent, Middle to Late Cambrian reefs are similar to Precambrian reefs, with the exception that the latter, including terminal Proterozoic reefs, do not contain Epiphyton or Girvanella. Here we report the discovery in Pavilion Lake, British Columbia, Canada, of a distinctive assemblage of freshwater calcite microbialites, some of which display microstructures similar to the fabrics displayed by Epiphyton and Girvanella. The morphologies of the modern microbialites vary with depth, and dendritic microstructures of the deep water (> 30 m) mounds indicate that they may be modern analogues for the ancient calcareous structures. These microbialites thus provide an opportunity to study the biogeochemical interactions that produce fabrics similar to those of some enigmatic Early Cambrian reef structures.     

塔里木盆地库车坳陷侏罗系恰克马克组叠层石及其环境意义

详细研究了库车坳陷卡普沙良河剖面恰克马克组叠层石的形态及内部构造、微量元素、氧碳同位素特征。指出该叠层石的形成环境为咸水湖盆。从恰克马克组沉积为湖盆扩张期这一事实出发，认为叠层石的发育与干盐湖无关，而可以作为海泛存在的证据。     

Occurrence of Sciadopitys-like fossil wood （Coniferales） in the Jurassic of western Liaoning and its evolutionary implications

The genus Sciadopitys, containing a single species (S. verticillata), is the only extant representative of the Family Sciadopityaceae (Coniferales), and is a remarkable living fossil. Although some leafy fossils have been ascribed to Sciadopityaceae, fossil xylem material with a close affinity to this family is very rare, and there have been no fossils found showing both pith and primary xylem structures, which are of great importance for wood identification. Thus, it has been difficult to use fossils for the understanding of wood anatomy evolution in the sciadopityaceous plants over geological time. In this note we briefly report on Sciadopitys-like fossil wood found in the Middle Jurassic of western Liaoning, which bears well-preserved Protosciadopityoxylon-type secondary xylem, endarch primary xylem and heterogeneous pith. This is the first report of fossil specimens of the Sciadopityaceae with such detailed preservation of wood structures. The discovery provides precise anatomical evidence for reconstructing the evolu- tionary history and geographical distribution of Sciadopityaceae, as well as contributing to understanding of the fossil diversity of the Jurassic Yanliao Flora in northern China.     

Discovery of the budding phosphatized globular fossils from the Neoproterozoic Doushantuo Formation at Weng’an, Guizhou Province, China

There is much debate on biological affinities of the phosphatized globular fossils from the Neoproterozoic Doushantuo phosphorites at Weng’an, Guizhou Province. Here we report for the first time the budding structures of some of these globular fossils, which have previously been interpreted as the resting eggs and early cleavage embryos of metazoans. The budding structures are similar to the germinating tubes of the spore and zygote of living algae, suggesting that some globular fossils from the Doushantuo phosphorites bear affinity with algae. The present new information indicated various biological affinity of the phosphatized globular fossils from the Doushantuo phosphorites.     

"寒武纪爆发"事件及其成因述评

主要后生动物门类化石在寒武纪初期的突然出现记录了生命史中一个从未有过的快速演化时期,这一事件被称为“寒武纪爆发(Cambrian explosion)”．多年来有关“寒武纪爆发”成因的各种猜测从未间断过．但是,将古生物化石记录看成是生物进化过程中种系形成的真实过程已遭到许多研究者的非议,这主要取决于以下二方面的证据：一是对早期后生动物系统发生关系的重新评估;二是来自于分子系统学和分子钟的研究．现在看来,“寒武纪爆发”事件的产生,一方面归因于化石体积的明显增加及其伴随的骨骼化过程,另一方面可能是其时的进化革新事件所导致．     

A record of Permian subaqueous vent activity in southeastern Brazil

The remarkable occurrence of more than 4,500 conical siliceous mounds in an area of less than 1.5 square kilometres has been reported in the Paraná basin, near Anhembi, S?o Paulo, in southeastern Brazil. These structures, which are up to two metres high, are thought to have been formed at the margin of a very shallow, broad but waning internal sea, and it was originally suggested that they are stromatolites. Yet their restricted occurrence, unusual abundance and nearly pure siliceous composition have never been satisfactorily explained by this hypothesis. Here we report field and laboratory observations on their shape, construction, composition and mineralogy. On the basis of our data we suggest that the conical mounds are the result of subaqueous Late Permian vent activity in southwestern Gondwana. The present siliceous cone field differs considerably from other Palaeozoic siliceous hot spring deposits, such as those at Rhynie, Scotland, and the Drummond basin, Australia, and therefore represents an unusual occurrence of vent activity.     

昆明二村早奥陶世遗迹化石

文章介绍了滇东地区下奥陶统红石岩组的层型剖面及汤池组下部首次发现的遗迹化石:Cruziana furcifera d' Orbigny, C. semiplicata Salter, C. rugosa minor Luo ichnosubsp. nov., Palaeophycus hongshiyanensis Luo ichnosp. nov.等。这些遗迹化石产于具波痕和斜层理的砂岩下层面上,为浅海潮下低能带的Cruziana遗迹相。     

An exceptionally preserved vermiform mollusc from the Silurian of England

Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerst?tte is a Silurian (about 425 Myr bp) deposit that preserves a marine biota in remarkable three-dimensional detail. The external surface of even non-biomineralized cuticle was preserved by entombment in volcanic ash, subsequent incorporation into concretions, and infilling of the fossils with sparry calcite. Here we describe, from this deposit, a complete vermiform mollusc, which we interpret as a plated aplacophoran. Serial grinding at intervals of tens of micrometres, combined with computer-based reconstruction methods, renders the fossils in the round.     

统计过程控制的研究现状及展望

回顾了统计过程控制的发展历史,介绍了统计过程控制的基本概念。将统计过程控制方法分为统计质量控制和统计性能监控两部分,统计质量控制包括单变量统计过程控制和基于统计回归的软测量技术,统计性能监控方法-包括主元分析、独立元分析等多变量投影技术以及统计控制图。最后指出非高斯过程、非线性过程、故障预报、故障诊断以及自适应算法的研究将是近期的发展趋势。