Early Cambrian Mollusc Watsonella crosbyi:A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2

The mollusc Watsonella crosbyi was studied on the basis of material from the lower Cambrian Dahai Member of the Zhujiaqing Formation in eastern Yunnan, China and the Pestrotsvet Formation of the Aldan River region in the Siberian Platform. This fossil had been excessively described under different names in the literature, such as Heraultia varensalensis Cobboid, 1935, H. sibirica Missarzhevsky, 1974, Heraultipegma yunnanensis He and Yang, 1982, H. yannanese He and Yang,1982, Watsonella yunnanensis, W. crosbyi Grabau, 1900, etc. Taxonomic revision shows that other species are junior synonyms of W. crosbyi. Analysis of functional morphology implies that W. crosbyi may be rather a heicionelloid than a rostroconch since its univalved conch is untorted endogastric and lacks a rostrum and a true internal pegma. Replicas of the original microstrnctures preserved on the surfaces of phosphatic internal moulds confirm that the shell consists of two layers. The inner layer is lamello-fibrillar, and the outer layer is spherulitic prismatic. The widespread geographical occurrences in both siliciclastic and carbonate rocks of the late Terreneuvian indicate that W. crosbyi is an important index fossil for global correlations and subdivision of the Cambrian Series I （Terreneuvian）.The first appearance datum （FAD） of W. crosbyi is suggested to be a potential GSSP （Global Boundary Stratotype Section and Point） candidate marker for defining the base of the Cambrian Stage 2.

Exploring the metamorphic consequences of secular change in the siliciclastic compositions of continental margins

Shale and greywacke compositions from the Archean to Phanerozoic record a secular change in the siliciclastic material that comprises much of Earth＇s continental margins, past and present. This study explores the metamorphic consequence of these compositional changes, by comparing phase equilibrium models constructed for average Archean, Proterozoic, and Phanerozoic shale and greywacke compositions equilibrated along two Barrovian-type geotherms： 1330℃/GPa（A） and 800 ℃/GPa（B）. Our models show that Archean siliciclastic rocks can retain up to 4 vol.% water at middle to lower crustal conditions, nearly twice that of Proterozoic and Phanerozoic compositions. The increased ferromagnesium content of Archean siliciclastic rocks stabilizes chlorite to higher temperatures and results in a biotite-rich assemblage at solidus temperatures. Accordingly, water-absent biotite dehydration melting is predicted to play a greater role in the generation of melt in the metamorphism of Archean aged units,and water-absent muscovite dehydration melting is of increasing importance through the Proterozoic and Phanerozoic. This secular variation in predicted mineral assemblages demonstrates the care with which metamorphic facies diagrams should be applied to Archean compositions. Moreover, secular changes in the composition of shale and greywacke is reflected in the evolution of anatectic melt towards an increasingly less viscous, Ca-rich, and Mg-poor monzogranite.

A brief history of the Rheic Ocean

The Rheic Ocean was one of the most important oceans of the Paleozoic Era. It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita- Alleghanian-Variscan orogen during the assembly of Pangea. Rifting began in the Cambrian as a continua- tion of Neoproterozoic orogenic activity and the ocean opened in the Early Ordovician with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana along the line of a former suture. The rapid rate of ocean opening suggests it was driven by slab pull in the outboard Iapetus Ocean. The ocean reached its greatest width with the closure of Iapetus and the accretion of the peri- Gondwanan arc terranes to Laurentia in the Silurian. Ocean closure began in the Devonian and continued through the Mississippian as Gondwana sutured to Laurussia to form Pangea. The ocean consequently plays a dominant role in the Appalachian-Ouachita orogeny of North America, in the basement geology of southern Europe, and in the Paleozoic sedimentary, structural and tectonothermal record from Middle America to the Middle East. Its closure brought the Paleozoic Era to an end.

The fossil record of durophagous predation in the James Ross Basin over the last 125 million years

We review the evidence for predation of shelly benthic prey over 125 million years of earth history in the James Ross Basin,Antarctica(~65°S).Although poor in the Early Cretaceous lower parts of the sequence,which represent essentially deeper water facies,evidence for both potential crushers and drillers becomes more apparent in the Santonian–Campanian Santa Marta Formation,and by the Maastrichtian López de Bertodano Formation there is an extensive fossil record of drill holes attributable to naticid gastropods,and some evidence of crushing by decapods crustaceans and possibly other taxa too.This continues at a similar level of intensity across the K/Pg boundary into the Danian Sobral Formation,but is less well constrained in the latest Paleocene–Early Eocene.The most extensive record of predation occurs in the Middle Eocene section of the La Meseta Formation on Seymour Island which also records the highest levels of benthic diversity within the entire basin.This key section is providing some important new evidence to suggest that the rate of acceleration of benthic predation intensity through the Late Mesozoic–Early Cenozoic in the polar regions may be similar to that seen in lower latitude regions.Predator–prey interaction was a key factor in the evolution of polar marine faunas too.

Manipulation of Crawling Growth for the Formation of Sub-millimeter Long ZnO Nanowalls

Vapor-phase growth of ZnO nanowires based on gold catalyst is usually accompanied with lateral crawling growth on the substrate surface. We present results from our systematic experiments where the growth temperature and catalyst size are controlled. The data corroborate that it is possible to obtain clean vertical nanowire arrays while avoiding the crawling growth. 0% the other hand, crawling growth can be manipulated to obtain root-interconnected nanowire arrays, which could be useful for certain applications. Our results also imply that the previously suggested growth mechanism for the wire-on-wall hybridstructure might be incorrect. Finally, we show the formation of sub-millimeter long, straight ZnO nanowalls by combining a gold-catalyzed epitaxial growth of vertical nanowires and their mergence due to a confined crawling growth. These unconventional nanostructures might have unique electric or optical transport properties.

The dynamic Archean to Paleoproterozoic crustal evolution of Brazil:Preface

Brazil is the largest country in South America and contains the majority of the exposed Archean and Paleoproterozoic crust on the continent. As such, Brazil provides a natural laboratory for studies of the ancient Earth. In this Special Issue, contributions reflect the dynamic and protracted growth and reworking of former continents during a time frame of over a billion years, and depict how changes across the evolution of plate tectonics may have influenced the evolution of the interlinked crust-ocean-atmospheric Earth cycles over this period.

Synthesis of carbon nitride in potassium hydroxide molten salt for efficient uranium extraction from radioactive wastewater

Photocatalysis-assisted removal of uranium has been proven as an effective method for the elimination of radioactive pollution from wastewater.In this work,carbon nitride materials were synthesized in potassium hydroxide(KOH)molten salt and applied to photocatalytic uranyl extraction.Obtained materials were confirmed to possess the triazine-s-heptazine structure by NMR,XPS and UV-Vis characterization,and exhibited a wider visible light absorption than graphitic carbon nitride(g-C_(3)N_(4)).The photocatalytic activity of the carbon nitride materials was tailored by varying the precursor mass fractions.The carbon nitride obtained at 80%melamine as precursor(K-CN-80)exhibited the highest photocatalytic extraction ability and its photocatalytic reaction rate is 6.6 times faster than that of g-C_(3)N_(4).The influence of sacrificial agents was studied and the results showed that triethanolamine inhibited U(Ⅵ)photoreduction,but methanol can accelerate U(Ⅵ)photoreduction by consuming photogenerated holes.This unary KOH molten salt synthesis method has exceptional potential applications in the preparation of carbon nitrides,and the obtained products showed potential in extracting U(Ⅵ)from aqueous solutions for use in nuclear fuel industry and for U(Ⅵ)environmental pollution cleanup.

Specialized springtail predation by Loricera beetles: An example of evolutionary stasis across the K-Pg extinction

Dear Editor,The Cretaceous-Paleogene(K-Pg)mass extinction precipitated one of the most profound restructurings of biodiversity in recent geological history.Despite the extinction of many iconic groups,particularly the non-avian dinosaurs,there is emerging evidence that previously overlooked taxa experienced stark morphological and evolutionary stasis.In this study,we report both adult and larva of beetles of the genus Loricera preserved in mid-Cretaceous Kachin amber(Figure 1),which display striking similarity to extant congeners,indicating a stasis of their specialized feeding behavior persisting at least 100 million years.

水性质的不连续证据:高温高压下水的红外光谱研究

在温度 35～ 35 0℃、压力 1 7～ 2 7GPa下用水热金刚石压腔进行了水的红外光谱测量和研究。研究结果表明 :在低于 2 1GPa时水的伸缩振动吸收峰的频率及半高宽分别随着压力增大而增高和减小 ,且在2 1GPa的压力存在着不连续 ,即随着压力的增大和在 2 1GPa压力下水的吸收峰具有明显和不连续的变化。这表明水在高压下的性质是不连续的 ,并与高压下纯水和NaCl溶液的电导率存在不连续的现象一致 ,也与含水矿物叶蜡石和蛇纹石在 2 0GPa处的脱水温度与压力的关系发生逆转现象一致。水的这种不连续性将对岩石圈中的矿物或岩石起重要作用 ,需要进行进一步的研究。

苏拉威西俯冲带结构与俯冲起始机制的三维地震观测

苏拉威西海具有独特的演化过程—位于北婆罗洲及苏禄岛弧下的苏拉威西海板块停止俯冲后,其俯冲板块的另一侧开始向苏拉威西岛俯冲,形成了诸如俯冲转换边缘、对向俯冲系统等独特的地质现象。针对这种同一板块一侧俯冲停止后在板块另一侧发育新俯冲的过程,科学界提出了众多的板块初始俯冲机制模式,如前陆盆地碰撞后发育新俯冲、大陆/岛弧边缘重力失稳后解耦后俯冲、岩石圈浅部小范围的地幔对流活动导致俯冲等14种初始模式。由于难以获得处于俯冲初始阶段俯冲带的深部岩石圈的地震观测资料,造成这些板块活动模式仍止步于推测。苏拉威西海区的天然地震观测资料不仅是研究苏拉威西海俯冲系统岩石圈深部构造及演化的基础,而且也是认识俯冲过程初始机制的关键一环。本文重点介绍了国家自然科学基金委员会重大研究计划“西太平洋地球系统多圈层相互作用”所属重点项目“苏拉威西海与古南海对向俯冲系统的三维地震观测与板块活动机制”在苏拉威西海区针对北苏拉威西海俯冲板片结构所开展的三维地震观测研究。该项研究实验以揭示俯冲系统深部结构与板块活动机制为目标,通过多边国际合作,于2019年8月15—25日在苏拉威西海区成功投放了27台国产宽频带海底地震仪(BBOBS),拟采集10个月的天然地震数据。同时计划利用印尼合作方的陆区地震台站数据,与OBS数据一同开展研究区岩石圈三维结构的地震学研究与数值模拟,认识俯冲下插板片的变形形态与特征、上覆地壳增厚程度及与俯冲系统持续作用过程之间的关系,讨论该地区独特俯冲系统的初始机制。

海洋生物气溶胶增加可能导致晚新生代全球变冷的模型计算

整合海洋碳、锶、锇同位素记录的地球化学元素循环模型表明,晚新生代大陆化学风化通量随着全球物理侵蚀的增强而升高,促使更多的营养元素磷输入到海洋中,引起海洋生物生产力的爆发,而浮游生物产生大量的二甲基硫最终导致海洋上空的大气气溶胶浓度急剧上升。气溶胶浓度增加一方面会增加云的覆盖率和反射率,据初步估计,该效应导致距今7Ma内地表接收的太阳能减少了16.5Wm-2,相当于全球平衡温度降低13℃;另一方面会抑止云层的降水效能,有利于水汽向高纬地区传输并形成降雪,最终促进两极冰盖生长,从而驱动新生代晚期全球性的气候变冷。

压力0.1～800MPa下液态水性质的红外光谱研究

20℃,0.1～800MPa下液态水的红外光谱测量结果,表明水分子红外吸收的组合频率与压力的关系是连续的,并随压力的增加而降低,但吸收峰的面积在压力约为200,370和700MPa时存在着不连续性.这种不连续性与高温高压下水的电导率测量结果一致,反映了在不同压力下水的性质具有明显差异.

澄江化石库中的双胚层动物新知

作为观察寒武纪大爆发主幕奥秘的最佳科学窗口,澄江化石库展示了三胚层动物(即两侧对称动物)首次全面大辐射的历史产物,让学术界终于看到了已知最古老的同时包括原口类和后口类两大支系的动物谱系庞大“树冠”的主体轮廓,从而给许多较高级动物类群的起源和早期演化研究提供了十分重要的信息。然而,该化石宝库中却很少见到作为“树干”的双胚层动物(即辐射动物)的化石记录,这给“真动物”的源头探秘蒙上了阴影。尽管广布于前寒武纪末期全球浅海域的“文德生物群”一直被认为是动物界早期一次“失败的演化试验”的牺牲品,但其中一支成功延续到早寒武世的春光虫(Stromatoveris)具有叠覆状梳齿构造,很可能代表着栉水母类的一类原始祖先。文中描述新的羽毛状动物王氏澄江海笔(Chengjiangopennawangii)不同于春光虫,前者具有彼此分离的羽枝,且羽枝上保存了排列规整的珊瑚个体虫室,因而与现代八射珊瑚中海笔类的形态学特征十分一致;新的谱系分析显示,它应该代表刺胞动物门中的一个原始类群。

晚新生代海洋磷循环模拟

理论分析表明,海水磷浓度控制了海洋自生磷沉积和热液磷沉积通量,并以此调节长尺度海洋磷循环的动态平衡。运用质量平衡原理,研究恢复了控制晚新生代海洋磷循环的各种通量,并据此模拟出海水磷浓度的演化。海水磷浓度演化与碳同位素分馏记录的浮游光合生物生长速度的变化一致,揭示在长时间尺度上,浮游光合生物的生长受海水磷含量控制。1500万年以来,大陆风化磷通量急剧增加,致使海洋磷浓度和磷沉积通量增加。海洋磷浓度增加促进了海洋生物生产力,导致海洋大气中生物气溶胶浓度升高,最终通过气溶胶的直接和间接辐射效应驱动晚新生代全球变冷。

由地震简正模式观测得到的内核各向异性区域变化

地球的固体内核被对流的液体外核包围,由此创建了驱动地球磁场的地核发电机。用压缩体波研究地震显示出内核各向异性结构的半球性变化,但由于受地震和接收器分布状况所限,这一结论还不够充分。本文中,利用大地震的简正模式分裂函数测定结果,并基于扩展交叉耦合理论,我们观测到了区域变化和内核中东、西两半球的各向异性。这一模式与地球磁场的相似性说明在固化或组构演变过程中由Maxwell应力引起的晶体排列的凝入是产生各向异性的根源。这些观测结果限制了内核超速旋转的总量,但与振荡相符。

Metamorphic Temperature Investigation of Coexisting Calcite and Dolomite Marble Examples from Nikani Ghar Marble and Nowshera Formation,Peshawar Basin,Pakistan

Using marble samples from the Nikani Ghar marble and Nowshera Formation from Northern Pakistan the determination of the temperature of metamorphism was undertaken with the help of calcite-dolomite solvus geothermometer. Two types of marbles, that is, calcite-dolomite marble and quartz-bearing calcite-dolomite marble were selected. Petrographic and scanning electron microscope analysis of dolomite samples indicated different grain sizes. X-ray diffraction technique indicated the calcites MgCO3 content up to 7.93 mol.%. Nikani Ghar marble samples have shown lower contents of MgCO3 as compared to samples from Nowshera Formation. The calcite-dolomite-quartz marble has also showed relatively lower MgCO3 content and hence rather low temperature （-500 ℃）. The temperature reached during peak metamorphism of the investigated marble occurrence, based on calcitedolomite solvus was 628 ℃. Metamorphic temperatures derived from the present study were shown as a linear graph and values were in good agreement with the published literature.

地震区划图上未明确标注的地震危险

沿板块边界分布的潜在地震危险在地震区划图中已经标注得比较清晰了。现在我们应该重点关注那些不在预料之内的位于大陆内部的地震所带来的威胁。

A combined experimental and theoretical investigation of donor and acceptor interface in efficient aqueous-processed polymer/nanocrystal hybrid solar cells

As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics(NAMD) based on time-dependent density-functional theory(TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations.

板片脱落——阿尔卑斯山脉同碰撞岩浆作用和构造模式

板片脱落就是在大陆碰撞期间俯冲的大洋岩石圈在浮力趋动下同一起俯冲的较轻大陆岩石圈拆离。Davies和von Blanckenburg(1994)在他们近期的文章中通过热力学模拟估算了引起脱落的物理条件,并预言了造山带演化过程中的各种结果。脱落在涌升软流圈的作用下使得掩复岩石圈地幔加热,富集层熔融,形成了双峰态岩浆作用。脱落也导致俯冲地壳岩石圈的受热弱化,使得在地幔深部裂散的地壳碎片因浮力而上升。我们将板片脱落模式用于研究欧洲阿尔卑斯山脉在第三纪的演化。阿尔卑斯山脉玄武质和花岗质岩浆作用出现在42 Ma和45 Ma之间,是在俯冲和大陆碰撞引起洋盆封闭之后发生的。现在认为,花岗岩类是由玄武岩与同化的大陆壳混合而形成的。为了确定部分地幔熔体形成的构造决定因素,我们收集并分析了已发表的整个阿尔卑斯弧的大量镁铁质岩墙的地球化学和同位素数据。痕量元素和同位素成分表明,它们是通过力学上稳定的岩石圈地幔的低度熔融形成的。我们没有见到软流圈地幔熔融的证据。在不到50 km的深处,没有发生减压。板片脱落一旦开始,便迅速地侧向迁移,并在受热弱化的地壳处形成线式岩浆活动带。这解释了为什么所有的阿尔卑斯岩浆几乎同时沿环亚得里亚线性断裂带的走滑断层侵位。通过对俯冲到100 km深处的Penninic高压岩石年龄的分析,发现俯冲作用发生在约55～40 Ma间,隆升作用发生在40～35 Ma间。从隆升和岩浆作用开始的短暂时间间隔来看,我们推断这两个过程都是由脱落作用引起的。板片脱落模式在阿尔卑斯地区得到了验证,因此,也支持了建立在地质基础上设想的理论模式。我们认为,岩浆活动与高压岩石回升地表的特征性组合将可在地表造山带鉴别板片脱落作用。