The last deglaciation of the Franz Victoria Trough, northern Barents Sea

A study of two piston cores and a 3.5 kHz seismic profile from the Franz Victoria Trough provides new stratigraphic, stable isotopic and foraminiferal AMS ¹⁴C data that help constrain the timing of ice-sheet retreat in the northern Barents Sea and the nature of the deglacial marine environment. Silty diamicton at the base of each core, interpreted as till or ice-marginal debris flow, suggests that the Barents ice sheet was grounded at the core sites (470 m water depth). Eight AMS ¹⁴C dates on sediment overlying the diamicton indicate that the ice sheet retreated from both core sites by 12.9 ka and that postglacial sedimentation began 10 ka ago. These dates, combined with a recently published ¹⁴C date from a nearby core, suggest that the Franz Victoria Trough may not have been deglaciated until c . 13 ka, 2000 years later than modeled ice-sheet reconstructions indicate. In the trough, oxygen isotopic ratios in planktonic foraminifera ^N. pachyderma (sinistral) were 0.5–0.750, lower during deglaciation than after, probably as a result of ice-sheet and/or iceberg melting. Foraminiferal assemblages suggest that Atlantic-derived intermediate water may have begun to penetrate the trough c . 13 ka ago.     

Overview and status of estuarine microphytobenthos ecological research in South Africa

This article presents a historical overview of estuarine microphytobenthos (MPB) research in South Africa published over the period 1950 to the present, highlighting major milestones, challenges and estuarine management problems, as well as future research needs within the South African context. The studies that were covered comprise peer-reviewed books and journal articles on relevant research conducted in any estuarine environment during the period reviewed. There was a general increase in MPB research outputs over the decades, from only two publications in the 1950s, to over 20 outputs between 2010 and the present. Whereas the MPB studies in South Africa cover a broad spectrum of themes, the research priorities in these works have changed from taxonomically biased studies to those of ecologically based research. Research in the 1950s and 1960s was exclusively taxonomic in nature, with the first ecological investigation incorporating MPB being produced in the 1970s. By the 1980s, ecological studies dominated the research outputs and this trend has persisted to the present. The 1990s and 2000s saw the rise of research into the role of fresh water as a driver of MPB dynamics, whereas the period 2010 to the present saw an increase in more diverse ecological themes, ranging from an autecological investigation to food-web studies and the assessment of multiple drivers of MPB dynamics. However, the majority of studies have focused on either diatoms or estimates of overall MPB biomass. Moreover, there is a regional underrepresentation that runs broadly along biogeographic lines, with the bulk of the work having been conducted in the warm-temperate and subtropical zones of South Africa. Challenges and future research needs for the region are outlined, as is the need to expand MPB research to include other aspects of the biology and ecology of this flora.     

Presence of microplastics in the tube structure of the reef-building polychaete Gunnarea gaimardi (Quatrefages 1848)

The prevalence of microplastics in the marine environment has resulted in a need to understand their association with various fauna. The aim of this study was to assess whether microplastic particles are present in the tube structure of the indigenous reef-building polychaete Gunnarea gaimardi, which occurs along the coast of South Africa. Sampling was conducted at nine stations along the west and southeast coastlines of South Africa, in July 2016 and April/May 2017. Microplastic particles were recorded in all tube structures of G. gaimardi, with the density ranging between 0.056 and 1.113 microplastic particles g^–1 dry weight (dwt). There were no significant differences between sites (p > 0.05), resulting in an overall average of 0.275 (SD 0.215) microplastic particles g^–1 (dwt). To the authors’ knowledge, this is the first study to show that synthetic polymers are found in the tubes of reef-building polychaetes along the coast of South Africa.     

Melt Inclusions of Sulfide in Mantle-Driven Amphibole Megacrysts

硫化物熔融包裹体研究是认识硫化物矿床成矿元素来源和演化的重要手段,由于硫化物熔融包裹体的体积较小(粒径仅为10～20 μm),其详细化学元素组分的难以获得一直是制约进一步研究的瓶颈.笔者在前人研究的基础上,借助于扫描电镜、电镜能谱和二次飞行时间离子探针(Tof-SIMS)对产于铜陵地区角闪石巨晶中的硫化物熔融包裹体进行了详细的研究,首次获得了一套精确的矿物化学资料和元素分布图.矿物学研究表明,角闪石巨晶在上地幔和下地壳均有结晶,温压区间分别为T:850～900℃(温度),P:0.70×109～0.82×109 Pa(压力),对应深度D:23.10～27.06 km;和T:900～950℃,P:1.09×109～1.17×109 Pa,D:35.97～38.61 km.元素分布图显示,硫化物熔融包裹体主要有两种元素组成体系:S-Fe-Mn-Ni-Rb-Sr-Ba和S-Fe-Cu-Sr,幔源硫化物体系中Mn、Ni、Rb、Ba等元素具有相似的性质特征可共溶,与Cu则表现出不混溶.在铜陵地区,上地幔的部分熔融形成了一套碱性玄武岩浆,后受岩浆底侵作用和壳幔相互作用影响,底侵进入下地壳深位岩浆房,发生结晶分异和同化混染作用,形成一套轻度演化的玄武岩浆,可能为辉长质.上地幔和下地壳的角闪石巨晶分别是由上地幔碱性玄武岩浆和下地壳轻度演化的玄武岩浆(辉长质)高压下结晶的产物.当上地幔碱性玄武岩浆上侵到下地壳深位岩浆房以后,发生结晶分异作用,又由于地壳硅镁层的混染作用,使得玄武岩浆中硫溶解度降低,促其熔离,从而释放大量的硫(S,以及Ni、Cu、Cr).角闪石巨晶中的硫化物熔融包裹体正是在下地壳深位岩浆房中,由正在结晶的角闪石巨晶在结晶分异和轻度演化的玄武质岩浆中捕获的不混溶硫化物熔融液滴形成的.铜陵地区在中生代经历了一个长期的大规模的岩浆底侵作用和壳幔相互作用过程,由于下地壳硅镁层混染作用使得轻度演化的玄武岩浆释放大量硫,必然会在莫霍面附近形成大规模高浓度的硫富集区,这些组分在岩浆上侵作用、地壳减薄作用或者裂谷作用的影响下很容易再活化,进入区域岩浆-热液流体系统,最终参与形成区域大规模的硫化物矿床.     

Holocene palaeoenvironmental reconstruction based on fossil beetle faunas from the Southern Altai region,north‐west China

We present here the results of the first‐ever Quaternary entomological research in China. The Halashazi Wetland, located in the southern Altai Mountain region in the northernmost part of Xinjiang Province, yielded Holocene insect fossils (mostly beetles) from two peat profiles. In total, 55 Coleoptera taxa were found, including 37 identified species. A new species, Helophorus sinoglacialis, was identified. The fauna is strongly northern Holarctic in character. The interval from 10 424 to 9705 cal a BP was probably a cold and wet period, and the study site was above the treeline. From 9665 to 9500 cal a BP it was probably warmer and drier, and treeline moved to higher elevations. Following a depositional hiatus, mid‐Holocene (5400–4400 cal a BP ) insect assemblages represent cold conditions with the site above the treeline. The exception was a brief warming around 5450 cal a BP , when bark beetle evidence suggests that the treeline moved to a higher elevation. Of the 37 identified beetle species from the Halashazi site, 34 (92%) have modern records in Siberia. The Altai Mountains probably served as a dispersal corridor between the Siberian arctic and alpine regions of northern China. Copyright © 2019 John Wiley & Sons, Ltd.     

Late-glacial climate in the Maritimes Region, Canada, reconstructed from mutual climatic range analysis of fossil Coleoptera

Mean July and January temperatures are reconstructed from radiocarbon-dated fossil beetle assemblages from late-glacial sites in the Maritimes Region of eastern Canada. Fossil-bearing sediments date from 12 700 ¹⁴ C yr BP (14 950 cal yr BP) to younger than 10 800 ¹⁴ C yr BP (12 730 cal yr BP), spanning a period which includes stratigraphic, palynological, chironomid and coleopteran evidence for a climatic deterioration during the Younger Dryas in North America. Mutual Climatic Range data suggest several 'events' in the coleopteran record from the Maritimes that appear similar to climate events recorded in the GRIP ice-core record, including the (Younger Dryas) cooling event from GI-1a to GS-1 beginning c. 12 650 GRIP yr BP Some of the major temperature oscillations of Greenland Interstadial 1 may also be reflected in the coleopteran record of the Maritimes.     

Carboniferous fossil forests

Forests of Carboniferous age, first described in detail in the nineteenth century, are often illustrated in textbooks, but their ecological and evolutionary significance has been largely overlooked or, worse, misrepresented. It has often been thought that the standing fossil forests found rooted in coals represent relicts of the peat-forming vegetation. Recent research has suggested that this is not always the case and that many of the standing trees represent an essentially non-peat-forming wetland ('clastic swamp') vegetation comprising a distinctive set of genera and species of plants. Recent investigation of several famous examples - Weaklaw, Arran and Joggins as well as new examples such as Mary Lee and Table Head - is throwing new light on the ecological and evolutionary significance of these fossil forests.     

Aptian综合年代地层事件:定量地层学的运用

以往发表的年代地层数据都是以Ma形式出现,以关键物种的首现面和末现面来界定的。一般而言,这些年龄是在用某种方法确定的某两个层的年龄基础上通过插值获得的,很大程度上仍然是估计值,而不是可以检验的科学结论。我们需要的是一个可以评价的、剖面重现的、标本重现的而且插值方法是经过严格检验的数据库。图形对比技术正是一个有用的方法,它可以综合众多剖面的分散分布的事件,并可以验证这些事件的顺序和年代。图形对比技术是一个定量的、非统计的方法,可以判别两个剖面之间存在的同时代关系。物种时限和非生物事件投点到X/Y图解上,时限可以通过对比线综合到单个的时间尺度上。其他剖面的数据通过重复以上过程把每个剖面的数据综合进来。获得的时限通过评价有这些物种出现的图形解而得到验证。Aptian阶(约124~112 Ma)时期环境发生巨大变化,用来确定Aptian阶的许多关键生物事件和年代地层事件并不都出现在同一个剖面。因此,这些事件的相对年龄始终是不确定的,也不是相关的。两个事件被提出来用于界定Aptian 阶的底界,包括菊石Deshayesites tuarkyricus 和磁极性带CM0。然而这两个事件标准地层剖面相隔600 km。图形对比显示这两次事件出现在7 万年间隔内。通过这一方法,来自23 条Barremian Aptian Albian