Redescription of Tuarangisaurus keyesi (Sauropterygia; Elasmosauridae), a key species from the uppermost Cretaceous of the Weddellian Province: Internal skull anatomy and phylogenetic position

The systematics of elasmosaurids are not well resolved partially because of the scarcity of well-preserved skull material. Among Weddellian elasmosaurids, one exception to this is the holotype of Tuarangisaurus keyesi from upper Campanian–lower Maastrichtian levels of the Maungataniwha Sandstone Member of the Tahora Formation, Mangahouanga Stream, inland Hawke's Bay, New Zealand. The material preserves an almost complete cranium and mandible. This material is re-described here, based on new observations and digital reconstruction of the internal anatomy. The result adds one new autapomorphy to the diagnosis of the taxon: ectopterygoid with large boss on the ventral surface and a posteriorly directed process. Additionally new features are recorded: presence of stapes; pterygoid overlapping the vomer, medial sulcus on the dorsal surface of the vomer, parasphenoid–basisphenoid complex covering the ventral surface of the body of the basioccipital. The presence of stapes in Tuarangisaurus keyesi is surprising as they were previously considered absent among elasmosaurids. Phylogenetic analysis indicates a clear elasmosaurid affinity, although there is low resolution within the Elasmosauridae. The previously proposed close relationship with the early Aptian Callawayasaurus colombiensis is rejected.     

A new genus and species of soldier beetle from Upper Cretaceous Burmese amber (Coleoptera,Cantharidae, Malthininae)

A new Upper Cretaceous genus and species of soldier beetles, Archaeomalthodes rosetta gen. et sp. nov., is described and illustrated from an individual preserved in Upper Cretaceous (Cenomanian, ca. 99 Ma) amber from northern Myanmar. It is undoubtedly placed in extant subfamily Malthininae based on its small-sized body, somewhat abbreviated elytra and fusiform terminal maxillary palpomere, representing the oldest documented occurrence of Malthininae. It suggests that this subfamily is an ancient group, which originated at least in the earliest Late Cretaceous. Our discovery sheds light on the palaeodiversity of Cantharidae in the Late Mesozoic. Together with other previously reported fossil cantharids, it is likely that Malthininae has been fairly diverse during the early evolution of Cantharidae. On the other hand, a morphological similarity between Archaeomalthodes and Recent malthinines and the occurrence of flowering plants in the Burmese amber implies a potential flower-visiting behaviour of this fossil species.     

Biostratigraphy and facies analysis of the Upper Cretaceous–Danian? platform carbonate succession in the Kuyucak area,western Central Taurides,S Turkey

The Upper Cretaceous succession outcropping in the Anamas–Akseki Autochton, consists of approximately 500 m thick purely platform carbonate sediments. It begins with Cenomanian limestones intercalated with limestone breccias (Unit-1) containing mainly Pseudorhapydionina dubia, Pseudonummoloculina heimi, Spiroloculina cretacea (Assemblage I) and unconformably overlies the Lower Cretaceous (Barremian–Aptian) limestones with Vercorsella laurentii, Praechrysalidina infracretacea and Salpingoporella hasi. The Cenomanian limestones include foraminiferal packstone–wackestone, peloidal packstone–wackestone and mudstone microfacies deposited in restricted platform conditions. The Cenomanian succession is truncated by an unconformity characterised by locale bauxite deposits. Immediately above the unconformable surface, dolomitic limestones and rudistid limestones (Unit-2) are assigned to the upper Campanian based on the benthic foraminiferal assemblage (Assemblage II) comprising mainly Murciella gr. cuvillieri, Pseudocyclammina sphaeroidea, Accordiella conica, Scandonea samnitica and Fleuryana adriatica (smaller-sized populations). The upper Campanian limestones composed of dominantly foraminiferal-microbial packstone–wackestone microfacies deposited in shallow water environment with low energy, restricted circulation. The following limestones of the Unit-2 is characterised by sporadic intercalation of “open shelf” Orbitoides, Omphalocyclus, Siderolites assemblage (Assemblage III), assigned to the Maastrichtian, in addition to pre-existing “restricted platform” species. In the upper part of this biozone, the Rhapydionina liburnica/Fleuryana adriatica concurrent range subzone (Assemblage IIIb) is distinguished by the presence of Valvulina aff. triangularis, Loftusia minor as well as the nominal species. The Maastrichtian limestones with sporadically open marine influence consist of bioclastic (rudist-bearing) packstone–floatstone, foraminiferal packstone–wackestone with rudist fragments and peloidal/intraclastic packstone–wackestone microfacies deposited in shallow subtidal–subtidal (lagoonal) environments. The Upper Cretaceous succession passes upwardly into 70 m thick limestones and clayey limestones (Unit-3) which do not contain rudists and pre-existing foraminiferal assemblage with one exception Valvulina aff. triangularis. Variable amounts of ostracoda, discorbids, miliolids, dasycladacean algae and Stomatorbina sp. (Assemblage IV) occur into mud-rich microfacies suggesting restricted conditions with low water energy. A probable Danian age is proposed for the Unit-3 based on the occurrence of Valvulina aff. triangularis and Stomatorbina sp. which were previously recorded from Danian of peri-Tethyan platforms.     

A new species of Glaesoconis Meinander (Neuroptera: Coniopterygidae) from the Santonian Taimyr amber

Glaesoconis popovi sp. nov. (Neuroptera: Coniopterygidae) is described from Upper Cretaceous (Santonian) Taimyr amber of northern Siberia (Yantardakh locality). The new species may be distinguished from others in the genus by much smaller eyes and the shape of the terminal segment of the maxillary palpus. The generic affinity of Glaesoconis baliopteryx Engel, 2004 from the mid-Cretaceous Burmese amber needs confirmation.     

Active and passive arching stresses in c′-ϕ′ soils: A sensitivity study using computational limit analysis

Vertical soil arching, commonly known as the “trapdoor mechanism,” is a pervasive phenomenon in various geotechnical applications that can be evaluated through a variety of analytical and numerical approaches, most of which exist due to a variety of proposed arching mechanisms, many of which are focused on either purely frictional or cohesive soils. This study investigates the realized arching mechanisms and associated loads for trapdoors under both active and passive arching conditions in c′-ϕ′ soils through a series of dimensionless charts using both upper and lower bound limit analyses. An associated sensitivity analysis demonstrates that arching loads are highly dependent on collapse mechanism, a function of not only geometry, but soil shear strength, with cohesion affecting the realized mechanism and arching loads.     

Application of low-pressure gas adsorption to nanopore structure characterisation of organic-rich lower Cambrian shale in the Upper Yangtze Platform,South China

The pores in shales are mainly on a nanometer scale, and the pore-size distribution is vital with regard to the preservation and exploitation of shale gas. This study focuses on the organic-rich lower Cambrian black shale in the Upper Yangtze Platform, South China and investigates their TOC, mineralogical composition and nanopore structure. Low-pressure N₂ and CO₂ adsorption experiments were conducted at 77.35 K and 273.15 K, respectively, and the nanopore structures were characterised by the modified Brunauer–Emmett–Teller, Dubinin–Radushkevich, t-plot, Barrett–Joyner–Halenda and density functional theory (DFT) methods. The results indicate the following. (1) The lower Cambrian shale has a high TOC content (1.77–7.23 wt%) and a high quartz content (27.7–51.6 vol%). The total specific surface area varies from 12.02 to 28.87 m²/g. Both the total specific surface area and quartz content are positively associated with the TOC content. (2) Shale samples with a higher TOC content have a greater number of micropores, resulting in more complicated nanopore structures. Micropore volumes/surface areas and non-micropore surface areas all increase with increasing TOC content, indicating that TOC is the key factor determining the nanopore structure of the lower Cambrian shale. (3) A combination of N₂ and CO₂ adsorption provides the most suitable detection range (～0.3–60 nm) and is both highly reliable and accurate with regard to nanopore structure characterisation.     

Evolution of the Late Triassic Paleo-uplift in the Southwestern Upper Yangtze Region and its Tectonic SignificanceEI北大核心CSCD

Based on field geological survey and stratigraphic analysis, a Late Triassic Paleo-uplift is identified in the southwestern upper Yangtze region. The tectonic features, evolution history and tectonic significance of this paleo-uplift are discussed in detail in this paper. The results suggest that the hiatus of the Upper Triassic in the southwestern upper Yangtze region was resulted from the paleo-uplift that roughly parallel to the southwest margin of the upper Yangtze region. The formation of the paleo-uplift is related to the closure of the Jinshajiang-Ailaoshan-Songma-Babu and Ganzi-Litang Oceans and their subsequent collisional orogenesis along the southwest margin of the upper Yangtze region. The forebulges of the Youjiang and Chuxiong Foreland Basins were formed by the closure of the Jinshajiang-Ailaoshan-Songma-Babu Ocean, comprising the paleo-uplift at the end of the Early Triassic. Then the forebulge of the Xichang Foreland Basin was developed by the closure of the Ganzi-Litang Ocean in the Norian, and became a new part of the paleo-uplift. Owing to the termination of the Youjiang Foreland Basin at the end of the Rhaetian, the paleo-uplift was composed only of the forebulges of the Chuxiong and Xichang Foreland Basins. The discovery of the paleo-uplift will help us to better understand the prototype of the Sichuan Basin and the tectonic evolution of the southwestern upper Yangtze region during the Late Triassic. © 2017, Science Press. All right reserved.     

不对称双连拱海底隧道施工引起的地层变形分析

在目前众多的预测隧道开挖引起的地层变形的方法中,经验公式法最为简便,也是目前应用最为广泛的方法,为此介绍了多种预测隧道开挖引起的地层沉降和水平位移的经验公式。并以青岛胶州湾海底隧道不对称双连拱断面为工程背景,由位于主隧道与匝道交叉口段的典型断面ZK2+800.78的几何参数和地质资料构建三维数值计算模型,采用岩土体工程通用有限差分软件FLAC3D进行动态施工三维数值模拟。通过对FLAC3D模拟和各经验公式计算的地层沉降和水平位移的对比分析,评价了FLAC3D软件和各经验公式在不对称双连拱隧道断面地层变形预测中的适用性。结果表明,当地层埋深较浅时,不同埋深地层的地层沉降和水平位移可近似用各经验公式来预测;但随着地层埋深的增大,各经验公式预测的偏差不断增大;经验公式只能对单一地层、单一隧道的地层变形进行估算,存在明显的局限性,而在预测复杂地质条件下不对称双连拱隧道断面开挖引起的地层变形时,FLAC3D较各经验公式有明显的优势     

基于广义极值理论的潜在地震海啸源震级上限及强震重现水平的估计——以琉球海沟俯冲带为例

以琉球海沟俯冲带作为研究区,将广义极值理论用于估计潜在地震海啸源震级上限,首先分析了琉球海沟俯冲带的地震地质构造特征以及历史地震资料,界定潜在地震海啸源区,然后根据地震活动性特征按时间域进行分割,并提取各时间段发生的极限震级的地震样本,最后通过广义极值分布模型估计了该区域的震级上限值和强震重现水平,并对其进行了不确定性分析。