Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China)

The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian.     

Study of the liquefaction resistance of a saturated sand reinforced with Geosynthetics

This article presents various tests using a cyclic triaxial instrument, on samples of saturated Hostun RF sand, reinforced with circular sheets of geosynthetic material. Tests performed with different types of geosynthetics of different compressibility, rigidity and roughness characteristics indicate a significant increase in liquefaction resistance for samples reinforced with compressible, non-woven geotextiles. The undrained behaviour of saturated Hostun RF sand reinforced with non-woven geotextiles is analysed on the basis of different test series. This analysis highlights the influence of reinforcement compressibility on interstitial pressure distribution in the sample, thus showing the role of this type of inclusion in the increase in liquefaction resistance.     

福建沙县地区早白垩世火山岩成因及构造环境分析

本文着重阐述了沙县地区早白垩世火山岩地球化学特征，论证了中性与酸性火山岩的成因及物质来源，认为二者为不同源岩浆演化的产物，其岩浆物质来源于壳幔混源区，为省内双峰式火两端员岩石间成因关系的分析研究提供了新的例征。     

岩层离距图法研究沉积岩断裂发育史——以松辽盆地敖古拉断裂为例

利用断裂活动过程中留下的各种地质标记研究断裂发育史是比较困难的 ,已有的研究方法主要可归纳出七种 ,都存在局限性。岩层离距图法是以地震剖面为基础 ,将穿过断裂的各剖面上的标志层投影到沿断裂走向的铅垂面上 ,得到多组标志层的垂向断距数据 ,然后用下部各标志层的断距减去最上部标志层的断距 ,并作多轮次计算 ,直到最后的断距差近似为零或仅剩一个非零标志层。每一轮次计算代表一个活动期次 ,如果出现负值 ,则表示有构造反转。对松辽盆地敖古拉断裂作了实例计算 ,结果为该断裂发育经历了三个正断活动期和一个逆断活动期 ,与盆地区域性活动有些差别。岩层离距图法比起其他已有方法 ,可靠程度大大提高     

Depositional sequence architecture and filling response model of the Cretaceous in the Kuqa depression, the Tarim basin

The Cretaceous system of the Kuqa depression is a regional scale (second order) depositional sequence defined by parallel unconformities or minor angular unconformities. It can be divided into four third-order sequence sets, eleven third-order sequences and tens of fourth- and fifth-order sequences. It consists generally of a regional depositional cycle from transgression to regression and is composed of three sets of facies associations: alluvial-fluvial, braided river-deltaic and lacustrine-deltaic facies associations. They represent the lowstand, transgressive and highstand facies tracts within the second-order sequence. The tectonic subsidence curve reconstructed by backstripping technique revealed that the Cretaceous Kuqa depression underwent a subsidence history from early accelerated subsidence, middle rapid subsidence and final slower subsidence phases during the Cretaceous time, with the correspondent tectonic subsidence rates being 30-35 m/Ma, 40-45 m/Ma and 5-10 m/Ma obtained from northern foredeep. This is likely attributed to the foreland dynamic process from early thrust flexural subsidence to late stress relaxation and erosion rebound uplift. The entire sedimentary history and the development of the three facies tracts are a response to the basin subsidence process. The slower subsidence foreland gentle slope was a favorable setting for the formation of braided fluvial deltaic systems during the late period of the Cretaceous, which comprise the important sandstone reservoirs in the depression. Sediment records of impermanent marine transgression were discovered in the Cretaceous and the major marine horizons are correctable to the highstands of the global sea level during the period.     

New palaeointensity results from Cretaceous basalt of Inner Mongolia, China

We present new Thellier-Thellier palaeointensity results from three cooling units (32 samples) of Inner Mongolia lava flows (91.7 Ma) emplaced during the Cretaceous Normal Superchron (CNS). Based on rock-magnetic and microscopy observations the magneto-mineralogy of all samples is determined to be primary and unaltered high-Ti titanomagnetite. Accepted palaeointensity determinations, obtained in the 80-200 °C temperature interval, are of good technical quality with positive standard partial thermoremanent magnetisation (pTRM) checks and pTRM-tail checks. Obtained palaeointensity estimates range from 14.7 to 28.0 μT, with virtual axial dipole moments (VADM) of 2.4 to 4.6 (× 10²² Am²). The data agree well with recently published results from the same region and, combining the two datasets, we obtain independent estimates from six different cooling units yielding a time-averaged VADM of 3.2 ± 1.6 (× 10²² Am²). These data suggest a relatively low dipole moment towards the end of the Cretaceous Normal Superchron.     

辽西医巫闾山地区中生代两期韧性变形的研究

医巫闾山地区的韧性剪切构造是中生代两期韧性变形作用的产物。早期韧性变形中a线理发育,线理走向和糜棱面理走向基本一致,线理在xy面上的侧伏角绝大多数<30°;该期韧性变形是以左行走滑运动为主。晚期韧性变形中a线理发育,线理倾伏向和糜棱岩中糜棱面理倾向相近,线理在xy面上侧伏角主要在45°～90°之间;该期韧性变形是伸展作用的产物。医巫闾山中生代两期韧性剪切变形作用表明,在侏罗纪至早白垩世期间辽西地区不仅发生了强烈挤压推覆作用和伸展作用,也发生了大规模左行走滑作用。该韧性变形作用的发现对进一步研究辽西中生代的构造演化序列、期次和构造格架转换等问题有重要意义。     

Pelecinid wasps (Insecta, Hymenoptera, Proctotrupoidea) from the Cretaceous of Russia and Mongolia

Thirteen new species referable to four genera, of which one is new, from the Cretaceous of Russia and Mongolia are established herein and assigned to the family Pelecinidae. Among the four genera, Protopelecinus gen. nov., including four new species, is referred to the subfamily Pelecininae, while Iscopinus Kozlov, including three new species, Eopelecinus Zhang, Rasnitsyn and Zhang, including five new species, and Scorpiopelecinus laetus sp. nov. are assigned to the subfamily Iscopininae. Of these new taxa, eight, namely Protopelecinus regularis, P. furtivus, Iscopinus simplex, ?I. suspectus, Eopelecinus exquisitus, E. scorpioideus, E. rudis and Scorpiopelecinus laetus, are from the Lower Cretaceous Zaza Formation of Baissa, Transbaikalia, Russia; two, E. minutus and E. fragilis, are from the basal Lower Cretaceous Tsagan-Tsab Formation of Khutel-Khara, Mongolia; two, P. dubius and P. deformis, are from the Lower Cretaceous (Aptian?) of Bon Tsagan, Mongolia; and one, I. separatus, is from the Upper Cretaceous (Cenomanian) Ola Formation of Obeshchayushchiy, Russia. A key to fossil pelecinid wasps is provided and a morphological analysis shows that the Pelecinidae might be paraphyletic with respect to the Proctotrupidae. The Chinese insect fauna from both the Yixian and Laiyang formations is dominated by Eopelecinus and Sinopelecinus whereas the Siberian + Mongolian fauna from the Zaza and Tsagan-Tsab formations is dominated by Eopelecinus and Iscopinus. Hence, Eopelecinus is common to both. The differences between the two faunas are likely to be the result of geographical variation in populations.     

Middle Campanian–lowermost Maastrichtian nannofossil and foraminiferal biostratigraphy of the northwestern Australian margin

The middle–late Campanian was marked by an increase in the bioprovinciality of calcareous microfossil assemblages into distinct Tethyan, Transitional, and Austral Provinces that persisted to the end of the Maastrichtian. The northwestern Australian margin belonged to the Transitional Province and the absence of key Tethyan marker species such as Radotruncana calcarata and Gansserina gansseri has led petroleum companies operating in the area to use the locally developed KCCM integrated calcareous microfossil zonation scheme. The KCCM zonation is a composite scheme comprising calcareous nannofossil (KCN), planktonic foraminiferal (KPF) and benthonic foraminiferal (KBF) zones. This paper presents the definitions and revisions of Zones KCCM8–19, from the highest occurrence (HO) of Aspidolithus parcus constrictus to the lowest occurrence (LO) of Ceratolithoides aculeus, and builds on our previous early–late Maastrichtian study. The presence of a middle–upper Campanian disconformity is confirmed by microfossil evidence from the Vulcan Sub-basin, Exmouth and Wombat plateaus, and the Southern Carnarvon Platform. In the Vulcan Sub-basin and on the Exmouth Plateau (ODP Hole 762C) the hiatus extends from slightly above the LO of common Rugoglobigerina rugosa to above the LO of Quadrum gothicum. On the Wombat Plateau (ODP Hole 761B) it spans from above the LO of Heterohelix semicostata to above the LO of Quadrum gothicum; and in the Southern Carnarvon Platform the disconformity has its longest duration from above the HO of Heterohelix semicostata to above the LO of Quadrum sissinghii. A significant revision of the events which define Zones KCCM18 and 19 was necessary owing to the observation that the LO of Ceratolithoides aculeus occurs below the HOs of Archaeoglobigerina cretacea and Stensioeina granulata incondita and the LO of common Rugoglobigerina rugosa. In the original zonation these events were considered to be coincident.     

Revision of the conchostracan genera Cratostracus and Porostracus from Cretaceous deposits in north-east China

The diagnoses of the conchostracan genera Cratostracus and Porostracus are revised following a re-examination of their type species under a scanning electron microscope. In Cratostracus each growth line has a serrated lower margin. Radial lirae branch into smaller ridges that merge with each other to give the upper part of each growth band in the ventral region of the carapace a slightly undulating surface. Cross-bars are present between these lirae. In Porostracus the radial lirae on the growth bands near the umbo are long and relatively widely spaced. There is a fine reticulum between them in the umbonal part of the carapace and cross-bars on the ventral surface. The ornament of Porostracus indicates that it can be assigned to the family Halysestheriidae rather than to the Afrograptidae, in which it has been placed previously. Morphological analysis of most of the species of the two genera and closely related Orthestheria (Migransia) under the scanning electron microscope is required before their stratigraphic potential can be fully realized.