A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay

The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the Tacuarembó Formation, naming its “Lower” and “Upper” members as the Batoví (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batoví Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodus arambourgi D’Erasmo is well represented. This species was previously recorded in Late Jurassic–Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member (P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian–Tithonian age, which in combination with the stratigraphic relationships of the Tacuarembó Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian–Hauterivian interval.     

Recognition criteria,characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation,Argentina)

The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes, a tract known as the fluvial to marine transition zone, which varies between systems due to the relative strength of these processes. To understand how fluvial and tidal process interactions and the fluvial to marine transition zone are preserved in the rock record, large‐scale outcrops of deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated. Fluvial–tidal indicators consist of cyclically distributed carbonaceous drapes in unidirectional, seaward‐oriented cross‐stratifications, which are interpreted as the result of tidal modulation of the fluvial current in the inner part of the fluvial to marine transition zone. Heterolithic deposits with decimetre‐scale interbedding of coarser‐grained and finer‐grained facies with mixed fluvial and tidal affinities are interpreted to indicate fluvial discharge fluctuations (seasonality) and subordinate tidal influence. Many other potential tidal indicators are argued to be the result of fluvial–tidal interactions with overall fluvial dominance or of purely fluvial processes. No purely tidal or tide‐dominated facies were recognized in the studied deposits. Moreover, fluvial–tidal features are found mainly in deposits interpreted as interflood (forming during low river stage) in distal (delta front) or off‐axis (interdistributary) parts of the system. Along major channel axes, the interpreted fluvial to marine transition zone is mainly represented by the fluvial‐dominated section, whereas little or no tide‐dominated section is identified. The system is interpreted to have been hyposynchronous with a poorly developed turbidity maximum. These conditions and the architectural elements described, including major and minor distributary channels, terminal distributary channels, mouth bars and crevasse mouth bars, are consistent with an interpretation of a fluvial‐dominated, tide‐influenced delta system and with an estimated short backwater length and inferred microtidal conditions. The improved identification of process interactions, and their preservation in ancient fluvial to marine transition zones, is fundamental to refining interpretations of ancient deltaic successions.     

贺兰山地区树轮碳氧同位素与夏季风降水的相关性讨论

分析了贺兰山地区油松树轮的稳定碳氧同位素组成对环境因素的响应关系 , 发现树轮碳氧同位素组成均与当年 5～ 9月总降水量具有较好的响应关系 , 碳同位素组成与 5～ 9月总降水量呈负相关关系 ,而氧同位素组成与 5～ 9月总降水量呈正相关关系 ,二者都可较好地反映该地区夏季风降水量的变化.同时 ,碳氧同位素的相关性分析表明二者具有一定程度的负相关性.树轮碳氧同位素的分馏机理十分复杂,其同位素组成不仅与降水量有关,同时还受其他环境因素的影响,单纯利用一种同位素指标来提取相应的气候信息,存在很大的不确定性.在本研究中 ,同时采用两种同位素指标来研究其气候意义 ,使得出的结论更加可靠.因此 ,夏季风降水量是控制该地区树轮稳定碳氧同位素组成的主要因素.     

末次冰期以来巽他陆架东北部陆坡区正构烷烃分布特征及其古植被意义

为了讨论末次冰期以来巽他陆架东北部植被情况及巽他陆架在冰期时的碳循环意义.对位于南海西南部陆坡的18252-3站位岩心柱沉积物中长链正构烷烃组分的平均链长(ACL27-33)、碳优势指数(CPI27-33)、烷烃含量(∑oddC27-C33)、及烷烃比值等指标进行了分析.结果显示:末次冰期以来CPI27-33表现出与海...     

柴达木北缘石榴石橄榄岩的发现及其意义

本文论证了柴达木北缘胜利口含镁铝榴石超基性岩不是“似金伯利岩”而是石榴石橄榄岩。岩相学、矿物化学资料显示其为大陆边缘上覆于俯冲板块的地幔楔形区物质。石榴石橄榄岩在土地幔平衡的Ｐ－Ｔ条件为２５×ｌ０￣８Ｐａ和８５０℃左右，显示造山带高压变质岩的地温特征。柴达木北缘石榴石橄榄岩与榴辉岩的发现表明它是一条高压变质带，是该地区古生代洋壳俯冲、大陆碰撞的产物。     

新一代手提式多元素X荧光仪在地质普查中的应用

现场X射线荧光分析的主要影响因素是基体效应，湿度效应和不平度效应等。基于室内、野外大量实验，结合软件技术，在新一代手提式元素X荧光仪中，综合运用强度影响系数法、特散比及经验系数法，使多元素现场X荧光快速分析技术取得实用性进展。地质大调查中，在样品多元快速测试，野外土壤、岩石的原位分析，异常追索查证等方面的应用，充分体现出轻便、快速、高效、低投入的效果。     

高分辨率采区地震勘探成果在新庄煤矿的应用

通过对新庄煤矿采区地震勘探经验的总结,证明采区地震勘探具有投资省、周期短、勘探精度高等优点,是一种良好的地质勘探手段,基本解决了影响煤炭生产的两大主要问题:中小构造及煤层赋存形态问题,对煤炭的生产、安全具有重大的指导意义。通过生产实践证明,采区地震勘探能取得良好的地质效果及巨大的经济效益,具有良好的应用前景。     

Numerical Simulation of the High-Latitude Non-Stationary Ionospheric Alfvén Resonator During an IPDP Event

The ionospheric Alfvén resonator (IAR) was numerically simulated under non-stationary ionospheric and magnetospheric conditions of the IPDP event of December 4, 1986. The full numerical wave method was applied using height profiles of the ionospheric plasma parameters obtained from the Scandinavian EISCAT radar measurements close to the Ivalo latitude. An attempt to model the inverse problem of numerical simulation—prolongation of the electron density profiles at altitudes above the ionospheric F layer—was made on the basis of the IAR simulation in correlation with the IPDP frequency increase. The change of the IAR wave characteristics during the substorm was illustrated by height profiles of the total wave amplitude and various polarization characteristics, taking into consideration the ordinary L-mode and the extraordinary R-mode waves for parallel and non-parallel incidence with respect to the magnetic field line.     

阿尔芬波动特征对卫星磁力仪零位标定的影响

磁通门磁力仪的零位偏移量在卫星轨道上会因诸多因素而发生改变.为此,基于剪切阿尔芬波动不改变总磁场强度这一特征的Davis-Smith方法被提出用于计算磁力仪的零位补偿.实际上,行星际空间中没有纯粹的阿尔芬波动.本文采用数值模拟分析了存在小的压缩波动情况下,阿尔芬波动的幅度、周期和相位以及数据窗口时间长度等对Davis-Smith方法计算零位补偿的影响.我们发现,只有当阿尔芬波动的周期与压缩波动周期相同时,阿尔芬波动的性质会对零位补偿的计算产生不可忽视的误差.阿尔芬波动的幅度越大,零位补偿的误差越小.磁场各分量零位补偿的误差大小还会受到阿尔芬波动初始相位的影响.此外,数据窗口时间长度越长,则零位补偿误差趋于减小至真实值.