The lower marine to lower freshwater Molasse transition in the northern Alpine foreland basin (Oligocene; central Switzerland–south Germany): age and geodynamic implications

The Wilhelmine Alpe section near Immenstadt (Allgäu, south Germany), which represents one of the best continuously exposed outcrops within the northern Alpine foreland basin, has been analyzed for magnetostratigraphic and palynostratigraphic signals. The section comprises the marine-to-terrestrial transition from Lower Marine (UMM) to Lower Freshwater Molasse (USM) sediments. Based on the correlation of the local magnetic pattern with the geomagnetic polarity timescale (GPTS) and palynostratigraphic data, an age of about 31 Ma is suggested for the UMM–USM transition in the Wilhelmine Alpe section. A comparison with coeval magnetostratigraphic sections from central and eastern Switzerland indicates that the regression of the UMM sea along the southern margin of the Molasse basin occurred strongly heterochronously between 31.5 and 30 Ma. The heterochroneity is attributed to the deposition of fan-delta and alluvial fan sediments which document that the overall marine conditions during the UMM were accompanied by strong clastic input derived from the rising Alps. This clastic contribution had a much stronger influence on the depositional pattern than previously thought.     

Development of an integrated conceptual model for the rational management of the transboundary Nestos River, Greece

This paper provides a detailed analysis of the geologic, hydrologic and hydrogeologic characteristics of Nestos River basin, which is formed within the Greek mountainous part of the river. The quantitative analysis was mainly based on the data of the river flow in different gauging points across the rivercourse as well as on the data of groundwater discharge from karst springs of the mountainous area while important conclusions were made regarding the hydraulic connection between the surface waters of the river and the groundwater of the karst aquifers of the basin. The qualitative analysis has shown that the quality of both surface waters and groundwaters of the investigated basin is high, whereas, no sources of contamination were indicated during this research. The possible effects of the two large dams of Platanovrisi and Thesavros are also analysed as they strongly affect the quantitative and qualitative regime of the river delta.     

Post-Collisional Transition from Subduction- to Intraplate-type Magmatism in the Westernmost Mediterranean: Evidence for Continental-Edge Delamination of Subcontinental Lithosphere

Post-collisional magmatism in the southern Iberian and northwesternAfrican continental margins contains important clues for theunderstanding of a possible causal connection between movementsin the Earth's upper mantle, the uplift of continental lithosphereand the origin of circum-Mediterranean igneous activity. Systematicgeochemical and geochronological studies (major and trace element,Sr–Nd–Pb-isotope analysis and laser ⁴⁰Ar/³⁹Ar-agedating) on igneous rocks provide constraints for understandingthe post-collisional history of the southern Iberian and northwesternAfrican continental margins. Two groups of magmatic rocks canbe distinguished: (1) an Upper Miocene to Lower Pliocene (8·2–4·8Ma), Si–K-rich group including high-K (calc-alkaline)and shoshonitic series rocks; (2) an Upper Miocene to Pleistocene(6·3–0·65 Ma), Si-poor, Na-rich group includingbasanites and alkali basalts to hawaiites and tephrites. Maficsamples from the Si–K-rich group generally show geochemicalaffinities with volcanic rocks from active subduction zones(e.g. Izu–Bonin and Aeolian island arcs), whereas maficsamples from the Si-poor, Na-rich group are geochemically similarto lavas found in intraplate volcanic settings derived fromsub-lithospheric mantle sources (e.g. Canary Islands). The transitionfrom Si-rich (subduction-related) to Si-poor (intraplate-type)magmatism between 6·3 Ma (first alkali basalt) and 4·8Ma (latest shoshonite) can be observed both on a regional scaleand in individual volcanic systems. Si–K-rich and Si-poorigneous rocks from the continental margins of southern Iberiaand northwestern Africa are, respectively, proposed to havebeen derived from metasomatized subcontinental lithosphere andsub-lithospheric mantle that was contaminated with plume material.A three-dimensional geodynamic model for the westernmost Mediterraneanis presented in which subduction of oceanic lithosphere is inferredto have caused continental-edge delamination of subcontinentallithosphere associated with upwelling of plume-contaminatedsub-lithospheric mantle and lithospheric uplift. This processmay operate worldwide in areas where subduction-related andintraplate-type magmatism are spatially and temporally associated. KEY WORDS: post-collisional magmatism; Mediterranean-style back-arc basins; subduction; delamination; uplift of marine gateways     

惠民凹陷沙三段岩性油藏勘探中地震技术的应用

针对惠民凹陷岩性油藏勘探存在的难题,开展了岩性油藏勘探技术研究。以地震、地质资料为基础,采用井震联合及小波变换技术,完善了层序地层等时格架建立方法,确定了各三角洲的时空展布规律。应用多元综合标定、地震相划分、正演模拟和测井约束反演一系列技术,实现了不同沉积类型有利砂体的描述。形成了适合惠民凹陷沙三段岩性油藏勘探的技术系列,可以指导惠民凹陷沙三段岩性油藏的勘探。     

晚中更新世以来武威盆地沉积特征——基于WV3 钻孔的释光年代学研究

青藏高原东北缘河西走廊形成了一系列新生代盆地,是研究盆地沉积演化的重要区域。武威盆地位于河西走廊东部,盆地内沉积了较厚的新生代冲洪积地层。为了厘清武威盆地晚中更新世以来的沉积演化历史,笔者等在武威盆地石羊河中上游处钻取了长207 m的WV3 钻孔岩心,获得了上部17 m岩心的 19 个钾长石两步法 pIR200IR290 年龄和 2 个多步法 MET-pIRIR 年龄,结合粒度资料,重建了武威盆地石羊河流域中下游晚中更新世以来的光释光年代学框架和沉积历史。结果表明：两步法 pIR200IR290 和多步法MET-pIRIR年龄在误差范围内一致。220~128 ka时期,沉积速率最小,为 0.35 mm/ka,水动力条件较强,以侵蚀为主;128~108 ka (MIS 5d、MIS 5e) 时期沉积速率为 1.94 mm/ka,沉积物粒径由粗变细,表明此时水动力条件由强变弱;末次冰盛期到全新世早期 (19~9 ka) 沉积速率为2.78 mm/ka,沉积物粒径较细,表明此时水动力条件较弱,沉积速率最大,沉积为主。该地区新构造运动比较活跃,在末次间冰期至末次冰盛期期间存在逆冲活动。该研究对于揭示晚中更新世以来祁连山东北部石羊河流域沉积演化特征具有重要意义。     

扬子及周缘地区上奥陶统-下志留统烃源岩发育环境及其控制因素

扬子地区下古生界发育了上奥陶统五峰组和下志留统龙马溪组两套有效烃源岩,查清其发育环境及其控制因素具有重要的科学理论和油气勘探意义.晚奥陶世开始,扬子地区进入碎屑岩陆棚演化阶段;五峰期-龙马溪期,扬子地区主体为局限的深水陆棚环境,总体呈现出浅水陆棚、深水陆棚、次深海共存的古地理格局.沉积体系展布和沉积演化主要受扬子陆块与华夏陆块的汇聚作用控制.扬子地区上奥陶统-下志留统烃源岩的形成与生烃母质生物的高生产力和高埋藏率、冰期-冰后期之交的气温快速转暖、海平面快速上升以及粘土矿物在有机质富集保存过程中的赋存驻留作用等密切相关.     

海洋立管复模态动力特性分析

考虑阻尼的影响,研究海洋立管的动力特性。通过分析管内流体及管外海洋环境荷载的共同作用,建立海洋立管涡激振动偏微分方程,进而得到立管动力特性方程,用复模态分析法求解动力特性方程得到立管考虑阻尼的自振频率。算例计算表明:考虑阻尼的立管自振频率略小于不考虑阻尼的立管自振频率;立管的自振频率随着内流流速的增加而减小,但内流流速不大时,影响较小;管道长度对立管的自振频率影响较大。