Gravity studies of the Rockall and Exmouth Plateaux using SEASAT altimetry

Abstract SEASAT altimetric measurements are used to determine the gravity anomalies across two passive continental margins: the western margin of the Rockall Plateau, UK, and the Exmouth Plateau off north-west Australia. The small gravity anomalies observed over the starved western margin of the Rockall Plateau require the existence of a major density contrast within the crust, as well as the Moho, and show that the elastic thickness is less than 5 km at the time of rifting. The gravity anomaly over the Exmouth Plateau is compared with the gravity anomaly calculated from the sediment loading of a thin elastic plate, taking account of the variation in crustal thickness. This comparison shows that the Exmouth Plateau also has a small effective elastic thickness of 5 km, even for loads emplaced between 60 and 120 Myr after rifting. Elastic thicknesses of about 5 km have also been reported for other sedimentary basins, and are to be expected if the rheological properties of the crust and mantle depend on the ratio of the present temperature to the melting temperature. Flexural effects are therefore likely to be of minor importance in sedimentary basins.     

近50年云南省雨日及降水量的气候变化

利用1959-2009年云南省30个测站逐日降水资料,通过计算趋势系数、相关系数等现代统计诊断方法,分析了近50年来云南省年、季、月雨日和降水的时空变化特征。结果表明,云南省多年平均雨日空间分布和降水量空间分布基本一致。降水量最大值出现在滇西南地区,滇中到滇东南地区相对较少;年雨日最大值也出现在滇西南地区,滇中地区最少...     

Melt Generation and Movement beneath Theistareykir, NE Iceland

A detailed study of the volume and composition of all the lavasfrom the Theistareykir segment of the Northern Volcanic Zoneof Iceland was designed to study basaltic melt generation andmovement beneath a spreading ridge. The trace element compositionsof the lavas are variable, and those of melt inclusions in olivine,clinopyroxene and plagioclase phenocrysts even more so. We showthat this variability can be produced by mixing instantaneousmelts produced by isentropic decompression of mantle whose initialpotential temperature is 1480°C, and that the calculatedvolume and composition of the average melt is consistent withgeophysical and petrological observations. Pressure and temperatureestimates suggest that the phenocrysts form in the upper mantle,at depths of 30–40 km, and trap melts formed at greaterdepths. Some mixing of the instantaneous melts occurs beforethe melt is trapped, and more mixing occurs before the lavasare erupted. A similar model can account for the compositionof melt inclusions from the FAMOUS area of the Mid-AtlanticRidge, and from the Gorda and Juan de Fuca Ridges. KEY WORDS: basalt; Iceland; melt inclusions; melting; ridges     

鄂尔多斯盆地姬塬地区长6储层渗流特征

对鄂尔多斯盆地姬塬地区长6储层特征、微观渗流特征及影响因素进行综合研究,为开发前期评价提供科学依据。以铸体薄片、扫描电镜等分析化验资料为基础,应用恒速压汞、核磁共振等储层评价新方法对岩石类型、孔隙结构进行分析。研究表明,该区长6储层物性较好,粒间孔发育,储层孔隙结构好,以小孔、微细喉为主,可动流体饱和度高,渗流能力强,有利于高效开发。储层孔隙结构、成岩相及储层润湿性是影响相渗特征的重要因素。     

三分量数字检波器在ZY油田应用效果分析

在水平分量的炮集记录中,数字三分量检波器直达波的椭圆率明显呈现出线性偏振的形态,并具有较高的分辨率,而模拟三分量检波器直达波的线性偏振不清晰,抗干扰能力差.在频谱分析和能量曲线分析的对比中,数字检波器的性能也高于模拟检波器.在PP波弱波阻抗界面的沙河组沙三12段,PS波表现出强反射界面,而且构造幅度比PP波剖面明显.在PS波剖面上,剖面深处两边的构造联系清晰可见,而在PP波剖面上很难解释剖面两边构造之间的关系,表明PS波资料对深层界面的成像能力有时不比PP波能力差,多分量资料在构造勘探上具有互补性.在沙四层底钻遇气层的马62井和马11井的测线CDP位置上,PP波和PS波的振幅比剖面上表现出低振幅比异常区,与钻井结果吻合.用多分量衰减系数或衰减比剖面,能够识别砂岩含气/水产生所产生的高频衰减异常.多分量地震属性及其比值剖面是储层含气异常指示的有效参数.     

Climate-Vegetation Interannual Variability in a Coupled Atmosphere-Ocean-Land Model

The coupled models of both the Global Ocean-Atmosphere-Land System (GOALS) and the Atmosphere-Vegetation Interaction Model (GOALS-AVIM) are used to study the main characteristics of interannual variations. The simulated results are also used to investigate some significant interannual variability and correlation analysis of the atmospheric circulation and terrestrial ecosystem. By comparing the simulations of the climate model GOALS-AVIM and GOALS, it is known that the simulated results of the interannual variations of the spatial and temporal distributions of the surface air temperatures and precipitation are generally improved by using AVIM in GOALS-AVIM. The interannual variation displays some distinct characteristics of the geographical distribution. Both the Net Primary Production (NPP) and the Leap Area Index (LAI) have quasi 1-2-year cycles. Meanwhile, precipitation and the surface temperatures have 2--4-year cycles. Conditions when the spectrum density values of GOALS are less than those of GOALS-AVIM, tell us that the model coupled with AVIM enhances the simulative capability for interannual variability and makes the annual cycle variability more apparent. Using Singular Value Decomposition (SVD) analysis, the relationship between the ecosystem and the atmospheric circulation in East Asia is explored. The result shows that the strengthening and weakening of the East Asian monsoon, characterized by the geopotential heights at 500 hPa and the wind fields at 850 hPa, correspond to the spatiotemporal pattern of the NPP. The correlation between NPP and the air temperature, precipitation and solar radiation are different in interannual variability because of the variation in vegetation types.     

鄂尔多斯盆地陕北地区长101高渗储层的控制因素

鄂尔多斯盆地中部的陕北地区,是盆地中生界油藏最为丰富的区带之一,主要含油层系为三叠系延长组长6层,其次是侏罗系延安组,以往的研究也多集中于以上含油层。长101层是近几年勘探评价的新层系,利用现代测试技术和数理统计研究了长101层的沉积、成岩特征,分析高渗储层控制因素。结果表明,沉积环境控制长101高渗储层分布,成岩作用对长101高渗储层的形成起主导作用。主河道砂岩厚度大、粒度粗、孔喉大、孔隙连通性好,河道侧翼砂岩厚度薄、粒度细、孔喉小、孔隙连通性差。因此,压实作用后主河道砂岩粒间孔含量多于河道侧翼砂岩,导致主河道砂岩胶结作用弱于河道侧翼砂岩,而溶蚀作用强于河道侧翼砂岩,主河道砂岩物性明显好于河道侧翼。沉积、成岩作用共同造成长101高渗储层发育于河道主带和分流交汇部位。     

燕山地区宣龙坳陷洪水庄组和铁岭组沉积环境

依据野外露头等资料,对燕山地区宣龙坳陷洪水庄组和铁岭组进行了详细的沉积相分析,认为该区洪水庄组和铁岭组沉积相为碳酸盐岩台地相,并可进一步划分出碳酸盐岩潮坪和潟湖2种亚相,其中洪水庄组主要为潟湖沉积环境;铁岭组主要发育潮坪亚相:包括潮上、潮间和潮下3个相带。在此基础上,结合区域地质背景,以及23件碳酸盐岩样品的常量元素和微量元素相关关系、组分含量及某些元素的比值对特征,探讨了研究区元素的沉积地球化学特征。研究表明:①研究区目的层段样品的化学成分以CaO和MgO为主,且ω(CaO)>ω(MgO),含较多的SiO2,该时期碳酸盐岩沉积时混入较多的陆源碎屑;②Mg/Ca比值显示洪水庄组与铁岭组沉积期气候温暖潮湿;③Sr/Ba比值显示铁岭组沉积期为古盐度正常的海相沉积环境,洪水庄期为古盐度较低的海相沉积环境。     

On applying viewshed analysis for determining least-cost paths on Digital Elevation Models

The concept of computing least-cost paths has been proposed and discussed for a few decades but only in simplified form due to the limited computational resources in the past. With the advancement of computer technology in speed and data storage, it is now possible to implement least-cost path algorithms with realistic conditions. In this paper, we present our implementations of least-cost paths by integrating viewshed information computed from digital elevation models. Our implementations and analyses include four possible types of paths. They are scenic paths, strategic paths, hidden paths, and withdrawn paths. While possible applications of these least-cost paths include planning of civil engineering, military and environmental planning, other extensions can be formulated without much difficulty.     

秦岭─大别造山带及其南北缘地震层析成像

利用秦岭─大别造山带及其毗邻地区３１０个地震台站记录到的区域地震２３６００条Ｐ波到时数据,重建了该区地壳和上地幔三维速度图像。结果表明：１．秦岭─大别造山带及其毗邻地区地壳和上地幔存在显著的横向不均匀性,直至１１０ｋｍ深度处依然明显。２．地壳上部的速度图像与地表地质构造密切相关：造山带隆起区显著高速;盆地及坳陷区明显低速。由速度鲜明对比勾勒出的秦岭─大别造山带南界基本上位于扬子北缘主边断裂带上。３．中地壳的速度图像表明,造山带内部的一些低速区对应于一些大型推覆构造。４．４０＋０ｋｍ深度处的速度图像反映了该区莫霍界面深度的起伏。大致以１０７°Ｅ为界,以东地区地壳厚度小于４０ｋｍ,以西地区大于４０ｋｍ,且呈现出往西地壳逐渐加厚的趋势。５．位于滦川、商县、丹凤的北秦岭构造带,上地幔顶部出现低速异常,异常速度值约为７．３９—７．５５ｋｍ／ｓ。结合地球物理测深的结果,可能是由下地壳、上地幔顶部的热过程所致。