On the geologic structure of the Explora Escarpment (Weddell Sea,Antarctica) revealed by satellite and Shipboard data evaluation

Bathymetric, gravity, and magnetic data from Antarctic expeditions with RV POLARSTERN and satellite altimeter data from the Geosat Geodetic Mission are analysed using methods from geostatistics and geophysical inverse theory.The Explora Escarpment represents the edge between the Antarctic Continental Shelf and the Weddell Abyssal Plain. It is an important link in the reconstruction of Gondwana breakup, but a feature as large as the 2000 m deep Wegener Canyon was only discovered in 1984, when extensive bathymetric, gravimetric, and magnetic surveys with RV POLARSTERN began.Geostatistics, the theory of regionalized variables, is applied to integrate dense surveys of Wegener Canyon and sparse observations in adjacent areas into maps with full coverage of the 230 km by 330 km area at 10°–20° W/70°–72° S. The resultant highresolution bathymetric and gravity maps reveal detailed structures of the Explora Escarpment. Using geophysical inversion, the gravity terrain effect is calculated. Satellite data are used for their better coverage, but have much lower resolution. Nevertheless, the structures of Wegener Canyon and other more prominent features appear with surprisingly good correlation also in the Geosat altimeter data. While it was initially supposed that Wegener Canyon is purely an erosional structure, the magnetic map now provides evidence of the canyon's tectonic origin.     

准噶尔盆地西北缘克-百地区不整合面及其动力学条件

不整合及其性质和强度的确定对理解克拉玛依至百口泉地区构造变形历史和油气聚集规律具有重要意义。根据地震资料研究显示,该区二叠纪至中生代地层中存在多个不整合面,且多为构造运动的反映。其中对克-百地区构造形成具有重要影响的有四期,其一发生在中二叠统下乌尔禾组沉积后,主要表现为冲断掀斜运动,使其前的二叠纪沉积向南东方向掀斜抬升,遭受剥蚀;其二发生在三叠纪末期,对克百断裂上盘大侏罗沟断层至百口泉段的构造有重要影响;其三发生在中侏罗世末,该期构造运动在克百断裂带及其上盘表现最为清楚,以冲断为主,局部地区有褶皱现象;其四发生在早白垩世末期,表现为掀斜运动,褶皱和断裂作用相对较弱。克-百地区不同时期、不同构造部位变形的差异性与构造动力条件密切相关。     

An Albian–Cenomanian unconformity in the northern Andes: Evidence and tectonic significance

The Villeta Group of Colombia and equivalent stratigraphic units of Venezuela and Ecuador comprise marine sequences ranging from Albian to Santonian in age. Deposition of the Villeta Group was presumed to take place entirely in quiet tectonic conditions in a passive margin setting that occupied NW South America. From a large database of 2D/3D seismic, well, surface geology, and biostratigraphic data, we present evidence for intra-Villeta (mostly late Albian–Cenomanian) deformation in parts of the Upper Magdalena Valley and Eastern Cordillera of Colombia, controlled by transpressional fault reactivation, produced by transpressional fault reactivation and thrusting that resulted in an angular unconformity. This event has been largely unnoticed in the literature, but previously scattered evidence supports our observations, suggesting regionally extensive tectonism. Published fission-track age determinations and other geologic evidence from Colombia and Venezuela suggest significant uplifts around 80–100 m.y., which may reflect changes in the subduction regime, with compressional deformation in certain regions and extensional deformation in others. A late Albian onset of compressional deformation along the Colombian and Peruvian segments of the Andes may be related to the opening of the South Atlantic Ocean at equatorial latitudes. Identification of tectonic activity with development of an unconformity in intra-Villeta times provides new insights into understanding the evolution of the Upper Magdalena Valley and adjacent areas of Colombia and western Venezuela and creates new possibilities for hydrocarbon exploration, with additional trapping phases, better reservoir preservation by early migration and secondary porosity, and ultimately facies changes with stratigraphic potential.     

内蒙古大青山地区寒武系与奥陶系之间的一个重要的层序界面

大青山地区寒武纪－奥陶纪地层分布零星，是由中生代逆冲推覆构造就位于此的一系列近东西向延展的构造岩片组成。下寒武统色麻沟组直接覆盖在太古界变质岩之上，缺失中元古界什那干群，寒武系与奥陶系之间呈假整合接触，标志着区内寒武纪与奥陶纪之间发生过一次抬升构造运动，其形成机制与古亚洲洋内的稳定陆快向华北板块拼贴事件有关，是早奥陶世末期华北板块整体抬升的序幕。这个层序界面的认识，对于恢复华北板块北部边缘构造演化历史具有重要意义。     

Hydrologic and geomorphic processes in the Colville River delta, Alaska

The Colville basin drains the North Slope of Alaska and is one of several large Arctic river systems located within permafrost. The timing and style of fluvial processes in the earth's permafrost regions differ from those occurring in midlatitude settings. Moreover, in comparison to temperate-zone systems, rivers located entirely within permafrost perform most of their work during relatively short periods of time. This paper examines river ice hydrology and the resulting geomorphic processes that occur within the Colville delta, Alaska. Fluvial processes and landform development within the Colville delta occur after the flood-pulse is initiated by the breakup of river ice. During this 4-month period, the geomorphic processes are largely influenced by the movement of ice. The flood-pulse and accompanying river ice influences erosional and depositional processes and results in unique styles of sediment transport, deposition, and riverbank erosion.     

论全吉运动

全吉运动发生于柴北缘地区的全吉山一带，除角度不整合的自然现象外，接触面上下岩层之岩性载然不同、变质程度迥异，同位素测试值显示，是一次强烈的区域动力变质构造运动。     

内蒙古大青山印支运动厘定

根据中下侏罗统五当沟组与下伏地层之间角度不整合接触关系，结合同位素年代与岩浆活动特征和各种构造要素之间叠加改造关系，证实了大青山地区存在强烈印支运动。构造样式和构造要素组合特点表明大青山印支运动是一次强烈逆冲推覆、褶皱造山运动，形成了东西向展布的大型逆冲推覆构造和褶皱构造，构成了大青山地区中生代造山带主体构造格架。在地壳构造变形过程中伴随有强烈岩浆活动，形成了一系列的岩株和岩墙。大青山地区印支构造运动的确定对研究阴山—燕山板内造山带形成演化历史和地球动力学机制具有重要意义。     

不整合界限地层单位确立及划分的重要意义──兼论华北地层区不整合界限地层单位的划分和命名

在进行岩石地层划分时，有必要进行不整合界限地层单位的划分。不整合界限地层单位是顶底以不整合界面为限，而由有关联的若干个基本岩石地层单位──组（群）组成的组合。和岩石地层单位一样，是自然界存在的客观实体。初步建议华北地区划分为８个不整合界限地层单位：桑干河序列、五台山序列、滹沱河序列、秦幽序列、冀鲁序列、三晋序列、燕辽序列、河海序列。不整合界限地层单位的划分、确立，是进行地层格架分析、进行层序地层学研究的前提，有利于以岩石地层单位（即以不整合界限地层单位）编制小比例尺地质图。     

鄂西娄山关组顶部古岩溶不整合面的发现及层序地层学意义

鄂西娄山关组顶部存在古岩溶不整合面，有众多陆上暴露和溶蚀标志，表明其产生受寒武纪末海平面下降事件的控制。它不仅形成了碳酸盐台地上典型的Ⅱ型层序界面，而且恰与寒武—奥陶纪年代地层界线相重合，体现了层序界面、年代界线和事件界线三位一体的有机结合     

议京西大台地区的燕山运动

作者研究了京西大台地区的燕山运动，初步研究表明：这里不存在强烈的挤压变形迹象和显著的角度不整合．缺乏磨拉石建造。龙门组是厚度有限的河流相沉积，九龙山组是具有弱火山活动的湖相一滨湖相沉积。在隆起带和沉降带之间侏罗系地层显著的厚度变化率、大安山一斋堂滑覆构造及其派生的髫髻山断陷盆和大量高角度滑动面理，都显示了伸展构造背景下基底断块的差异升降。髫髻山组与壳幔相互作用有关的一套火山岩显示了上述运动的深部背景。