鄂尔多斯盆地三叠系延长组长8—长7油层组高分辨率层序地层格架及其地质意义

鄂尔多斯盆地三叠系长8—长7油层组位于延长组中下部,代表湖盆最大扩张期,主要属于湖成三角洲相。运用高分辨率层序地层学原理,详细分析了鄂尔多斯盆地三叠系延长组长8—长7油层组地层沉积的基准面旋回特征,识别出1个长期旋回、3个中期旋回(MSC3、MSC4、MSC5)和15~25个短期旋回,分析得出长8油层组为三角洲环境,到长7油层组则演变为半深—深湖环境。3个中期旋回当中,MSC3、MSC4是以上升半旋回为主的不对称旋回,并在MSC4上升半旋回顶部形成盆地最大湖泛面,MSC5以下降半旋回为主的不对称旋回,发育浊积扇。对不同井基准面旋回的分析得出:储集层段多发育于短期基准面上升半旋回的水下分流河道、河口坝和浊流沉积砂体中,且砂体与前三角洲泥构成的烃源岩相匹配,形成岩性油气藏。运用高分辨率层序地层学原理建立地层格架对指导鄂尔多斯盆地延长组油气勘探具有重要指导意义。     

黑龙江省五常市多目标地球化学调查与评价研究

文章对五常市开展二年多的首次多目标地球化学调查研究工作进行了总结,对多目标地球化学调查的工作方法及取得的初步成果进行了简要的介绍,针对多目标地球化学调查工作中存在的土壤元素地球化学的基准值确定方法、土壤污染检查与评价、农业生态地球化学研究等相关问题,提出了自己的见解和今后开展类似工作的具体思路。     

北羌塘坳陷冬曲地区上三叠统巴贡组扇三角洲沉积特征

北羌塘坳陷冬曲地区上三叠统巴贡组为一套碎屑岩沉积,在垂向上具有两个向上变粗的充填序列。根据沉积体产出形态和叠置序列、岩石组合与结构、沉积构造及流体性质等沉积特征,确定该套沉积体为扇三角洲相沉积,进而可划分出扇头、扇中、扇尾3个亚相。发育底冲刷构造、粒序层理、平行层理、交错层理等,表明其流体性质既有重力流又有牵引流特征。通过该套扇三角洲沉积体的认识,对研究该区古构造背景、沉积环境及油气地质条件等具有重要意义。     

西天山大哈拉军山组火山岩SHRIMP锆石U-Pb年龄及其构造意义

新疆早石炭世大哈拉军山组火山岩由西向东表现出由早到晚的演化规律。伊宁县博尔博松河孟玛热勒林场附近大哈拉军山组底部的英安质晶屑岩屑凝灰岩的SHRIMP锆石U-Pb年龄为359±2Ma,表明西天山西段该组底界时代为晚泥盆世末期—早石炭世之间。岩石地球化学数据统计表明,大哈拉军山组火山岩主要受岩浆结晶分异作用控制,是泥盆纪末期—石炭纪时期洋壳消减、壳幔混熔的产物。其岩石组成、时空分布的变化与天山洋由西向东的俯冲―碰撞过程相对应,不需要对其进行解体。     

莺-琼盆地基底控制断裂样式的模拟探讨

莺歌海盆地与琼东南盆地(即莺一琼盆地)是南海西北部2个重要的含油气盆地。莺歌海盆地走向NW,发育在红河断裂带上;琼东南盆地走向NE,与莺歌海盆地近直角相交。根据物理模拟实验,认为莺歌海盆地的演化受到了NW与近S-N向基底断裂的控制,在印支地块顺时针挤出应力场下发育和演化;而琼东南盆地则受到NE向基底断裂的控制,在SSE向伸展应力场控制下发育,NW与NE向构造带相互影响,造成了琼东南盆地北侧边界断裂走向近E—W,向南呈台阶式下掉,南侧边界断裂走向NE,莺琼过渡区隆凹格局复杂。由于莺歌海盆地NW向构造活动早于琼东南盆地NE向裂陷作用,从而导致NW向构造控制地位的形成,NW向断裂和构造表现为对NE向断裂和构造的阻截。     

Emplacement of massive deposits by sheet flow

Turbidity current and coastal storm deposits are commonly characterized by a basal sandy massive (structureless) unit overlying an erosional surface and underlying a parallel or cross-laminated unit. Similar sequences have been recently identified in fluvial settings as well. Notwithstanding field, laboratory and numerical studies, the mechanisms for emplacement of these massive basal units are still under debate. It is well accepted that the sequence considered here can be deposited by waning-energy flows, and that the parallel-laminated units are deposited under transport conditions corresponding to upper plane bed at the dune–antidune transition. Thus, transport conditions that are more intense than those at the dune–antidune transition should deposit massive units. This study presents experimental, open-channel flow results showing that sandy massive units can be the result of gradual deposition from a thick bedload layer of colliding grains called sheet flow layer. When this layer forms with relatively coarse sand, the non-dimensional bed shear stress associated with skin friction, the Shields number, is larger than a threshold value approximately equal to 0·4. For values of the Shields number smaller than 0·4 the sheet flow layer disappeared, sediment was transported by a standard bedload layer one or two grain diameters thick, and the bed configuration was characterized by downstream migrating antidunes and washed out dunes. Parallel laminae were found in deposits emplaced with standard bedload transport demonstrating that the same dilute flow can gradually deposit the basal and the parallel-laminated unit in presence of traction at the depositional boundary. Further, the experiments suggested that two different types of upper plane bed conditions can be defined, one associated with standard bedload transport at the dune–antidune transition, and the other associated with bedload transport in sheet flow mode at the transition between upstream and downstream migrating antidunes.     

STATISTICAL EVALUATION OF GLACIER BOREHOLES AS INDICATORS OF BASAL DRAINAGE SYSTEMS

Between 1988 and 1992 closely spaced arrays of boreholes were drilled at Small River Glacier, British Columbia. The borehole arrays have been used to investigate the interannual and spatial consistency of patterns of basal hydraulics beneath the glacier. A simple robust classification was devised identifying unconnected, high standing, low standing and dry base water levels in boreholes. Spatial and interannual comparisons were made using a simple nearest neighbour statistic, corrected for differences in frequency of different borehole types and evaluated using Monte Carlo confidence intervals to compensate for array form. Arrays in the lower ablation zone showed spatial and interannual coherence, with three distinct areas characterized by low water pressure, till-associated non-connection and high pressure. There was no indication of a dominant conduit. Slightly higher up-glacier borehole patterns were less coherent, and varied from year to year, probably a result of subglacial karst capturing basal waters at a number of low pressure points at the bed. Therefore both the upper and lower arrays at Small River Glacier appear to encompass unusual drainage conditions. The nearest neighbour analysis provides valuable constraints on more specific interpretation.     

武汉某深基坑锚式连锁灌注排桩变形的有限元分析

以武汉某深基坑为例,采用有限单元数值模拟方法,研究基坑开挖深度,锚杆预应力,桩体厚度,桩体嵌入深度的变化与其锚式连锁灌注排桩支护结构水平变形位移的关系。     

A Gravel Outwash/Deformation till Continuum, Skalafellsjokull, Iceland

A stratigraphic sequence exposed by river erosion in the foreland of Skalafellsjokull, southern Iceland, displays five lithofacies documenting glaciofluvial deposition followed by glaciotectonic disturbance and subglacial deformation. Lithofacies 1a and 1b are glaciotectonically thrust glaciofluvial outwash and subglacial deformation till respectively from an early advance of Skalafellsjokull. Lithofacies 2, massive gravels and clast–supported diamictons, documents the deposition of glaciofluvial outwash in the proto–River Skala prior to overriding by Skalafellsjokull during the Little Ice Age. During overriding, lithofacies 2 was glaciotectonically disturbed and now possesses the clast fabric and structural characteristics of G _B (non–penetratively deformed) and G _A (penetratively deformed) type glaciotectonites. A shear zone separates lithofacies 2 from overlying lithofacies 3, the latter possessing the clast fabric signature of a D _A (dilatant) type deformation till although it was originally deposited as a discontinuous diamicton within a glaciofluvial sequence, probably as a hyperconcentrated flow, and appears to have been at least partially derived from underlying materials by glaciotectonic cannibalization. Lithofacies 4 is a glaciofluvial deposit comprising two coarseningupward sequences of gravel and diamicton. These facies have been overprinted with G _B glaciotectonite and D _A?B (dilatant to non–dilatant) deformation till structures and clast fabrics recording a vertical progression towards more pervasively deformed material. The sequence is capped by lithofacies 5, a two–tiered deformation till possessing the characteristics of D _A and D _B horizon subglacial tills previously reported from Icelandic glacier snouts. The whole sequence comprising lithofacies 2–5 represents a gravel outwash/deformation till continuum displaying variable strain signaturesproduced in response to stress induced by the overriding of Skalafellsjokull during the Little Ice Age. These signatures are dictated by the sediment rheology and a vertical strain profile for the sediment pile during glacier overriding is reconstructed.     

黑河水库大坝右坝肩滑体底滑带结构特征分析

从微观现象到宏观构造 ,从物理力学性质到地震波测试 ,详细描述了滑体底滑带的结构特征 ,论证了底滑带和泥化带的力学特征和蠕变特征。对滑体的评价和稳定性计算提供了依据。