青藏高原东北缘若尔盖盆地黄土的成因

通过对盆地黄土的粒度组分、石英砂的表面结构以及其它地质现象的综合研究,对若尔盖盆地黄土成因进行了探讨.在黄土的概率累计曲线上,跃进组分和悬移组分反映明显,以悬移组分为主,并采用矩阵法计算了黄土的粒度参数.对黄土扫描电镜观察和石英颗粒表面特征的统计分析,反映出气流搬运的特点,以发育碟形坑为其主要标志,具有风成环境的表面特征组合.黄土中孢粉稀少,并在邻区黄土层中发现有冰楔构造.根据上述特征分析出,若尔盖盆地黄土应为冰缘风成黄土.以测年资料为依据,黄土形成年代主要为马兰期茶镇梁子黄土和离石期索克藏寺黄土.      

新疆库车坳陷古近系苏维依组高精度层序地层及其发育的主控因素探讨

库车坳陷位于塔里木盆地北缘南天山山前,古近系苏维依组沉积期为前陆盆地发育阶段,沉积了巨厚的河流一三角洲和滨浅湖碎屑岩建造.库车坳陷独特的地理位置和苏维依组野外大面积连续出露,为高精度层序地层分析和层序发育的主控因素探讨提供了有利条件.以相对易于追踪对比的水进期稳定泥岩为界.在苏维依组2个三级层序中进一步划分出10个四级层序和数十个五级层序.四级层序中发育有三角洲前缘河口坝、水下分流河道、下切水道、曲流砂坝、干盐湖等沉积.其中四级层序Pssl和Pss6中的曲流河道砂坝、下切谷充填和四级层序Pss3,Pss5,Pss8中的三角洲前缘河口坝、水下分流河道等砂体构成区内的主力储层,与上覆的浅湖泥或干盐湖膏泥岩构成良好的储盖组合.四级层序地球化学特征和准层序的叠置样式表明,高精度层序发育是构造沉降背景下气候作用、湖平面波动和沉积物源供给综合作用的结果,其中气候因素和沉积物源供给起了决定性作用.干旱和潮湿气候影响了湖平面波动,控制着层序充填和准层序叠置形式;逆冲带近端、远端与盆地中部沉积物源供给不同,决定了盆地内不同部位的层序发育样式和准层序的叠置形式不同.     

Groundwater geology of the western Siberian craton (implications for petroleum exploration)

According to the suggested model of groundwater stratigraphy obtained on the basis of geological and groundwater data, the sedimentary cover of the western Siberian craton includes the suprasalt, salt, and subsalt groundwater units subdivided into regional and subregional reservoirs. It has been found reasonable to carry out special groundwater studies, either before or concurrently with petroleum exploration, in order to ensure supply of drinking, household, and technological waters to meet the demand of oil and gas production and to make groundwater available for oil-well pressure maintaining systems and for underground burial of waste waters.     

基于高分辨率层序地层学的大庆长垣南部浅层气分布特征研究

松辽盆地大庆长垣南部黑帝庙油层具有良好的浅层气开发潜力。应用高分辨率层序地层学原理,通过对各级基准面旋回结构、叠加样式的沉积动力学分析,利用1164口测井曲线和6口井岩芯资料,把松辽盆地大庆长垣南部黑帝庙油层划分为1个长期基准面旋回、4个中期基准面旋回、25个短期基准面旋回,提出了研究区北部为后期构造抬升而缺失的层序地层新格架。短期基准面旋回内储层沉积特征及单砂体展布规律研究表明:黑帝庙油层为松辽盆地北部物源控制的湖盆逐渐萎缩背景下形成的河控缓坡三角洲前缘亚相沉积体系,微相类型以水下分流河道、河口坝和远砂坝为主。依据区域性湖侵成因的9套暗色泥岩盖层把黑帝庙油层垂向上划分为9套储盖组合;生储盖组合特征及动态资料综合分析表明浅层气主要分布于长期旋回下降早期的中期旋回下降晚期或上升早期储层砂体中;单砂体展布规律与气源断层和构造的合理匹配是浅层气富集的主控因素,气藏类型主要为构造—岩性、断层—岩性圈闭,在以上研究的基础上应用气水解释模板在全区预测地质储量,其研究对指导整个松辽盆地北部浅层气勘探与开发具有重要理论意义和实际应用价值。     

新疆塔河油田石炭系层序地层分析及低水位岩性圈闭预测

对新疆塔河油田石炭系岩性圈闭的地震和钻井层序地层分析结果表明,石炭系由SQ1、SQ2、SQ3三个三级层序组成,分别以障壁岛-泻湖体系、潮控碎屑滨岸体系、辫状河三角洲体系为特征,总体反映了陆源供给由弱到强、研究区北部抬升的阶段性过程.在SQ2层序发育时期,地形平缓,砂体储层发育于海进体系域和高水位体系域的下部,导致与沉积作用相关的岩性圈闭发育.SQ1、SQ2层序的发育主要受海平面变化的控制;SQ3层序的形成主要受控于大塘中-晚期的构造挤压和抬升作用.SQ1层序内的鼻状凸起的两侧--西北部和东南部斜坡区、SQ3层序内的由北部褶皱隆起和南部差异压实联合作用形成的次级凹陷,是形成低水位岩性圈闭的有利场所.     

松辽盆地盆西斜坡白垩系姚家组下切谷充填结构

白垩纪青山口组沉积末期至姚家组沉积初期,松辽盆地发生了湖平面大幅度下降,湖区大规模萎缩,形成了SSQq-qn和SSQy-n之间的二级层序界面.这一时期,西部斜坡普遍暴露,缺失了三级层序SQqn4和SQy1地层,并在齐齐哈尔古水系的作用下在西部斜坡的北部形成了下切谷.下切谷长约70km,宽约20km,呈NW-SE延伸.在SQy23层序水进域,下切谷逐渐被充填.下切谷发育区SQy23水进域的地层厚度明显高于相邻区域,在沉积走向上的高地层厚度梯度带反映了下切谷的边界.下切谷充填序列具有多期旋回性特征,一个完整的短期充填旋回的底界为侵蚀面,侵蚀面之上依次发育泥砾岩、具交错层理含陆源砾石和泥砾中-细粒砂岩、具波纹层理粉砂质泥岩和泥岩.充填下切谷的不同短期旋回的砂体在空间上具有叠瓦状结构.在倾向剖面上,砂体沿下切谷底界面逐层叠置超覆,向盆地方向分叉并尖灭在泥岩中,反映了河-湖共同作用.在横剖面上,砂体呈透镜状错叠.早期的砂体主要发育于相对深谷部位,相对高部位以泥质充填为主,后期的砂体不受原始深谷限制.在SQy23最大湖泛期,下切谷内以泥质充填为主.      

Geology of the Side Crater of the Erebus volcano,Antarctica

The summit cone of the Erebus volcano contains two craters. The Main crater is roughly circular (∼ 500 m diameter) and contains an active persistent phonolite lava lake ∼ 200 m below the summit rim. The Side Crater is adjacent to the southwestern rim of the Main Crater. It is a smaller spoon-shaped Crater (250–350 m diameter, 50–100 m deep) and is inactive. The floor of the Side Crater is covered by snow/ice, volcanic colluvium or weakly developed volcanic soil in geothermal areas (a.k.a. warm ground). But in several places the walls of the Side Crater provide extensive vertical exposure of rock which offers an insight into the recent eruptive history of Erebus. The deposits consist of lava flows with subordinate volcanoclastic lithologies. Four lithostratigraphic units are described: SC 1 is a compound lava with complex internal flow fabrics; SC 2 consists of interbedded vitric lavas, autoclastic and pyroclastic breccias; SC 3 is a thick sequence of thin lavas with minor autoclastic breccias; SC 4 is a pyroclastic fall deposit containing large scoriaceous lava bombs in a matrix composed primarily of juvenile lapilli-sized pyroclasts. Ash-sized pyroclasts from SC 4 consist of two morphologic types, spongy and blocky, indicating a mixed strombolian-phreatomagmatic origin. All of the deposits are phonolitic and contain anorthoclase feldspar.     

Rhyolitic ignimbrites in the Rogerson Graben,southern Snake River Plain volcanic province: volcanic stratigraphy,eruption history and basin evolution

The 80 km long NNE-trending Rogerson Graben on the southern margin of the central Snake River Plain, Idaho, USA, hosts a rhyolitic pyroclastic succession, 200 m thick, that records a period of successive, late-Miocene, large-volume explosive eruptions from the Yellowstone–Snake River Plain volcanic province, and contemporaneous extension. The succession, here termed the Rogerson Formation, comprises seven members (defined herein) and records at least eight large explosive eruptions with numerous repose periods. Five high-grade and extremely high-grade ignimbrites are intercalated with three non-welded ignimbrites and two volcaniclastic deposits, with numerous repose periods (palaeosols) throughout. Two of the ignimbrites are dominantly rheomorphic and lava-like but contain subordinate non-welded pyroclastic layers. The ignimbrites are typical Snake River Plain high-silica rhyolites, with anhydrous crystal assemblages and high inferred magmatic temperatures (≤ 1,025°C). We tentatively infer that the Jackpot and Rabbit Springs Members may have been emplaced from the Bruneau–Jarbidge eruptive centre on the basis of: (1) flow lineation trends, (2) crystal assemblage, and (3) radiometric age. We infer that the overlying Brown’s View, Grey’s Landing, and Sand Springs Members may have been emplaced from the Twin Falls eruptive centre on the basis of: (1) kinematic indicators (from the east), and (2) crystal assemblage. Furthermore, we have established the contemporaneous evolution of the Rogerson Graben from the emplacement of the Jackpot Member onwards, and infer that it is similar to younger half-graben along the southern margin of the Snake River Plain, formed by local reactivation of Basin and Range structures by the northeastwardly migration of the Yellowstone hot-spot. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Late Cretaceous – Early Tertiary sedimentation and tectonic inversion in the southern Netherlands

Analysis of the Upper Cretaceous stratigraphy of the Peel Block reveals the basin development of the block to have been influenced by both the inversion of the Roer Valley Graben and Central Netherlands Basin, and the overall Late Cretaceous transgression. Sediments of Santonian to Danian age were deposited on the block. These sediments are compared with the detailed lithostratigraphy of southern Limburg, where Late Cretaceous strata are exposed. Four successions can be recognised in southern Limburg. The two oldest successions, the Santonian Oploo Formation (new name, proposed in the present contribution) and the mainly Early Campanian Vaals Formation, are restricted to the central and northern parts of the block. These siliciclastic formations were deposited under the influence of inversion of the Roer Valley Graben and the Central Netherlands Basin, as well as under the influence of a rising sea level. Towards the north, sands of the Oploo Formation grade into marls and chalks of the Ommelanden Formation. The two youngest successions comprise the largely Late Campanian to Maastrichtian Gulpen and Maastricht Formations and the Danian Houthem Formation. These chalk formations were deposited under the influence of regional subsidence during a sea-level highstand. Subsequent to deposition of the Houthem Formation, a regional regression triggered a change from shallow-marine carbonate to paralic siliciclastic deposition.     

A sequence stratigraphic model for the Lower Coal Measures (Upper Carboniferous) of the Ruhr district, north-west Germany

Upper Carboniferous Coal Measures strata have been interpreted traditionally in terms of cyclothems bounded by marine flooding surfaces (marine bands) and coal seams. Correlation of such cyclothems in an extensive grid of closely spaced coal exploration boreholes provides a robust stratigraphic framework in which to study the Lower Coal Measures (Namurian C–Westphalian A) of the Ruhr district, north-west Germany. Three distinct types of cyclothem are recognized, based on their bounding surfaces and internal facies architecture. (1) Type 1 cyclothems are bounded by marine bands. Each cyclothem comprises a thick (30–80 m), regionally extensive, coarsening-upward delta front succession of interbedded shales, siltstones and sandstones, which may be deeply incised by a major fluvial sandstone complex. The delta front succession is capped by a thin (<1 m), regionally extensive coal seam and an overlying marine band defining the top of the cyclothem. (2) Type 2 cyclothems are bounded by thick (≈1 m), regionally extensive coal seams with few splits. The basal part of a typical cyclothem comprises a thick (15–50 m), widespread, coarsening-upward delta front or lake infill succession consisting of interbedded shales, siltstones and sandstones. Networks of major (>5 km wide, 20–40 m thick), steep-sided, multistorey fluvial sandstone complexes erode deeply into and, in some cases, through these successions and are overlain by the coal seam defining the cyclothem top. (3) Type 3 cyclothems are bounded by regionally extensive coal seam groups, characterized by numerous seam splits on a local (0·1–10 km) scale. Intervening strata vary in thickness (15–60 m) and are characterized by strong local facies variability. Root-penetrated, aggradational floodplain heteroliths pass laterally into single-storey fluvial channel-fill sandstones and coarsening-upward, shallow lake infill successions of interbedded shales, siltstones and sandstones over distances of several hundred metres to a few kilometres. Narrow (<2 km) but thick (20–50 m) multistorey fluvial sandstone complexes are rare, but occur in a few type 3 cyclothems. Several cyclothems are observed to change character from type 1 to type 2 and from type 2 to type 3 up the regional palaeoslope. Consequently, we envisage a model in which each cyclothem type represents a different palaeogeographic belt within the same, idealized delta system, subject to the same allogenic and autogenic controls on facies architecture. Type 1 cyclothems are dominated by deltaic shorelines deposited during a falling stage and lowstand of sea level. Type 2 cyclothems represent the coeval lower delta plain, which was deeply eroded by incised valleys that fed the falling stage and lowstand deltas. Type 3 cyclothems comprise mainly upper delta plain deposits in which the allogenic sea-level control was secondary to autogenic controls on facies architecture. The marine bands, widespread coals and coal seam groups that bound these three cyclothem types record abandonment of the delta system during periods of rapid sea-level rise. The model suggests that the extant cyclothem paradigm does not adequately describe the detailed facies architecture of Lower Coal Measures strata. Instead, these architectures may be better understood within a high-resolution stratigraphic framework incorporating sequence stratigraphic key surfaces, integrated with depositional models derived from analogous Pleistocene–Holocene fluvio-deltaic strata.