黑龙江省三江盆地鹤岗凹陷下白垩统猴石沟组沉积特征

笔者等通过对鹤岗凹陷北部露头和钻孔资料的综合利用,结合少量的样品分析及薄片鉴定工作,对研究区下白垩统猴石沟组主要岩石学特征、沉积相类型及展布特征进行了综合研究,在此基础上,以砂岩型铀矿成矿理论为指导,对猴石沟组有利成矿砂体的沉积相类型进行了初步讨论。认为①猴石沟组砂体以长石岩屑砂岩和岩屑砂岩为主,主要为陆相淡水沉积环境,具较高的还原容量;②研究区内猴石沟组主要为扇三角洲沉积环境,并划分为辫状河道、漫滩沼泽、水下分流河道、河口坝、席状砂和分流间湾等6种微相;③猴石沟组沉辫状河道砂体可作为寻找潜水氧化带型砂岩型铀矿的重点类型,而水下分流河道砂体是作为寻找层间氧化带型砂岩型铀矿的主攻类型。     

Messinian carbonate and alluvial fan sedimentation in Alonnisos Island,Greece: sedimentary response to basement controls,inversion tectonics and climatic fluctuations

A marginal marine carbonate environment, giving away to an alluvial one, was established during Messinian time on Alonnisos Island, the footwall upland of the Southern Marginal Fault of the Sporades Basin (SMFS). Analysis of the evolving depositional systems, with emphasis on their sedimentation processes, faulting patterns and palaeopedological factors, has permitted an interpretation of the simultaneous controls of tectonism and climate. The carbonate sediments were deposited in a shallow marine environment formed along a faulted continental margin under warm and semi-arid climatic conditions. Faulting consisted of NE-trending dextral reverse faults and NW-trending strike slip faults, produced by WNW-directed compression. The basement structural elements affected the spatial distribution of the offshore and shoreface facies, whereas fifth-order cycles of sea-level change were responsible for the development of metre-scale, shallowing-up cycles. The compressional structures were subsequently reactivated by NNE extension. This tectonic inversion, together with a global sea-level fall, triggered alluvial fan sedimentation. Fan sedimentation was disrupted by long periods of non-deposition and soil formation under warm climatic conditions. Three distinct units are recognized in the fan: a lower unit consisting of clast-poor debris flows, attributed to semi-arid–humid periods; an intermediate unit of clast-rich sheetfloods and channel flows, deposited during arid periods; and an upper unit consisting of matrix-rich sheetfloods related to a return to semi-arid–humid conditions. We interpret that the water-flow processes responsible for deposition were most prevalent on fans of arid and semi-arid climates, whereas debris-flow processes were more typical of climates with higher rainfall. As the extension proceeded during the Plio-Quaternary time, the main tectonic activity of the Sporades Basin was taken up by the SMFS causing significant footwall uplift. Due to this process, Alonnisos Island was elevated above the Pliocene highstand and became an area starved of Quaternary sedimentation. Copyright © 1998 John Wiley & Sons, Ltd.     

干旱条件下冲积扇的沉积构型和演化过程: 基于水槽模拟实验

利用延时相机以及3D激光扫描仪等设备,通过水槽实验获得了74组扇面地貌数据,并采用定量化的软件对这些数据进行了精细的沉积学分析,明确了干旱条件下冲积扇的沉积演化过程及其控制的沉积构型。研究表明: (1)干旱条件下冲积扇沉积演化过程中水动力、水流样式、扇体增生规律等均存在明显的差异性,根据这些差异将整个模拟实验分为早期、中期、晚期3个阶段。(2)实验早期,扇体水动力较强,主控沉积作用为片流沉积,根据片流沉积的分布范围,可将其分为整体片流沉积和局部片流沉积。(3)实验中期,扇体中远端水动力及扇面扩大速率均有所减小,主控沉积作用为非限定性水道,主要沉积体为朵体沉积,非限定性水道主要分布在近源端,而朵体主要分布在水道末端的开阔地带。(4)实验晚期,受巨大的扇体影响,水动力进一步减小,主控沉积作用为限定性水道沉积。(5)通过实验研究,建立了具有明显3层结构的干旱条件下冲积扇沉积构型模式,其中底层是片流朵体复合体、中层为非限制性水道与末端朵体复合体、顶层是水道和小型末端朵体复合体。     

正断层控制下冲积扇沉积过程与沉积构型模拟实验

正断层构造广泛发育于盆地内和造山带中,其对可容空间分配及沉积物分布具有明显的控制作用,从而影响了冲积扇形态。为进一步探究正断层构造对冲积扇沉积过程及其内部构型的控制作用,利用水槽实验对正断层构造发育背景下的冲积扇发育过程进行模拟再现。研究表明,携带大量沉积物的碎屑流优先在上盘近断层处泄载,后经牵引流的改造,形成沿断面垂向生长、尖端指向物源的三角形分水滩。水动力较强时碎屑流越过分水滩并在分水滩尾部发育越滩朵体,水动力较弱时碎屑流遇分水滩尖端分流后沿断面在分水滩两侧发育断面朵体。受控于断面及分水滩的阻挡,冲积扇表面不同位置的沉积物泄载过程差异较大,粒度差异明显,上盘扇体中分水滩沉积物偏粗,越滩朵体次之,断面朵体最细。冲积扇的发育过程依据分水滩砂体厚度和断距大小之间的差异,共分为3个阶段。断距大小还会影响冲积扇沉积构型,断距越大,上盘可容空间越大,分水滩发育时间越长,扇体内部砂体叠置样式越复杂。受控于正断层的冲积扇内部构型在垂直物源剖面上从近端至远端,分别发育纵向沙坝、分水滩及碎屑流朵体,在平行物源剖面上以复合水道主控、分水滩叠复体主控、多期朵体叠复体主控为主。     

博兴洼陷西部沙三段有利储集砂体分布探讨

博兴洼陷油气勘探已进入隐蔽油气藏为主的勘探阶段,储集砂体的分布,尤其是能够形成地层岩性油藏的有利储集砂体的分布,是油气勘探的关键.研究区主要发育有浊积扇、辫状三角洲前缘和近岸水下扇三种类型的储集砂体,其中浊积扇扇体是岩性圈闭勘探的最有利砂体.通过已发现油气藏的地层位置分析,发现MSC8、MSC7、MSC6、MSC5、MSC2旋回的上升半旋回是有利储集砂体发育的主要层段,浊积扇砂体发育,且具有有利的油气成藏条件.平面上,MSC8旋回的有利储集砂体主要发育在高青断层东南侧的狭长区域内,MSC5、MSC6、MSC7旋回的有利储集砂体发育在坡折带之下的洼陷区.综合上述分析,预测了坡折带下部洼陷区、高青断裂下降盘和高24-高27井间区域3个岩性和构造-岩性圈闭勘探有利区.     

西秦岭关家沟组物源分析

西南秦岭摩天岭地区关家沟组的时代、沉积环境及构造背景一直是争论的焦点。对关家沟组粉砂岩、板岩进行了常量、微量及稀土元素地球化学分析表明关家沟组物源主要来自活动大陆边缘的岛弧环境。以本区地层斜层理产状及砾石优选方位为依据,对关家沟组岩层古水流方向综合分析,推测其古水流方向为230°~356°,以北西向为主;砾石的优选方位在228°~338°之间,以北北西向为主;砾石分布特征由南向北颗粒由大逐渐变小、磨圆度由差至较好、优选方位由杂乱到较好的变化趋势。结合前人成果,关家沟组应属于碧口弧前盆地系统内,推测关家沟组内的沉积物主要来自南东向的岛弧。     

高邮凹陷黄珏地区戴二段扇三角洲沉积特征

黄珏地区戴二段发育了以砂砾岩扇体为主的沉积体系。本文在岩心观察和描述的基础上,结合测井等资料,对黄珏地区戴二段砂砾岩体的沉积特征进行了研究。结果表明黄珏地区戴二段沉积时期在同生断层的下降盘主要发育水退型扇三角洲沉积体系。扇三角洲前缘是该区水退扇三角洲砂体堆积的主体,可进一步划分为水下分流河道、席状砂和分流间湾等砂体微相。不同的相带储层物性差异明显,扇三角洲前缘水下分流河道砂体储集物性较好,为油气聚集有利相带。该区沉积体系的形成受构造特征、古地貌和物源区等性质的影响,古地貌特征是该区水退型扇三角洲形成的决定性因素。     

A precipiton‐based approach to model hydro‐sedimentary hazards induced by large sediment supplies in alluvial fans

Mountain ranges are frequently subjected to mass wasting events triggered by storms or earthquakes and supply large volumes of sediment into river networks. Besides altering river dynamics, large sediment deliveries to alluvial fans are known to cause hydro‐sedimentary hazards such as flooding and river avulsion. Here we explore how the sediment supply history affects hydro‐sedimentary river and fan hazards, and how well can it be predicted given the uncertainties on boundary conditions. We use the 2D morphodynamic model Eros with a new 2D hydrodynamic model driven by a sequence of flood, a sediment entrainment/transport/deposition model and a bank erosion law. We first evaluate the model against a natural case: the 1999 Mount Adams rock avalanche and subsequent avulsion on the Poerua river fan (West Coast, New Zealand). By adjusting for the unknown sediment supply history, Eros predicts the evolution of the alluvial riverbed during the first post‐landslide stages within 30 cm. The model is subsequently used to infer how the sediment supply volume and rate control the fan aggradation patterns and associated hazards. Our results show that the total injected volume controls the overall levels of aggradation, but supply rates have a major control on the location of preferential deposition, avulsion and increased flooding risk. Fan re‐incision following exhaustion of the landslide‐derived sediment supply leads to sediment transfer and deposition downstream and poses similar, but delayed, hydro‐sedimentary hazards. Our results demonstrate that 2D morphodynamics models are able to capture the full range of hazards occurring in alluvial fans including river avulsion aggradation and floods. However, only ensemble simulations accounting for uncertainties in boundary conditions (e.g., discharge history, initial topography, grain size) as well as model realization (e.g., non‐linearities in hydro‐sedimentary processes) can be used to produce probabilistic hazards maps relevant for decision making. Copyright © 2017 John Wiley & Sons, Ltd.     

USING UAV PHOTOGRAMMETRY TECHNOLOGY TO EXTRACT INFORMATION OF TECTONIC ACTIVITY OF COMPLEX ALLUVIAL FAN——A CASE STUDY OF AN ALLUVIAL FAN IN THE SOUTHERN MARGIN OF BARKOL BASIN

Alluvial fans that are in the process of development always show complex geomorphic features due to natural modification. Accordingly, analyzing these fans whether to be influenced by tectonic deformation is one of the technique difficulties in active tectonic studies. Complex alluvial fans are the focus of the study of active tectonics such as fracture mapping and activity behavior analysis, for they have often retained important structural information. Traditional measurement methods, such as satellite remote sensing, RTK GPS and Lidar, are difficult to meet the demand for the study of micro tectonic deformation because of the reason of accuracy or cost performance. The recent UAV photogrammetry technology, due to its many advantages such as low cost, high resolution, and efficiency of exporting DEM and DOM data, has been widely used in three-dimensional modeling, ground mapping and other fields. In the quantitative study of active tectonics, this technology fills up the deficiency in the research of the micro structure of the traditional measurement. Through detailed field investigations and paleoseismic trenching, we further used this technology to obtain the topographic data of a complex alluvial fan located at the southern marginal fault of Barkol Basin, Xinjiang. Pointing at the alluvial fans that are in the process of development, and on the basis of topographic analysis and image processing for DEM, we take the research method of secondary partitions of the geomorphic surface and cut the alluvial fans longitudinally according to the difference of its age. Through the establishment of profile cluster within each partition, separate analysis and data contrast with the adjacent partitions, we acquired the tectonic activity information during the development of alluvial fan. The tectonic vertical deformation of this alluvial fan is about 2.5m.