Recent geodynamics of Asia: Map,principles of its compilation,and geodynamic analysis

A new map of the recent geodynamics of Asia is presented along with the principles and methods of its compilation and a characterization of the used factual material. For the first time, a map is based on the three parameters that determine recent geodynamics: the thickness of the lithosphere, the stress state, and the vectors of recent movements in the brittle upper portion of the lithosphere. In addition, active volcanoes and epicenters of earthquakes with M ≥ 6.0 are shown.     

Diagenetic evolution of a shallow marine Kimmeridgian carbonate ramp (Jabaloyas,NE Spain): implications for hydrocarbon reservoir quality

The upper Kimmeridgian outcrops in Jabaloyas (NE Spain) studied here have significant similarity in terms of carbonate ramp morphology and its facies architecture with Member D of the Upper Jurassic Arab Formation reservoirs in the Middle East. Geological models from analogue outcrops enhance or challenge the understanding of multi-scale sedimentological and diagenetic heterogeneities in the subsurface hydrocarbon reservoir models by providing morphometric parameters. For this purpose, conventional diagenetic studies (petrographic microscopy analysis and cathodoluminescence) have been performed to assess the impact of diagenetic modifications through burial. More than 50 thin sections have been used to define a full paragenetic sequence. Additional mineralogical mapping (Qemscan®) on a selection of thin sections serves as a calibration tool for semiquantitative analytic studies of every mineral phases and the proposed porosity evolution. This work unravels the whole paragenetic diagenetic processes and focused on those that occurred right after deposition to shallow burial (eogenesis). High-sequence stratigraphy allows linking these events to variations of the environmental domains that, in fact, respond most likely to sea-level fluctuations. In particular, it provides key parameters to frame the diagenetic overprint such as cementation processes plugging primary interparticle porosity and selective dissolution linked to master bounding surfaces: calcite meniscus cements in vadose zones and selective dissolution processes linked to firmgrounds. Ultimately, they offer valuable trends that would be potentially relevant to decipher and characterize reservoir parameters for the upscaling workflow of fabrics from microscopic to inter-well scale in carbonate hydrocarbon reservoirs.     

Au的生物地球化学异常和对植物细胞的变异效应

对从金矿区和背景区采集和试验种植的植物样品的研究表明,在杉木、马尾松和蕨的叶灰分中,矿区相对于背景区,前者的Au含量是后者的135倍、111倍和147倍;前者的Cu是后者的12倍、8倍和11倍;前者的Pb是后者的11倍、11倍和14倍.试验的高Au含量土壤中生长的青菜和芥菜Au含量分别是对照自然土壤中生长的229倍和205倍.Au等元素高含量土壤中生长的植物的细胞,在电子显微镜下变异效应明显,主要表现为细胞中出现大量电子致高密度体物质或内部组织的微结构遭受损伤.金矿区的植物样品中电子致高密度体物质含有20.160%～37.321%的Au、3.828%～23.324%的Cu及较多的Pb和Ag.种植的样品电子致高密度体物质含Au34.969%.说明Au等元素以电子致高密度体物质的"形式"淀积在细胞的内部组织结构中.     

Geodynamic conditions of evolution of the Tunka Branch in the Baikal Rift System

The Cenozoic paleostress state of the Earth’s crust at the southwestern flank of the Baikal Rift System (Tunka system of basins) is reconstructed. With allowance for known facts about the geologic history of the Tunka system of basins, the evolution of the stress field and its formation conditions are established by comparison of the obtained reconstructions, including the dated stress fields, with the Pleistocene-Holocene deformations in active fault zones and the present-day stress state (seismotectonic deformations calculated from the focal mechanisms of earthquakes). The opening of basins in the NW-SE direction was proceeding in the transtensional regime from the Oligocene to the late Miocene or early Pliocene. At the early-late Pliocene boundary, this process was followed by the transpressional regime with compression in the NW direction. In the late Pliocene, the situation at the southwestern flank changed drastically. Since that time, deformation has occurred in the transpressional regime and the compression axis has been oriented in the NE direction. The alternative models of the evolution of the Tunka system of basins—oblique extension, the transform fracture zone, or a pull-apart system—are considered. Both models are combined in the framework of the suggested stress-field reconstruction. The oblique extension (transtension) was related to the early stages of evolution, whereas a possibility of forming pull-apart basin was existent at the late stages.     

鄂尔多斯盆地志靖安塞地区长9油层组沉积相及其沉积演化特征

志靖安塞地区位于鄂尔多斯盆地陕北斜坡中部。以钻井取心观察为基础,结合砂岩厚度、砂地比、自生绿泥石分布、古生物化石分布等因素,对长9油层组2个层段沉积相空间展布特征及沉积演化规律进行研究。结果表明,长9油层组发育一套三角洲-湖泊沉积,北部主要发育三角洲前缘沉积,在南部发育浅湖沉积。长92沉积期,湖盆范围较小,长91沉积期湖盆初始扩张,湖岸线向北推进,湖域面积增大。从长92沉积期到长91沉积期,研究区经历了沉积水体由浅变深的过程,并在长91顶部发育一套具有生烃潜力的高阻泥岩。三角洲前缘水下分流河道砂体是较有利的储集砂体。     

Tsunami awareness: a comparative assessment between Japan and the USA

Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure.     

Evaluating methods to quantify sediment volumes trapped behind check dams,Salda(n)a badlands (Spain)

The determination of sediment yield in catchments based on the sediment trapped by check dams is becoming a subject of interest.In fact,several methods have been developed in recent years to estimate the sediment retained by check dams.The complexity,precision and accuracy of each method vary greatly.In this study,we evaluate the sediment trapped by check dams comparing the Sections method respect to the Prism,Pyramid,DTMs and Trapezoid methods.We analyzed a sample of 25 check dams(α-1=90%;ε=10%) in the Saldana badlands(Spain).The results showed that the Sections method offered a volume of retained sediment between the others,which gave an absolute variation from 22%to40%.The high variability of the check dam and sediment wedge sizes made necessary to compare methods in groups combining both characteristics.No significant differences in sediment volumes could be found between the methods for very small(height(h):1.8-2.3 m;trapped volume(V):6-102 m~3) or large check dams(h 2.3 m;V:165-387 m~3),while significant differences are found for small(h 1.5 m;V:1-229 m~3) or middle-sized check dams(h:2.2-3.2 m;V:65-235 m3).Nevertheless,volume differences between groups ranged up to + 25%.For these reason,the size of the check dam,the shape of the sediment wedge and the accuracy of the measure methods must considered when selecting an appropriate method to obtain the volume of retained sediment by check dams.A correct estimation of the sediment retention is needed to evaluate the role and efficiency of check dams in restoration projects or to estimate sediment yields.     

Sharp and laterally constrained multitrace impedance inversion based on blocky coordinate descent

Seismic impedance inversion is a well-known method used to obtain the image of subsurface geological structures. Utilizing the spatial coherence among seismic traces, the laterally constrained multitrace impedance inversion (LCI) is superior to trace-by-trace inversion and can produce a more realistic image of the subsurface structures. However, when the traces are numerous, it will take great computational cost and a lot of memory to solve the large-scale matrix in the multitrace inversion, which restricts the efficiency and applicability of the existing multitrace inversion algorithm. In addition, the multitrace inversion methods are not only needed to consider the lateral correlation but also should take the constraints in temporal dimension into account. As usual, these vertical constraints represent the stratigraphic characteristics of the reservoir. For instance, total-variation regularization is adopted to obtain the blocky structure. However, it still limits the magnitude of model parameter variation and therefore somewhat distorts the real image. In this paper, we propose two schemes to solve these issues. Firstly, we introduce a fast algorithm called blocky coordinate descent (BCD) to derive a new framework of laterally constrained multitrace impedance inversion. This new BCD-based inversion approach is fast and spends fewer memories. Next, we introduce a minimum gradient support regularization into the BCD-based laterally constrained inversion. This new approach can adapt to sharp layer boundaries and keep the spatial coherence. The feasibility of the proposed method is illustrated by numerical tests for both synthetic data and field seismic data.