基于构造约束的波阻抗边界刻画          下载免费PDF全文

张宏兵  杨长春  尚作萍 《地球物理学进展》2007,22(3):817-825

通过边界保护正则化和约束反演，在反演的目标函数中引入各种先验信息约束，以解决波阻抗反演的病态问题和带限问题.为了克服波阻抗模型边界过于平滑，在反演中引入地层和断层等构造信息约束，并且通过调整地层分界面和断层处的正则参数值来实现构造约束.此外，采用各向异性扩散法进行平滑处理，改善反演结果.通过合成数据测试和实际资料反演，证明了本文提出的方法对刻画模型边界是有效的.  相似文献   

青藏高原羌塘中部果干加年山上三叠统望湖岭组的建立及意义   总被引：7，自引：3，他引：7  

李才  翟庆国  董永胜  于介江  黄小鹏 《地质通报》2007,26(8):1003-1008

在果干加年山的主脊及其以北识别出一套稳定的沉积岩系,角度不整合于蛇绿混杂岩之上,以细砂岩、硅质粉砂岩为主,其中夹有大小不等的古生代外来岩块,底砾岩成分因地而异并具有快速堆积的特点,底部夹有流纹岩。厚度大于1633m。流纹岩夹层获得的锆石SHRIMPU-Pb谐和年龄为214Ma±4Ma,时代为晚三叠世诺利期。在剖面测制和区域对比的基础上建立了上三叠统望湖岭组,代表龙木错-双湖缝合带闭合以后接受的最早的沉积盖层。望湖岭组之下的蛇绿混杂岩获得阳起石Ar-Ar年龄219.7Ma±6.5Ma。同位素定年确定构造转化事件发生在214～220Ma之间,为龙木错-双湖缝合带的闭合时间提供了确切的时间约束,望湖岭组是这一事件的沉积记录,是龙木错-双湖缝合带蛇绿混杂岩之上首次发现的沉积盖层。  相似文献   

Mesozoic extension in the Basque–Cantabrian basin (N Spain): Contributions from AMS and brittle mesostructures     

Ruth Soto  Antonio M. Casas-Sainz  Juan J. Villalaín  Beln Oliva-Urcia 《Tectonophysics》2007,445(3-4):373-394

In this work we analyse and check the results of anisotropy of magnetic susceptibility (AMS) by means of a comparison with palaeostress orientations obtained from the analysis of brittle mesostructures in the Cabuérniga Cretaceous basin, located in the western end of the Basque–Cantabrian basin, North Spain. The AMS data refer to 23 sites including Triassic red beds, Jurassic and Lower Cretaceous limestones, sandstones and shales. These deposits are weakly deformed, and represent the syn-rift sequence linked to basins formed during the Mesozoic and later inverted during the Pyrenean compression. The observed magnetic fabrics are typical of early stages of deformation, and show oblate, triaxial and prolate magnetic ellipsoids. The magnetic fabric seems to be related to a tectonic overprint of an original, compaction, sedimentary fabric. Most sites display a NE–SW magnetic lineation that is interpreted to represent the stretching direction of the Early Cretaceous extensional stage of the basin, without recording of the Tertiary compressional events, except for sites with compression-related cleavage.Brittle mesostructures include normal faults, calcite and quartz tension gashes and joints, related to the extensional stage. The results obtained from joints and tension gashes show a dominant N–S to NE–SW, and secondary NW–SE, extension direction. Paleostresses obtained from fault analysis (Right Dihedra and stress inversion methods) indicate NW–SE to E–W, and N–S extension direction. The results obtained from brittle mesostructures show a complex pattern resulting from the superposition of several tectonic processes during the Mesozoic, linked to the tectonic activity related to the opening of the Bay of Biscay during the Early Cretaceous. This work shows the potential in using AMS analysis in inverted basins to unravel its previous extensional history when the magnetic fabric is not expected to be modified by subsequent deformational events. Brittle mesostructure analysis seems to be more sensitive to far-field stress conditions and record longer time spans, whereas AMS records deformation on the near distance, during shorter intervals of time.  相似文献   

Tonian Tectonic-Strata Regions and their Geological Significance in China     

XU Yadong  ZHANG Kexin  HE Weihong  YU Yang  KOU Xiaohu  SONG Bowen  LUO Mansheng  WANG Lijun  MA Zhongjie  YANG Fengli 《《地质学报》英文版》2020,94(4):914-941

The continent of China developed through the coalescence of three major cratons(North China, Tarim and Yangtze) and continental micro-blocks through the processes of oceanic crust disappearance and acceretionary-collision of continental crusts. The strata of the Chinese continental landmass are subdivided into 12 tectonic-strata regions. Based on the composition of geological features among the three main cratons, continental micro-blocks and other major global cratons, their affinities can be preliminarily deduced during the Tonian period, using evidence from sedimentary successions, paleobiogeography, tectonic and magmatic events. The Yangtze and Tarim cratons show that they have close affinities during the assembly-dispersal milestone of the Rodinia Supercontinent. The sedimentary record and magmatic age populations in the blocks suggest that there was a widespread, intensive magmatic event that resulted from a subduction process during ～1000–820 Ma, related to continental rifting around the Yangtze and Tarim cratons. However, they differ greatly from the North China Craton. The continental micro-blocks in the Panthalassic Ocean could have some missing connection with the North China Craton that persisted until the Middle-Late Devonian. In contrast, the Alxa Block showed a strong affinity with the Tarim Craton. The revised Tonian paleogeography of the Rodinia Supercontinent is a good demonstration of how to show the relationship between the main cratons and the continental micro-blocks.  相似文献   

DEDUCTION OF CONSTRAINT CONDITIONS IN THE CALIBRATION OF STEREO-VISION SYSTEN     

FENG Wenhao  Professor  School of Information Engineering  WTUSM  Wuhan  China   《地球空间信息科学学报》1998,(1)

In the test-field calibration,multi-azimuth stereo image pairs areproduced of the outdoor large control-field by the stereo-vision system under cali-bration.While in the analytical processing,the relationship between image pairsis adopted as a constraint condition,which ensures the stability and quality of thecalibration results.This paper introduces the deduction process of the constraintconditions.  相似文献   

Low enthalpy geothermal energy resources in Denmark     

Niels Balling  Svend Saxov 《Pure and Applied Geophysics》1978,117(1-2):205-212

The deep oil exploration drillings in Denmark have shown that especially the Danish Embayment contains low enthalpy geothermal resources associated with warm aquifers. The most promising reservoirs have been found in highly permeable Upper Triassic sand and sandstone beds, which cover at least 5000 km² at depths of 2000–3000 m and at temperatures of 60–100°C. The porosity of the main reservoir is of 15–25%, and the permeability is presumed to be approximately 1 darcy (10^–12 m²) or higher. A layer thickness of 30–60 m has been observed on a number of localities. Also the Middle Jurassic and the Lower Triassic contain reservoirs of interest. A major geothermal exploration work is planned with seismic investigations, drillings to depths of 2000–4000 m and probably establishment of pilot district heating plants.  相似文献   

Correspondence Between Astronomical Periods and Sedimentary Cycles     

Cheng Rihui  You Haitao 《东北亚地学研究》2000,(2)

The term of geological cycle was used firstly inHutton's" The Earth Theory" in 1788 (Williams,1980). The geological cycles including tectonic cycles and sedimentary cycles have been describedwidely since than. Some researchers have perceivedthat the geolo…  相似文献   

Describing and generating facies models for reservoir characterisation: 2D map view     

E.J. Hill  C.M. Griffiths   《Marine and Petroleum Geology》2009,26(8):1554-1563

This paper documents a new method for describing channel-related sedimentary deposits based on formal language theory. Using this method an analogue model of a sedimentary deposit can be encoded as a grammar. A program, called a parser, has been developed which can generate stochastic maps of these sedimentary deposits based on information in a specified grammar. The maps of sedimentary deposits generated by the parser have the same type, spatial arrangement, shape and size distribution as the analogue model. The successful generation of depositional maps represents a crucial step in the ongoing development of a new technique designed to generate 3D static geological models of sedimentary successions. The maps can be conditioned to match sparse hard data in the form of channel segments interpreted from seismic horizon maps.  相似文献   

Mantle plumes and the metamorphism of the lower crust and their influence on basin evolution     

Heinz-Jürgen Brink 《Marine and Petroleum Geology》2009

Since the stretching model appears to be not applicable to the subsidence of accretionary crust, basins located on this crust type may have an alternative origin. Examples of such basins are the West Siberia Basin and the North German Basin. Both basins showed intensive volcanism and magmatism during the initial phase of their development. Remarkably, the West Siberia Basin is closely located to the (hotspot related) Siberian flood basalts with a similar Permo-Triassic age, and the location of the North German Basin in Permian times is identical with the present day position of the Tibesti hotspot in Northern Africa. These two basins may have specific relations to hotspot heat sources of the Earth's underlying mantle. Due to these heat sources, thermal metamorphism within the lower layers of the (accretionary) crust may occur, resulting in rock density increase and subsequent shrinkage of the affected rock volumes. These shrinkage processes will lead to the development of topographic lows, their filling with sediments, and the subsequent start of an exponentially declining isostatic/metamorphic basin subsidence. In addition to the analyses of metamorphic processes, potential field anomalies, temperature fields, and histories of subsidence have been integrated into one single model that can explain the development of the North German Basin. Similarly, the East African Rift and Eifel Hotspots affected parts of the overriding continental plates. The East African Rift Hotspot can be traced back to the Afar flood basalts and the Dniepr–Donets Basin, whereas the Eifel Hotspot can be linked to the North Sea Basin. Continental drift templates, present day hotspot locations, flood basalt areas, metamorphic facies as function of temperature, and crust categories are taken as published in recent literature.  相似文献   

High-resolution record of tectonic and sedimentary processes in growth strata     

Stphane Pochat  Sbastien Castelltort  Gaël Choblet  Jean Van Den Driessche 《Marine and Petroleum Geology》2009,26(8):1350-1364

Growth strata are used to determine the kinematics of synsedimentary structures such as faults. Classical methods of analysis such as thickness versus throw plot consider that the available space created by fault slip in the hanging wall of faults is instantaneously filled up by sediments. This has lead many previous works to identify a cyclic activity for growth faults. Here we perform a careful analysis of the variation of strata thicknesses on each side of a very well documented normal growth fault in the Niger delta. We show that these thickness variations are induced by the alternation of sedimentary processes during continuous fault slip. Suspended-load processes induce either uniform or slightly variable thickness of a large majority of mudstone layers. Bedload processes result in a preferential thickening of sand layers in the hanging wall. These high quality data thus provide strong grounds for doubting the polycyclic growth diagnosed for some faults at the scale of sedimentary cycles and supports the notion that fault displacement rates can be very well behaved. Our study emphasizes the important conclusion that stable fault growth, and related displacement rates, can appear to be punctuated when viewed at the scale of sedimentary cycles. It follows that care should be taken when attempting to derive displacement rates on temporal scales equivalent to those of alternating sedimentological cycles.  相似文献