Heterogeneous tectonic inversion of the Mid-Polish Trough related to crustal architecture, sedimentary patterns and structural inheritance

Using a 3-D structural model, we performed a basin-scale analysis of the tectonically inverted Mid-Polish Swell, which developed above the NW–SE-oriented Teisseyre-Tornquist Zone. The later separates the Paleozoic West European Platform from the Precambrian East European Craton. The model permits a comparison between the present depths and sedimentary thicknesses of five layers within the Permian–Mesozoic and Cenozoic successions. The inversion of the NW–SE-trending Mid-Polish Trough during the Late Cretaceous–Paleogene resulted in uplift of a central horst, the Mid-Polish Swell, bounded by two lateral troughs. These structural features are induced by squeezing of a weak crust along the Teisseyre-Tornquist Zone. The swell is characterized by an inherited segmentation which is due to NE–SW transversal faults having crustal roots. From NW to SE, we distinguish the Pomeranian, Kujavian, and Ma opolska segments, that are separated by two transversal faults. During the inversion, the Zechstein salt occurring in the Pomeranian and Kujavian segments in the NW acted as decoupling level between the basement and the post-salt cover, leading to disharmonic deformation. Conversely, because no salt occurs in the SE, both basement and cover were jointly deformed. The vertical tectonic uplift at the surface is estimated to amount to 3 km in the Ma opolska segment. The structural inheritance of the basement is expressed by the heterogeneous geometry of the swell and tectonic instability during Mesozoic sedimentation. The reasons for the inheritance are seen in the mosaic-type Paleozoic basement SW of the Teisseyre-Tornquist Zone, contrasting the Precambrian East European Craton which acted as a stable buttress in the NE. The horst and trough geometry of Cenozoic sediments blanketing the Mid-Polish swell reveals the ongoing intracontinental compressional stress in Poland.     

Different modes of the Late Cretaceous–Early Tertiary inversion in the North German and Polish basins

Several selected seismic lines are used to show and compare the modes of Late-Cretaceous–Early Tertiary inversion within the North German and Polish basins. These seismic data illustrate an important difference in the allocation of major zones of basement (thick-skinned) deformation and maximum uplift within both basins. The most important inversion-related uplift of the Polish Basin was localised in its axial part, the Mid-Polish Trough, whereas the basement in the axial part of the North German Basin remained virtually flat. The latter was uplifted along the SW and to a smaller degree the NE margins of the North German Basin, presently defined by the Elbe Fault System and the Grimmen High, respectively. The different location of the basement inversion and uplift within the North German and Polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the WNW-ESE trending Elbe Fault System and by the NW-SE striking Teisseyre-Tornquist Zone, the latter underlying the Mid-Polish Trough. Therefore, the inversion of the Polish and North German basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis. The inversion of the Mid-Polish Trough was connected with the reactivation of normal basement fault zones responsible for its Permo-Mesozoic subsidence. These faults zones, inverted as reverse faults, facilitated the uplift of the Mid-Polish Trough in the order of 1–3 km. In contrast, inversion of the North German Basin rarely re-used structures active during its subsidence. Basement inversion and uplift, in the range of 3–4 km, was focused at the Elbe Fault System which has remained quiescent in the Triassic and Jurassic but reproduced the direction of an earlier Variscan structural grain. In contrast, N-S oriented Mesozoic grabens and troughs in the central part of the North German Basin avoided significant inversion as they were oriented parallel to the direction of the inferred Late Cretaceous–Early Tertiary compression. The comparison of the North German and Polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field. A thick Zechstein salt layer in the central parts of the North German Basin and the Mid-Polish Trough caused mechanical decoupling between the sub-salt basement and the supra-salt sedimentary cover. Resultant thin-skinned inversion was manifested by the formation of various structures developed entirely in the supra-salt Mesozoic–Cenozoic succession. The Zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution. Only in parts of the NGB and MPT characterised by either thin or missing Zechstein evaporites, thick-skinned inversion directly controlled inversion-related deformations of the sedimentary cover. Inversion of the Permo-Mesozoic fill within the Mid-Polish Trough was achieved by a regional elevation above uplifted basement blocks. Conversely, in the North German Basin, horizontal stress must have been transferred into the salt cover across the basin from its SW margin towards the basins centre. This must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion-related basement faults are seismically detected apart from the basin margins. This strain decoupling in the interior of the North German Basin was enhanced by the presence of the Elbe Fault System which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred Late Cretaceous–Early Tertiary far-field compression.     

松辽盆地北部白垩纪末反转变形的三维构造物理模拟

构造物理模拟对构造反转机制分析和地震资料的构造解释和模型建立至关重要.作者在深入研究松辽盆地的基底、形成发育和改造史的基础上,对松辽盆地进行6次能再现可重复性的三维构造物理模拟,探讨了断陷盆地晚期反转变形的动态过程,表明在同一构造应力场作用下因受基底中构造边界的制约而可能产生多组方向的背斜构造带.先存的边界条件还决定了晚期变形的产状：断面缓的一侧率先变形,对应的背斜带翼部陡且褶皱幅度大;它还制约了呈雁列式展布的正断层的发育.松辽盆地不同方向的正向二级背斜构造带均为明水组沉积后（白垩纪末）同一挤压应力场作用的结果,该期反转变形控制了新生代松辽地区的沉积发育.     

Crustal memory and basin evolution in the Central European Basin System—new insights from a 3D structural model

The Central European Basin System (CEBS) is composed of a series of subbasins, the largest of which are (1) the Norwegian–Danish Basin (2), the North German Basin extending westward into the southern North Sea and (3) the Polish Basin. A 3D structural model of the CEBS is presented, which integrates the thickness of the crust below the Permian and five layers representing the Permian–Cenozoic sediments. Structural interpretations derived from the 3D model and from backstripping are discussed with respect to published seismic data. The analysis of structural relationships across the CEBS suggests that basin evolution was controlled to a large degree by the presence of major zones of crustal weakness. The NW–SE-striking Tornquist Zone, the Ringkøbing-Fyn High (RFH) and the Elbe Fault System (EFS) provided the borders for the large Permo–Mesozoic basins, which developed along axes parallel to these fault systems. The Tornquist Zone, as the most prominent of these zones, limited the area affected by Permian–Cenozoic subsidence to the north. Movements along the Tornquist Zone, the margins of the Ringkøbing-Fyn High and the Elbe Fault System could have influenced basin initiation. Thermal destabilization of the crust between the major NW–SE-striking fault systems, however, was a second factor controlling the initiation and subsidence in the Permo–Mesozoic basins. In the Triassic, a change of the regional stress field caused the formation of large grabens (Central Graben, Horn Graben, Glückstadt Graben) perpendicular to the Tornquist Zone, the Ringkøbing-Fyn High and the Elbe Fault System. The resulting subsidence pattern can be explained by a superposition of declining thermal subsidence and regional extension. This led to a dissection of the Ringkøbing-Fyn High, resulting in offsets of the older NW–SE elements by the younger N–S elements. In the Late Cretaceous, the NW–SE elements were reactivated during compression, the direction of which was such that it did not favour inversion of N–S elements. A distinct change in subsidence controlling factors led to a shift of the main depocentre to the central North Sea in the Cenozoic. In this last phase, N–S-striking structures in the North Sea and NW–SE-striking structures in The Netherlands are reactivated as subsidence areas which are in line with the direction of present maximum compression. The Moho topography below the CEBS varies over a wide range. Below the N–S-trending Cenozoic depocentre in the North Sea, the crust is only 20 km thick compared to about 30 km below the largest part of the CEBS. The crust is up to 40 km thick below the Ringkøbing-Fyn High and up to 45 km along the Teisseyre–Tornquist Zone. Crustal thickness gradients are present across the Tornquist Zone and across the borders of the Ringkøbing-Fyn High but not across the Elbe Fault System. The N–S-striking structural elements are generally underlain by a thinner crust than the other parts of the CEBS.The main fault systems in the Permian to Cenozoic sediment fill of the CEBS are located above zones in the deeper crust across which a change in geophysical properties as P-wave velocities or gravimetric response is observed. This indicates that these structures served as templates in the crustal memory and that the prerift configuration of the continental crust is a major controlling factor for the subsequent basin evolution.     

Basin evolution of the northern part of the Northeast German Basin — Insights from a 3D structural model

A 3D structural model for the entire southwestern Baltic Sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area. The model was compiled with information from several geological time-isochore maps and digital depth maps from the area and consists of six post-Rotliegend successions: The Upper Permian Zechstein; Lower Triassic; Middle Triassic; Upper Triassic–Jurassic; Cretaceous and Cenozoic. This structural model was the basis for a 3D backstripping approach, considering salt flow as a consequence of spatially changing overburden load distribution, isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region. This method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement. In general, the successions above the highly deformed Zechstein evaporites reveal a thickening trend towards the Glückstadt Graben, which also experienced the highest amount of tectonic subsidence during the Mesozoic and Cenozoic. Two periods of accelerating salt movement in the area has been correlated with the E–W directed extension during the Late Triassic–Early Jurassic and later by the Late Cretaceous–Early Cenozoic inversion, suggesting that the regional stress field plays a key role in halokinesis. The final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium. The result reveals that many of the salt structures in the region are still active and that future coastline will run with a WNW–ESE trend, arguing that the compressional stresses related to the Alpine collision are the prime factor for the present-day landscape evolution.     

湖北荆当盆地何家湾地区三维地质地球物理模型研究

荆当盆地位于湖北中部偏西,自20世纪中期以来,区域上先后进行过多次大范围的区域地质调查工作,发现了茶林子、小汉口、泥水洞、三宝山、铜家湾、花园冲等多处铜多金属矿点。然而在荆当盆地中部的何家湾地区,找矿工作一直未有进展,原因主要受限于研究区地表被第四系大范围覆盖,传统的地质调查方法很难开展。因此,2015年在研究区内又开展了1∶5万地质草测、1∶5万重力测量、1∶5万磁法测量等工作。通过研究获得的这些地质资料及重磁数据,结合收集到的其他区域地质资料及相关研究成果,建立了三维地质模型,为研究区今后的找矿工作提供新的思路。     

尼日尔Termit盆地三维地质构造建模研究与应用

三维构造建模是构造研究的前沿手段和发展方向,具有实用性、精确性、可视性等多种优势,在国内外应用越来越广泛,但目前主要以局部油藏和断块为研究对象,针对全盆地尺度的三维构造建模比较少。尼日尔Termit盆地在早白垩世和古近纪发育两期裂谷,导致盆地断裂发育,构造复杂,构造研究的难度大。本文通过摸索和研究,利用大量二维和三维地震以及100余口井资料,将Termit盆地(约30 000 km2)作为一个整体进行三维构造建模,克服断层多、构造复杂、数据量庞大等难题,采用层位模拟、断层三角网格剖分、断层自动命名、断面交切关系处理、闭合边界自动生成等技术,在Termit盆地实现了盆地级三维构造建模,该模型可提取全盆地任意方向、任意层位的构造剖面以及任意连井剖面,同时可以任意提取每个区带及局部构造的三维立体模型,以便进行更精细的构造分析。该建模技术为大范围工区精细构造研究提供了新的技术手段,可应用于构造单元的划分、区带评价、目标优选及井位论证等许多方面。Termit盆地三维地质构造模型显示该盆地具有断坳叠置、下大上小的盆地结构,早期晚白垩世坳陷期海相烃源岩广泛分布,后期古近纪叠置裂谷坐落在晚白垩世坳陷期海相烃源岩之上,有利于后期古近纪叠置裂谷聚集油气。基于建立的盆地构造模型,进一步明确了该盆地各区带的构造特征及成藏潜力。研究认为Fana低凸起位于Moul凹陷和Dinga凹陷之间,断裂较为发育,有利于油气的运移、聚集和成藏,是盆地最有利的勘探区带;Dinga断阶带紧邻Dinga凹陷,断裂最发育,也是有利的勘探区带;Araga地堑断裂发育,成藏条件较好;而Moul凹陷和Dinga凹陷虽然油源条件好,但构造活动较弱,断裂不发育或较弱,不利于油气的向上运移,勘探潜力较差。此外,基于盆地构造模型可以对两期叠置裂谷形成的构造样式及断裂进行精细分析,研究其对油气聚集成藏的控制作用,从而优选出有利的目标,为井位部署提供决策建议。该成果和认识在Termit盆地的勘探中取得了很好的应用效果,进一步促进了古近系上组合和白垩系下组合的勘探突破。     

Stochastic simulations of fault networks in 3D structural modeling

3D structural modeling is a major instrument in geosciences, e.g. for the assessment of groundwater and energy resources or nuclear waste underground storage. Fault network modeling is a particularly crucial step during this task, for faults compartmentalize rock units and plays a key role in subsurface flow, whether faults are sealing barriers or drains. Whereas most structural uncertainty modeling techniques only allow for geometrical changes and keep the topology fixed, we propose a new method for creating realistic stochastic fault networks with different topologies. The idea is to combine an implicit representation of geological surfaces which provides new perspectives for handling topological changes with a stochastic binary tree to represent the spatial regions. Each node of the tree is a fault, separating the space in two fault blocks. Changes in this binary tree modify the fault relations and therefore the topology of the model.     

川东北何家营地区三维构造模型：来自高精度线束三维资料的约束

川东北地区方斗山构造带发育典型的多重滑脱构造,中生代以来受大巴山南北向挤压与雪峰山北西向挤压叠加改造。其构造模型在区域性滑脱层的分布、不同构造变形层构造样式的厘定以及不同构造变形层在空间上耦合特征等方面存在争议,因此定量分析不同变形层构造样式的差异与空间组合特征成为研究分层变形成因机制的关键。本文应用数字高程、浅表地质信息与线束三维地震数据等资料,开展方斗山北段何家营地区地层与断裂构造解析,建立了何家营地区的三维构造模型,讨论方斗山北段多重滑脱层体系下,垂向上不同构造变形层的差异变形特征及其控制因素。研究表明：何家营地区沉积盖层中存在中-下寒武统膏盐层、下志留统泥岩层、下三叠统嘉陵江组膏盐层等3套区域性滑脱层以及二叠系煤层局部滑脱层。区域性滑脱层控制了褶皱—冲断构造的变形样式,构造在垂向解耦,形成基底、深部、中部与浅部等4套变形层。基底变形层发育指向北西的构造楔;深部变形层夹持于寒武系与志留系滑脱层之间,发育双重构造,形成低幅度背斜;中部变形层为志留系与嘉陵江组之间的高角度冲断构造,二叠系煤层作为局部滑脱层,发育顺层剪切;浅部变形层,以嘉陵江组盐滑脱褶皱为主。不同变形层的垂向叠置,共同形成了现今的高陡背斜。不同构造变形层地层能干性组合与缩短量的差异决定了构造样式的差异。软弱层传递位移,中寒武统膏盐层、志留系页岩与下三叠统膏盐层,缩短量最大,变形最强,是控制区域变形的主要滑脱层。何家营地区发育倾向南东的基底断层,不同变形层的主干断层与褶皱轴迹方向一致,均以北东、北东东向为主,反映出何家营地区构造变形主要受控于来自雪峰山方向的挤压作用。

     

鄂尔多斯盆地构造沉降特征及对盆地成因的启示

构造沉降作为盆地成因研究中的重要组成部分,对其特征进行分析有助于盆地成因的解析。本次通过对鄂尔多斯盆地内5口典型探井的多期不整合所代表的的剥蚀厚度进行恢复,结合去压实矫正模型以及平均密度、平均古水深等参数的确定,较为精确地刻画出了鄂尔多斯盆地不同构造单元自早寒武世至今的构造沉降特征,同时结合裂谷盆地瞬时拉张模型、裂后热坳陷模型以及前陆盆地挠曲模型对构造沉降曲线进行了模拟,对盆地成因进行分析。鄂尔多斯盆地中寒武世—中生代末期主要由早古生代沉降旋回、二叠—三叠纪沉降旋回与侏罗—白垩纪沉降旋回组成。其中岩石圈热冷却作用引起的沉降贯穿全地质时期。早古生代沉降旋回中,中寒武世的加速沉降主要体现在盆地南部,沉降机制为岩石圈伸展减薄,中奥陶世马家期为全盆地尺度的加速沉降,沉降机制仍为岩石圈伸展减薄。二叠—三叠纪沉降旋回中,晚二叠世—早-中三叠世为该旋回的加速沉降期,该期加速沉降具有多幕裂陷的特征。侏罗—白垩纪沉降旋回中,中侏罗世盆地南部处于缓慢沉降期,沉降机制为岩石圈热冷却作用,晚侏罗世—早白垩世,除伊盟隆起,盆地整体处于加速沉降期,沉降机制为前陆盆地引起的挠曲沉降。     

Salt redistribution during extension and inversion inferred from 3D backstripping

A 3D backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution, isostatic rebound and sedimentary compaction for each backstripping step is used to reconstruct the subsidence history in the Northeast German Basin. The method allows to determine basin subsidence and the salt-related deformation during Late Cretaceous–Early Cenozoic inversion and during Late Triassic–Jurassic extension. In the Northeast German Basin, the deformation is thin-skinned in the basinal part, but thick-skinned at the basin margins. The salt cover is deformed due to Late Triassic–Jurassic extension and Late Cretaceous–Early Cenozoic inversion whereas the salt basement remained largely stable in the basin area. In contrast, the basin margins suffered strong deformation especially during Late Cretaceous–Early Cenozoic inversion. As a main question, we address the role of salt during the thin-skinned extension and inversion of the basin. In our modelling approach, we assume that the salt behaves like a viscous fluid on the geological time-scale, that salt and overburden are in hydrostatical near-equilibrium at all times, and that the volume of salt is constant. Because the basement of the salt is not deformed due to decoupling in the basin area, we consider the base of the salt as a reference surface, where the load pressure must be equilibrated. Our results indicate that major salt movements took place during Late Triassic to Jurassic E–W directed extension and during Late Cretaceous–Early Cenozoic NNE–SSW directed compression. Moreover, the study outcome suggests that horizontal strain propagation in the salt cover could have triggered passive salt movements which balanced the cover deformation by viscous flow. In the Late Triassic, strain transfer from the large graben systems in West Central Europe to the east could have caused the subsidence of the Rheinsberg Trough above the salt layer. In this context, the effective regional stress did not exceed the yield strength of the basement below the Rheinsberg Trough, but was high enough to provoke deformation of the viscous salt layer and its cover. During the Late Cretaceous–Early Cenozoic phase of inversion, horizontal strain propagation from the southern basin margin into the basin can explain the intensive thin-skinned compressive deformation of the salt cover in the basin. The thick-skinned compressive deformation along the southern basin margin may have propagated into the salt cover of the basin where the resulting folding again was balanced by viscous salt flow into the anticlines of folds. The huge vertical offset of the pre-Zechstein basement along the southern basin margin and the amount of shortening in the folded salt cover of the basin indicate that the tectonic forces responsible for this inversion event have been of a considerable magnitude.     

松辽盆地火山岩储层三维可视化描述

以松辽盆地升平地区作为目标区,优选出Petrel软件。首先利用构造层面及断层数据建立了构造模型和断层模型,然后通过确定性建模和随机建模结合的方法,同时结合断层和构造模型建立了该区火山岩相三维地质模型,在三维空间上详细刻画了典型火山岩体的岩相特征和在三度空间的变化规律,实现了对营城组升平地区复杂构造目标区火山岩储层的三维可视化动态表述和展示。通过三维构造模型可以看出,工区西北部及南部缺失营城组地层,其内部发育由两个构造高点所构成的穹窿构造,该构造以-2 810 m等深线圈闭,构造面积32.45 km²,构造高点海拔为-2 660.5 m,构造幅度150.5 m,断层多为南北向展布,长度一般为2～5 km,断距一般为8～30 m。     

Deep 3D structure of the Sydney Basin using gravity modelling

A detailed deep 3D geological model is an important basis for many types of exploration and resource modelling. Renewed interest in the structure of the Sydney Basin, driven primarily by sequestration studies, geothermal studies and coal seam gas exploration, has highlighted the need for a model of deep basin geology, structure and thermal state. Here, we combine gravity modelling, seismic reflection surveys, borehole drilling results and other relevant information to develop a deep 3D geological model of the Sydney Basin. The structure of the Sydney Basin is characteristic of a typical intracontinental rift basin, with a deep north–south orientated channel in the Lachlan Fold Belt basement, filled with up to 4 km of rift volcanics, and overlain with Permo-Triassic sediments up to 4 km thick. The deep regional architecture presented in this study will form the framework for more detailed geological, hydrological and geothermal models.     

Neotectonic evolution of the Tarim Basin Craton from Neogene to quaternary

The Tarim Basin Craton is located in the center of the Tarim Basin. Since the beginning of the Miocene, the tectonic activity has been weaker in the Tarim Basin Craton than in the marginal depression and the peripheral orogenic belts. This study investigates the tectonic movements in the Tarim Basin Craton by calculating the sedimentation rates and constructing balanced cross-sections based on well, seismic and geologic data. The tectonic movements in the Tarim Basin Craton have mainly been revealed by geological processes such as sedimentation and subsidence, structural inversion, changes in the structural feature, migration of the structural highs, and faulting. The Neogene sedimentary strata were mainly deposited in two sedimentation centers, the southern and northern sedimentation centers, and the strata in the Central Uplift Zone are relatively thin. The different depressions in different geological periods experienced wide variations in tectonic activity. Tectonic subsidence was significant and the sedimentation rates were high in the Tarim Basin Craton during the Pliocene Period (phase II). During the Neotectonic period, the stresses in the South-North direction converged in the Central Uplift Zone (the Bachu uplift–Central Tarim uplift), and the tectonic activity in this region was more intense than that in the Northern Depression and the Maigaiti Slope in the southwest. In addition, the scale of the paleo-uplift, including paleo-North Tarim Uplift and paleo-Central Uplift Zone, gradually decreased. The faults and fault systems developed zonationally in Neotectonic formations in different structural units, and always distributed discontinuously in vertical direction in sections.     

Three-Dimensional Structural Modelling and Source Rock Evaluation of the Quseir Formation in the Komombo Basin, Egypt

The Quseir Formation consists mainly of dark gray mudstones with a high organic matter content and excellent hydrocarbon-generating potential. The main objectives of this study are to highlight the dominant structural elements in the Komombo Basin, Egypt, and evaluate the geochemical characteristics of the Quseir Formation. Depth maps and a 3 D structural model indicate two normal fault trends NW–SE and ENE–WSW. The NW–SE trend is the dominant one that created the primary half-graben system. The...     

Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin,NW Iberian Peninsula: 3D structural model and kinematic evolution

We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.     

Salt movements in the Northeast German Basin and its relation to major post-Permian tectonic phases—results from 3D structural modelling, backstripping and reflection seismic data

The NW–SE-striking Northeast German Basin (NEGB) forms part of the Southern Permian Basin and contains up to 8 km of Permian to Cenozoic deposits. During its polyphase evolution, mobilization of the Zechstein salt layer resulted in a complex structural configuration with thin-skinned deformation in the basin and thick-skinned deformation at the basin margins. We investigated the role of salt as a decoupling horizon between its substratum and its cover during the Mesozoic deformation by integration of 3D structural modelling, backstripping and seismic interpretation. Our results suggest that periods of Mesozoic salt movement correlate temporally with changes of the regional stress field structures. Post-depositional salt mobilisation was weakest in the area of highest initial salt thickness and thickest overburden. This also indicates that regional tectonics is responsible for the initiation of salt movements rather than stratigraphic density inversion.Salt movement mainly took place in post-Muschelkalk times. The onset of salt diapirism with the formation of N–S-oriented rim synclines in Late Triassic was synchronous with the development of the NNE–SSW-striking Rheinsberg Trough due to regional E–W extension. In the Middle and Late Jurassic, uplift affected the northern part of the basin and may have induced south-directed gravity gliding in the salt layer. In the southern part, deposition continued in the Early Cretaceous. However, rotation of salt rim synclines axes to NW–SE as well as accelerated rim syncline subsidence near the NW–SE-striking Gardelegen Fault at the southern basin margin indicates a change from E–W extension to a tectonic regime favoring the activation of NW–SE-oriented structural elements. During the Late Cretaceous–Earliest Cenozoic, diapirism was associated with regional N–S compression and progressed further north and west. The Mesozoic interval was folded with the formation of WNW-trending salt-cored anticlines parallel to inversion structures and to differentially uplifted blocks. Late Cretaceous–Early Cenozoic compression caused partial inversion of older rim synclines and reverse reactivation of some Late Triassic to Jurassic normal faults in the salt cover. Subsequent uplift and erosion affected the pre-Cenozoic layers in the entire basin. In the Cenozoic, a last phase of salt tectonic deformation was associated with regional subsidence of the basin. Diapirism of the maturest pre-Cenozoic salt structures continued with some Cenozoic rim synclines overstepping older structures. The difference between the structural wavelength of the tighter folded Mesozoic interval and the wider Cenozoic structures indicates different tectonic regimes in Late Cretaceous and Cenozoic.We suggest that horizontal strain propagation in the brittle salt cover was accommodated by viscous flow in the decoupling salt layer and thus salt motion passively balanced Late Triassic extension as well as parts of Late Cretaceous–Early Tertiary compression.     

3D seismic analysis of gravity-driven and basement influenced normal fault growth in the deepwater Otway Basin,Australia

We use three-dimensional (3D) seismic reflection data to analyse the structural style and growth of a normal fault array located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia. The Otway Basin is a Late Jurassic to Cenozoic, rift-to-passive margin basin. The seismic reflection data images a NW-SE (128–308) striking, normal fault array, located within Upper Cretaceous clastic sediments and which consists of ten fault segments. The fault array contains two hard-linked fault assemblages, separated by only 2 km in the dip direction. The gravity-driven, down-dip fault assemblage is entirely contained within the 3D seismic survey, is located over a basement plateau and displays growth commencing and terminating during the Campanian-Maastrichtian, with up to 1.45 km of accumulated throw (vertical displacement). The up-dip normal fault assemblage penetrates deeper than the base of the seismic survey, but is interpreted to be partially linked along strike at depth to major basement-involved normal faults that can be observed on regional 2D seismic lines. This fault assemblage displays growth initiating in the Turonian-Santonian and has accumulated up to 1.74 km of throw.Our detailed analysis of the 3D seismic data constraints post-Cenomanian fault growth of both fault assemblages into four evolutionary stages: [1] Turonian-Santonian basement reactivation during crustal extension between Australia and Antarctica. This either caused the upward propagation of basement-involved normal faults or the nucleation of a vertically isolated normal fault array in shallow cover sediments directly above the reactivated basement-involved faults; [2] continued Campanian-Maastrichtian crustal extension and sediment loading eventually created gravitational instability on the basement plateau, nucleating a second, vertically isolated normal fault array in the cover sediments; [3] eventual hard-linkage of fault segments in both fault arrays to form two along-strike, NW-SE striking fault assemblages, and; [4] termination of fault growth in the latest Maastrichtian. We document high variability of throw along-strike and down-dip for both fault assemblages, thereby providing evidence for lateral and vertical segment linkage. Our results highlight the complexities involved in the growth of both gravity-driven normal fault arrays (such as those present in the Niger Delta and Gulf of Mexico) and basement-linked normal fault arrays (such as those present in the North Sea and Suez Rift) with the interaction of an underlying and reactivating basement framework. This study provides an excellent example of spatial variability in growth of two normal fault assemblages over relatively short spatial scales (∼2 km separation down-dip).     

重磁2.5D/3D互相约束反演技术在三维地质填图中的应用研究

三维地质填图为我国启动的新一轮地质调查项目,为提高重磁资料在三维地质填图中的应用效果,笔者提出重磁资料2.5D/3D相互约束重磁反演技术方案:利用重磁资料2.5D剖面反演结果、3D物性反演结果作为彼此反演约束条件,并通过了理论模型试验。试验结果表明,该技术方案使反演结果中物性参数、空间位置更接近理论模型体。通过对本溪—临江地区思山岭铁矿磁异常及酸性岩体重力异常进行反演实践——估算磁异常铁矿资源量、研究酸性侵入岩深部展布形态的效果良好,可为大面积三维填图提供有效途径。     

三维区域地面沉降数值模拟

由于地裂缝研究及地表变形监测技术（例如GPS,InSAR等）的快速发展,抽取地下水引起的地层水平位移受到关注。传统区域地面沉降模型虽然求解快速但不能模拟水平位移;比奥模型虽然能够模拟土体的三维变形,但模型求解的计算量较大,较少应用于大尺度的区域地面沉降数值模拟。为解决以上问题,推导了解耦三维地面沉降数学模型,模型推导过程显示：比奥模型假设法向总应力和不变,则可简化为解耦三维地面沉降模型;解耦三维地面沉降模型假设土体仅有垂向一维变形,则可简化为传统区域地面沉降模型。同时通过数值试验验证了解耦三维地面沉降模型可以作为比奥模型的替代模型和传统区域地面沉降模型的改进模型,用来模拟抽取地下水引起的三维区域地面沉降。