首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 477 毫秒
1.
Present-day stress orientations in the Northern Perth Basin have been inferred from borehole breakouts and drilling-induced tensile fractures observed on image logs from eight wells. Stress indicators from these wells give an east – west maximum horizontal stress orientation, consistent with stress-field modelling of the Indo-Australian Plate. Previous interpretations using dipmeter logs indicated anomalous north-directed maximum horizontal stress orientations. However, higher-quality image logs indicate a consistent maximum horizontal stress orientation, perpendicular to dominant north – south and northwest – southeast fault trends in the basin. Vertical stress was calculated from density logs at 21.5 MPa at 1 km depth. Minimum horizontal stress values, estimated from leak-off tests, range from 7.4 MPa at 0.4 km to 21.0 MPa at 0.8 km depth: the greatest values are in excess of the vertical stress. The maximum horizontal stress magnitude was constrained using the relationship between the minimum and maximum horizontal stresses; it ranges from 8.7 MPa at 0.4 km to 21.3 MPa at 1 km depth. These stress magnitudes and evidence of neotectonic reverse faulting indicate a transitional reverse fault to strike-slip fault-stress regime. Two natural fracture sets were interpreted from image logs: (i) a north- to northwest-striking set; and (ii) an east-striking set. The first set is parallel to adjacent north- to northwest-striking faults in the Northern Perth Basin. Several east-striking faults are evident in seismic data, and wells adjacent to east-striking faults exhibit the second east-striking set. Hence, natural fractures are subparallel to seismically resolved faults. Fractures optimally oriented to be critically stressed in the present-day stress regime were probably the cause of fluid losses during drilling. Pre-existing north- to northwest -striking faults that dip moderately have potential for reactivation within the present-day stress regime. Faults that strike north to northwest and have subvertical dips will not reactivate. The east-striking faults and fractures are not critically stressed for reactivation in the Northern Perth Basin.  相似文献   

2.
The Gorgon Platform is located on the southeastern edge of the Exmouth Plateau in the North Carnarvon Basin, North West Shelf, Australia. A structural analysis using three-dimensional (3D) seismic data has revealed four major sets of extensional faults, namely, (1) the Exmouth Plateau extensional fault system, (2) the basin bounding fault system (Exmouth Plateau–Gorgon Platform Boundary Fault), (3) an intra-rift fault system in the graben between the Exmouth Plateau and the Gorgon Platform and (4) an intra-rift fault system within the graben between the Exmouth Plateau and the Exmouth Sub-basin. Fault throw-length analyses imply that the initial fault segments, which formed the Exmouth Plateau–Gorgon Platform Boundary Fault (EG Boundary Fault), were subsequently connected vertically and laterally by both soft- and hard-linked structures. These major extensional fault systems were controlled by three different extensional events during the Early and Middle Jurassic, Late Jurassic and Early Cretaceous, and illustrate the strong role of structural inheritance in determining fault orientation and linkage. The Lower and Middle Jurassic and Upper Jurassic to Lower Cretaceous syn-kinematic sequences are separated by unconformities.  相似文献   

3.
A series of linear to arcuate fault scarps separate the Mount Lofty Ranges from the Cenozoic St Vincent and Murray basins of South Australia. Their tectonic, sedimentary and geomorphic evolution is traced from the oldest rock record through to present-day seismicity. The scarps are the latest manifestation of repeated compressive reactivation of ancient, deep-seated crustal faults and fractures whenever the stress field was of appropriate orientation. Formation of the basins and uplift of the ranges resulted from the same processes of repeated compressive reactivation. Continental crust was intensely fractured during three episodes of Neoproterozoic–Cambrian rifting that led to the formation of the Adelaide Geosyncline and break-up of Rodinia. Neoproterozoic eastward-dipping, listric extensional faults provided accommodation space for deposition of the Burra Group. Sediments of the Umberatana and Wilpena groups were deposited under mainly sag-phase conditions. In the early Cambrian, new extensional faults formed the deeply subsident Kanmantoo Trough. Cambrian rift faults swung from east–west on Kangaroo Island through northeasterly on Fleurieu Peninsula to north–south in the easten Mount Lofty Ranges, cutting across the older meridional rifts. These two sets of extensional faults were reactivated as basement-rooted thrusts in the ensuing Delamerian Orogeny. The Willunga Fault originated as a Cambrian rift fault and was reactivated in the Delamerian Orogeny as a thrust dipping southeast under a regional basement-cored antiform on southern Fleurieu Peninsula. Much of southern Australia, including the eroded remnants of the Delamerian highlands, was covered by a continental ice sheet in the Carboniferous–Permian. The preferential preservation of glacial sediments on Fleurieu Peninsula may have resulted from extensional reactivation of the Willunga Fault, possibly in the early Mesozoic. Fleurieu Peninsula was then warped into an open, southwest-plunging antiform, spatially coincident with the much higher amplitude Delamerian antiform. Glacial sediments were eroded from uplifted (up-plunge) areas before formation of a ‘summit surface’ across deeply weathered bedrock and preserved glacial sediments in the later Mesozoic. This surface was covered with fluvial to lacustrine sediments in the middle Eocene. Neotectonic movements under a renewed compressive regime commenced with reactivation of the Willunga Fault, restricting subsequent Eocene to Miocene sedimentation to the St Vincent Basin. The Willunga scarp was onlapped in the Oligocene–Miocene concomitant with continuing uplift and formation of a hanging-wall antiform. In the late Cenozoic, repeated faulting and mild folding, angular unconformities, ferruginisation and proximal coarse sedimentation took place on various faults at different times until the late Pleistocene.  相似文献   

4.
The St. Lawrence rift system from the Laurentian craton core to the offshore St. Lawrence River system is a seismically active zone in which fault reactivation is believed to occur along late Proterozoic to early Paleozoic normal faults related to the opening of the Iapetus ocean. The rift-related faults fringe the contact between the Grenvillian basement to the NW and Cambrian–Ordovician rocks of the St. Lawrence Lowlands to the SE and occur also within the Grenvillian basement. The St. Lawrence rift system trends NE–SW and represents a SE-dipping half-graben that links the NW–SE-trending Ottawa–Bonnechère and Saguenay River grabens, both interpreted as Iapetan failed arms. Coastal sections of the St. Lawrence River that expose fault rocks related to the St. Lawrence rift system have been studied between Québec city and the Saguenay River. Brittle faults marking the St. Lawrence rift system consist of NE- and NW-trending structures that show mutual crosscutting relationships. Fault rocks consist of fault breccias, cataclasites and pseudotachylytes. Field relationships suggest that the various types of fault rocks are associated with the same tectonic event. High-resolution marine seismic reflection data acquired in the St. Lawrence River estuary, between Rimouski, the Saguenay River and Forestville, identify submarine topographic relief attributed to the St. Lawrence rift system. Northeast-trending seismic reflection profiles show a basement geometry that agrees with onshore structural features. Northwest-trending seismic profiles suggest that normal faults fringing the St. Lawrence River are associated with a major topographic depression in the estuary, the Laurentian Channel trough, with up to 700 m of basement relief. A two-way travel-time to bedrock map, based on seismic data from the St. Lawrence estuary, and comparison with the onshore rift segment suggest that the Laurentian Channel trough varies from a half-graben to a graben structure from SW to NE. It is speculated that natural gas occurrences within both the onshore and offshore sequences of unconsolidated Quaternary deposits are possibly related to degassing processes of basement rocks, and that hydrocarbons were drained upward by the rift faults.  相似文献   

5.
Eight two-dimensional, multichannel seismic reflection lines were acquired, processed, and interpreted to study the structure of the Altar Basin, which is part of the Salton Trough tectonic province. We identified two basin-bounding zones characterized by different degrees of strain: the Cerro Prieto–Altar deformation zone (CPADZ) and the Altar–Caborca deformation zone (ACDZ). The CPADZ is bounded on the west by the Cerro Prieto fault and on the east by the Altar fault. To the north, the strike of both faults changes slightly from a NW to more NNW direction. In the CPADZ, the thickness of the crust decreases southward towards the Gulf of California, and is associated with a deformation-developing fault. The CPADZ has a rotation component orientating these faults in an oblique direction to the Cerro Prieto fault, whereas within the ACDZ, a geometric coherence of synthetic and antithetic faults exists, creating horsts and graben striking N37° W. The Altar fault is recognized by basement interruption, with a vertical component of ～1 km, striking at N37° W and dipping 83° SW. On the northeastern side of the Altar Basin, the basement configuration shows that the minimum time of basement record (～0.4 s of two-way travel time) and the time curve gradient decrease in the NE–SW direction. The depocentre is ～6 km deep in the central-west portion of the basin. We identified a graben between the Rosario and Tinajas Altas mountains (Rosario Basin). The extension–connection of the Altar and Rosario basins to the south is not well defined; nevertheless, these basins could represent the link between the Colorado River and the Gulf of California during the late Miocene, whereas this link was abandoned in the Pliocene as subsidence migrated towards the northwest into the Cerro Prieto and Laguna Salada basins.  相似文献   

6.
Basaltic eruptions across the Central Highlands of Victoria have sealed in-place Early to middle Cenozoic palaeodrainage systems (also known as deep leads). The basal gravels of the deep leads have been mined extensively in the past for their rich placer-gold deposits. Detailed mapping of the distribution of all palaeorivers has been carried out using drilling results and modern aeromagnetic/radiometric surveys. The palaeochannel isopachs (including basalt and sediment) do not thicken in a modern downvalley direction. Instead, deeper depressions alternate with shallower areas. The variations in thickness, and parts of the palaeochannel courses, are controlled by a series of east-northeast-trending basement highs. The basement highs are caused by a set of east-northeast-trending (Otway Basin-style) faults visible on radar shuttle imagery in the Central Highlands. They have not previously been recognised in regional geological mapping. Most published fault trends are north – south oriented, parallel to the strike of the Palaeozoic basement rocks. Exceptions occur at Ballarat where there is an orthogonal east-northeast set mapped in underground quartz reef workings that show right-lateral strike-slip movements. The east-northeast faults show half-graben block-style rotational movement on basement, creating north- and south-facing fault scarps along the horst ridges. Where palaeochannels overlie the grabens, valleys broadened, infill thickens, and locally drainage directions may change. When the drainage cuts through the horsts, steeper incised valleys result, and this is where, in the historical past, some gold leads were ‘lost’. The initial timing of the block movement pre-dates at least the Early Oligocene to Late Miocene ages of the basal palaeovalley sediments, as shown by revised palynological dating. In places, the modern drainage divide coincides with east-northeast-trending faults. In the Ballarat area, an earlier divide accentuated by the aeromagnetic palaeodrainage mapping occurs up to 25 km south and appears to pre-date the earliest basalt flows at around 7.0 Ma. This evidence suggests the divide can change position through time by differential movements along east-northeast faults and transferral of maximum uplift to adjacent blocks.  相似文献   

7.
Analysis of the Gachsar structural sub-zone has been carried out to constrain structural evolution of the central Alborz range situated in the central Alpine Himalayan orogenic system. The sub-zone bounded by the northward-dipping Kandovan Fault to the north and the southward-dipping Taleghan Fault to the south is transversely cut by several sinistral faults. The Kandovan Fault that controls development of the Eocene rocks in its footwall from the Paleozoic–Mesozoic units in the fault hanging wall is interpreted as an inverted basin-bounding fault. Structural evidences include the presence of a thin-skinned imbricate thrust system propagated from a detachment zone that acts as a footwall shortcut thrust, development of large synclines in the fault footwall as well as back thrusts and pop-up structures on the fault hanging wall. Kinematics of the inverted Kandovan Fault and its accompanying structures constrain the N–S shortening direction proposed for the Alborz range until Late Miocene. The transverse sinistral faults that are in acute angle of 15° to a major magnetic lineament, which represents a basement fault, are interpreted to develop as synthetic Riedel shears on the cover sequences during reactivation of the basement fault. This overprinting of the transverse faults on the earlier inverted extensional fault occurs since the Late Miocene when the south Caspian basin block attained a SSW movement relative to the central Iran. Therefore, recent deformation in the range is a result of the basement transverse-fault reactivation.  相似文献   

8.
Four major fault systems oriented N–S to NNE–SSW, NE–SW, E–W and NW–SE are identified from Landsat Thematic Mapper (TM) images and a high resolution digital elevation model (DEM) over the Ethiopian Rift Valley and the surrounding plateaus. Most of these faults are the result of Cenozoic - extensional reactivation of pre-existing basement structures. These faults interacted with each other at different geological times under different geodynamic conditions. The Cenozoic interaction under an extensional tectonic regime is the major cause of the actual volcano-tectonic landscape in Ethiopia. The Wonji Fault Belt (WFB), which comprises the N–S to NNE–SSW striking rift floor faults, displays peculiar propagation patterns mainly due to interaction with the other fault systems and the influence of underlying basement structures. The commonly observed patterns are: curvilinear oblique-slip faults forming lip-horsts, sinusoidal faults, intersecting faults and locally splaying faults at their ends. Fault-related open structures such as tail-cracks, releasing bends and extensional relay zones and fault intersections have served as principal eruption sites for monogenetic Plio-Quaternary volcanoes in the Main Ethiopian Rift (MER).  相似文献   

9.
The Asturian Arc was produced in the Early Permian by a large E–W dextral strike–slip fault (North Iberian Megashear) which affected the Cantabrian and Palentian zones of the northeastern Iberian Massif. These two zones had previously been juxtaposed by an earlier Kasimovian NW–SE sinistral strike–slip fault (Covadonga Fault). The occurrence of multiple successive vertical fault sets in this area favoured its rotation around a vertical axis (mille-feuille effect). Along with other parallel faults, the Covadonga Fault became the western margin of a proto-Tethys marine basin, which was filled with turbidities and shallow coal-basin successions of Kasimovian and Gzhelian ages. The Covadonga Fault also displaced the West Asturian Leonese Zone to the northwest, dragging along part of the Cantabrian Zone (the Picos de Europa Unit) and emplacing a largely pelitic succession (Palentian Zone) in what would become the Asturian Arc core. The Picos de Europa Unit was later thrust over the Palentian Zone during clockwise rotation. In late Gzhelian time, two large E–W dextral strike–slip faults developed along the North Iberian Margin (North Iberian Megashear) and south of the Pyrenean Axial Zone (South Pyrenean Fault). The block south of the North Iberian Megashear and the South Pyrenean Fault was bent into a concave, E-facing shape prior to the Late Permian until both arms of the formerly NW–SE-trending Palaeozoic orogen became oriented E–W (in present-day coordinates). Arc rotation caused detachment in the upper crust of the Cantabrian Zone, and the basement Covadonga Fault was later resurrected along the original fault line as a clonic fault (the Ventaniella Fault) after the Arc was completed. Various oblique extensional NW–SE lineaments opened along the North Iberian Megashear due to dextral fault activity, during which numerous granitic bodies intruded and were later bent during arc formation. Palaeomagnetic data indicate that remagnetization episodes might be associated with thermal fluid circulation during faulting. Finally, it is concluded that the two types of late Palaeozoic–Early Permian orogenic evolution existed in the northeastern tip of the Iberian Massif: the first was a shear-and-thrust-dominated tectonic episode from the Late Devonian to the late Moscovian (Variscan Orogeny); it was followed by a fault-dominated, rotational tectonic episode from the early Kasimovian to the Middle Permian (Alleghenian Orogeny). The Alleghenian deformation was active throughout a broad E–W-directed shear zone between the North Iberian Megashear and the South Pyrenean Fault, which created the basement of the Pyrenean and Alpine belts. The southern European area may then be considered as having been built by dispersal of blocks previously separated by NW–SE sinistral megashears and faults of early Stephanian (Kasimovian) age, later cut by E–W Early Permian megashears, faults, and associated pull-apart basins.  相似文献   

10.
A retrograde sequence of fluid-controlled, low-temperature mineral reactions has been preserved along an east-west striking, dextral-oblique-slip fault in the uplifted Rhine Graben shoulder. This fault (the Schauenburg Fault, near Heidelberg), juxtaposes Permian rhyolite against Carboniferous (Variscan) granite and shows syn- or post-rift displacement of the north–south trending, eastern boundary fault of the rift basin. Both mineral texture and rock fabric indicate that the fault forms a site of high rock permeability and fluid flow, and records the exhumation and fluid-rock history of the rift shoulder since the Mesozoic. The reaction sequence and mineral compositions of the clay minerals within the cataclasite, and adjacent granite and rhyolite lithologies, document progressively decreasing fluid temperatures, with back-reactions of pure 2M1 illite to 1Md (R3) illite-smectite, and eventually smectite and kaolinite assemblages. Compositional variations are attributed to Tertiary to Recent fluid flushing of the fault zone associated with rift flank uplift, and with progressive dilution of the electrolyte-rich, acidic to neutral hydrothermal brines by down-flowing electrolyte-poor, meteoric waters.  相似文献   

11.
A quantitative analysis is presented of the scaling properties of faults within the exceptionally well-exposed Kino Sogo Fault Belt (KSFB) from the eastern part of the 200-km-wide Turkana rift, Northern Kenya. The KSFB comprises a series of horsts and grabens within an arcuate 40-km-wide zone that dissects Miocene–Pliocene lavas overlying an earlier asymmetric fault block. The fault belt is 150 km long and is bounded to the north and south by transverse (N50°E and N140°E) fault zones. An unusual feature of the fault system is that it accommodates very low strains (<1%) and since it is no older than 3 Ma, it could be characterised by extension rates and strain rates that are as low as 0.1 mm/yr and 10−16 s−1, respectively. Despite its immaturity, the fault system comprises segmented fault arrays with lengths of up to 40 km, with individual fault segments ranging up to 9 km in length. Fault length distributions subscribe to a negative exponential scaling law, as opposed to the power law scaling typical of other fault systems. The relatively long faults and segments are, however, characterised by maximum throws of no more than 100 m, providing displacement/length ratios that are significantly below those of other fault systems. The under-displaced nature of the fault system is attributed to early stage rapid fault propagation possibly arising from reactivation of earlier underlying basement fabrics/faults or magmatic-related fractures. Combined with the structural control exercised by pre-existing transverse structures, the KSFB demonstrates the strong influence of older structures on rift fault system growth and the relatively rapid development of under-displaced fault geometries at low strains.  相似文献   

12.
运用丰富的三维地震资料, 在断裂体系静态刻画与动态分析的基础上, 分析珠一坳陷新生代断裂发育的时空差异性, 并就断裂转型机制进行探讨.结果表明: 断裂体系发育差异性及转型受控于不同区域动力学背景及岩石圈的差异伸展机制.裂陷期(E2w-E2e), 控盆断裂由始新世的北北东、北东-北东东向向近东西、北西西向转变, 岩石圈伸展作用由宽裂谷方式向窄裂谷方式转变以及由陆(北)向海(南)的迁移, 造成了断裂活动北强南弱及其向北扩展, 推测是因为印支地块的旋转挤出和古南海的俯冲导致区域应力场由北西向顺时针转变为近南北向拉张, 进而产生了断裂的幕式特征变化; 裂后拗陷期(E3z-N1z-N1h), 断裂活动微弱, 推测与岩石圈伸展中心逐渐向南迁移至南海扩张中心, 南海北部陆缘整体处于裂后沉降阶段有关; 构造活化期(N1y-N2w-Q), 先期北西西向、近东西向控盆断裂复活, 近东西、北东和北西向走滑断裂形成, 推测与弧-陆碰撞作用产生的北东东向右旋走滑作用有关.现今断裂体系特征体现了多期构造运动的叠加效应, 明确断裂发育的时空差异性对于珠一坳陷油气勘探具有重要指导意义.  相似文献   

13.
The Salado River fault (SRF) is a prominent structure in southern Mexico that shows evidence of reactivation at two times under different tectonic conditions. It coincides with the geological contact between a structural high characterized by Palaeozoic basement rocks to the north, and an ～2000 m thick sequence of marine and continental rocks that accumulated in a Middle Jurassic–Cretaceous basin to the south. Rocks along the fault within a zone up to 150 m across record crystal-plastic deformation affecting the metamorphic basement of the Palaeozoic Acatlán Complex. Later brittle deformation is recorded by both the basement and the overlying Mesozoic sedimentary rocks. Regional features and structural textures at both outcrop and microscopic scale indicate two episodes of left-lateral displacement. The first took place under low-to medium-grade P-T conditions in the late Early Jurassic (180 Ma) based on the interpretation of 40Ar/39Ar ratios from muscovite within the fault zone; the second occurred under shallow conditions, when the fault served as a transfer zone between areas with differing magnitudes of shortening north and south of the fault. In the southern block, fold hinges were dragged westward during Laramide tectonic transport to the east, culminating in brittle deformation characterized by strike–slip faulting in the Mesozoic sedimentary rocks. North of the fault, folds are not well defined, and it is clear that the fold hinges observed in the southern block do not continue north of the fault. Although the orientation and kinematics of the SRF are similar to major Cainozoic shear zones in southern Mexico, our new data indicate that the fault had become inactive by the time of Oligocene volcanism.  相似文献   

14.
This study was undertaken to determine the structural evolution of a normal fault array using detailed kinematic analysis of normal fault tip propagation and linkage, adding to the growing pool of research on normal fault growth. In addition, we aim to provide further insight into the evolution of the offshore Otway Basin, Australia. We use three-dimensional (3D) seismic reflection data to analyse the temporal and spatial evolution of a Late Cretaceous–Cenozoic age normal fault array located in the Gambier Embayment of the offshore Otway Basin, South Australia. The seismic reflection data cover a NW–SE-oriented normal fault array consisting of six faults, which have grown from the linkage of numerous, smaller segments. This fault array overlies and has partial dip-linkage to E–W-striking, basement-involved faults that formed during the initial Tithonian–Barremian rifting event in the Otway Basin. Fault displacement analysis suggests four key stages in the post-Cenomanian growth history of the upper array: (1) nucleation of the majority of faults resulting from resumed crustal extension during the early Late Cretaceous; (2) an intra-Late Cretaceous period of general fault dormancy, with the nucleation of only one newly formed fault; (3) latest Cretaceous nucleation of another newly formed fault and further growth of all other faults; and (4) continued growth of all faults, leading to the formation of the Cenozoic Gambier Sub-basin in the Otway Basin. Our analysis also demonstrates that Late Cretaceous faults, which are located above and dip-link to basement-involved faults, display earlier nucleation and greater overall throw and length, compared with those which do not link to basement-involved faults. This is likely attributed to increased rift-related stress concentrations in cover sediments above the upper tips of basement faults. This study improves our understanding of the geological evolution of the presently under-explored Gambier Embayment, offshore Otway Basin, South Australia by documenting the segmented growth style of a Late Cretaceous normal fault array that is located over, and interacts with, a reactivated basement framework.  相似文献   

15.
针对基底先存构造对裂陷盆地断层控制作用研究中存在的问题,应用脆性断裂新理论--“不协调性准则”来阐述、分析裂陷盆地基底先存构造控制断层形成和演化的力学机理,确定基底先存构造活动性的变化规律,探讨并初步确定基底先存构造对裂陷盆地断层形成和演化的控制作用具有如下规律: (1)先存构造(特别是先存断裂)优先活动,这是基底先存构造能控制沉积盆地断层形成和演化的根本原因。(2)先存构造对盆地断层控制作用的强度决定于其活动性,它由先存构造的产状、力学性质和应力状态决定,可以用先存构造活动性系数(fAS)来定量描述。(3)受基底先存断裂控制的断层发育的位置和延伸方向(走向)、形成次序、继承性特征,以及分布规模等都表现出显著的规律性。(4)与伸展方向垂直,且与σ1夹角为45°-(/2)的基底先存断裂对断层的控制作用最强;随着走向与伸展方向的夹角α逐渐变小,以及倾角偏离45°+(/2),对断层的控制作用就逐渐减小。(5)基底先存断裂的规模越大,对断层的控制作用就越强;受大规模基底先存断裂控制的断层往往构成裂陷盆地的构造格架。(6)随着薄弱带抗剪强度的减小,基底先存薄弱带发生破裂的可能性不断增大,对断层的控制作用不断增强;而相对基底先存断裂而言,其影响程度则相对偏弱。上述认识可以为裂陷盆地地震资料的构造解释提供理论模型,为裂陷盆地断裂系统的形成和演化的深入研究提供理论指导。  相似文献   

16.
The north Egyptian continental margin has undergone passive margin subsidence since the opening of Tethys, but its post-Mesozoic history has been interrupted by tectonic events that include a phase of extensional faulting in the Late Miocene. This study characterizes the geometry and distribution of Late Miocene normal faulting beneath the northern Nile Delta and addresses the relationship of this faulting to the north–northwestwards propagation of Red Sea–Gulf of Suez rifting at this time. Structural interpretation of a 2D grid of seismic reflection data has defined a Tortonian–Messinian syn-rift megasequence, when tied to well data. Normal fault correlations between seismic lines are constrained by the mapping of fault-related folds. Faults are evenly distributed across the study area and are found to strike predominantly NW–SE to NNW–SSE, with some N–S faults in the north. Faults are interpreted to be <10 km in length, typically in the range 3–6 km. This suggests that rifting in the northern Nile Delta did not proceed beyond a continental rift initiation phase, with distributed, relatively small-scale faults. This contrasts with the Gulf of Suez Rift, where faulting continued to a more evolved fault localization phase, with block-bounding faults >25 km in length. Results suggest that future studies could quantify fault evolution from rift initiation to fault linkage to displacement localization, by studying the spatial variation in faulting from the northern Nile Delta, south–southeastwards to the Gulf of Suez Rift.  相似文献   

17.
位于滇西北断陷带东北部、程海-宾川断裂带北端的永胜地区上新世以来断裂活动强烈,构造地貌特征显著。永胜地区1:50000活动构造填图发现,区内共存在各类断裂14条。其中金官断裂（F1）、永胜断裂（F2）、木耳坪羊坪断裂（F3）三者规模最大,活动性亦远超其他断裂,属于程海-宾川断裂带的一级分支断裂,其他断裂为程海-宾川断裂的二级分支断裂。构造地貌特征、错断地质体及擦痕统计等均指示区内断裂现今主要以伸展正断活动为主,根据活动性的差异可将其分为强、较强、中等、弱、极弱5类,其中金官断裂的活动性最强,垂向活动速率可达0.20~0.26 mm/a。对永胜地区主要断裂几何学、运动学特征的研究及动力学机制的讨论可知,永胜地区主要断裂在平面上构成向东突出的弧形旋扭构造体系,在剖面上表现为张扭性断裂常见的负花状构造;程海-宾川断裂带现今活动主要是在近南北向主压应力作用下产生的近东西向的伸展正断,并因为叠加了旋扭作用而具有一定左旋走滑。永胜地区的弧形旋扭构造体系及滇西北断陷带等均是在川滇内弧带顺时针旋转及南汀河断裂、畹町断裂与理塘断裂的走滑拉分共同作用下形成的。   相似文献   

18.
The study area is located between Çorum and Amasya along the Ezinepazar?–Sungurlu Fault Zone (ESFZ) which is regarded as the splay of the North Anatolian Fault Zone (NAFZ). By this study, the 1/25,000 scaled geological map of the study area was prepared, and its stratigraphic and tectonic characteristics were unraveled as a result of palaeontological and petrographical analyses of the samples collected from different rock units. Particularly, geologic ages of the Late Jurassic–Early Cretaceous Ferhatkaya and Carcurum and Middle Eocene Çekerek formations were provided from palaeontological determinations. Using Landsat TM and Shuttle Radar Topography Mission 3 (SRTM 3) data of the region, the borders between the rock units and the tectonic characteristics in the study area were clarified by spectral and spatial enhancement methods. Kinematic characteristics of ESFZ obtained from the young sedimentary rocks along both sides of the fault zone were also inferred in this study. Understanding the kinematic and geometrical characteristics of the faults is important in terms of the seismotectonics of the region. In the statistical study conducted on the basis of the directions of the lineaments indicates the highest concentrations in general between N 50° - 60° E and N 60° - 70° E. Band 7 of the study area was enlightened in SE direction taking into consideration the relation of the geologic structures in the region with NAFZ and ESFZ and their general strike directions. Along with the formation of NAFZ, the region has undergone a counterclockwise rotation of approximately 20°–30°, which has developed between the “splay” faults in the south block of that fault. These faults are strike-slip faults formed under the compressional regime roughly in a NW–SE direction. It is noted that this tectonic regime has developed under compression in NW–SE direction, which was dominant in similar kinematic analysis studies conducted on NAFZ.  相似文献   

19.
云金表  王新 《吉林地质》1999,18(4):19-23
辽河外围西部发育了一系列晚中生代陆相沉积盆地。它们经历了前裂谷盆地期、同裂谷盆地期、后裂谷盆地期,以及盆地形成后的改造期四个阶段。在裂谷体制作用下,它们形成了相似的断陷构造样式。但基底结构的基异产生了盆地沉积建造与后裂谷阶段的重大差异。盆地盖层的发育主要决定于后者,因此在裂谷型盆地的油气成藏条件及其演化发带与成块特征。  相似文献   

20.
New structural and seismologic evidence from the Rwenzori Mountains, Uganda, indicate that continental rifts can capture and rotate fragments of the lithosphere while rift segments interact, in a manner analogous to the interaction of small-scale fractures. The Rwenzori Mountains are a basement block within the western branch of the East African Rift System that is located at the intersection of two rift segments and is apparently rotating clockwise. Structural data and new seismological data from earthquake epicentres indicate a large-scale, 20-km-long transsection fault is currently detaching the Rwenzori micro-plate on its northern margin from the larger Victoria plate (Tanzania craton), whereas it is already fully detached in the south. We propose that this fault develops due to the rotation of the Rwenzori block. In a numerical model we show how rift segment interaction, block rotation and the development of transsection faults (faults that cut through the Rwenzori Mountains) evolve through time. The model suggests that uplift of the Rwenzori block can only take place after the rift has opened significantly, and rotation leads to the development of transsection faults that connect two rift segments, so that the block is captured within the rifts. Our numerical model suggests that the majority of the uplift has taken place within the last 8 Ma.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号