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1.
The Fula Sub-basin of the Muglad Basin of southern Sudan is an active-fault bounded basin with an area of approximately 3300 km2. The Lower Cretaceous Abu Gabra Formation formed during the first of three rifting cycles. It can be subdivided into five 3rd-order sequences named SQA∼SQE from bottom to top, indicating five stages of tectonostratigraphy and tectonosedimentary evolution. The spatial distribution and temporal evolution of clastic depositional systems are described in this paper based on integrated analysis of seismic, core and well logging data. In the Abu Gabra Formation of the Fula Sub-basin, a variety of depositional systems are recognized, namely, fan delta, braided delta, delta, sublacustrine fan and lacustrine system. The Fula Sub-basin has undergone a complex and phased rifting evolution, and a high abundance of transfer zones developed, causing the resulting distribution and architecture of both the sequence and depositional system to be controlled by various types of transfer zones. The following three types of sequence architectures from northern to southern part of the Fula Sub-basin have been identified: simple dustpan-shaped sequence architecture in the north, transfer-zone sequence stratigraphic architecture in the middle and graben-shaped sequence architecture in the south. The sequence architecture is under the control of the large-scale central transfer zone, and nine models are built to study the effect of at least three categories of small-scale transfer zones on the depositional systems in the Fula Sub-basin. The small-scale transfer zones play significant roles in basin fill, primarily in controlling of the positions of deposit-input points. This study provides valuable insights into tectonic control of depositional systems and sequence architectures in a continental rift basin such as the Fula Sub-basin.  相似文献   

2.
Structural analysis of the Indian Merge 3D seismic survey identified three populations of normal faults within the Exmouth Sub-basin of the North West Shelf volcanic margin of Australia. They comprise (1) latest-Triassic to Middle Jurassic N-NNE-trending normal faults (Fault Population I); (2) Late Jurassic to Early Cretaceous NE-trending normal faults (Fault Population II); and (3) latest-Triassic to Early Cretaceous N-NNE faults (Fault Population III). Quantitative evaluation of >100 faults demonstrates that fault displacement occurred during two time periods (210–163 and 145–138 Ma) separated by ∼20 Myr of tectonic quiescence. Latest Jurassic to Early Cretaceous (145–138 Ma) evolution comprises magmatic addition and contemporaneous domal uplift ∼70 km wide characterised by ≥ 900 m of denudation. The areally restricted subcircular uplift centred on the southern edge of the extended continental promontory of the southern Exmouth Sub-basin supports latest Jurassic mantle plume upwelling that initiated progradation of the Barrow Delta. This polyphase and bimodal structural evolution impacts current hydrocarbon exploration rationale by defining the nature of latest Jurassic to Early Cretaceous fault nucleation and reactivation within the southern Exmouth Sub-basin.  相似文献   

3.
The Cariaco basin, located ∼40 km off the central part of the coast of Venezuela, is the largest (∼4000 km2) and bathymetrically deepest (1400 m BSL) Neogene fault-bounded basin within the right-lateral strike-slip plate boundary zone that separates the Caribbean and South American plates. Using subsurface geophysical data, we test two previously proposed tectonic models for the age, distribution and nature of east-west-striking, strike-slip faults, and basin-forming mechanism for the two main depocenters of the Cariaco basin. The earliest interpretation for the opening of the twin Cariaco depocenters by Schubert (1982) proposes that both depocenters formed synchronously by extension along transverse (north-south) normal faults at a ∼30-km-wide rhomboidally-shaped pull-apart basin between the right-lateral, east-west-striking, and parallel San Sebastian and El Pilar fault zones. A later model by Ben-Avraham and Zoback (1992) proposes that both depocenters formed synchronously by a process of ”transform-normal parallel extension”, or rifting in a north-south direction orthogonal to the east-west-striking and parallel strike-slip faults.We use more than 4000 km of 2D single- and multi-channel seismic data tied to 11 wells to map 5 tectono-stratigraphic sequences and to produce a series of structural and isopach maps showing how the faults that controlled both Cariaco depocenters evolved from Paleogene to the present. Comparison of fault and isopach maps for dated horizons from Paleogene to late Neogene in age show three main phases in basin development: 1) from middle Miocene to Pliocene, the West Cariaco basin formed as a rhomboidally-shaped pull-apart at a 30-km-wide stepover between the northern branch of the San Sebastian fault and the El Pilar fault zone; 2) during the early Pliocene, a new strike-slip fault transected the West Cariaco basin (southern branch of the San Sebastian fault) and caused extension to cease; and 3) during the early Pliocene to recent, a “lazy-Z” shaped pull-apart formed along the curving connection between the southern branch of the San Sebastian and El Pilar fault zones.  相似文献   

4.
Previous GPS-based geodetic studies and onland paleoseismologic studies in Trinidad have shown that the 50-km-long, linear, onland segment of the Central Range fault zone (CRFZ) accommodates at least 60% of the total rate of right-lateral displacement (∼20 mm/yr) between the Caribbean and South American plates. 2D and 3D seismic reflection data from a 60-km-long and 30-km-wide swath of the eastern shelf of Trinidad (block 2AB) were used to map the eastern offshore extension of this potentially seismogenic and hazardous fault system and to document its deeper structure and tectonic controls on middle Miocene to recent clastic stratigraphy. Two unconformity surfaces and seafloor were mapped using 3D seismic data to generate isochron maps and to illustrate the close control of the CRFZ and associated secondary faults on small, clastic basins formed along its anastomosing strands and the east-west-striking North Darien Ridge fault zone (NDRFZ) that exhibits a down-to-the-north normal throw. Mapped surfaces include: 1) the middle Miocene angular unconformity, a prominent, regional unconformity surface separating underlying thrust-deformed rocks from a much less deformed overlying section; this regional unconformity is well studied from onland outcrops in Trinidad and in other offshore areas around Trinidad; 2) a Late Neogene angular unconformity developed locally within block 2AB that is not recognized in Trinidad; and 3) the seafloor of the eastern Trinidad shelf which exhibits linear scarps for both the CRFZ and the east-west-striking North Darien Ridge fault zone. Clastic sedimentary fill patterns identified on these isochron maps indicate a combined effect of strike-slip and reverse faulting (i.e., tectonic transpression) produced by active right-lateral shear on the CRFZ, which is consistent with the obliquity of the strike of the fault to the interplate slip vector known from GPS studies in onland Trinidad. The NDRFZ and a sub-parallel and linear family of east-west-striking faults with normal and possibly transtensional motions also contributed to the creation of accommodation space within localized, post-middle Miocene clastic depocenters south of the CRFZ.  相似文献   

5.
南黄海盆地中部隆起区发育2套海相构造层,以下志留统高家边组泥岩滑脱带为界可划分为海相上构造层和海相下构造层。海相上构造层构造相对较复杂,以冲断结构为主,褶皱及叠瓦状逆冲断裂发育。对南黄海盆地中部隆起区多道地震资料进行处理解释表明,中部隆起区广泛发育海相上构造层,平面上总体表现为自西向东厚度呈厚—薄—厚的沉积格局。断裂系统发育,以近EW向断裂最为发育,其次为NE向断裂,NW向断裂则较为零星。构造应力以挤压和走滑为主,主要发育挤压、压扭和张扭3种构造样式。  相似文献   

6.
Two petroleum source rock intervals of the Lower Cretaceous Abu Gabra Formation at six locations within the Fula Sub-basin, Muglad Basin, Sudan, were selected for comprehensive modelling of burial history, petroleum maturation and expulsion of the generated hydrocarbons throughout the Fula Sub-basin. Locations (of wells) selected include three in the deepest parts of the area (Keyi oilfield); and three at relatively shallow locations (Moga oilfield). The chosen wells were drilled to depths that penetrated a significant part of the geological section of interest, where samples were available for geochemical and source rock analysis. Vitrinite reflectances (Ro %) were measured to aid in calibrating the developed maturation models.The Abu Gabra Formation of the Muglad Basin is stratigraphically subdivided into three units (Abu Gabra-lower, Abu Gabra-middle and Abu Gabra-upper, from the oldest to youngest). The lower and upper Abu Gabra are believed to be the major source rocks in the province and generally contain more than 2.0 wt% TOC; thus indicating a very good to excellent hydrocarbon generative potential. They mainly contain Type I kerogen. Vitrinite reflectance values range from 0.59 to 0.76% Ro, indicating the oil window has just been reached. In general, the thermal maturity of the Abu Gabra source rocks is highest in the Abu Gabra-lower (deep western part) of the Keyi area and decreases to the east toward the Moga oilfied at the Fula Sub-basin.Maturity and hydrocarbon generation modelling indicates that, in the Abu Gabra-Lower, early oil generation began from the Middle- Late Cretaceous to late Paleocene time (82.0–58Ma). Main oil generation started about 58 Ma ago and continues until the present day. In the Abu Gabra-upper, oil generation began from the end of the Cretaceous to early Eocene time (66.0–52Ma). Only in one location (Keyi-N1 well) did the Abu Gabra-upper reach the main oil stage. Oil expulsion has occurred only from the Abu Gabra-lower unit at Keyi-N1 during the early Miocene (>50% transformation ratio TR) continuing to present-day (20.0–0.0 Ma). Neither unit has generated gas. Oil generation and expulsion from the Abu Gabra source rocks occurred after the deposition of seal rocks of the Aradeiba Formation.  相似文献   

7.
Cenozoic eastward migration of the Caribbean plate relative to the South American plate is recorded by an 1100-km-long Venezuela-Trinidad foreland basin which is oldest in western Venezuela (65-55 Ma), of intermediate age in eastern Venezuela (34-20 Ma) and youngest beneath the shelf and slope area of eastern offshore Trinidad (submarine Columbus basin, 15.0 Ma-Recent). In this study of the regional structure, fault families, and chronology of faulting and tectonic events affecting the hydrocarbon-rich Columbus foreland basin of eastern offshore Trinidad, we have integrated approximately 775 km of deep-penetration 2D seismic lines acquired by the 2004 Broadband Ocean-Land Investigations of Venezuela and the Antilles arc Region (BOLIVAR) survey, 325 km of vintage GULFREX seismic data collected by Gulf Oil Company in 1974, and published industry well data that can be tied to some of the seismic reflection lines. Top Cretaceous depth structure maps in the Columbus basin made from integration of all available seismic and well data define for the first time the elongate subsurface geometry of the 11-15 km thick and highly asymmetrical middle Miocene-Recent depocenter of the Columbus basin. The main depocenter located 150-200 km east of Trinidad and now the object of deepwater hydrocarbon exploration is completely filled by shelf and deepwater sediments derived mainly from the Orinoco delta. The submarine Darien ridge exhibits moderate (20-140 m) seafloor relief, forms the steep (12°-24°), northern structural boundary of the Columbus basin, and is known from industry wells to be composed of 0.5-4.5 km thick, folded and thrust-imbricated, hydrocarbon-bearing section of Cretaceous and early Tertiary limestones and clastic rocks. The eastern and southern boundaries of the basin are formed by the gently (1.7°-4.5°), northward-dipping Cretaceous-Paleogene passive margin of South America that is in turn underlain by Precambrian rocks of the Guyana shield.Interpretation of seismic sections tied to wells reveals the following fault chronology: (1) middle Miocene thrusting along the Darien ridge related to highly oblique convergence between the Caribbean plate and the passive margin of northern South America; continuing thrusting and transpression in an oblique foreland basin setting through the early Pleistocene; (2) early Pliocene-recent low-angle normal faults along the top of the Cretaceous passive margin; these faults were triggered by oversteepening related to formation of the downdip, structurally and bathymetrically deeper, and more seaward Columbus basin; large transfer faults with dominantly strike-slip displacements connect gravity-driven normal faults that cluster near the modern shelf-slope break and trend in the downslope direction; to the south no normal faults are present because the top Cretaceous horizon has not been oversteepened as it is adjacent to the foreland basin; (3) early Pliocene-Recent strike-slip faults parallel the trend of the Darien ridge and accommodate present-day plate motions.  相似文献   

8.
南海热流特征及其构造意义   总被引：13，自引：1，他引：13  
根据南海 592个热流数据 ,为克服热流站位分布不均及局部异常热流的影响 ,结合各单元的地质史及其地壳厚度等资料对研究区热流特征进行了详细分析。结果表明 ,具拉张背景的区域如北部陆缘、湄公盆地以及北巴拉望盆地具有中等偏高热流 ;海沟区热流相对较低 ,东部海沟区除台西南盆地外均为低热流区 ,而南部边缘东段古海沟区处于热恢复中 ;南部边缘西区因边界断裂的扭张及深部热源的异常补给而具高热流 ;属于剪切断裂带的西部陆缘也具高热流特征 ;中沙—西沙地区热流中等偏高 ,并由NW往SE方向增加 ,而南沙地区热流较低 ,约为 60mW·m- 2 ;海盆的热流基本满足随洋壳年龄增加而降低的规律 ,东部次海盆实测热流与理论预测基本一致 ,而西南次海盆实测热流普遍低于预测值 ;在南海北部下陆坡区识别出一条高热流带 ,该带与前人给出的海盆北缘断裂带位置基本一致。研究区不同区域地热特征直接或间接地受控于其所处的构造环境。据此 ,给出了研究区的热流趋势图。  相似文献   

9.
This study presents an analysis of the single-channel high-resolution shallow seismic reflection data from Lake Erçek, eastern Anatolia, to provide key information on the deformational elements, on the fault patterns and on the overall tectonic structure of the Lake Erçek Basin. High-resolution seismic data reveal major structural and deformational features, including N–S trending normal faults and W–E trending reverse faults bounding the Lake Erçek Basin, basement highs and folded structures along the marginal sections of the lake. The N–S trending normal faults asymmetrically control the steep western margin and the gentle eastern deltaic section, while the W–E trending reverse faults appear at the northern and southern margins. The N–S trending normal faults, half-graben structure, and the gradual thickening of sediments in the Erçek Basin toward the fault scarps strongly suggest an extensional tectonic regime resulting from an N–S compression. The Erçek Basin is an extension-controlled depocenter; it is a relatively undeformed and flat-lying deep Basin, forming a typical example of the half-graben structure. The N–S trending normal faults appear to be currently active and control the lake center and the E-delta section, resulting in subsidence in the lake floor. In the N- and S-margins of the lake, there is evidence of folding, faulting and accompanying block uplifting, suggesting a significant N–S compressional regime that results in the reverse faulting and basement highs along the marginal sections. The folding and faulting caused strong uplift of the basement blocks in the N- and S- margins, subsequently exposing the shelf and slope areas. The exposed areas are evident in the erosional unconformity of the surface of the basement highs and thinned sediments. The tilted basement strata and subsequent erosion over the basement block highs suggest prominent structural inversion, probably long before the formation of the lake. New high-resolution seismic data reveal the fault patterns and structural lineaments of the Lake Erçek and provide strong evidence for an ongoing extension and subsidence. The present study provides new structural insights that will support future tectonic and sedimentary studies and the development of strategies related to active earthquake faults and major seismic events in the region of Lake Erçek.  相似文献   

10.
The Mesozoic-Cenozoic tectonic history of the Muglad Basin, is dominated by extension and inversion tectonics, but evidence of the inversion tectonics has not been well documented yet. In some other rift basins of CARS and WARS the phase of the inversion tectonics is well documented by several authors.This paper presents a structural study of the Heglig field area located on the eastern flank of the Muglad Basin. Detailed 3D seismic interpretation allows a better understanding of the structural style of the Heglig field. The new structural analysis has shown that the Heglig field has a complex structural framework reflected in the presence of a combination of two structural styles. The extensional structure is influenced by inversion tectonics during the Santonian time that creates four-way dip anticline structure, overprinted by the subsequent extensional movement that creates tilted fault block. The presence of inversion tectonics has supported by different means including seismic reflection, velocity, and source rock maturity data. The authors attributed the trapping of oil in the Lower Bentiu reservoir, that requires a horizontal seal, to the presence of the four-way dip anticline structure created by the inversion tectonics.The current interpretation of the Heglig field 3D seismic data sheds new light on the development and evolution of a key structure in the Muglad Basin. The results help to resolve long-standing discussion concerning hydrocarbon accumulation of the lower part of Bentiu Formation that lacks horizontal sealing.  相似文献   

11.
The Central Trough of the North Sea is not a simple rift graben. It is an elongated area of regional subsidence which was initiated in mid Cretaceous times and continued to subside through to the late Tertiary. Its form is not representative of pre-mid Cretaceous tectonics.In Late Permian times the North Sea was divided into a northern and southern Zechstein basin by the E-W trending Mid North Sea-Ringkøbing-Fyn High. The latter was dissected by a narrow graben trending NNW through the Tail End Graben and the Søgne Basin. The Feda Graben was a minor basin on the northern flank of the Mid North Sea High at this time. This structural configuration persisted until end Middle Jurassic times when a new WNW trend separated the Tail End Graben from the Søgne Basin. Right lateral wrench movement on this new trend caused excessive subsudence in the Tail End and Feda Grabens while the Søgne Basin became inactive.Upper Jurassic subsidence trends continued during the Early Cretaceous causing the deposition of large thicknesses of sediments in local areas along the trend. From mid Cretaceous times the regional subsidence of the Central Trough was dominant but significant structural inversions occurred in those areas of maximum Early Cretaceous and Late Jurassic subsidence.  相似文献   

12.
The petroleum system of the Kunsan Basin in the Northern South Yellow Sea Basin is not well known, compared to other continental rift basins in the Yellow Sea, despite its substantial hydrocarbon potential. Restoration of two depth-converted seismic profiles across the Central Subbasin in the southern Kunsan Basin shows that extension was interrupted by inversions in the Late Oligocene-Middle Miocene that created anticlinal structures. One-dimensional basin modeling of the IIH-1Xa well suggests that hydrocarbon expulsion in the northeastern margin of the depocenter of the Central Subbasin peaked in the Early Oligocene, predating the inversions. Hydrocarbon generation at the dummy well location in the depocenter of the subbasin began in the Late Paleocene. Most source rocks in the depocenter passed the main expulsion phase except for the shallowest source rocks. Hydrocarbons generated from the depocenter are likely to have migrated southward toward the anticlinal structure and faults away from the traps along the northern and northeastern margins of the depocenter because the basin-fill strata are dipping north. Faulting that continued during the rift phase (∼ Middle Miocene) of the subbasin probably acted as conduits for the escape of hydrocarbons. Thus, the anticlinal structure and associated faults to the south of the dummy well may trap hydrocarbons that have been charged from the shallow source rocks in the depocenter since the Middle Miocene.  相似文献   

13.
The study presents the methodology used by the French Geological Survey (BRGM) for the building, reprocessing and interpretation of selected regional seismic lines in the Paris intracratonic basin (France): the 14 constructed E-W and N-S regional transects represent a total of 2,516 km length, and are based on the merge of 240 seismic single profiles recorded by petroleum operators between 1971 and 1995. The regional lines have been selected to cross the main oil fields of the Paris Basin, as well as high potential areas for oil exploration. A first difficulty was to recover the raw data necessary to build-up the regional transects. The signal reprocessing, harmonization and merge of the single seismic lines, constituent of the regional transects, are then described; these operations represent the cornerstone of the study. We put the emphasis on the primary static corrections, as the targeted structures are commonly spatially associated with large seismic velocity variations in the upper Cretaceous chalk and Tertiary sedimentary cover.The interpreted regional transects definitely give complementary information to the existing studies, which generally lack seismic (and therefore structural) data: we give an overview of the main structural and geometrical features of the Paris Basin: inversion structures, major unconformities, as well as Permo-Carboniferous basins. We also describe the structural pattern, and show the close relationships between the faults geometry, the faults density, and the geological evolution of the Paris Basin: we distinguish (1) few large-scale polyphase faults, with a Variscan origin, representing the first order structural frame of the Paris Basin; (2) monophase normal faults, with strike-slip features, representing the subsurface prolongation of Cenozoic grabens cropping out in the neighbourhood; (3) deep normal faults, sealed by the base Calcareous Dogger sequence, related to the Permo-Liassic extensional tectonic regime. This large-scale view of the Paris Basin has highlighted several potential exploration targets.  相似文献   

14.
The Fingerdjupet Subbasin in the southwestern Barents Sea sits in a key tectonic location between deep rifts in the west and more stable platform areas in the east. Its evolution is characterized by extensional reactivation of N-S and NNE-SSW faults with an older history of Late Permian and likely Carboniferous activity superimposed on Caledonian fabrics. Reactivations in the listric NNE-SSW Terningen Fault Complex accommodated a semi-regional rollover structure where the Fingerdjupet Subbasin developed in the hangingwall. In parallel, the Randi Fault Set developed from outer-arc extension and collapse of the rollover anticline.N-S to NNE-SSW faults and the presence of other fault trends indicate changes in the stress regime relating to tectonic activity in the North Atlantic and Arctic regions. A latest Triassic to Middle Jurassic extensional faulting event with E-W striking faults is linked to activity in the Hammerfest Basin. Cessation of extensional tectonics before the Late Jurassic in the Fingerdjupet Subbasin, however, suggests rifting became localized to the Hammerfest Basin. The Late Jurassic was a period of tectonic quiescence in the Fingerdjupet Subbasin before latest Jurassic to Hauterivian extensional faulting, which reactivated N-S and NNE-SSW faults. Barremian SE-prograding clinoforms filled the relief generated during this event before reaching the Bjarmeland Platform. High-angle NW-prograding clinoforms on the western Bjarmeland Platform are linked to Early Barremian uplift of the Loppa High. The Terningen Fault Complex and Randi Fault Set were again reactivated in the Aptian along with other major fault complexes in the SW Barents Sea, leading to subaerial exposure of local highs. This activity ceased by early Albian. Post-upper Albian strata were removed by late Cenozoic uplift and erosion, but later tectonic activity has both reactivated E-W and N-S/NNE-SSW faults and also established a NW-SE trend.  相似文献   

15.
Seven dives in the submersible ALVIN and four deep-towed (ANGUS) camera lowerings have been made at the eastern ridge-transform intersection of the Oceanographer Transform with the axis of the Mid-Atlantic Ridge. These data constrain our understanding of the processes that create and shape the distinctive morphology that is characteristic of slowly-slipping ridge-transform-ridge plate boundaries. Although the geological relationships observed in the rift valley floor in the study area are similar to those reported for the FAMOUS area, we observe a distinct change in the character of the rift valley floor with increasing proximity to the transform. Over a distance of approximately ten kilometers the volcanic constructional terrain becomes increasingly more disrupted by faulting and degraded by mass wasting. Moreover, proximal to the transform boundary, faults with orientations oblique to the trend of the rift valley are recognized. The morphology of the eastern rift valley wall is characterized by inward-facing scarps that are ridge-axis parallel, but the western rift valley wall, adjacent to the active transform zone, is characterized by a complex fault pattern defined by faults exhibiting a wide range of orientations. However, even for transform parallel faults no evidence for strike-slip displacement is observed throughout the study area and evidence for normal (dip-slip) displacement is ubiquitous. Basalts, semi-consolidated sediments (chalks, debris slide deposits) and serpentinized ultramafic rocks are recovered from localities within or proximal to the rift valley. The axis of accretion-principal transform displacement zone intersection is not clearly established, but appears to be located along the E-W trending, southern flank of the deep nodal basin that defines the intersection of the transform valley with the rift floor.  相似文献   

16.
To date there is one proven hydrocarbon accumulation on the Ashmore Platform, Bonaparte Basin, Australia, with hydrocarbon charge remaining a key exploration risk. To the south, the neighbouring Browse Basin has proven lateral migration of generated hydrocarbons to the basin bounding highs, as evidenced by seeps located on the Yampi Shelf. This paper describes the findings of a natural seeps study carried out to establish if migrating subsurface hydrocarbons reach the southern flanks of the Ashmore Platform basement high. The integrated study combined remote sensing, geophysical, acoustic, photographic and geochemical techniques and has identified three areas of seepage; one area characteristic of persistent seepage and two areas of interpreted episodic leakage. Geochemical data collected from samples at one of these sites demonstrates the presence of thermogenic liquid hydrocarbons, with isotopic compositions falling within the range of values exhibited by oils sourced by the Lower Cretaceous Echuca Shoals Formation. The identification of active natural seepage along the southern flank of the Ashmore Platform provides evidence that hydrocarbons generated within the Caswell Sub-basin are able to laterally migrate onto the flanks of the Ashmore Platform structural high. As such, these findings reduce charge risk for the Ashmore Platform and regional exploration risks in the northern Browse Basin.  相似文献   

17.
The northern Mascarene Basin, lying between Madagascar and the Seychelles Plateau in the north-west Indian Ocean, is marked at its north-western end by the Amirante Arc, an enigmatic ridge-trench complex superficially resembling an island arc. Structural trends in the area have been mapped using GLORIA sidescan sonar data, seismic reflection profiles and bathymetric maps. It is concluded that the north-west Mascarene Basin was created during the Late Cretaceous by sea-floor spreading about a north-west trending spreading axis cut by northeast trending transform faults. A major transform fault between the northern tip of Madagascar and the western margin of the Seychelles Plateau is proposed as a boundary between the Late Cretaceous Mascarene basin and the older Somali Basin to the north-west. The northern segment of the Amirante Ridge may mark part of the transform. The southern segment of the Ridge and its associated trench are, however, wholly contained within the Late Cretaceous ocean floor of the Mascarene Basin, and are best explained as compressional features related to a change in sea-floor spreading geometry in the Late Cretaceous or earliest Tertiary. Two models for the evolution of the Mascarene Basin are proposed, the major differences between them being the amount of subduction at the southern Amirante Arc and the timing of the initial separation between India and the Seychelles.  相似文献   

18.
The North Anatolian Fault crosses the Sea of Marmara from east to west. Tectonic features of the Sea of Marmara were studied using multi-channel deep seismic reflection data. The northern branch of the North Anatolian Fault is active as a right lateral strike-slip fault zone and indicates both negative and positive flower structures. The North Anatolian Fault splays into two faults at the Sea of Marmara as a northern branch and north segment of the southern branch. The northern branch named the Main Marmara Fault extends in a complicated manner from the north of the Kapıdağı Peninsula to westward in the Sea of Marmara. The north segment of southern branch extends between the Gemlik and Bandırma gulfs in the south of the Sea of Marmara. In addition, uplift areas arose by compression and a push-up style in between the Kapıdağı Peninsula and the Main Marmara Fault. The North Anatolian Fault is characterized by a negative flower structure in basins and push-up style in uplift areas in the Sea of Marmara. An uplift area arose between the north segment of the southern branch and the northern branch of the North Anatolian Fault. The north segment of the southern branch of the North Anatolian Fault is a strike-slip fault and displays a pull-apart style in the seismic reflection data.  相似文献   

19.
东海陆架盆地南部构造样式及分布特征   总被引：2，自引：0，他引：2  
以东海陆架盆地南部为重点研究对象,基于区域地震反射资料,结合盆地的结构特征,分析、总结了其构造样式特征。结果表明:根据构造样式形成的动力学机制,可以将东海陆架盆地南部划分为伸展型构造样式、挤压型构造样式和复合型构造样式3类;伸展型构造样式可继续分为半地堑(箕状断陷)构造组合、复式地堑式构造组合、多米诺式断裂构造组合、掀斜断块和火成岩构造;挤压型构造样式分为挤压背斜、断背斜和叠瓦式断裂组合;复合型构造样式分为正反转构造和负花状构造。  相似文献   

20.
A tectono-sedimentary scenario for the Southern Sardinia (Italy) Cenozoic graben system is proposed using field observations and the interpretation of onshore and offshore seismic profiles. The major structural events are tied to the general geodynamic evolution of the Western Central Mediterranean. Thus, the extensional late Oligocene–Aquitanian event is a consequence of an ‘Apenninic’ westward subduction process associated with a volcanic arc (29–30 to 15–16 My) which is particularly well exposed in Sardinia. Deposition of Sub-aerial clastics, was followed by transgression of the rift depression at the beginning of the Aquitanian. Subduction terminated at the opening of the oceanic Provençal Basin and the rotation of Sardinia–Corsica during Burdigalian time (20–21 to 15–16 My). The Messinian compressional event (NE–SW oriented), documented from microtectonic data, strongly affected the Oligo-Miocene basin. The superimposed Plio-Quaternary Campidano Graben, which is probably related to the formation of the Tyrrhenian Basin, contains more than 600 m of syntectonic deposits. A change in polarity of the master faults bounding the Oligo-Miocene rift created a central horst-type twist zone separating two depocenters in the Oristano and Cagliari regions. Emplacement of large volcanic bodies and inversion of the basin during the Messinian in Cagliari area has reduced the areas with potential for hydrocarbon exploration. The two remaining prospective zones are the Oristano sub-basin and the offshore, south of Cagliari where burial of lower Miocene marine organic matter may have been sufficient to generate hydrocarbons. Potential reservoirs could be pre-rift Mesozoic or Eocene strata but are mainly excellent Miocene sands derived from erosion of the granitic basement in tilted blocks.  相似文献   

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