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1.
《Marine and Petroleum Geology》2003,20(3-4):287-308
This work provides new palinspastic palaeofacies reconstructions of SW Gondwana incorporating rotation of a Falkland/Malvinas microplate. We discuss the implications of this for the tectonic evolution of the southern South Atlantic and hence for the regional hydrocarbon potential.Existing Gondwana reconstructions display good fits of major continents but poorly constrained fits of microcontinents. In most continental reconstructions, the Falkland/Malvinas Plateau was assumed to be a rigid fragment of pre-Permian South American crust. However, it has been suggested, on the basis of palaeomagnetic data, that the Falkland/Malvinas Islands were rotated by ∼180° after 190 Ma. This rotation hypothesis has been successfully tested on the basis of Devonian stratigraphy and palaeontology, Permian stratigraphy and sedimentology and Late Palaeozoic and Early Mesozoic structure, making it unlikely that the plateau behaved as a rigid structure during breakup. We have explored the consequences of accepting this hypothesis for the tectonic evolution of SW Gondwana by compiling new palaeogeographic maps for the Permian–Cretaceous of the southern Atlantic area. To achieve a realistic close fit, we have devised a pre-rift proxy for the ocean–continent boundary for the South Atlantic. In order to produce the best fit, it is necessary to subdivide South America into four plates. The consequences of this are far-reaching. Our work suggests that although sedimentary basins were initiated at different times, three major tectonic phases can be recognised; in regional terms these can be thought of as pre-, syn- and post-rift.During the pre-rift time (until the Late Triassic), the area was dominated by compressional tectonism and formed part of the Gondwana foreland. The Falkland/Malvinas Islands lay east of Africa, the Falkland/Malvinas Plateau was ∼33% shorter and Patagonia was displaced east with respect to the rest of South America, in part along the line of the Gastre Fault System. Potential source facies are dominantly post-glacial black shales of Late Permian age deposited in lacustrine or hyposaline marine environments; these rocks would also be an effective regional seal. Sandstones deposited in the Late Permian would be dominantly volcaniclastic with poor reservoir qualities; Triassic sandstones tend to be more mature.There was significant extension from about 210 Ma (end-Triassic) until the South Atlantic opened at about 130 Ma (Early Cretaceous). In the early syn-rift phase, extension was accompanied by strike-slip faulting and block rotation; later extension was accompanied by extrusion of large volumes of lava. Early opening of the South Atlantic was oblique, which created basins at high angle to the trend of the ocean on the Argentine margin, and resulted in microplate rotation in NE Brazil. Intermittent physical barriers controlled deposition of Upper Jurassic–Cretaceous anoxic sediments during breakup; some of these mudrock units are effective seals with likely regional extent. During crustal reorganisation, clastic sediments changed from a uniform volcaniclastic provenance to local derivation, with variable reservoir quality.In the late rift and early post-rift phase, continental extension changed from oblique to normal and basins developed parallel to the continental margins of the South Atlantic. This change coincides with the main rifting in the Equatorial basins of Brazil and the early impact of the Santa Helena Plume. It resulted in widespread development of unconformities, the abandonment of the Recôncavo–Tucano–Jatoba rift and the end of NE Brazil plate rotation, which remained attached to South America. There was extensive deposition of evaporites, concentrated in (but not restricted to) the area north of the Rio Grande Rise/Walvis Ridge.Widespread deposits can be used to define potential regional elements of hydrocarbon systems and to provide a framework for relating more local elements. Our main conclusion is that the regional hydrocarbon potential of the southern South Atlantic has been constrained by the tectonic evolution. 相似文献
2.
We use recently acquired magnetic and SeaBeam bathymetric data to examine the spreading rates and plate boundary geometry of the Mid-Atlantic Ridge 30°–36° S. Using a statistically rigorous estimation of rotation poles we develop a precise spreading history of the African—South American plate boundary. The total opening rate for 1–4.23 Myr (Plio-Pleistocene) is nearly constant at 32.3 ± 1 km Myr–1. The spreading rate apparently is faster in the Late Miocene (7.3-5.3 Myr), though this may reflect inaccuracies in the geomagnetic time scale. The rotation poles enable a plate boundary reconstruction with an accuracy of 2–3 km. The reconstructions also show that the plate boundary geometry underwent several changes since the late Miocene including the growth of one ridge segment from 40 to 105 km in length, and the reorientation of another ridge segment which has spread obliquely from 7 to 1 Myr. Pole calculations using both right- and left-stepping fracture zones show an offset of 1–2 km between the deepest, most linear part of a fracture zone trough and the former plate boundary location. The high-resolution plate kinematics suggests that the plate boundary, as a whole, evolves 2-dimensionally as prescribed by rigid plates. On a local scale, asymmetric accretion, asymmetric extension, small lateral ridge jumps (< 3 km), and intra-segment propagation result in minor plate boundary adjustments and deformation to the rigid plates. 相似文献
3.
The area reviewed covers the Mid-Norway continental margin between latitudes 62°N and 68°N. Main structural elements, as defined at the base Cretaceous level, are the Tröndelag Platform, underlying the inner shelf, the Möre and Vöring Basins, located beneath the outer shelf and slope, and the Möre Platform and the Outer Vöring Plateau, forming a base of slope trend of highs. Sediments contained in the Mid-Norway Basin range in age from Late Palaeozoic to Cenozoic. The basement was consolidated during the Caledonian orogenic cycle. Devonian and Early Carboniferous wrench movements along the axis of the Arctic-North Atlantic Caledonides are thought to have preceded the Namurian onset of crustal extension. Rifting processes were intermittently active for some 270 My until crustal separation between Greenland and Fennoscandia was achieved during the Early Eocene. During the evolution of the Norwegian-Greenland Sea rift system a stepwise concentration of tectonic activities to its axial zone (the area of subsequent continental separation) is observed. During the Late Palaeozoic to Mid-Jurassic a broad zone was affected by tensional faulting. During the Late Jurassic and Cretaceous the Tröndelag Platform was little affected by faulting whilst major rift systems in the Möre and Vöring Basins subsided rapidly and their shoulders became concomitantly upwarped. During the latest Cretaceous and Early Palaeogene terminal rifting phase only the western Möre and Vöring Basins were affected by intrusive and extrusive igneous activity. Following the Early Eocene crustal separation and the onset of sea floor spreading in the Norwegian-Greenland Sea, the Vöring segment of the Mid-Norway marginal basin subsided less rapidly than the Möre segment. During the Early and Mid Tertiary, minor compressional deformations affected the Vöring Basin and to a lesser degree the Möre Basin. Tensional forces dominated the Late Palaeozoic to Early Cenozoic evolution of the Mid-Norway Basin and effected strain mainly in the area where the crust was weakened by the previous lateral displacements. The lithosphere thinned progressively and the effects of the passively upwelling hot asthenospheric material became more pronounced. Massive dyke invasion of the thinned crust preceded its rupture. 相似文献
4.
The southern Mid-Atlantic Ridge (MAR) is spreading at rates (34–38 mm yr−1) that fall within a transitional range between those which characterize slow and intermediate spreading center morphology.
To further our understanding of crustal accretion at these transitional spreading rates, we have carried out analysis of magnetic
anomaly data from two detailed SeaBeam surveys of the MAR between 25°–27°30′S and 31°–34°30′S. Within these areas, the MAR
is subdivided into 9 ridge segments bounded by large- and short-offset discontinuities of the ridge axis. From two-dimensional
Fourier inversions of the magnetic anomaly data we establish the history of spreading within each ridge segment for the past
5 my and the evolution of the bounding ridge-axis discontinuities. We see evidence for the initiation and diminishment of
small-offset discontinuities, and for the transition of rigid large-offset transform faults to less stable short-offset features.
Individual ridge segments display independent spreading histories in terms of both the sense and amount of asymmetric spreading
within each which have given rise to changes through time in the lengths of bounding ridge-axis discontinuities. Over the
past 3–5 my, the short-offset discontinuities within the area have lengthened/shortened by approximately the same amount (∼
10 km). During this same time period, larger-offset transform faults have remained comparatively constant in length. A shift
in plate motion at anomaly 3 time may have given rise to change in the length of short-offset second-order discontinuities.
However, the pattern of lengthening/shortening short-offset discontinuities we see is not simply related to the geometry of
the plate boundary in these regions which precludes a simply relationship between plate motion changes and response at the
plate boundary. We document a case of rapid (minimum 60 mm yr−1) small-scale rift propagation, occurring between 2.5 and 1.8 my, associated with transition of the Moore transform fault
to an oblique-trending ridge-axis discontinuity. Propagation across the Moore discontinuity and similar propagation within
the 31°–34°30’S area may be associated with the reduced age contrast in lithosphere across second-order discontinuities.
Total opening rates within our northern survey area decreased from anomaly 4′ to 2 time and rates within both areas have increased
since the Jaramillo. Total opening rates measured for anomaly intervals differ along the plate boundary significantly, more
than expected with changing distance to the pole of rotation. These differences imply a degree of short-term non-rigid plate
behaviour which may be associated with ridge segments acting as independent spreading cells. Magnetic polarity transition
widths from our inversion studies may be used to infer a zone of crustal accretion which is 3–6 km wide, within the inner
floor of the rift valley. A systematic increase of transition width with age would be expected if deeper crustal sources dominate
the magnetic signal in older crust but this is not observed. We present results from three-dimensional analysis of magnetic
anomaly data which show magnetization highs located at the intersection of the MAR with both large- and short-offset discontinuities.
Within the central anomaly the highs exceed 15 A m−1 compared with a background of approximately 8–10 A m−1 and they persist for at least 2.5 my. The highs may be caused by eruption of fractionated strongly magnetized basalts at
ridge-axis discontinuities with both large and small offsets. 相似文献
5.
The Kane Fracture Zone probably is better covered by geophysical survey data, acquired both by design and incidentally, than
any other fracture zone in the North Atlantic Ocean. We have used this data to map the basement morphology of the fracture
zone and the adjacent crust for nearly 5700 km, from near Cape Hatteras to the middle of the Mesozoic magnetic anomalies west
of Cap Blanc, northwest Africa. We use the trends of the Kane transform valley and its inactive fracture valley to determine
the record of plate-motion changes, and we interpret the basement structural data to examine how the Kane transform evolved
in response to changes in plate motion. Prior to about 133 Ma the Kane was a small-offset transform and its fracture valley
is structurally expressed only as a shallow ( < 0.5 km) trough. In younger crust, the offset may have increased to as much
as 190 km (present offset 150 km) and the fracture valley typically is up to 1.2 km deep. This part of the fracture valley
records significant changes in direction of relative plate motion (5°–30°) near 102 Ma, 92 Ma, 59 Ma, 22 Ma, and 17 Ma. Each
change corresponds to a major reorganization of plate boundaries in areas around the Atlantic, and the fracture-zone orientation
appears to be a sensitive recorder of these events.
The Kane transform has exhibited characteristic responses to changes in relative plate motion. Counterclockwise plate-motion
changes put the left-lateral transform offset into extension, and the response was for ridge tips at the ridge-transform intersections
to propagate across the transform valley and against the truncating lithosphere. Heating of this lithosphere appears to have
produced uplift and formation of a well developed transverse ridge that bounds the inactive fracture valley on its older side.
The propagating ridge tips also rotated toward the transform fault in response to the local stress field, forming prominent
hooked ridges that now extend into or across the inactive fracture valley. Clockwise (compressional) changes in relative plate
motion produced none of these features, and the resulting fracture valleys typically have a wide-V shape.
The Kane transform experienced severe adaptions to the changes in relative plate motion at about 102 Ma (compressional shift)
and 92 Ma (extensional shift), and new transform faults were formed in crust outside the contemporary transform valley. Subsequently,
the transform offset has been smaller and the rates of change in plate motion have been more gradual, so transform-fault adjustment
has been contained within the transform valley. The fracture-valley structure formed during extensional and compressional
changes in relative plate motion can be decidedly asymmetrical in conjugate limbs of the fracture zone. This asymmetry appears
to be related to the ‘absolute’ motion of the plate boundary with respect to the asthenosphere. 相似文献
6.
Jean-Pierre Lefort 《Marine Geology》1973,14(5):33-38
The study of recent geological and geophysical data, collected west of France, allows of delineating a large fracture zone, with a 130° N dextral slip, between Ireland and Aquitaine (France). This zone belongs to a wider structure which extended from Labrador to Spain and which sheared the Caledonian and Hercynian systems before the opening of the North Atlantic. 相似文献
7.
Bastiaan J. Collette Hans Schouten Kees Rutten A. Peter Slootweg 《Marine Geophysical Researches》1974,2(2):143-179
An analysis is given of air-gun profiler and magnetic data obtained in the central North Atlantic between 12° and 18°N. Eight fracture zones were crossed, one of which (the 15°20N fracture zone) was traced over a distance of 1500 km. The mode of adjustment of fracture zones to a change in direction of spreading is discussed. It is shown that also if this new direction would lead to an opening of the fracture zone, and adjustment fracture can originate and actually does so in several instances.The about E-W fracture zones dominate the structure of the Ridge province entirely, both with regard to the topography and to the magnetics. A magnetic model is proposed accounting for the different types of anomalies found over fracture zones. No intrusive bodies are needed to explain these anomalies.The origin of fracture zones is related to thermal contraction of a cooling lithosphere while moving from the ridge. Thermal contraction may also explain how the American and the African plates are freed from the grip they are caught in by the fanning of the fracture zones in the central North Atlantic. The fanning of fracture zones has consequences for the determination of the pole of spreading. This pole can only be found as a best fit from a synthesis of the total plate boundary, i.e. from the Azores to Bouvet Island. Local poles have only restricted value, since deviations up to 5 deg occur from a small circle pattern based on existing data.Several huge structures, viz. Researcher Ridge and Royal Trough, are found in the area which seem to parallel the flow lines of the fracture zone system. No adequate explanation exists for these structures. 相似文献
8.
W. R. Roest J. J. Dañobeitia J. Verhoef B. J. Collette 《Marine Geophysical Researches》1992,14(1):1-24
The data from a recent magnetic compilation by Verhoefet al. (1991) off west Africa were used in combination with data in the western Atlantic to review the Mesozoic plate kinematic evolution of the central North Atlantic. The magnetic profile data were analyzed to identify the M-series sea floor spreading anomalies on the African plate. Oceanic fracture zones were identified from magnetic anomalies and seismic and gravity measurements. The identified sea floor spreading anomalies on the African plate were combined with those on the North American plate to calculate reconstruction poles for this part of the central Atlantic. The total separation poles derived in this paper describe a smooth curve, suggesting that the motion of the pole through time was continuous. Although the new sea floor spreading history differs only slightly from the one presented by Klitgord and Schouten (1986), it predicts smoother flowlines. On the other hand, the sea floor spreading history as depicted by the flowlines for the eastern central Atlantic deviates substantially from that of Sundvik and Larson (1988). A revised spreading history is also presented for the Cretaceous Magnetic Quiet Zone, where large changes in spreading direction occurred, that can not be resolved when fitting magnetic isochrons only, but which are evident from fracture zone traces and directions of sea floor spreading topography.Deceased 11 November 1991 相似文献
9.
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
10.
Several diagenetic models have been proposed for Middle and Upper Jurassic carbonates of the eastern Paris Basin. The paragenetic sequences are compared in both aquifers to propose a diagenetic model for the Middle and Late Jurassic deposits as a whole. Petrographic (optical and cathodoluminescence microscopy), structural (fracture orientations) and geochemical (δ18O, δ13C, REE) studies were conducted to characterize diagenetic cements, with a focus on blocky calcite cements, and their connection with fracturation events. Four generations of blocky calcite (Cal1–Cal4) are identified. Cal1 and Cal2 are widespread in the dominantly grain-supported facies of the Middle Jurassic limestones (about 90% of the cementation), whereas they are limited in the Oxfordian because grain-supported facies are restricted to certain stratigraphic levels. Cal1 and Cal2 blocky spars precipitated during burial in a reducing environment from mixed marine-meteoric waters and/or buffered meteoric waters. The meteoric waters probably entered aquifers during the Late Cimmerian (Jurassic/Cretaceous boundary) and Late Aptian (Early Cretaceous) unconformities. The amount of Cal2 cement is thought to be linked to the intensity of burial pressure dissolution, which in turn was partly controlled by the clay content of the host rocks. Cal3 and Cal4 are associated with telogenetic fracturing phases. The succession of Cal3 and Cal4 calcite relates to the transition towards oxidizing conditions during an opening of the system to meteoric waters at higher water/rock ratios. These meteoric fluids circulated along Pyrenean, Oligocene and Alpine fractures and generated both dissolution and subsequent cementation in Oxfordian vugs in mud-supported facies and in poorly stylolitized grainstones. However, these cements filled only the residual porosity in Middle Jurassic limestones. In addition to fluorine inputs, fracturation also permitted inputs of sulphur possibly due to weathering of Triassic or Purbeckian evaporites or H2S input during Paleogene times. 相似文献
11.
Lateral variations in tectono-magmatic style along the Lofoten–Vesterålen volcanic margin off Norway
《Marine and Petroleum Geology》2001,18(7):807-832
The ∼400 km-long passive continental margin west of the Lofoten–Vesterålen archipelago, off northern Norway, links the volcanic rifted Vøring margin and the sheared W Barents Sea margin. Multi-channel seismic reflection profiles, supplemented with crustal velocity, gravity and magnetic anomaly data are used to outline the regional setting and main tectono-magmatic features. A well-defined along-strike margin segmentation comprising three segments characterized by distinct crustal properties, structural and magmatic styles, sediment thickness, and post-opening history of vertical motion is revealed. The margin segments are governed by changes in fault polarity on Late Jurassic–Early Cretaceous border faults and are separated by coeval cross-margin transfer zones which acted as persistent barriers to rupture propagation and reflect the trend and character of older structural heterogeneities. The transfer zones spatially correlate to small-offset, early opening oceanic fracture zones, implying a structural inheritance from one rift episode to another culminating with lithospheric breakup at the Paleocene–Eocene transition. The pre-seafloor spreading margin structural evolution is governed by the older, predominantly Late Jurassic–Early Cretaceous structural framework. However, the margin also provides evidence for mid- and Late Cretaceous extension events that are poorly understood elsewhere off Norway. Furthermore, the Lofoten–Vesterålen post-breakup subsidence history contrasts with the adjacent margins reflecting breakup in thicker crust and a diminishing volume of high-velocity lower crust emplaced during breakup. 相似文献
12.
Marine geophysical data including Seabeam, seismic reflection, magnetics, gravimetry and side-scan sonar have been recently collected along the northern Caribbean strike-slip plate boundary between Cuba and Hispaniola, in the Windward Passage area. The analysis of this comprehensive data set allows us to illustrate active strike-slip tectonic processes in relation to the kinematics of the Caribbean Plate. We show that the transcurrent plate boundary trace runs straight across the Windward Passage, from the southern Cuban Margin in the west (Oriente Fault) to the Tortue Channel in the east. The Windward Passage Deep is thus not an active pull-apart basin, as previously suggested. The plate boundary geometry implies that the motion of the Caribbean Plate relative to the North American Plate is partitioned between a strike-slip component, accommodated by the Windward Passage active fault zone, and a convergence component, accommodated by compression at the bottom of the Northern Hispaniola Margin. On the basis of a correlation with onland geological data, an age is given to the stratigraphic sequences identified on seismic profiles. A kinematic reconstruction is proposed that follows the tectonic unconformities recognized at sea and on land (Late Eocene, Early Miocene, Middle Miocene and Late Pliocene). Each one of these tectonic events corresponds to a drastic reorganization of the plate boundary geometry. We propose to correlate these events with successive collisions of the northern Caribbean mobile terranes against the Bahamas Bank. During each event, the plate boundary trace is shifted to the south and a part of the Caribbean Plate is accreted to North America. 相似文献
13.
The South Caspian Basin (SCB) is a relic of the back-arc basin in the margin of the Tethys paleoocean. The SCB has an oceanic-type
crust and is filled with a thick (15–28 km) sedimentary series. In the modern structure, it is a part of the South Caspian
microplate, which also comprises the Lower Kura and West Turkmenian depressions, parts of the Kopet Dagh and Alborz ranges.
The geological and seismological data evidence an underthrust (or, probably, subduction) of the South Caspian Basin’s lithosphere
beneath the Apsheron threshold and the simultaneous westward displacement of the South Caspian Microplate (SCM). Different
authors refer the South Caspian Basin’s formation to the Early Mesozoic, Late Jurassic, and Paleocene. In this paper, on the
basis of geologic information, a two-phase model of the South Caspian Basin’s opening is considered. The first phase is referred
to the Late Triassic-Early Jurassic, when the sinking of the Kopet Dagh Basin and the opening of the Great Caucasus rift began
as well. Jointly, these three structures formed a prolonged basin related to the development of the Early Mesozoic subduction
zone. The age of the oceanic crust in the central part of the South Caspian Basin calculated by the thermal flux is 200 Ma.
The second phase of the South Caspian Basin opening referred to the Eocene is related to the extension in the back-arc part
of the Elbrus volcanic arc. The formation of the oceanic crust in the southwestern part of the South Caspian Basin and in
the Lower-Kura depression is associated with this phase, which is proved by the high values of the thermal flux. 相似文献
14.
This study provides the results of the first integrated study of Oligocene–Pliocene basins around Norway.Within the study area, three main depocentres have been identified where sandy sediments accumulated throughout the Oligocene to Early Pliocene period. The depocentre in the Norwegian–Danish Basin received sediments from the southern Scandes Mountains, with a general progradation from north to south during the studied period. The depocentre in the basinal areas of the UK and Norwegian sectors of the North Sea north of 58°N received sediments from the Scotland–Shetland area. Because of the sedimentary infilling there was a gradual shallowing of the northern North Sea basin in the Oligocene and Miocene. A smaller depocentre is identified offshore northern Nordland between Ranafjorden (approximately 66°N) and Vesterålen (approximately 68°N) where the northern Scandes Mountains were the source of the Oligocene to Early Pliocene sediments. In other local depocentres along the west coast of Norway, sandy sedimentation occurred in only parts of the period. Shifts in local depocentres are indicative of changes in the paleogeography in the source areas.In the Barents Sea and south to approximately 68°N, the Oligocene to Early Pliocene section is eroded except for distal fine-grained and biogenic deposits along the western margin and on the oceanic crust. This margin was undergoing deformation in a strike-slip regime until the Eocene–Oligocene transition. The Early Oligocene sediments dated in the Vestbakken Volcanic Province and the Forlandssundet Basin represent the termination of this strike-slip regime.The change in the plate tectonic regime at the Eocene–Oligocene transition affected mainly the northern part of the study area, and was followed by a quiet tectonic period until the Middle Miocene, when large compressional dome and basin structures were formed in the Norwegian Sea. The Middle Miocene event is correlated with a relative fall in sea level in the main depocentres in the North Sea, formation of a large delta in the Viking Graben (Frigg area) and uplift of the North and South Scandes domes. In the Norwegian–Danish Basin, the Sorgenfrei-Tornquist Zone was reactivated in the Early Miocene, possibly causing a shift in the deltaic progradation towards the east. A Late Pliocene relative rise in sea level resulted in low sedimentation rates in the main depositional areas until the onset of glaciations at about 2.7 Ma when the Scandes Mountains were strongly eroded and became a major source of sediments for the Norwegian shelf, whilst the Frigg delta prograded farther to the northeast. 相似文献
15.
K Thomson 《Marine and Petroleum Geology》1998,15(8):277
Similarities in the styles and relative timings of tectonic events in the Outeniqua Basin, South Africa and the North Falkland Basin suggest that basin formation in both regions may have preceded rotation of the Falklands microplate. Contrary to previous models for the break-up of Gondwana, which suggest Jurassic rotation, the data implies Valanginian rotation, contemporaneous with the first recorded motion on the Agulhas Falkland Fracture Zone and South Atlantic rifting. The data also suggests that the formation of the Falkland Plateau Basin may also be a Cretaceous event as opposed to the previously assumed Jurassic age. Such a model is consistent with new offshore seismic evidence while the inconclusive nature of the supportive evidence for Jurassic rotation does not exclude later rotation as a possibility. 相似文献
16.
从地质演化特征探讨墨西哥湾地区油气富集的基本规律 总被引：2，自引：0，他引：2
墨西哥湾东部主体经历了中生代裂谷拉张、中侏罗世裂谷和地壳衰减、晚侏罗世洋壳形成及早白垩世的区域沉降4个演化阶段;西部主要受中生代太平洋板块向北美板块的俯冲影响,属弧后拉张。由于持续稳定的沉降,墨西哥湾沉积了巨厚的以海相地层为主的中生代地层,并提供了有利的烃源岩、储层和盖层。大量的构造、地层和复合型圈闭为油气富集提供了有利的场所。墨西哥湾盆地为典型的高演化拉张盆地,巴西东部(包括海区)为中等演化拉张盆地,二者均已成为重要的油气富集区。我国东部海区中生界南部以海相地层为主,北部以陆相地层为主,为一个低—中等演化的拉张盆地。前二者的油气富集规律为我国东部海区中生代盆地的找油提供了借鉴作用。 相似文献
17.
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
18.
A corridor 315 km wide centered along the southeast projection of the Atlantis fracture zone between 21°W and 29°W was investigated with seismic reflection, bathymetric, gravity, and magnetic profiles. Six sub-parallel, sediment-filled troughs in acoustic basement trend about 106° across the abyssal hills and lower continental rise off northwest Africa. Where the southernmost structural lineations cross the abyssal plain, they are interrupted by a ridge trending 080° surmounted by volcanic peaks.The structural lineations become less distinct landward of the western margin of the abyssal plain coincident with a decrease in topographic relief on acoustic basement and increasing sediment thickness. This transition is coincident with a reduction in the amplitude of gravity and magnetic anomalies. 相似文献
19.
Deniz Cukur Senay Horozal Gwang H. Lee Dae C. Kim Hyun C. Han Moo H. Kang 《Marine Geophysical Researches》2011,32(3):363-381
The northern East China Sea Shelf Basin consists of three depressions (the Domi, Jeju, and Socotra Depressions), separated by basement highs or rises. Reconstruction of depth-converted seismic reflection profiles from these depressions reveals that the northern East China Sea Shelf Basin experienced two phases of rifting, followed by regional subsidence. Initial rifting in the Late Cretaceous was driven by the NW?CSE crustal stretching of the Eurasian plate, caused by the subduction of the Pacific plate beneath the plate margin. Major extension (~15 km) took place during the early phase of basin formation. The initial rifting was terminated by regional uplift in the Late Eocene-Early Oligocene, which was probably due to reorganization of plate boundaries. Rifting resumed in the Early Oligocene; the magnitude of extension was mild (<1 km) during this period. A second phase of uplift in the Early Miocene terminated the rifting, marking the transition to the postrift phase of regional subsidence. Up to 2,600 m of sediments and basement rock were removed by erosion during and after the second phase of uplift. An inversion in the Late Miocene interrupted the postrift subsidence, resulting in an extensive thrust-fold belt in the eastern part of the area. Subsequent erosion removed about 900 m of sediments. The regional subsidence has dominated the area since the Late Miocene. 相似文献
20.
通过选取南黄海盆地东北凹典型地震剖面,开展精细的构造解释,系统梳理了东北凹构造样式特征。采用平衡剖面恢复技术和伸缩率计算方法,恢复了东北凹各时期的地质演化剖面,分析了东北凹不同构造演化阶段的伸缩率变化特征。研究表明,南黄海盆地东北凹主要发育伸展构造、走滑构造(负花状)和反转构造等多种构造组合样式,经历了晚侏罗世的仪征运动和渐新世末的三垛运动,相应地在中—上侏罗统和渐新统沉积时期,东北凹处于明显的收缩阶段,伴随发育TK40和T20不整合界面。同时,本文结合区域应力场特征,探讨了南黄海盆地东北凹的构造演化历程:以两次构造运动为界,划分为3个构造演化阶段(晚三叠世—侏罗纪的初始断陷阶段、白垩纪—渐新世的裂陷-反转阶段、新近纪—第四纪的区域沉降阶段)。南黄海盆地东北凹伸缩率的时空变化及构造演化过程,是对“晚中生代以来,古太平洋板块相对欧亚板块俯冲汇聚速率和方向的改变”的局部响应。 相似文献