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1.
The Lower Permian sedimentary succession of the Paraná Basin in southernmost Brazil has an overall transgressive sedimentation regime, recorded by a clear retrogradation of the facies belt. However, important depositional strike-orientated variations and regional inversions occur in the sedimentation regime along the paleo-shoreline (i.e., along-strike) of the basin. At the regional scale, a huge source area was uplifted by the end of the Artinskian in the north and caused regression; the southern part of the study area increasingly was transgressed by the epicontinental sea (= regional inversion). This important tectonic overprint on the stratigraphic signature of the basin’s infill has a tectonic origin. The variable sedimentation regime along the paleo-shoreline is controlled by the structural framework of the basement, which is formed by several crustal blocks with different responses to tectonic strain induced by terrain accretion on the occidental margin of Gondwana during the Permian. Stratigraphic data indicate that during the Early Permian, there were at least two differential subsidence and uplift events, one by the end of the Sakmarian–Artinskian and another during the Late Artinskian–Kungurian.  相似文献   

2.
The NW-SE oriented Sorgenfrei–Tornquist Zone (STZ) has been thoroughly studied during the last 25 years, especially by means of well data and seismic profiles. We present the results of a first brittle tectonic analysis based on about 850 dykes, veins and minor fault-slip data measured in the field in Scania, including paleostress reconstruction. We discuss the relationships between normal and strike-slip faulting in Scania since the Permian extension to the Late Cretaceous–Tertiary structural inversions. Our paleostress determinations reveal six successive or coeval main stress states in the evolution of Scania since the Permian. Two stress states correspond to normal faulting with NE-SW and NW-SE extensions, one stress state is mainly of reverse type with NE-SW compression, and three stress states are strike-slip in type with NNW-SSE, WNW-ESE and NNE-SSW directions of compression.The NE-SW extension partly corresponds to the Late Carboniferous–Permian important extensional period, dated by dykes and fault mineralisations. However extension existed along a similar direction during the Mesozoic. It has been locally observed until within the Danian. A perpendicular NW-SE extension reveals the occurrence of stress permutations. The NNW-SSE strike-slip episode is also expected to belong to the Late Carboniferous–Permian episode and is interpreted in terms of right-lateral wrench faulting along STZ-oriented faults. The inversion process has been characterised by reverse and strike-slip faulting related to the NE-SW compressional stress state.This study highlights the importance of extensional tectonics in northwest Europe since the end of the Palaeozoic until the end of the Cretaceous. The importance and role of wrench faulting in the tectonic evolution of the Sorgenfrei–Tornquist Zone are discussed.  相似文献   

3.
We present new data and interpretations on the Neogene tectonics of the Shan scarp area (central Myanmar) and its relationship with the India–Indochina oblique convergence. We describe ductile and brittle fabrics associated with the major features in this area, the Mogok Metamorphic Belt (MMB), the Shan scarp and the Sagaing fault. From these data we identify a succession of two tectonic regimes. First, a dominant NNW–SSE-trending extension, marked by ductile stretching that characterizes the MMB, and associated N70E brittle normal faults. Later, from Middle or Upper Miocene to the Present, these structures were cross-cut by brittle right-lateral faults, among which the most important are the N20W transpressive Shan scarp fault zone and the N–S Sagaing fault. To explain this transition from a dominant transtensive to a transpressive stress regime, that occurred during Miocene, we place our data within a larger geodynamic context. We suggest that, like the intraplate deformation in the Indian Ocean, the end of spreading in the South China sea, the opening of the Andaman basin or the end of subduction within the Indo-Burma range, the change in the tectonic regime in central Myanmar could be in response to a major Miocene regional plate kinematic reorganization.  相似文献   

4.
The orogenic Balkanid belt, which developed between the Moesian Plate and the Moravian-Rhodopi-Thracian Massifs, was affected by the Late Carboniferous and Early Permian opening of W-E oriented graben structures. The progressive tectonic rejuvenation of the basins is demonstrated by the deposition of repeated regional sedimentary cycles, associated with volcanism that was mostly localised along the tectonic boundaries, in an intramontane setting.The Late Carboniferous volcanism is represented by rhyodacitic explosive products and hyaloclastites, and by andesitic flows. During the Early Permian, subvolcanic rhyodacitic and rhyolitic bodies and the explosive products prevailed in the western sectors, whereas rhyolitic ignimbrites occur to the east.The tectonically active basins are interpreted due to late orogenic collapse, and the alternation of extensional tectonics and minor compressional phases is consistent with the regional transtensional regime, active along the Variscan suture of Pangaea. The volcanic activity associated with the evolution of the basins matches the petrogenetic features and the evolution from early dacitic – andesitic to late rhyolitic activity in the Southern European segment of the Variscan system.These Late Carboniferous-Early Permian sedimentary and tectono-magmatic events in Bulgaria are characterized, and compared with the homologous Permo-Carboniferous sequences along some western European segments of the Variscan belt.  相似文献   

5.
The Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the Salt Range of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the 350?m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacial episode in which a range of glacio-fluvial, marine and fluvial environments evolved and accumulated. The Early Permian succession of the Salt Range has been classified into four formations, which together indicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most, Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite and fresh water facies, which contain a floral assemblage (Gangamopteris and Glossopteris) that confirms an Asselian age. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation (Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia). Accumulation of the Dandot Formation was terminated by a regional sea-level fall and a change to the deposition of the fluvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was deposited by high sinuosity meandering, avulsion prone river with well developed floodplains. This episode of fluvial sedimentation was terminated by a widespread marine transgression, as represented by the abrupt upward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early Permian Gondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf carbonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these four lithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian, which is mainly controlled by eustatic sea-level change due to climatic variation associated with climatic amelioration at the end of the major Gondwana glacial episode, and the gradual regional northward drift to a lower latitude of the Indian plate.  相似文献   

6.
Tectonic activity, sea-level changes, and the climate controlled sedimentation in Late Paleozoic basins of western Argentina. The role of each factor is investigated from the geologic record of the Río Blanco and Paganzo basins using three hierarchical orders of stratigraphic bounding surfaces. First-order surfaces correspond to regional unconformities, second-order ones to local unconformities with a lesser regional extent, and third-order surfaces represent locally extended sedimentary truncation. Using this methodology, the Carboniferous–Permian record of the Paganzo and Río Blanco basins may be divided into two megasequences, four sequences, and 12 stratigraphic sections. Megasequences are bounded by regional unconformities that result from tectonic events important enough to cause regional paleogeographic changes. Sequences are limited by minor regional extension surfaces related to local tectonic movements or significant sea-level falls. Finally, stratigraphic sections correspond to extended sedimentary truncations produced by transgressive events or major climatic changes. Sequence I is mainly composed of marine deposits divided into basal infill of the basin (Section 1) and Tournaisian–Visean transgressive deposits (Section 2). Sequence II is bounded by a sharp erosional surface and begins with coarse conglomerates (Section 3), followed by fluvial and shallow marine sedimentary rocks (Section 4) that pass upward into shales and diamictites (Section 5). The base of Sequence III is marked by an extended unconformity covered by Early Pennsylvanian glacial sedimentary rocks (Section 6) that represent the most important glacial event along the western margin of Gondwana. Postglacial deposits (Section 7) occur in the two basins and comprise both glaciolacustrine (eastern region) and transgressive marine (central and western regions) deposits. By the Moscovian–Kasimovian, fluvial sandstones and conglomerates were deposited in most of the Paganzo Basin (Section 8), while localized volcanic activity took place in the Río Blanco Basin. Near the end of the Carboniferous, an important transgression is recorded in the major part of the Río Blanco Basin (Section 9), reaching the westernmost portion area of the Paganzo Basin. Finally, Sequence IV shows important differences between the Paganzo and Río Blanco basins; fluvial red beds (Section 10), eolian sandstones (Section 11), and low-energy fluvial deposits (Section 12) prevailed in the Paganzo Basin whereas volcaniclastic sedimentation and volcanism dominated in the Río Blanco Basin. Thus, tectonic events, sea-level changes and climate exerted a strong and complex control on the evolution of the Río Blanco and Paganzo basins. The interaction of these allocyclic controls produced not only characteristic facies association patterns but also different kinds of stratigraphic bounding surfaces.  相似文献   

7.
Yigui  Shihong  Franco  Yu  Yuanhou   《Gondwana Research》2009,16(2):255
The Machaoying fault zone extends along the southern margin of the North China Craton (NCC) and controlled the regional structures and hydrothermal mineral systems in this area. The fault underwent at least two major deformational phases, as revealed by macro- and micro-structural observations from a well-developed segment of the fault in the Hongzhuang–Baitu area, located south of the Xiong'er Mountains. Early ductile deformation is characterized by thrusting from north to south, which was subsequently overprinted by late brittle faulting. Syntectonic strain shadows of biotite are preserved around rotated porphyroclasts of quartz amygdales in mylonite. The biotite yields a 40Ar–39Ar plateau age of 524.9 ± 1.9 Ma, which is interpreted as the time of regional thrusting along the Machaoying fault zone. The thrusting may be temporally correlated with an Early Cambrian discontinuity in sedimentation observed in the rocks sequences of the NCC, suggesting a compressional regime in this area and a craton-wide tectonic event. Many 540–500 Ma tectonic events have been previously identified in the Qinling–Qilian–Kunlun Orogenic Belt of central China and in massifs in northeastern China, both of which surround the NCC, and some of these were interpreted to be associated with assembly of Gondwana. However, paleomagnetic data indicate that the NCC was unlikely to have been connected with Gondwana in the Early Cambrian and thus our new biotite date cannot record deformation along the Gondwanan margin. Dating of K-feldspar from a quartz–K-feldspar vein formed along one of the brittle faults of the Machaoying fault zone yields a much younger 40Ar–39Ar plateau age of 119.5 ± 0.7 Ma. This is a minimum age for the brittle deformation along the southern margin of the NCC, which also overlaps the age of widespread gold and molybdenum mineralization in the region.  相似文献   

8.
The Uralides, a linear N–S trending Palaeozoic fold belt, reveals an intact, well-preserved orogen with a deep crustal root within a stable continental interior. In the western fold-and-thrust belt of the southern Uralides, Devonian to Carboniferous siliciclastic and carbonate rocks overlay Mesoproterozoic to Neoproterozoic sedimentary rocks. Deformation in the Devonian, Carboniferous and Permian caused thick-skinned tectonic features in the western and central parts of the western fold-and-thrust belt. A stack of several nappes characterizes the deformation in the eastern part. Along the E–W transect AC-TS'96 that crosses the western fold-and-thrust belt, apatite fission track data record various stages of the geodynamic evolution of the Uralide orogeny such as basin evolution during the Palaeozoic, synorogenic movements along major thrusts, synorogenic to postorogenic exhumation and a change in the regional stress field during the Upper Jurassic and Lower Cretaceous. The Palaeozoic sedimentary cover and the Neoproterozoic basement of the Ala-Tau anticlinorium never exceed the upper limit of the PAZ since the Devonian. A temperature gradient similar to the recent one (20 °C/km) would account for the FT data. Reactivation of the Neoproterozoic Zilmerdak thrust was time equivalent to the onset of the Devonian and Carboniferous collision-related deformation in the east. West-directed movement along the Tashli thrust occurred in the Lower Permian. The Devonian and Carboniferous exhumation path of the Neoproterozoic siliciclastic units of the Tirlyan synclinorium mirrors the onset of the Uralian orogeny, the emplacement of the Tirlyan nappe and the continuous west-directed compression. The five main tectonic segments Inzer Synclinorium, Beloretzk Terrane, Ala-Tau anticlinorium, Yamantau anticlinorium and Zilair synclinorium were exhumed one after another to a stable position in the crust between 290 and 230 Ma. Each segment has its own t–T path but the exhumation rate was nearly the same. Final denudation of the western fold-and-thrust belt and exhumation to the present surface probably began in Late Tertiary. In Jurassic and Cretaceous, south-directed movements along W–E trending normal faults indicate a change in the tectonic regime in the southern Uralides.  相似文献   

9.
The Jinshajiang orogenic belt (JOB) of southwestern China, located along the eastern margin of the Himalayan–Tibetan orogen, includes a collage of continental blocks joined by Paleozoic ophiolitic sutures and Permian volcanic arcs. Three major tectonic stages are recognized based on the volcanic–sedimentary sequence and geochemistry of volcanic rocks in the belt. Westward subduction of the Paleozoic Jinshajiang oceanic plate at the end of Permian resulted in the formation of the Chubarong–Dongzhulin intra-oceanic arc and Jamda–Weixi volcanic arc on the eastern margin of the Changdu continental block. Collision between the volcanic arcs and the Yangtze continent block during Early–Middle Triassic caused the closing of the Jinshajiang oceanic basin and the eruption of high-Si and -Al potassic rhyolitic rocks along the Permian volcanic arc. Slab breakoff or mountain-root delamination under this orogenic belt led to post-collisional crustal extension at the end of the Triassic, forming a series of rift basins on this continental margin arc. Significant potential for VHMS deposits occurs in the submarine volcanic districts of the JOB. Mesozoic VHMS deposits occur in the post-collisional extension environment and cluster in the Late Triassic rift basins.  相似文献   

10.
The NW–SE-striking Northeast German Basin (NEGB) forms part of the Southern Permian Basin and contains up to 8 km of Permian to Cenozoic deposits. During its polyphase evolution, mobilization of the Zechstein salt layer resulted in a complex structural configuration with thin-skinned deformation in the basin and thick-skinned deformation at the basin margins. We investigated the role of salt as a decoupling horizon between its substratum and its cover during the Mesozoic deformation by integration of 3D structural modelling, backstripping and seismic interpretation. Our results suggest that periods of Mesozoic salt movement correlate temporally with changes of the regional stress field structures. Post-depositional salt mobilisation was weakest in the area of highest initial salt thickness and thickest overburden. This also indicates that regional tectonics is responsible for the initiation of salt movements rather than stratigraphic density inversion.Salt movement mainly took place in post-Muschelkalk times. The onset of salt diapirism with the formation of N–S-oriented rim synclines in Late Triassic was synchronous with the development of the NNE–SSW-striking Rheinsberg Trough due to regional E–W extension. In the Middle and Late Jurassic, uplift affected the northern part of the basin and may have induced south-directed gravity gliding in the salt layer. In the southern part, deposition continued in the Early Cretaceous. However, rotation of salt rim synclines axes to NW–SE as well as accelerated rim syncline subsidence near the NW–SE-striking Gardelegen Fault at the southern basin margin indicates a change from E–W extension to a tectonic regime favoring the activation of NW–SE-oriented structural elements. During the Late Cretaceous–Earliest Cenozoic, diapirism was associated with regional N–S compression and progressed further north and west. The Mesozoic interval was folded with the formation of WNW-trending salt-cored anticlines parallel to inversion structures and to differentially uplifted blocks. Late Cretaceous–Early Cenozoic compression caused partial inversion of older rim synclines and reverse reactivation of some Late Triassic to Jurassic normal faults in the salt cover. Subsequent uplift and erosion affected the pre-Cenozoic layers in the entire basin. In the Cenozoic, a last phase of salt tectonic deformation was associated with regional subsidence of the basin. Diapirism of the maturest pre-Cenozoic salt structures continued with some Cenozoic rim synclines overstepping older structures. The difference between the structural wavelength of the tighter folded Mesozoic interval and the wider Cenozoic structures indicates different tectonic regimes in Late Cretaceous and Cenozoic.We suggest that horizontal strain propagation in the brittle salt cover was accommodated by viscous flow in the decoupling salt layer and thus salt motion passively balanced Late Triassic extension as well as parts of Late Cretaceous–Early Tertiary compression.  相似文献   

11.
The interpretation of newly released commercial 2D reflection seismic data in the Kattegat area, Denmark, has provided us with a better understanding of the Palaeozoic tectonic processes along the Tornquist Fault Zone. A Base Palaeozoic time structure map, a Lower Palaeozoic TWT isopach map, a “true” Lower Palaeozoic TWT isopach map, an Upper Carboniferous/Lower Permian syn-rift TWT isopach map, a Top pre-Zechstein time structure map and a Zechstein combined TWT isopach and Palaeogeography map have been generated. The uniform Lower Palaeozoic sequence thickness in the Kattegat, both inside and outside the Tornquist Zone indicates only minor lateral movements if any, whereas the extensive Upper Silurian sequence, increasing in thickness to the north, indicates a relatively fast regional subsidence. The Base Palaeozoic time structure map and the Late Palaeozoic syn-rift isopach map show a clear Late Palaeozoic extension in the area. The syn-rift isopach map, in combination with the time-equivalent opening of the Skagerrak graben at right angles to the Tornquist Zone in the Kattegat, indicates that this extensional tectonic event had a dextral slip component. Measurements on internal extensional faults in the Tornquist Zone, give a minimum right-lateral displacement of 10.4 km. The footwall blocks were deeply eroded during the Early Permian rifting, and at Zechstein times the area became a peneplane. The Tornquist Zone was later exposed to several tectonic phases, where dextral slip played a role, indicated by the “push up” and “pull down” structures caused by restraining and releasing bends of the Børglum Fault. The dextral displacement along the Børglum Fault since the beginning of the Permian is in the order of 5–7 km based on the displacement of a Lower Palaeozoic local depocentre. Early Permian depocentres and faults, which gives a total amount of right-lateral displacement since the Early Palaeozoic in the order of 15–20 km. The continuously repeated tectonic episodes along the Tornquist Zone throughout most of the Phanerozoic, show that the zone was easily reactivated, implying deep-seated basement faults. The Tornquist Zone can be seen as a “buffer zone”, between continental blocks, whenever changes in the regional stress field are induced.  相似文献   

12.
A 3D structural model for the entire southwestern Baltic Sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area. The model was compiled with information from several geological time-isochore maps and digital depth maps from the area and consists of six post-Rotliegend successions: The Upper Permian Zechstein; Lower Triassic; Middle Triassic; Upper Triassic–Jurassic; Cretaceous and Cenozoic. This structural model was the basis for a 3D backstripping approach, considering salt flow as a consequence of spatially changing overburden load distribution, isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region. This method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement. In general, the successions above the highly deformed Zechstein evaporites reveal a thickening trend towards the Glückstadt Graben, which also experienced the highest amount of tectonic subsidence during the Mesozoic and Cenozoic. Two periods of accelerating salt movement in the area has been correlated with the E–W directed extension during the Late Triassic–Early Jurassic and later by the Late Cretaceous–Early Cenozoic inversion, suggesting that the regional stress field plays a key role in halokinesis. The final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium. The result reveals that many of the salt structures in the region are still active and that future coastline will run with a WNW–ESE trend, arguing that the compressional stresses related to the Alpine collision are the prime factor for the present-day landscape evolution.  相似文献   

13.
Third-order sequence stratigraphic analysis of the Early Permian marine to continental facies of the Karoo Basin provides a case study for the sedimentation patterns which may develop in an underfilled foreland system that is controlled by a combination of supra- and sublithospheric loads. The tectonic regime during the accumulation of the studied section was dominated by the flexural rebound of the foreland system in response to orogenic quiescence in the Cape Fold Belt, which resulted in foredeep uplift and forebulge subsidence. Coupled with flexural tectonics, additional accommodation was created by dynamic loading related to the process of subduction underneath the basin. The long-wavelength dynamic loading led to the subsidence of the peripheral bulge below base level, which allowed for sediment accumulation across the entire foreland system.A succession of five basinwide regressive systems tracts accumulated during the Artinskian (5 My), consisting of foredeep submarine fans and correlative forebulge deltas. The progradation of submarine fans and deltaic systems was controlled by coeval forced and normal regressions of the proximal and distal shorelines of the Ecca interior seaway respectively. The deposition of each regressive systems tract was terminated by basinwide transgressive episodes, that may be related to periodic increases in the rates of long-wavelength dynamic subsidence.  相似文献   

14.
A 3D structural modelling of the Permian–Mesozoic Polish Basin was performed in order to understand its structural and sedimentary evolution, which led to basin maturation (Permian–Cretaceous) and its tectonic inversion (Late Cretaceous–Paleogene). The model is built on the present-day structure of the basin and comprises 13 horizons within the Permian to Quaternary rocks. The analysis is based on 3D depth views and thickness maps. The results image the basin-scale symmetry, the perennial localization of the NW–SE-oriented basin axis, the salt movements due to tectonics and/or burial, and the transverse segmentation of the Polish Basin. From these observations, we deduce that salt structures are correlated to the main faults and tectonic events. From the model analysis, we interpret the stress conditions, the timing, and the geometry of the tectonic inversion of the Polish Basin into a NW–SE-oriented central horst (Mid-Polish Swell) bordered by two lateral troughs. Emphasis is placed on the Zechstein salt, considering its movements during the Mesozoic sedimentation and its decoupling effect during the tectonic inversion. Moreover, we point to the structural control of the Paleozoic basement and the crustal architecture (Teisseyre–Tornquist Zone) on the geometry of the Polish Basin and the Mid-Polish Swell.  相似文献   

15.
The Rhine Rift System (RRS) forms part of the European Cenozoic Rift System (ECRIS) and transects the Variscan Orogen, Permo-Carboniferous troughs and Late Permian to Mesozoic thermal sag basins. Crustal and lithospheric thicknesses range in the RRS area between 24–36 km and 50–120 km, respectively. We discuss processes controlling the transformation of the orogenically destabilised Variscan lithosphere into an end-Mesozoic stabilised cratonic lithosphere, as well as its renewed destabilisation during the Cenozoic development of ECRIS. By end-Westphalian times, the major sutures of the Variscan Orogen were associated with 45–60 km deep crustal roots. During the Stephanian-Early Permian, regional exhumation of the Variscides was controlled by their wrench deformation, detachment of subducted lithospheric slabs, asthenospheric upwelling and thermal thinning of the mantle-lithosphere. By late Early Permian times, when asthenospheric temperatures returned to ambient levels, lithospheric thicknesses ranged between 40 km and 80 km, whilst the thickness of the crust was reduced to 28–35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle-derived melts with its basal parts. Re-equilibration of the lithosphere-asthenosphere system governed the subsidence of Late Permian-Mesozoic thermal sag basins that covered much of the RRS area. By end-Cretaceous times, lithospheric thicknesses had increased to 100–120 km. Paleocene mantle plumes caused renewed thermal weakening of the lithosphere. Starting in the late Eocene, ECRIS evolved in the Pyrenean and Alpine foreland by passive rifting under a collision-related north-directed compressional stress field. Following end-Oligocene consolidation of the Pyrenees, west- and northwest-directed stresses originating in the Alps controlled further development of ECRIS. The RRS remained active until the Present, whilst the southern branch of ECRIS aborted in the early Miocene. Extensional strain across ECRIS amounts to some 7 km. Plume-related thermal thinning of the lithosphere underlies uplift of the Rhenish Massif and Massif Central. Lithospheric folding controlled uplift of the Vosges-Black Forest Arch.  相似文献   

16.
The paleogeographic evolution of Late Paleozoic basins located in southern South America is addressed. Three major types of basins are recognized: infracratonic or intraplate, arc-related, and retroarc. Intraplate basins (i.e., Paraná, Chaco-Paraná, Sauce Grande-Colorado, and La Golondrina) are floored by continental or quasi-continental crust, with low or moderate subsidence rates and limited magmatic and tectonic activity. Arc-related basins (northern and central Chile, Navidad–Arizaro, Río Blanco, and Calingasta–Uspallata basins and depocenters along Chilean Patagonia) show a very complex tectonic history, widespread magmatic activity, high subsidence rates, and in some cases metamorphism of Late Paleozoic sediments. An intermediate situation corresponds to the retroarc basins (eastern Madre de Dios, Tarija, Paganzo, and Tepuel-Genoa), which lack extensive magmatism and metamorphism but in which coeval tectonism and sedimentation rates were likely more important than those in the intraplate region. According to the stratigraphic distribution of Late Paleozoic sediments, regional-scale discontinuities, and sedimentation pattern changes, five major paleogeographic stages are proposed. The lowermost is restricted to the proto-Pacific and retroarc basins, corresponds to the Mississippian (stage 1), and is characterized by shallow marine and transitional siliciclastic sediments. During stage 2 (Early Pennsylvanian), glacial–postglacial sequences dominated the infracratonic (or intraplate) and retroarc basins, and terrigenous shallow marine sediments prevailed in arc-related basins. Stage 3 (Late Pennsylvanian–Early Cisuralian) shows the maximum extension of glacial–postglacial sediments in the Paraná and Sauce Grande-Colorado basins (intraplate region), whereas fluvial deposits interfingering with thin intervals of shallow marine sediments prevailed in the retroarc basins. To the west, arc-related basins were dominated by coastal to deep marine conditions (including turbiditic successions). In the Late Cisuralian (stage 4), important differences in sedimentation patterns are registered for the western arc-related basins and eastern intraplate basins. The former were locally dominated by volcaniclastic sediments or marine deposits, and the intraplate basins are characterized by shallow marine conditions punctuated by several episodes of deltaic progradation. Finally, in the Late Permian (stage 5), volcanism and volcaniclastic sedimentation dominated in basins located along the western South American margin. The intraplate basins in turn were characterized by T–R cycles composed of shallow marine, deltaic, and fluvial siliciclastic deposits.  相似文献   

17.
The study provides a regional seismic interpretation and mapping of the Mesozoic and Cenozoic succession of the Lusitanian Basin and the shelf and slope area off Portugal. The seismic study is compared with previous studies of the Lusitanian Basin. From the Late Triassic to the Cretaceous the study area experienced four rift phases and intermittent periods of tectonic quiescence. The Triassic rifting was concentrated in the central part of the Lusitanian Basin and in the southernmost part of the study area, both as symmetrical grabens and half-grabens. The evolution of half-grabens was particularly prominent in the south. The Triassic fault-controlled subsidence ceased during the latest Late Triassic and was succeeded by regional subsidence during the early Early Jurassic (Hettangian) when deposition of evaporites took place. A second rift phase was initiated in the Early Jurassic, most likely during the Sinemurian–Pliensbachian. This resulted in minor salt movements along the most prominent faults. The second phase was concentrated to the area south of the Nazare Fault Zone and resulted here in the accumulation of a thick Sinemurian–Callovian succession. Following a major hiatus, probably as a result of the opening of the Central Atlantic, resumed deposition occurred during the Late Jurassic. Evidence for Late Jurassic fault-controlled subsidence is widespread over the whole basin. The pattern of Late Jurassic subsidence appears to change across the Nazare Fault Zone. North of the Nazare Fault, fault-controlled subsidence occurred mainly along NNW–SSE-trending faults and to the south of this fault zone a NNE–SSW fault pattern seems to dominate. The Oxfordian rift phase is testified in onlapping of the Oxfordian succession on salt pillows which formed in association with fault activity. The fourth and final rift phase was in the latest Late Jurassic or earliest Early Cretaceous. The Jurassic extensional tectonism resulted in triggering of salt movement and the development of salt structures along fault zones. However, only salt pillow development can be demonstrated. The extensional tectonics ceased during the Early Cretaceous. During most of the Cretaceous, regional subsidence occurred, resulting in the deposition of a uniform Lower and Upper Cretaceous succession. Marked inversion of former normal faults, particularly along NE–SW-trending faults, and development of salt diapirs occurred during the Middle Miocene, probably followed by tectonic pulses during the Late Miocene to present. The inversion was most prominent in the central and southern parts of the study area. In between these two areas affected by structural inversion, fault-controlled subsidence resulted in the formation of the Cenozoic Lower Tagus Basin. Northwest of the Nazare Fault Zone the effect of the compressional tectonic regime quickly dies out and extensional tectonic environment seems to have prevailed. The Miocene compressional stress was mainly oriented NW–SE shifting to more N–S in the southern part.  相似文献   

18.
准噶尔盆地西北缘克-百地区不整合面及其动力学条件   总被引：3，自引：1，他引：2  
不整合及其性质和强度的确定对理解克拉玛依至百口泉地区构造变形历史和油气聚集规律具有重要意义。根据地震资料研究显示,该区二叠纪至中生代地层中存在多个不整合面,且多为构造运动的反映。其中对克-百地区构造形成具有重要影响的有四期,其一发生在中二叠统下乌尔禾组沉积后,主要表现为冲断掀斜运动,使其前的二叠纪沉积向南东方向掀斜抬升,遭受剥蚀;其二发生在三叠纪末期,对克百断裂上盘大侏罗沟断层至百口泉段的构造有重要影响;其三发生在中侏罗世末,该期构造运动在克百断裂带及其上盘表现最为清楚,以冲断为主,局部地区有褶皱现象;其四发生在早白垩世末期,表现为掀斜运动,褶皱和断裂作用相对较弱。克-百地区不同时期、不同构造部位变形的差异性与构造动力条件密切相关。  相似文献   

19.
The Dniepr–Donets Basin (DDB) is a Late Devonian rift structure located within the East-European Craton. Numerical heat flow models for 13 wells calibrated with new maturity data were used to evaluate temporal and lateral heat flow variations in the northwestern part of the basin.The numerical models suggest that heat flow was relatively high during Late Carboniferous and/or Permian times. The relatively high heat flow is probably related to an Early Permian re-activation of tectonic activity. Reconstructed Early Permian heat flow values along the axial zone of the rift are about 60 mW/m2 and increase to 90 mW/m2 along the northern basin margin. These values are higher than those expected from tectonic models considering a single Late Devonian rifting phase. The calibration data are not sensitive to variations in the Devonian/Carboniferous heat flow. Therefore, the models do not allow deciding whether heat flows remained high after the Devonian rifting, or whether the reconstructed Permian heat flows represent a separate heating event.Analysis of the vitrinite reflectance data suggest that the northeastern Dniepr–Donets Basin is characterised by a low Mesozoic heat flow (30–35 mW/m2), whereas the present-day heat flow is about 45 mW/m2.  相似文献   

20.
Specific structural–textural and mineralogical–petrographic features of clastic rocks, which make up sparse thin layers within Permian and Triassic cherty sequences in Sikhote Alin and Japan, are discussed. The cherty sequences were retained in the Jurassic accretionary complex as fragments of sedimentary cover of an ancient oceanic basin. They were mainly formed by turbidity currents that originated on intrabasinal uplifts composed of tholeiitic basalts in the Permian. In the Triassic, the currents originated on uplifts consisting of ocean-island alkali basalts along with Permian and Lower Triassic cherty and cherty–clayey rocks. The compositional difference of provenances was apparently caused by tectonic events in the oceanic basin at the Permian/Triassic boundary.  相似文献   

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