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A Cordilleran model for the evolution of Avalonia 总被引：2，自引：0，他引：2
Striking similarities between the late Mesoproterozoic–Early Paleozoic record of Avalonia and the Late Paleozoic–Cenozoic history of western North America suggest that the North American Cordillera provides a modern analogue for the evolution of Avalonia and other peri-Gondwanan terranes during the late Precambrian. Thus: (1) The evolution of primitive Avalonian arcs (proto-Avalonia) at 1.2–1.0 Ga coincides with the amalgamation of Rodinia, just as the evolution of primitive Cordilleran arcs in Panthalassa coincided with the Late Paleozoic amalgamation of Pangea. (2) The development of mature oceanic arcs at 750–650 Ma (early Avalonian magmatism), their accretion to Gondwana at ca. 650 Ma, and continental margin arc development at 635–570 Ma (main Avalonian magmatism) followed the breakup of Rodinia at ca. 755 Ma in the same way that the accretion of mature Cordilleran arcs to western North America and the development of the main phase of Cordilleran arc magmatism followed the Early Mesozoic breakup of Pangea. (3) In the absence of evidence for continental collision, the diachronous termination of subduction and its transition to an intracontinental wrench regime at 590–540 Ma is interpreted to record ridge–trench collision in the same way that North America's collision with the East Pacific Rise in the Oligocene led to the diachronous initiation of a transform margin. (4) The separation of Avalonia from Gondwana in the Early Ordovician resembles that brought about in Baja California by the Pliocene propagation of the East Pacific Rise into the continental margin. (5) The Late Ordovician–Early Silurian sinistral accretion of Avalonia to eastern Laurentia emulates the Cenozoic dispersal of Cordilleran terranes and may mimic the paths of future terranes transferred to the Pacific plate.This close similarity in tectonothermal histories suggests that a geodynamic coupling like that linking the evolution of the Cordillera with the assembly and breakup of Pangea, may have existed between Avalonia and the late Precambrian supercontinent Rodinia. Hence, the North American Cordillera is considered to provide an actualistic model for the evolution of Avalonia and other peri-Gondwanan terranes, the histories of which afford a proxy record of supercontinent assembly and breakup in the late Precambrian. 相似文献
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Predictions from dynamic modelling of the lithospheric deformation are presented for Northern Europe, where several basins underwent inversion during the Late Cretaceous and Early Cenozoic and contemporary uplift and erosion of sediments occurred. In order to analyse the evolution of the continental lithosphere, the equations for the deformation of a continuum are solved numerically under thin sheet assumption for the lithosphere. The most important stress sources are assumed to be the Late Cretaceous Alpine tectonics; localized rheological heterogeneities can also affect local deformation and stress patterns. Present-day observations available in the studied region and coming from seismic structural interpretations and stress measurements have been used to constrain the model. Our modelling results show that lateral variation in lithospheric strength below the basin systems in Central Europe strongly controls the regional deformation and the stress regime. Furthermore, we have demonstrated that the geometry of the boundary between Baltica and Avalonia, together with different rheological characteristics of the two plates, had a crucial role on local crustal deformation and faulting regime resulting in the Baltica–Avalonia transition zone from the S–N Alpine convergence. 相似文献
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Tim Pharaoh 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):278-328
The surface geology of central England and Belgium obscures a large ‘basement’ massif with a complex history and stronger crust and lithosphere than surrounding regions. The nucleus was forged by subduction-related magmatism at the Gondwana margin in Ediacaran time. Partitioning into a platform, in the English Midlands, and a basin stretching to Belgium, in the east, was already evident in Cambrian/earliest Ordovician time. The accretion of the Monian Composite Terrane during the Penobscotian deformation phase preceded late Tremadocian rifting, and Floian separation, of the Avalonia Terrane from the Gondwana margin. Late Ordovician magmatism in a belt from the Lake District to Belgium records subduction beneath Avalonia of part of the Tornquist Sea. This ‘Western Pacific-style’ oceanic basin closed in latest Ordovician time, uniting Avalonia and Baltica. Closure of the Iapetus Ocean in early Silurian time was soon followed by closure of the Rheic Ocean, recorded by subduction along the southern margin of the massif. The causes of late Caledonian deformation are poorly understood and controversial. Partitioned behaviour of the massif persisted into late Palaeozoic time. Late Devonian and Carboniferous sequences show strong onlap onto the massif, which was little affected by crustal extension. Compressional deformation during the Variscan Orogeny also appears slight, and was focussed in the west where a wedge-shaped mountain foreland uplift was driven by orogenic indentation, splitting the massif from the Welsh Massif along the reactivated Malvern Line. Permian to Mesozoic sequences exhibit persistent but variable degrees of onlap onto the massif. 相似文献
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Early Ordovician (Late Arenig) limestones from the SW margin of Baltica (Scania–Bornholm) have multicomponent magnetic signatures, but high unblocking components predating folding, and the corresponding palaeomagnetic pole (latitude=19°N, LONGITUDE=051°E) compares well with Arenig reference poles from Baltica. Collectively, the Arenig poles demonstrate a midsoutherly latitudinal position for Baltica, then separated from Avalonia by the Tornquist Sea.Tornquist Sea closure and the Baltica–Avalonia convergence history are evidenced from faunal mixing and increased resemblance in palaeomagnetically determined palaeolatitudes for Avalonia and Baltica during the Mid-Late Ordovician. By the Caradoc, Avalonia had drifted to palaeolatitudes compatible with those of SW Baltica, and subduction beneath Eastern Avalonia was taking place. We propose that explosive vents associated with this subduction and related to Andean-type magmatism in Avalonia were the source for the gigantic Mid-Caradoc (c. 455 Ma) ash fall in Baltica (i.e. the Kinnekulle bentonite). Avalonia was located south of the subtropical high during most of the Ordovician, and this would have provided an optimum palaeoposition to supply Baltica with large ash falls governed by westerly winds.In Scania, we observe a persistent palaeomagnetic overprint of Late Ordovician (Ashgill) age (pole: LATITUDE=4°S, LONGITUDE=012°E). The remagnetisation was probably spurred by tectonic-derived fluids since burial alone is inadequate to explain this remagnetisation event. This is the first record of a Late Ordovician event in Scania, but it is comparable with the Shelveian event in Avalonia, low-grade metamorphism in the North Sea basement of NE Germany (440–450 Ma), and sheds new light on the Baltica–Avalonia docking. 相似文献
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D. Spahić T. Gaudenyi 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(2):142-156
This review deals with a highly complex set of dismembered peri-Gondwanan exotic polymetamorphic basement systems accommodated outside of the well-explored European Variscides, extending from the controversial Serbo-Macedonian hinterland up to the East Moesian Alpine foreland. The isotopic and limited detrital zircon ages are coupled with the lithotectonic and palinspastic record in order to restore the earliest peri-Gondwanan developments in modern-day South-east Europe (Carpatho-Balkanides and surrounding areas). The results suggest that these rather bewildering, occasionally underexplored tectonometamorphic suites exhibit Cadomian arc inheritance in a flanking part of this belt, whilst inferior Avalonian are positioned more internally. 相似文献
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Further evidence for the existence of the terrane East Avalonia (Cadomia) in north-west Europe, its boundaries and its role in the Caledonian collisional processes comes from studies of deep seismic reflection data at sea and on land. Various sutures are found in the north-east and the north-west, and a generally poor reflectivity dominates in the major part. Further details of reflectivity patterns support the idea that a huge terrane which split from the northern rim of Gondwana moved northward and collided with the merging plates Laurentia-Baltica. Its docking features are analysed. 相似文献
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Summary The Ordovician of the Rügen area shows no affinities with that of the adjacent regions of the East European Platform, situated immediately to the north (i.e. Bornholm and Skåne). By contrast, the detritus in the sandstones and greywackes points to an active continental margin in the southwest, along the southern border of the suspect Tornquist Ocean (i.e. northern Peri-Gondwana). Deformation features can be assigned to Caledonian tectonic events. The more than 3 km thick pile comprises a stacked wedge complex, which was emplaced against and onto the southwestern border of Baltica. 相似文献