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Gondwana

About: Gondwana is a research topic. Over the lifetime, 6078 publications have been published within this topic receiving 263050 citations. The topic is also known as: Gondwanaland.


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Journal ArticleDOI
TL;DR: In this paper, geochronological data from low-to medium-grade metamorphic areas of the Eastern Pyrenees (Canigo, Roc de Frausa and Cap de Creus massifs) confirm the presence of two significant pre-Variscan igneous events: Ediacaran-Early Cambrian and Early Ordovician.

97 citations

Journal ArticleDOI
TL;DR: In this article, laser ablation-inductively coupled plasma mass spectrometry U-Pb data for detrital zircons from Cambrian clastic rocks in two localities in Avalonia are presented.
Abstract: Most Neoproterozoic and Early Palaeozoic tectonic syntheses place Avalonia and related peri-Gondwanan terranes facing an open ocean along the northern margin of Gondwana, thereby providing important constraints for palaeocontinental reconstructions during that time interval. However, the precise location of Avalonia along the margin and its position relative to other peri-Gondwanan terranes is controversial. We present laser ablation–inductively coupled plasma mass spectrometry U–Pb data for detrital zircons from Cambrian clastic rocks in two localities in Avalonia: the Antigonish Highlands of Nova Scotia (62 analyses) and the British Midlands (55 analyses). The data from both samples are very similar, and taken together indicate an overwhelming dominance of Neoproterozoic ( c . 580–680 Ma) or Early Cambrian source rocks with minor older Neoproterozoic clusters at c . 710 Ma or of Mesoproterozoic age, three Palaeoproterozoic zircons and one Archaean zircon. The zircons can all be derived from local Avalonian sources. The Neoproterozoic zircons are attributed to erosion of the underlying Avalonian arc. Mesoproterozoic and Palaeoproterozoic zircons of similar ages are also found in Avalonian Neoproterozoic clastic rocks and their presence in the Cambrian clastic rocks could represent recycling of Neoproterozoic strata and do not necessarily imply the presence of Mesoproterozoic or Palaeoproterozoic basement rocks within their respective drainage basins. Comparison with the data from the Neoproterozoic arc-related clastic sequences suggests significant differences between their respective drainage systems. Whereas the Neoproterozoic data require extensive drainage systems, the Cambrian data can be attributed to localized drainage systems. The change in drainage patterns could reflect rifting and isolation of Avalonia from Amazonia between c . 585 and 540 Ma. Alternatively, it might reflect the creation of topographical barriers along the northern Gondwanan margin, in a manner analogous to the Cenozoic rise of the Andes or the creation of the Basin-and-Range topography in the Western USA.

97 citations

Journal ArticleDOI
TL;DR: The Progress Granite as discussed by the authors is one of numerous S-type granitoid plutons exposed in the Larsemann Hills region, southwest Prydz Bay, east Antarctica, and was emplaced into a migmatitised pelitic to felsic paragneiss sequence during a regional high grade transpressional event (D2) that pre-dates high grade extension (D3).
Abstract: The Progress Granite is one of numerous S‐type granitoid plutons exposed in the Larsemann Hills region, southwest Prydz Bay, east Antarctica. The granite was emplaced into a migmatitised pelitic to felsic paragneiss sequence during a regional high‐grade transpressional event (D2) that pre‐dates high‐grade extension (D3). SHRIMP (II) U‐Pb dating for two occurrences of the Progress Granite from D2 and D3 structural domains gives 206Pb/238U ages of 516.2 ± 6.8 Ma and 514.3 ± 6.7 Ma, respectively. These ages are interpreted as crystallisation ages for the Progress Granite and confirm Early Palaeozoic orogenesis in the Larsemann Hills region. This orogen appears to have evolved during continental convergence and is probably responsible for widespread radiogenic isotopic resetting and the near‐complete exhumation of the adjacent northern Prince Charles Mountains which evolved during a ca 1000 Ma event. The identification of a major Early Palaeozoic orogen in Prydz Bay allows tentative correlation of other domai...

97 citations

Journal ArticleDOI
TL;DR: The Itremo Group metasediments of the central Madagascar probably represent a passive margin sequence predating Gondwana assembly as mentioned in this paper, and they are well-sorted quartz arenites that contain flat lamination, wave ripples, current ripple cross-lamination, and dune cross bedding.
Abstract: Proterozoic metasediments of the Itremo Group in central Madagascar probably represent a passive margin sequence predating Gondwana assembly. The quartzites are well-sorted quartz arenites that contain flat lamination, wave ripples, current ripple cross-lamination, and dune cross bedding. The carbonate rocks preserve abundant stromatolites and algal laminates. A continental source is indicated by mudrock major and trace element chemistry. The combination of lithologic association, sediment architecture and mudrock chemistry indicates that the sequence was deposited on a continental shelf or platform. SHRIMP data from detrital zircons indicate that the source area included early Proterozoic and late Archean rocks with ages between 1.85 and 2.69 Ga, and that the depositional age of the Itremo Group must be less than 1855 ± 11 Ma. The sequence has been deformed into a series of large-scale folds separated by ductile shear zones. SHRIMP data indicate both massive lead loss from detrital zircons and new zircon growth in the metasediments at 833 ± 112 Ma, which we interpret as the age of metamorphism of the sequence. Comparison of detrital grain ages with basement ages in East Africa and in India indicates that the source area for the Itremo Group probably lay on the present African mainland.

97 citations

Journal ArticleDOI
TL;DR: In this article, a review and a discussion of the clast-bearing formations (diamicts) which occur in the uppermost part of the Ordovician succession of numerous regions in Southwestern Europe is presented.

96 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023269
2022497
2021307
2020281
2019293
2018230