Search results for "Gondwana"
showing 6 items of 76 documents
How to make a transverse triple junction—New evidence for the assemblage of Gondwana along the Kaoko-Damara belts, Namibia
2016
T-shaped orogenic triple junctions between mobile belts usually form in two unrelated stages by subsequent and oblique continental collisions separated by a significant time span. Besides these “oblique triple junctions”, another type, named “transverse triple junctions”, may exist. Such junctions are created by a more complex mechanism of partly contemporaneous convergence of three cratons in a restricted time frame, involving strike slip. The Neoproterozoic–Cambrian Kaoko-Damara junction between the Rio de la Plata, Congo, and Kalahari cratons in Namibia is an example of such a transverse orogenic triple junction, formed by at least four subsequent but partly related deformation events. I…
A Damara orogen perspective on the assembly of southwestern Gondwana
2008
The Pan-African Damara orogenic system records Gondwana amalgamation involving serial suturing of the Congo-Sao Francisco and Ro ´o de la Plata cratons (North Gondwana) from 580 to 550 Ma, before amalgamation with the Kalahari - Antarctic cratons (South Gondwana) as part of the 530 Ma Kuunga-Damara orogeny. Closure of the Adamastor Ocean was diachronous from the Aracuao ´ Belt southwards, with peak sinistral transpressional deformation followed by craton overthrusting and foreland basin development at 580- 550 Ma in the Kaoko Belt and at 545-530 Ma in the Gariep Belt. Peak deformation/metamorphism in the Damara Belt was at 530-500 Ma, with thrusting onto the Kalahari Craton from 495 Ma thro…
Serbo-Macedonian revisited: A Silurian basement terrane from northern Gondwana in the Internal Hellenides, Greece
2009
Abstract New geochronological and geochemical data on basement orthogneisses from the Vertiskos Unit of the Serbo-Macedonian Massif (SMM), Internal Hellenides, northern Greece, are used in order to constrain the pre-Alpine tectonic history of the basement units in the metamorphic hinterland of the Hellenides. The prevailing rock types in the Vertiskos crystalline basement are coarse-grained biotite augengneisses with subordinate leucocratic muscovite gneisses and two-mica gneisses. Zircon Pb–Pb and U–Pb ages on 20 samples range from 425.9 ± 4.2 Ma to 443.4 ± 5.5 Ma with a mean of 432.2 ± 3.2 Ma and are interpreted as primary crystallisation ages of the basement granites on the basis of the …
U-Pb and Pb-Pb zircon ages for metamorphic rocks in the Kaoko Belt of Northwestern Namibia: A Palaeo- to Mesoproterozoic basement reworked during the…
2004
The Kaoko Belt belongs to the Neoproterozoic mobile belt system of western Gondwana, whose geodynamic evolution is assumed to have resulted from collision between the Congo Craton (present Africa) and the Rio de la Plata Craton (present South America). Several magmatic intrusion periods can be distinguished in the coastal area of this belt, based on conventional U-Pb, SHRIMP and Pb-Pb evaporation analyses on zircons. The prevailing igneous rock types are of granitic to tonalitic composition. A Palaeoproterozoic terrain with U-Pb magmatic emplacement ages between ~2.03 and 1.96 Ga may be correlated with the Eburnian event (~1.8 to 2.0 Ga), which is widespread in Africa. Additionally, two dis…
Taxonomy and evolution of the Triassic conodont Pseudofurnishius
2013
Pseudofurnishius is a late Anisian (Pelsonian)—early Carnian (Cordevolian) conodont genus of gondolellid stock, characteristic for the Sephardic Province and restricted to the “Southern Tethys” region of the northern margin of Gondwana. Its most commonly found species, Pseudofurnishius murcianus, appears at the base of the Ladinian (Fassanian). The Ladinian material of Spain reveals its ontogeny characterised by initial lateral protrusions from the carina that may develop first mono-platform and later bi-platform units, finally evolving into elaborated multi-denticulated forms. The late Anisian—early Carnian phylogenesis of Pseudofurnishius priscus → P. shagami → P. murcianus is proposed. A…
New occurrence of the Ordovician eocrinoid Cardiocystites: Palaeogeographical and palaeoecological implications
2007
10 pages; International audience; Flattened eocrinoids are very rare in the fossil record, notably because of their fragility. Recent investigations in the Anti−Atlas (Morocco) have provided one of the oldest known specimens of Cardiocystites from the Upper Ordovician (early–middle Sandbian). This discovery increases the number of eocrinoid genera known in Morocco. This new material is the fifth published specimen of the genus Cardiocystites. It is well preserved, thus allowing morphological details, such as the location of the anal pyramid and the plane of thecal flattening, to be observed. Palaeoecological reconstruction can be deduced or confirmed from these new details. The respiration …