Search results for "Gondwana"

Modeling suggests that oblique extension facilitates rifting and continental break-up

2012

[1] In many cases the initial stage of continental break-up was and is associated with oblique rifting. That includes break-up in the Southern and Equatorial Atlantic, separation from eastern and western Gondwana as well as many recent rift systems, like Gulf of California, Ethiopia Rift and Dead Sea fault. Using a simple analytic mechanical model and advanced numerical, thermomechanical modeling techniques we investigate the influence of oblique extension on the required tectonic force in a three-dimensional setting. While magmatic processes have been already suggested to affect rift evolution, we show that additional mechanisms emerge due to the three-dimensionality of an extensional syst…

Structure, Composition and Evolution of the South Indian and Sri Lankan Granulite Terrains from Deep Seismic Profiling and Other Geophysical and Geol…

2005

We here argue the need for a multidisciplinary, integrated geophysical/geological survey across southern India and Sri Lanka, part of the largest exposed Neoproterozoic high-grade metamorphic terrain in the world. The purpose is to stimulate deep seismic profiling and other geophysical and geological investigations in order to better understand the structure, composition and evolution of a keystone of Precambrian continental crust and the role it played in the amalgamation and subsequent break-up of the Gondwana supercontinent. Of particular importance is that this lithospheric fragment records a 2 billion year long history of magmatism, sedimentation, deformation and metamorphism and now e…

Single zircon U–Pb ages and geochemistry of granitoid gneisses from SW Poland: evidence for an Avalonian affinity of the Brunian microcontinent

2010

AbstractSeven granitoid gneisses from the contact zone between the eastern margin of the Variscan belt and the Brunian microcontinent in SW Poland have been dated by ion-microprobe and207Pb/206Pb single zircon evaporation methods. The zircons define two age groups for the gneiss protoliths: (1) late Neoproterozoicc.576–560 Ma and (2) early Palaeozoicc.488–503 Ma granites. The granitoid gneisses belonging to the basement of the Brunian microcontinent contain abundant Mesoproterozoic to latest Palaeoproterozoic inherited material in the range of 1200–1750 Ma. The gneisses of the Variscan crustal domain lack Mesoproterozoic inherited zircon cores. Trace element geochemistry of Proterozoic gnei…

Tectonic significance of the Variscan suture between Brunovistulia and the Bohemian Massif

2021

The Velke Vrbno Dome crops out at the boundary between the Brunovistulian Terrane and the internal parts of the Bohemian Massif. Here, eclogite boudins occur within an Ediacaran volcano-sedimentary sequence. Strong Nb depletion (Nb/Nb* = 0.19–0.82) combined with moderately positive Nd isotopic compositions (eNd(i) = +3.89 – +5.77) is used to argue for emplacement of the eclogite protoliths in a transitional supra-subduction to continental-rift setting. Conversely, heterogeneously enriched large ion lithophile elements and highly radiogenic Sr isotopic ratios (87Sr/86Sr = 0.705–0.720) are interpreted to have been modified following fluid infiltration subsequent to eclogite-facies metamorphis…

Single zircon ages, PT evolution and Nd isotopic systematics of high-grade gneisses in southern Malawi and their bearing on the evolution of the Moza…

2001

Abstract The high grade gneiss assemblage of central and southern Malawi belongs to the Neoproterozoic Mozambique belt of East Africa, and reached peak metamorphic conditions at 900±70°C and 9.5±1.5 kbar, followed by an isobaric cooling path. We report single zircon U–Pb and Pb–Pb ages and Nd isotopic data for orthogneisses and metapelites collected around Lilongwe and farther south in the region around Blantyre and Zomba. The ages document three distinct events, (1) a Kibaran-age period of intrusion of calc-alkaline granitoids around 1040–929 Ma; Nd isotope data indicate overall juvenile compositions consistent with a magmatic arc environment, or emplacement into thinned continental crust …

Indo-Antarctic derived detritus on the northern margin of Gondwana: evidence for continental-scale sediment transport

2013

Provenance studies from Cambro-Ordovician sediments of the North Gondwana passive margin typically ascribe a North African source, a conclusion that cannot be reconciled with all observations. We present new U-Pb ages from detrital rutile and zircon from Late Ordovician sediments from Saxo-Thuringia, Germany. Detrital zircons yield age populations of 500–800 Ma, 900–1050 Ma and 1800–2600 Ma. The detrital rutile age spectra are unimodal with ages between 500 and 650 Ma and likely represent, together with the 500–800 Ma and 1800–2600 Ma zircon populations, detritus sourced predominantly from North Africa. In contrast, the c. 950 Ma zircons, which are persistently found in Cambro-Ordovician se…

Palaeogeographical and palaeoecological aspects of the Cambro–Ordovician radiation of echinoderms in Gondwanan Africa and peri-Gondwanan Europe

2003

Abstract Ecology and tempo of the Lower Palaeozoic radiation of echinoderms are discussed in this paper based on comparison of the diversity patterns observed in Cambro–Ordovician faunas from Laurentia and the northern Gondwana margin. The Cambrian ‘agronomic revolution’ triggered a global radiation of echinoderms, with the progressive disappearance of biomat-related lifestyles, and the colonisation of new environments. Both in Laurentia and on the northern Gondwana margin, soft-substrate echinoderm assemblages related to cold and/or deep environments were dominated by blastozoans and stylophorans. These assemblages show a pattern of continuous diversification from the Middle Cambrian to th…

Cambrian orogeny in the Ribeira Belt (SE Brazil) and correlations within West Gondwana: ties that bind underwater

2008

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…

Upper Ovetian trilobites from Spain and their implications for the palaeobiogeography and correlation of the Cambrian Stage 3 in Gondwana

2016

Abstract The upper part of the La Herreria Formation in Los Barrios de Luna (Leon Province, N Spain) has been revised from a palaeontological and biostratigraphical point of view. Two stratigraphic sections have been studied including their trilobite and ichnofossils contents. The ichnofossil assemblages have a high diversity of species characterising the Cruziana ichnofacies, suggesting a shallow sublittoral environment for the upper part of the La Herreria Formation. The trilobites species recognised are Lunagraulos antiquus , Dolerolenus formosus , Dolerolenus longioculatus , Lunolenus lunae , Metadoxides richterorum , Metadoxides armatus and Sardaspis ? sp. from the upper Ovetian (lower…