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.

Jurassic to Eocene plate tectonic reconstructions in the Kerguelen Plateau region

Abstract: We present a series of preliminary reconstructions for the Kerguelen Plateau region from the Late Jurassic to the Eocene that summarize and review the outstanding questions about its plate tectonic evolution. The development of the Indian and adjacent Southern oceans began in Middle to Late Jurassic time with the breakup of Gondwana. Marine magnetic anomalies and limited Deep Sea Drilling Project and Ocean Drilling Program core samples have been used to date the oceanic crust. Fracture zone trends interpreted from satellite (SEASAT and GEOSAT) altimetry, and marine seismic, gravity, and magnetic data have been combined with crustal dates to produce kinematic models of the plates through time. Between the Jurassic and the Late Cretaceous, time controls on the plate tectonic evolution of the region are few. Mesozoic marine magnetic anomalies off the shore of East Africa, Antarctica, and Western Australia document plate motions during the interval; however, extensive areas of oceanic crust from which no anomalies have been identified, including that created during the Cretaceous Long Normal Polarity Interval, and a dearth of fracture zones prevent detailed links with the much better defined plate kinematic synthesis for the past 84 m.y. The Kerguelen Plateau/Broken Ridge complex was emplaced at ~ 110 Ma in a region flanked by Greater India, Australia, and Antarctica. Between then and —43 Ma, when seafloor spreading between the Kerguelen Plateau and Broken Ridge began, our model includes transform motions between the northern and southern sectors of the Kerguelen Plateau.

Rifting during separation of Eastern Avalonia from Gondwana: Evidence from subsidence analysis

Abstract: Subsidence curves for Cambrian-Ordovician sequences from the Anglo-Welsh segment of the paleocontinent of Avalonia reveal two periods of regionally enhanced basement subsidence: Early Cambrian (545–518 Ma) and Late Cambrian to early Tremadocian (505–490 Ma). The earlier event may record transtension following the Avalonian-Cadomian orogeny. The second event may be a transtensional precursor to the late Tremadocian volcanic arc on Eastern Avalonia. However, paleomagnetic, faunal, volcanic, and sedimentary evidence suggests that the main separation of Eastern Avalonia from Gondwana occurred after middle Arenigian time. Rifting during separation is probably recorded by localized middle Arenigian to Llanvirnian (480–462 Ma) subsidence along the Welsh basin margin, but rifting must have occurred mainly on the now-obscured southern margin of the Avalonian continent. Pronounced Caradocian (462–449 Ma) subsidence is associated with back-arc rifting after separation from Gondwana.

Sequential intercontinental suturing as the ultimate control for Pennsylvanian Ancestral Rocky Mountains deformation

Abstract: The geotectonic setting of Pennsylvanian uplifts and associated basins of the Ancestral Rocky Mountains province has long been unclear because analogy of the deformed intracontinental domain with either arc or collisional orogens is not apt Diachronous subsidence of Ancestral Rocky Mountains basins was coincident with sequential closure, from east to west, of the Ouachita suture to the southeast This geotectonic relationship suggests that Ancestral Rocky Mountains deformation was induced by intracontinental stresses associated with continued subduction of westerly parts of Laurentia after more easterly parts had locked against Gondwana

Neoproterozoic extensional detachment in central Madagascar: implications for the collapse of the East African Orogen

Abstract: A laterally extensive, Neoproterozoic extensional detachment (the Betsileo shear zone) is recognized in central Madagascar separating the Itremo sheet (consisting of Palaeoproterozoic to Mesoproterozoic sediments and underlying basement rocks) from the Antananarivo block (Archaean/Palaeoproterozoic crust re-metamorphosed in the Neoproterozoic). Non-coaxial deforma- tion gradually increases to a maximum at a lithological contrast between the granitoids and gneisses of the footwall and the metasedimentary rocks of the hangingwall. Ultramylonites at this highest- strained zone show mineral-elongation lineations that plunge to the southwest. σ-, δ- and C/S-type fabrics imply top-to-the-southwest extensional shear sense. Contrasting meta- morphic grades are found either side of the shear zone. In the north, where this contrast is greatest, amphibolite-grade footwall rocks are juxtaposed with lower-greenschist-grade hangingwall rocks. The metamorphic grade in the hangingwall increases to the south, suggesting that a crustal section is pre- served. The Betsileo shear zone facilitated crustal-scale extensional collapse of the East African Orogeny, and thus represents a previously poorly recognized structural phase in the story of Gondwanan amal- gamation. Granitic magmatism and granulite/amphibolite-grade metamorphism in the footwall are all associated with formation of the Betsileo shear zone, making recognition of this detachment important in any attempt to understand the tectonic evolution of central Gondwana.