Sökning: "supercontinent"

Visar resultat 1 - 5 av 6 avhandlingar innehållade ordet supercontinent.

  1. 1. New constraints on paleoreconstructions through geochronology of mafic dyke swarms in North Atlantic Craton

    Författare :Mimmi Nilsson; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; baddeleyit; U-Pb; geokronologi; large igneous province; mantelplym; superkontinent; paleorekonstruktion; North Atlantic craton; baddeleyite; Large Igneous Province; Mantle plume; supercontinent; paleoreconstruction; U-Pb; geochronology; North Atlantic craton;

    Sammanfattning : Earth history is punctuated by a series of events of supercontinent amalgamation and break-up. Fragments of old continents display rifted margins and orogenic sutures that testify their involvement in supercontinent cycles. LÄS MER

  3. 2. Validating the existence of the supercraton Vaalbara in the Mesoarchaean to Palaeoproterozoic

    Författare :Ashley Gumsley; Berggrundsgeologi; []
    Nyckelord :Vaalbara; Kaapvaal Craton; Pilbara Craton; U-Pb geochronology; paleomagnetism; supercontinent; large igneous province; dyke swarm; sill province;

    Sammanfattning : In this thesis, the longevity and continuity of the Vaalbara supercraton is addressed in six papers aimed at placing new temporal and spatial constraints onthe supercraton in the Mesoarchean to Paleoproterozoic. It has been speculated since the 1960’s that the Kaapvaal Craton in southern Africa, together withthe Pilbara Craton in Western Australia existed as a single landmass during the Precambrian – the Vaalbara supercraton. LÄS MER

  4. 3. Crustal evolution of the Arabian–Nubian Shield : Insights from zircon geochronology and Nd–Hf–O isotopes

    Författare :Fitsum Girum Yeshanew; Victoria Pease; Martin J. Whitehouse; Robert J. Stern; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Gondwana; Arabian–Nubian Shield; Azania; zircon U–Pb–O–Hf isotopes; Nd isotopes; Cambrian Sandstones; juvenile; pre–Neoproterozoic; reworking; Geology; geologi;

    Sammanfattning : The Arabian–Nubian Shield (ANS) represents a major site of juvenile Neoproterozoic crustal addition on Earth and documents Neoproterozoic tectonics bracketed by two supercontinent cycles, namely the fragmentation of Rodinia and the amalgamation of Gondwana. There is general consensus that the ANS formed by juvenile magmatic arc accretion and subsequent shield–wide post–tectonic magmatism. LÄS MER

  5. 4. The tectonic evolution of northwest Svalbard

    Författare :Carl Henrik Pettersson; Victoria Pease; Robert Strachan; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Svalbard; Rodinia; Laurentia; Zircon; Provenance; Migmatites; Clockwise P-T; Solid earth geology and petrology; Berggrundsgeologi och petrologi; Geology; geologi;

    Sammanfattning : Svalbard represents the uplifted and exhumed northwest corner of the Barents Sea Shelf. Pre-Carboniferous rocks of Svalbard are divided into the Eastern, Northwestern and Southwestern Terranes, were amalgamated during the Caledonian Orogen and are separated by north-south-trending strike-slip faults. LÄS MER

  7. 5. Mesoproterozoic crustal evolution in Southern Africa

    Författare :Åsa Pettersson; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Namaqua-Natal province; Mezoproterozoic; geochronology; U-Pb zirkon dating; Sm-Nd model ages; Ar-Ar dating; Southern Africa;

    Sammanfattning : The objects of this thesis were to use geochronology to investigate crustal evolution of part of Southern Africa that formed during a global event, resulting in the ~1 Ga supercontinent Rodinia. The timing of assembly by continent-continent collisions and the position of the individual continental blocks of this ancient landmass is still largely unknown. LÄS MER