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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Africa
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Southern Africa
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Kaapvaal Craton (2)
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South Africa
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Bushveld Complex (1)
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Gauteng South Africa
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Pretoria South Africa (1)
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Witwatersrand (1)
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elements, isotopes
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Lu/Hf (1)
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geochronology methods
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Lu/Hf (1)
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Pb/Pb (1)
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U/Pb (1)
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geologic age
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Precambrian
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Archean
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Mesoarchean (1)
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Central Rand Group (1)
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Transvaal Supergroup (1)
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upper Precambrian
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Proterozoic
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Paleoproterozoic (1)
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Pretoria Group (1)
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Witwatersrand Supergroup (1)
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igneous rocks
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igneous rocks
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plutonic rocks (1)
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Primary terms
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absolute age (1)
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Africa
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Southern Africa
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Kaapvaal Craton (2)
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South Africa
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Bushveld Complex (1)
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Gauteng South Africa
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Pretoria South Africa (1)
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Witwatersrand (1)
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igneous rocks
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plutonic rocks (1)
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intrusions (1)
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lava (1)
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magmas (2)
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Precambrian
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Archean
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Mesoarchean (1)
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Central Rand Group (1)
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Transvaal Supergroup (1)
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upper Precambrian
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Proterozoic
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Paleoproterozoic (1)
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Pretoria Group (1)
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Witwatersrand Supergroup (1)
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sedimentary rocks
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clastic rocks
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conglomerate (1)
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sandstone (1)
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sedimentary rocks
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sedimentary rocks
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clastic rocks
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conglomerate (1)
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sandstone (1)
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volcaniclastics (1)
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sediments
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volcaniclastics (1)
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The age and palaeomagnetism of Jurassic dykes, western Dronning Maud Land: implications for Gondwana breakup
Abstract New 40 Ar/ 39 Ar data from dykes intruded into Sverdrupfjella and Ahlmanryggen, Dronning Maud Land, Antarctica, indicate that dyke emplacement commenced at c. 207 Ma and lasted until c. 178 Ma. Whereas the ages ascribed to the Karoo-age magmatism contributing to Gondwana breakup are typically inferred as being c. 182 Ma, the data indicate that ages older than c. 192 Ma in the broader Karoo Province are restricted to western Dronning Maud Land, Antarctica, indicating the locality where breakup was initiated. Limited palaeomagnetic data from c. 178–185 Ma dykes combined with published palaeomagnetic data from similar-aged dykes in Vestfjella and the Ferrar Province, suggest that Antarctica had already drifted/rifted significantly away from southern Africa from c. 207 to c. 180 Ma, earlier than previously thought. The data, if correct, require a re-evaluation of the ages ascribed to ocean-floor anomalies used to constrain reconstructions of Gondwana and may provide insight into the history of microcontinental blocks including the Falkland Islands, Haag nunataks, Ellsworth–Whitmore block and Maurice Ewing Bank.