The age and palaeomagnetism of Jurassic dykes, western Dronning Maud Land: implications for Gondwana breakup

• Main Authors: Morake, Mabuela A., O'Kennedy, Johan N.F., Knoper, Michael W., de Kock, Michiel, Kramers, Jan D., Grantham, Geoffry H., Belyanin, Georgy A., Elburg, Marlina A.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Geological Society of London 2021
• Subjects: Geology; FOS Earth and related environmental sciences; Dronning Maud Land; Maurice; Ewing; Vestfjella; Haag; Maurice Ewing Bank; Sverdrupfjella; Haag Nunataks; Antarc*; Antarctica
• Online Access: https://dx.doi.org/10.6084/m9.figshare.c.5612838.v1; https://geolsoc.figshare.com/collections/The_age_and_palaeomagnetism_of_Jurassic_dykes_western_Dronning_Maud_Land_implications_for_Gondwana_breakup/5612838/1

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 Ma 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.