Wed 23st May @ noon, Rm 312.222
Abstract:
Arguably, Nuna represents the first actual supercontinent. Many uncertainties still exist regarding its paleogeographic evolution. Especially considering the position of proto-Australia, a lack of robust paleomagnetic data prevent a well-defined picture for large intervals during the Paleo- to Mesoproterozoic. I present new paleomagnetic results from two sets of Australian sills with intrusion ages close to the proposed formation and breakup periods of Nuna. Paleomagnetic analysis yield two well defined paleopoles for the ~1.8 Ga Hart Dolerite and the ~1.3 Ga Derim-Derim sills. Comparison with other paleopoles from Nuna, mainly from Laurentia and the North China Craton (NCC), reveals a high degree of similarity, which led us to construct a common apparent polar wander path (APWP) for an updated core of Nuna between ~1.8 Ga and 1.3 Ga, consisting of Laurentia, Siberia, Baltica, proto-Australia and the NCC. A striking feature of this APWP is an overall steady but slow rotational movement of the supercontinent. Superimposed, a much more rapid and irregular polar wander is visible. Based on the most recent paleomagnetic pole list, the breakup time for Nuna can be constrained between ~1.3 and ~1.2 Ga, manifested in relative motion between Laurentia, Australia and North China. We suggest an initial proto-SWEAT connection between Laurentia and Australia between 1.8 and 1.75 Ga, followed by a modified Nuna configuration for the 1.63 –1.3 Ga period. Nuna likely remained intact till ca. 1.3 Ga, when a broad intracontinental basin, bounded by Australia, the NCC and potentially Siberia, existed. Anisotropy of magnetic susceptibility suggests that the same magmatic event likely produced the Derim-Derim Sills and the Galiwinku dykes in Australia, and the Yanliao large igneous province in the NCC, originated from underneath the broad intracontinental basin.
Short bio:
Uwe Kirscher studied geophysics at the Ludwig- Maximilians University in Munich, Germany. He then did a PhD there working on the evolution of the Central Asian Orogenic Belt using paleomagnetic data. He is currently a research associate in Professor Li’s Laureate team working on paleomagnetic constraints for supercontinents.
