A review of Precambrian palaeomagnetism of Australia: Palaeogeography,supercontinents, glaciations and true polar wander |
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| Institution: | 1. Department of Earth Science and Astronomy, The University of Tokyo, 1-3-8 Komaba, Meguro, Tokyo 153-8902, Japan;2. Early Life Institute, Northwest University, Xi''an 710069, PR China;3. State Key Laboratory of Continental Dynamics, Northwest University, Xi''an 710069, PR China;4. Earth Life Science Institute, 2-12-1 O-okayama, Meguro, Tokyo 152-8551, Japan;5. Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8551, Japan;6. School of Earth Science and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, PR China;1. EarthByte Group, School of Geosciences, The University of Sydney, Madsen Building F09, Camperdown, NSW 2006, Australia;2. Data61, CSIRO, Australian Technology Park, Eveleigh, NSW 2015, Australia;3. Centre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia;4. The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, GPO Box U1987, WA 6845, Australia;5. Earth Dynamics Research Group, ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Australia;6. Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W5, Canada;7. Department of Applied Geology, Curtin University, Perth WA 6845, Australia |
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| Abstract: | This is the first review of the Australian Precambrian palaeomagnetic database since that undertaken by Idnurm and Giddings (1988) 25 years ago. In this period the data have almost tripled in number from about 60 to more than 170 and while some segments of the pole path are now quite well defined, overall the data are sparse. It is debatable whether the extant rock record amenable to palaeomagnetism is complete enough for full palaeogeographic histories to be reconstructed. The SWEAT connection is apparently ruled out for Rodinia as both the 1200 Ma and 1070 Ma poles from (ancestral) Australia and Laurentia disallow it. However, older palaeopoles do support a SWEAT-like configuration for the pre-Rodinia supercontinent Nuna but the geological reasoning for SWEAT applies to Rodinia so a Nuna SWEAT is less than gratifying. The concept of a “grand-pole” is introduced here, which includes all the “key-pole” features but is predicated on the condition that two or more independent laboratories are in agreement.Precambrian data from Australia include the oldest palaeopole yet defined, the record of one of the oldest geomagnetic polarity reversals, the most definitive evidence for low-latitude Neoproterozoic glaciation, the first study of BIFs and the timing/nature of iron-ore genesis, the most unusual ‘field test’ (impact melt rock and ejecta horizon host rocks), some of the best examples of complete contact tests and the timing of craton assembly. Some old caveats that can no longer be ignored, such as corrections for inclination flattening and the permitting of rotations between contiguous intracontinental cratons to bring conflicting palaeopoles into alignment are required. Care should be exercised when inferring palaeolatitudes from sedimentary derived palaeoinclinations. TPW should only be considered if there is evidence from more than one, and preferably more, independent continents. Future work identified includes a complete magnetostratigraphic study of ~ 300 my Adelaidean succession, better age constraints for the Adelaidean and Officer Basin successions and a better age for the Gawler Craton GB dykes. |
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