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Paper No. 70-9
Presentation Time: 4:35 PM

A TRANS-IAPETUS TRANSFORM CONTROL FOR THE EVOLUTION OF THE RHEIC OCEAN


WU, Lei, Department of Earth and Planetary Sciences, McGill University, 3450 Rue University, Montréal, QC H3A 0E8, Canada, MURPHY, J. Brendan, Department of Earth Sciences, St. Francis Xavier University, Box 1623, Nova Scotia, Antigonish, NS B2G 2W5, Canada, COLLINS, William J., 3Department of Geological Sciences, Stanford University, 450 Serra Mall, Stanford, WA 94305, Australia, QUESADA, Cecilio, Instituto Geológico y Minero de España, and Facultad de Geológicas; Universidad Complutense de Madrid, 23 Rios Rosas, Madrid, 28003, Spain, LI, Zheng-Xiang, Department of Applied Geology, Curtin University of Techology, Department of Applied Geology, Curtin University of Techology, Perth, WA 6845, Australia, PISAREVSKY, Sergei, Earth Dynamics Research Group, School of Earth and Planetary Sciences, Curtin University, Bentley, Perth, WA GPO Box U1987, Australia, HALVERSON, Galen P., Department of Earth and Planetary Sciences, McGill University, Montreal, QC H3A 0E8, Canada, WALDRON, John W.F., Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G2E3, Canada and WILLIAMS, Simon E., School of Geosciences, The University of Sydney, Sydney, 2006, Australia

The Rheic Ocean opened at ca. 500 Ma when several peri-Gondwanan domains (e.g., Carolinia, Ganderia, Avalonia and Megumia) sequentially drifted from the northern margin of Gondwana and eventually collided with Baltica and/or northern Laurentia to close the Iapteus Ocean. Over the same time interval, the Precordillera (Cuyania) drifted away from southern Laurentia (the Ouachita margin) to join the paleo-Andean margin of Gondwana. Here we propose a new tectonic model to explain the coeval but opposite sense of transfer of those peripheral terranes by a trans-Iapetus transform fault that was likely located between Carolina-Ganderia and the Precordillera, and was active from 500-450 Ma. Together with two pre-existing Iapetus-bounding transforms, this postulated trans-Iapetus transform suggests that Gondwana and Laurentia were connected in the early to middle Paleozoic, which has important implications for reconstructing their relative paleolongitudes during this time interval. Deactivation of this trans-Iapetus transform at 450-440 Ma coincided with the docking of parts of Ganderia against Laurentia, Avalonia on Baltica, and the Precordillera on the proto-Andean margin of Gondwana. This deactivation event demarcates a fundamental change on the plate boundary topology in the Iapetus–Rheic domain, which is coincident with several global changes during the Late Ordovician to early Silurian, including strongly synchronized global continental motions, mantle mass redistribution, and the short-lived Hirnantian glaciation and associated mass extinction.

Session No. 70

T11. Recent Advances in Supercontinents: Paleogeography, Geodynamics, and Paleoclimate Evolution I
Tuesday, 27 October 2020: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol 52, No. 6
doi: 10.1130/abs/2020AM-354350
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