168-1 Long-lived Proterozoic Triad of Western Laurentia, Australia and Antarctica within Nuna and Rodinia

Session: Laurentia Without Borders: Pre-Pangea Intercontinental Connections

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Cratonic East Antarctica was joined with various Australian cratons through much of Proterozoic time, forming a key element of the Nuna and Rodinia supercontinents. The eastern margin of this composite Austral-Antarctica had a long-lived but elastic geotectonic association with western Laurentia, spanning 700 m.y. from 1.8 to 1.1 Ga. Proterozoic connections between Antarctica, Australia and western Laurentia extended over four main periods: (a) pre-Nuna growth and accretion (1.8-1.7 Ga), (b) Mazatzal assembly (1.65-1.6 Ga), (c) extant Nuna (1.6-1.3 Ga), and (d) Rodinia convergence and amalgamation (1.1-0.9 Ga). The period from 1.8-1.3 Ga is marked by persistent geologic ties between all three regions involving mutual accretionary growth, periodic extension and collisional orogeny, thermal and magmatic consolidation, and partial breakup leading to large basin development, together documented by age, isotopic, provenance, and paleomagnetic data. This prolonged association was first posited as the SWEAT core to Neoproterozoic Rodinia, but the general pattern had much earlier origins. Despite episodic extension and intra-cratonic basin formation, a proto-SWEAT triad was remarkably enduring through much of the Proterozoic. And although detailed late Mesoproterozoic (~1.1 Ga) connections between southern Laurentia (Grenville Orogen) and the East Antarctic and Kalahari cratons remain unresolved, models for Grenvillian origins of Rodinia must account for strong connections between western Laurentia and Austral-Antarctica from at least 1850 to 1300 Ma. Grenvillian signatures in the Antarctic conjugate margin to southern Laurentia include: (1) felsic igneous rocks from nunataks in Coats Land; (2) orogenic patterns in the Maud Belt of Dronning Maud Land; (3) isotopic data from granitoids in the southern Transantarctic Mountains; and (4) glacial erratics recovered from modern glacial moraines sourced in central East Antarctica. These data indicate contemporaneous but differing geotectonic activity in separate areas facing Laurentia—Coats Land connections to the Laurentian Grenville Orogen proper, accretionary orogenesis within the Maud Belt, and late Mesoproterozoic evidence from the Transantarctic Mountains of inboard pre- to syn-Grenville magmatic activity related to Rodinian convergence and assembly. Direct tests of these ideas can be provided by subglacial basement drilling behind the Transantarctic Mountains in the area near South Pole using existing technologies. New O-Hf-Pb isotopic data from Mesoarchean and Paleoproterozoic basement rocks exposed in the central Transantarctic Mountains should also shed light on Laurentian connections with East Antarctica.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6621

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