Tectonic evolution of the Patagonia-Antarctic Peninsula system: a paleomagnetic perspective
Abstract
One of the foremost feature of the Scotia Arc is the symmetry between Patagonia and the Antarctic Peninsula. Understanding the mechanisms and the age of formation of these structures is critical to understand the tectonic evolution of the region and its possible role on the pattern of ocean circulation, climate change and faunal dispersal. While paleomagnetic studies suggest that the curvature of the Antarctic Peninsula is a structure inherited from at least the Cretaceous, the origin of the Patagonian Bend is a matter of debate. Contrasting models suggest that this would have been an inherited structure or, as paleomagnetic results suggest, due to oroclinal bending related to the closure of the Rocas Verdes basin and the development of the Magallanes fold and thrust belt (MFTB). In Navarino Island, located to the south of Tierra del Fuego, crop out extensively the oceanic floor (Tortuga Ophiolite) and the sedimentary infill (Yaghan formation) of the basin as well as intrusive rocks of cretaceous age. A detailed study of these rocks could provide clues to distinguish between the different tectonic models.
We conducted a fieldwork in Navarino Island where we sampled 27 sites for paleomagnetic and geochronological studies in sedimentary rocks of the Yaghan formation and intrusive rocks of Cretaceous age. Preliminary paleomagnetic results would confirm the rotations observed in previous studies, however, a new U-Pb zircon age of 65 Ma suggests that they could be younger than previously thought. These data, combined with published paleomagnetic results and geological information in the region, allow us to propose a tectonic model of the Patagonia-Antarctic Peninsula system that can be divided into 3 stages: (1) Upper Jurassic-mid Cretaceous: extensional stage and development of the Rocas Verdes basin, (2) Upper Cretaceous: closure of the Rocas Verdes basin and early development of the MFTB, and finally (3) Cenozoic: exhumation of the Darwin Cordillera and advance of the MFTB. In our model, Patagonia and the Antarctic Peninsula would have formed a land bridge at least until 50 Ma precluding deep water interchange between the Pacific and the South Atlantic Ocean, but would have allowed faunal interchange between South America and the Antarctic Peninsula. We thank Universidad de O'Higgins and SERNAGEOMIN for financial support.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP53A0663P
- Keywords:
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- 1525 Paleomagnetism applied to tectonics: regional;
- global;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 8157 Plate motions: past;
- TECTONOPHYSICS;
- 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS