The late Neoproterozoic Sierra de las Ánimas Magmatic Complex and Playa Hermosa Formation, southern Uruguay, revisited: Paleogeographic implications of new paleomagnetic and precise geochronologic data
A new paleomagnetic study was carried out on 15 sites of the Sierra de las Ánimas complex, exposed in SE Uruguay. A paleomagnetic remanence was isolated at six sites, and this direction is likely to be pre-tectonic and primary. Mean directions from five of these sites are consistent with the SA2 pal...
Guardado en:
| Autores principales: | , , , , , |
|---|---|
| Formato: | INPR |
| Materias: | |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_03019268_v_n_p_Rapalini |
| Aporte de: |
| Sumario: | A new paleomagnetic study was carried out on 15 sites of the Sierra de las Ánimas complex, exposed in SE Uruguay. A paleomagnetic remanence was isolated at six sites, and this direction is likely to be pre-tectonic and primary. Mean directions from five of these sites are consistent with the SA2 paleomagnetic pole, which is based on a previous paleomagnetic study of the complex. A new paleomagnetic pole was computed for compiled results from the Sierra de las Ánimas complex (SAn, 12.2°. S, 258.9°. E, A95: 14.9°). A geochronological study based on U/Pb (SHRIMP) dating of magmatic zircons was also carried out on three samples of the Sierra de las Animas Complex, yielding a grand mean age of 578. ±. 4. Ma. The new SAn paleomagnetic pole anchors the Early Ediacaran segment of the Apparent Polar Wander Path for the Ri´o de la Plata craton. Consistency of the new pole with other Ediacaran poles from the Congo-São Francisco craton suggests a coherent Central Gondwana by this time. These data also support a wide Clymene Ocean between the conjoined Ri´o de la Plata-Congo-São Francisco blocks and Western Gondwana, i.e., Amazonia-West Africa. Additional sampling (sixteen samples) was carried out on the basal levels of the glaciogenic Playa Hermosa Formation, exposed in the same area. These samples retain a paleomagnetic component consistent with the previously reported data, confirming the original pole position. U-Pb (SHRIMP) dating of detrital zircons reveal a bimodal distribution of Paleoproterozoic (around 2.1. Ga) and late Neoproterozoic ages. The youngest zircons are interpreted as pre-dating to penecontemporaneous with deposition and points to a ≤594. Ma age for deposition of the older levels of the Playa Hermosa Formation. A minimum age of deposition is set by the 578. ±. 4. Ma age of the Sierra de las Ánimas magmatism. The low inclination of magnetization indicates that low-latitude (13.0°. +. 9.5°/-5.5°), Gaskiers-aged glacial deposits are preserved atop the Rio de la Plata craton. © 2014 Elsevier B.V. |
|---|