Palaeomagnetism of the Upper Carboniferous-Lower Permian transition from Paganzo basin, Argentina

Abstract

S U M M A R YA palaeomagnetic study of Upper Palaeozoic rocks was performed on Paganzo basin, centralwestern Argentina and its western extension, Río Blanco subbasin. The volcanic-volcaniclastic Río del Peñón and marine sedimentary Punta del Agua formations were sampled in the Rincón Blanco syncline. Both units represent the Upper Carboniferous-Lower Permian transition according to palaeontological and geochronological evidence. The Chancaní and Cerro ColoradoCaminiaga formations were sampled in their type localities, in the eastern Paganzo basin. All-reversed, pre-tectonic characteristic magnetizations were isolated in all three localities, spanning a wide lithological variation. Particularly in the Rincón Blanco syncline, the same reversed magnetization is observed in the entire 1500 m-thick sequence in volcanic and sedimentary rocks; at least part of the deformation there is thought to be Permian in age, related to the San Rafael orogenic phase (SROP). The palaeomagnetic poles are: Rincón Blanco (RB) Lat. 77 • S, Long. 294 • E, N = 19, A 95 = 4.9, K = 47; Chancaní (CH) Lat. 85 • S, Long. 359 • E, N = 3, A 95 = 8.8, K = 196; Cerro Colorado-Caminiaga (CC) Lat. 79 • S, Long. 291 • E, N = 6, A 95 = 8.0, K = 71.Neither of the poles is coincident with expected Late Carboniferous-Early Permian directions according to accepted apparent polar-wander paths (APWPs) from South America and from other plates forming Pangaea in Late Palaeozoic times. This discrepancy could be the result of: (i) polar wander affecting the western Gondwana margin, probably related to SROP; (ii) tectonic rotations related to strike-slip faults active in the area since the Palaeozoic and controlling the position of the main depocentres; (iii) incorrect age assignment for the sedimentary sequences or for the remanence acquisition, i.e. local remagnetizations. Tectonic rotations and local remagnetization have both been proven in particular localities and further work needs to be done to establish the Late Palaeozoic APWP for South America, however, SROP seems to have played a major role controlling both processes, rotation and remagnetization.

A pure dipole analysis of the Gondwana apparent polar wander path: Paleogeographic implications in the evolution of Pangea

“…Some poles from the Andean Cordillera [e.g., Jesinkey et al, 1987;Gilder et al, 2003;Rakotosolofo et al, 2006] were included in recent compilations even though they have undergone a complex kinematic evolution, including vertical axis rotations [Somoza and Tomlinson, 2002;Geuna and Escosteguy, 2004;Arriagada et al, 2008;Henry et al, 2016]. For this reason, poles from the Andean Cordillera were not included in this contribution.…”

Neogene and Quaternary tectonics of the Eastern Sierras Pampeanas, Argentina: Active intraplate deformation inboard of flat‐slab subduction

“…To the north, the Neogene strata in the Traslasierra Valley (Figure B) are best exposed at the Nono fault exposure, where there are ~12 m of Pliocene and ~4 m of Pleistocene strata exposed [ Kraemer et al ., ]. Farther west, the range‐bounding Pocho fault is mostly covered by vegetation and modern alluvial fan and aeolian sediment [ Carignano , ], but local exposures of footwall strata contain folded Carboniferous strata overlain by Quaternary strata [ Geuna and Escosteguy , ]. The thickness of the Quaternary strata in the basin west of the Sierra de Pocho has not been well constrained.…”

Paleomagnetism of Upper Triassic rocks in the Los Colorados hill section, Mendoza province, Argentina

“…Smith (1997), however, suggested that it is not necessary to postulate that the Earth had marked non-dipole components, and Kent and Olsen (2000) demonstrate a strong correlation between magnetic paleolatitudes and lithofacies distributions, in support of the notion of a dipolar field. In contrast, Geuna and Ecostegui (2003) recently have suggested that the misfit in some Late Paleozoic PPs of Argentina is due to local tectonic rotation of the sampling areas around a vertical axis.…”