Paleomagnetism of the Santa Fé Group, central Brazil: Implications for the late Paleozoic apparent polar wander path for South America

Abstract

[1] Paleomagnetic and rockmagnetic data are reported for the Floresta Formation (Santa Fé Group) of the Sanfranciscana Basin, central Brazil. This formation represents the Permo-Carboniferous glacial record of the basin and comprises the Brocotó (diamictites and flow diamictites), Brejo do Arroz (red sandstones and shales with dropstones and invertebrate trails), and Lavado (red sandstones) members, which crop out near the cities of Santa Fé de Minas and Canabrava, Minas Gerais State. Both Brejo do Arroz and Lavado members were sampled in the vicinities of the two localities. Alternating field and thermal demagnetizations of 268 samples from 76 sites revealed reversed components of magnetization in all samples in accordance with the Permo-Carboniferous Reversed Superchron. The magnetic carriers are magnetite and hematite with both minerals exhibiting the same magnetization component, suggesting a primary origin for the remanence. We use the high-quality paleomagnetic pole for the Santa Fé Group (330.9°E 65.7°S; N = 60; a 95 = 4.1°; k = 21) in a revised late Carboniferous to early Triassic apparent polar wander path for South America. On the basis of this result it is shown that an early Permian Pangea A-type fit is possible if better determined paleomagnetic poles become available.

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

“…[] and Brandt et al . [] on glacial deposits in Late Paleozoic basins in South America give robust results for this group. Although their age is not well established, Cagliari et al .…”

Behavior of the Paleosecular Variation During the Permian‐Carboniferous Reversed Superchron and Comparisons to the Low Reversal Frequency Intervals Since Precambrian Times

“…The differences between the best fit Model G curve fittings for both lithologies could be explained by a number of different reasons, as follows: (i) possible effects related to the PSV record in sedimentary rocksfor instance, by smoothing effects (due to factors such as sedimentation rate, grain size, sediment accommodation time, and subsequent consolidation (Kruiver et al, 2002), that may lead to attenuation of the geomagnetic record); (ii) ''flattening'' (shallowing) effect, which could result in significant deviations in paleolatitude estimates. Shallowing corrections using anisotropy of remanence (first proposed by Jackson et al, 1991) or the method from Tauxe and Kent (2004) were employed in only a few works from our selection (e.g., Brandt et al, 2009Brandt et al, , 2016Franco et al, 2012;Haldan et al, 2009); and (iii) igneous rocks provide geologically instantaneous records of the paleomagnetic field (Johnson & McFadden, 2007), which according to several authors (e.g., Bazhenov et al, 2016;Biggin et al, 2008b;Johnson et al, 2008;Veikkolainen & Pesonen, 2014) probably provide more reliable PSV estimates than those provided by sedimentary rocks. Therefore, the best fit Model G curve fitting for the igneous data set would best represent the S(k) trending patterns for the PCRS.…”

The Early Triassic magmatism of the Alto ParaguayProvince, Central South America: Paleomagneticand ASM data

“…The calculated paleomagnetic pole along other Late-Permian to Early Triassic poles places South America in a position that favors the A-type reconstruction of Pangea [cf. 32,33]. Magnetic anisotropy indicates subhorizontal foliated fabric for lava flows which may be related to original magma fluxes.…”