Gondwana’s Apparent Polar Wander Path during the Permian-new insights from South America

Abstract

A long-standing debate regarding the configuration of Pangea during the Late Paleozoic has been going on among the paleomagnetic community concerning the validity of one of two significantly different Pangea reconstructions (Pangea A vs Pangea B) since the proposal of Pangea B. Although, Pangea B avoids any continental overlap marring classical Pangea A configuration (Wegener’s type), it requires a Carboniferous-Permian megashear of up to 1500 km to achieve the pre-Jurassic configuration. The existence of this megashear is controversial and has led to a wide range of hypotheses, in order to avoid Pangea A continental overlaps and consequently the need for major intra-Pangea movements and to accommodate the paleomagnetic database within a Pangea A reconstruction. We present paleomagnetic results from Permian volcanic rocks of the El Centinela, La Pampa, Argentina. Undeformed volcanic rocks are not affected by any inclination bias and are, therefore, ideal to test different paleogeographic models. The presence of two different paleopole positions, at the base and the top of the same stratigraphic sequence, makes this location optimal to constrain the track of the Gondwana’s path during the Late Paleozoic, which shows the transition from Pangea B during the Carboniferous-Permian, to Pangea A at the Permian – Triassic boundary.

Following the steps of CHIPA: Chilenia and Patagonia formed the same drift terrain that collided with the southwest Gondwana margin during the middle Paleozoic

“…The K min axes are always grouped in a northeast direction close to the horizontal and perpendicular of those planes, defining dominantly oblate ellipsoids of tectonic origin (AMS fabric, transitional between types C and D, following the conceptual model of Weil and Yonkee, 2009). This AMS axes arrangement indicates a SW-NE maximum compression direction (Tomezzoli et al, 2018; Figure 3B). From paleomagnetic studies, it emerges that these rocks bear a postectonic remagnetization carried by hematite and/or magnetite, which is located in the apparent polar wander path (APWP) of South America (Tomezzoli, 2009;Gallo et al, 2017) in the Permian position close to that of the Tunas II paleomagnetic pole (PP; Tomezzoli, 2001;Figure 3E) aged 280.8 ± 1.9 Ma (López- Gamundi et al, 2013;Arzadún et al, 2018).…”

“…Cerro El Centinela exposed in the northwest of La Pampa province (Figure 1; Tomezzoli et al, 2018), Argentina, as part of the Gondwanides belt; the profile was sampled from the base to the top. (A) Cerro El Centinela consists of a continuous volcanic sequence of lava flows that degrade to volcanic breccias, interbedded with pyroclastic rocks.…”

“…(A) Cerro El Centinela consists of a continuous volcanic sequence of lava flows that degrade to volcanic breccias, interbedded with pyroclastic rocks. Stratigraphic boundary between the different ChRM is in the upper part of the sequence (Tomezzoli et al, 2018). (B) Two high quality PPs have been calculated (Tomezzoli et al, 2018).…”

“…The last manifested itself in a non-collisional way, generating intracontinental deformation as part of the adjustment of the previously coupled terrains. At the same time, Gondwana and Laurentia underwent latitudinal movements toward the Equator, resulting in the formation of the Triassic Pangea (Tomezzoli, 2001;Tomezzoli et al, 2018).…”

The Permian Monos Formation: Stratigraphic and detrital zircon evidence for Permian Cordilleran arc development along the southwestern margin of Laurentia (northwestern Sonora, Mexico)

“…Southern Laurentia straddled or was just north of the equator in Permian time, placing the Caborca block in tropical to subtropical latitudes, although the precise location is still a matter of debate (Scotese and Langford, 1995;Domeier and Torsvik, 2014;Tomezzoli et al, 2018;Muttoni and Kent, 2019;Correia and Murphy, 2020;Kent and Muttoni, 2020;Fig. 1B).…”