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Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the Sãíêéãããõãããão Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U–Pb baddeleyite ages from five dykes previously thought to be 1.02–1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called ‘A-normal’ remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the ‘C’ remanence direction at 921.5±4.3 Ma. An ‘A-normal’ dyke at Ilhãíêéãããõããããéus is dated at 926.1±4.6 Ma, and two ‘A-normal’ dykes at Olivenca have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the ‘A-normal’ and ‘C’ directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results render previous 40Ar/39Ar ages from the dykes suspect, leaving late Mesoproterozoic palaeolatitudes of the Sãíêéãããõããããéão Francisco/Congo craton unconstrained. The combined ‘A-normal’ palaeomagnetic pole from coastal Bahia places the Sãíêéãããõããããéãão Francisco/Congo craton in moderate to high palaeolatitudes at c.920 Ma, allowing various possible positions of that block within Rodinia.

The South American record of remagnetizations is linked to specific events of its tectonic history stretching back to Precambrian times. At the Ediacaran–Cambrian time interval (570–500 Ma), the final stages of the western Gondwana assemblage led to remagnetization of Neoproterozoic carbonates within the São Francisco–Congo Craton and at the border of the Amazon Craton, along the Araguaia–Paraguay–Pampean Belt. From the late Permian to early Triassic, the San Rafaelic orogeny and the emplacement of the Choiyoi magmatic province was responsible for widespread remagnetizations in Argentina and Uruguay. Cretaceous remagnetization has also been documented in Brazil and interpreted to result from magmatism and fault reactivations linked to the opening of the South Atlantic Ocean. We present a review of these widespread remagnetization events principally based on palaeomagnetic data and, when available, on rock magnetic and radiogenic isotope age data. This study gives an overview of the geographical distribution of the remagnetization events in South America, and provides important clues to better understand the geodynamic evolution of the South American plate at these times. In addition, magnetic mineralogy data for the different case studies presented here constrain the physical–chemical mechanisms that led to partial or total resetting of magnetic remanences in sedimentary rocks.

Abstract—The 40 km wide Araguainha structure in central Brazil is a shallowly eroded impact crater that presents unique insights into the final stages of complex crater formation. The dominant structural features preserved at Araguainha relate directly to the centripetal movement of the target rocks during the collapse of the transient cavity. Slumping of the transient cavity walls resulted in inward‐verging inclined folds and a km‐scale anticline in the outer ring of the structure. The folding stage was followed by radial and concentric faulting, with downward displacement of kilometer‐scale blocks around the crater rim. The central uplift records evidence for km‐scale upward movement of crystalline basement rocks from the transient cavity floor, and lateral moment of sedimentary target rocks detached from the cavity walls. Much of the structural grain in the central uplift relates to structural stacking of km‐scale thrust sheets of sedimentary strata onto the core of crystalline basement rocks. Outward‐plunging radial folds indicate tangential oblate shortening of the strata during the imbrication of the thrust sheets. Each individual sheet records an early stage of folding and thickening due to non‐coaxial strains, shortly before sheet imbrication. We attribute this folding and thickening phase to the kilometer‐scale inward movement of the target strata from the transient cavity walls to the central uplift. The outer parts of the central uplift record additional outward movement of the target rocks, possibly related to the collapse of the central uplift. An inner ring structure at 10–12 km from the crater center marks the extent of the deformation related to the outward movement of the target rocks.

The Araçuaí Orogen (AO) has been interpreted as a Neoproterozoic example of a large, “hot” orogen, based on a broad zone (250 km) of midcrustal metamorphic assemblages with a long, 70‐Myr history of crustal melting and episodic magmatism throughout the late Neoproterozoic and earliest Paleozoic. Here, we present results of U‐Pb sensitive high‐resoution ion microprobe (SHRIMP) zircon dating and detailed anisotropy of magnetic susceptibility (AMS) study on a late Cambrian, bimodal pluton related to final period of collapse of the AO. New U‐Pb zircon ages constrain the crystallization age of different suites within the Santa Angélica Pluton, 506 ± 3 Ma for the early felsic phase and 498 ± 5 Ma for the mafic core. New AMS data indicate that the emplacement of the Santa Angélica Pluton corresponds to two coupled plutons with concentric structures arrayed about a twin, bull's eye pattern. During the final stages of intrusion, upward relative movement of the northeastern lobe exposed the deeper levels of the intrusion, relative to the more shallowly eroded southwestern lobe. These observations suggest that magma emplacement was controlled by magma buoyancy forces, with little influence of regional tectonic stress. This behavior contrasts with the well‐defined, tectonic‐controlled fabrics of coeval plutons occurring to the north which was still hot, therefore highlighting the contrasting thermal evolution between different sectors of the orogen during its final stages. Anisotropy of magnetic susceptibility (AMS) to determine the emplacement mechanisms of a late Cambrian plutonStrain partitioning in a collapsing hot orogeny