The paleogeographic evolution of the Antarctic Peninsula during the Gondwana breakup remains poorly constrained. Reconstructing the eruptive sources of the voluminous Jurassic Chon Aike Province is crucial for refining or challenging existing tectonic models. This study presents new Anisotropy of Magnetic Susceptibility (AMS) data from Mid-to-Late Jurassic pyroclastic units in the northern Antarctic Peninsula to address these uncertainties. Bulk magnetic susceptibility values between 30–80 µSI, thermomagnetic curves, and hysteresis cycles indicate a normal (non-inverse) AMS fabric. Lack of evidence of tectonic overprint sustains a primary origin for the AMS fabric. Volcanic paleoflow directions were determined using K3 imbrication and, to a lesser extent, K1 magnetic lineations. Our results for the pirolastic Kenney Glacier Formation reveal a significant shift in volcanic sourcing: a source area located to the NW of Mount Flora in the basal units (Kenney 1 and lower Kenney 2 Members). A systematic change in the source area, coming from the ESE in Kenney 2 and 3 and from the SE in Kenney 4 Member. Integrating these results into a 160 Ma paleoreconstruction, we propose a model for the Kenney Glacier Formation that aligns with current tectonic frameworks for the Graham Land Volcanic Group. In this restored geometry, flows originated from the SE (Kenney 1), shifting to the NNW (Kenney 2 and 3), and finally to the NE (Kenney 4). These findings provide evidence of shifting volcanic centers during the V2 episode of Jurassic magmatism in West Gondwana.

The paleomagnetic archive provides invaluable insights into Earth's history, but its records are often obscured by various geological processes. A prime example is remagnetization, which can replace the original natural remanent magnetization. Although magnetic overprints can be detected by traditional paleomagnetic tests, the mechanisms responsible for them often remain elusive because linking bulk magnetic properties to their microscopic sources is inherently challenging. Here, we bridge this gap by pairing an extensive rock magnetic and geochemical dataset with statistical learning techniques for the first time. Using a Random Forest regressor trained on geochemical data, we accurately predict the growth of fine-grained magnetite in an undeformed late Ediacaran section of remagnetized carbonate rocks from Paraguay. Our modeling results identify the K/Al ratio- alongside K and Sr contents-as key predictors of this remagnetization mechanism. Notably, clay mineralogy analyses further link the K/Al ratio to enhanced clay authigenesis (illitization) driven by K-feldspar dissolution and albitization-processes that also release iron. Together, these findings indicate that remagnetization occurred via authigenic magnetite formation under isochemical diagenesis-without the involvement of external fluids. This novel application of statistical learning to uncover the geochemical drivers of chemical remagnetizations provides a robust framework to investigate and understand these events. It could also open new avenues for their direct dating, thereby significantly enriching the global paleomagnetic record.

A paleomagnetic study of basaltic lava flows exposed in the northern Neuqu & eacute;n Cordillera, southernmost Central Andes, along the Anti & ntilde;ir-Copahue fault zone (ACFZ), involved 25 sites of the Cola de Zorro Formation (Pliocene-Early Pleistocene) along two different sections. The sites show exclusive normal polarity, corresponding to the Late Pliocene Gauss chron (3.6-2.6 Ma). The angular standard deviation of virtual geomagnetic poles (VGPs; ASD = 14.8 degrees) is consistent with the expected values from recent geomagnetic models, in opposition to anomalously low dispersion found in previous studies in Pleistocene VGPs of reverse polarity from neighboring areas to our study zone. Mean paleomagnetic directions for Bella Vista (Dec = 0.0 degrees, Inc = -50.0 degrees, alpha(9)(5) = 7.6 degrees, K = 36.7, N = 11) and R & iacute;o Huaraco sections (Dec = 354.9 degrees, Inc = -57.0 degrees, alpha(9)(5) = 7.5 degrees, K = 55.7, N = 8) do not show tectonic rotation around vertical axes. Combining and regrouping our and previous data by area confirmed the absence of tectonic rotations in the Huaraco-Trohunco block and a statistically significant clockwise rotation of 14.4 degrees +/- 10.3 degrees of three adjacent tectonic blocks located south of our study locality in Pleistocene times. These results suggest that strike-slip deformation along some sections of the ACFZ was significant in the Pleistocene structural evolution of this region.

Permian times were characterized by distribution of land masses forming a supercontinent called Pangea. Although its existence has been accepted for many decades, there is still debate about its configuration. In order to provide new constraints on the position of Gondwana during late Paleozoic times, a paleomagnetic study was carried out on Carboniferous-Permian red beds exposed in the Famatinian Ranges, western Argentina (27 degrees 43 ' S 67 degrees 58 ' W). Eighty four oriented samples (11 sites) were submitted to standard stepwise demagnetization procedures. Magnetic analysis was complemented by acquisition of isothermal remanent magnetization (IRM), backfield curves and anisotropy of magnetic susceptibility (AMS) on selected specimens. Inclination shallowing due to compaction was evaluated by application of oriented acquisition of IRM and demagnetization experiments. The high-temperature magnetic components of sites are characterized by southward declinations with positive inclinations that yield a positive fold test. A new paleomagnetic pole is calculated and suggests an age of magnetization between 300 and 270 Ma, that- matches with a Pangea B distribution although a Pangea A2 model can not be ruled out if the magnetization age is restricted to 280-270 Ma.

This work delves into the intricate Paleoproterozoic geological setting of Uruguay, focusing on the Rio de la Plata Craton (RPC) and its prominent constituent Piedra Alta Terrane (PAT). The PAT constitutes the core of the RPC, characterized as a complex geological entity that encompasses a granite-migmatite basement, metamorphic belts, granite intrusions, and Proterozoic magmatism. To the west, it interfaces with the Transbrasiliano-Kandi tectonic corridor, bounded by the Late-Neoproterozoic Pampia Terrane. The PAT s southeastern boundary extends to Sierra de Tandil and perhaps to Sierra de La Ventana, demarcating its limits with Phanerozoic rocks of the North Patagonian Massif. The Sarandi del Yi shear zone defines the eastern limit of the PAT. Despite varied interpretations of the Piedra Alta Terrane's significance, it is important to note that consensus prevails regarding its four major associations: a granite-gneiss-migmatitic basement complex, three volcanosedimentary belts of low to medium metamorphic grade, diverse late igneous intrusions, and extensional Statherian magmatism (1.79 Ga), represented by tholeiitic gabbroic dikes. In this study, a novel tectonic model for the PAT evolution emerges, supported by an extensive zircon dataset comprising new U-Pb ages, Hf isotopes, and trace element geochemistry. The analytical core involves U-Pb analyses on zircon for dating igneous rocks and establishing the provenance and maximum age of deposition of metavolcanosedimentary sequences. Lu-Hf isotopic analyses on the same zircon crystals provide petrogenetic insights, revealing episodes of crustal growth and minor recycling. Trace element geochemistry and zircon epsilon Hf(t) data further accentuate these findings, hinting at mantle source enrichment due to subduction within an intraoceanic magmatic-arc arc setting.

The Patagonian Andean foreland system includes several intermountain basins filled with a Miocene non-marine record deposited under syn-tectonic conditions related to the Andean uplift and a regional climate change triggered by a rain shadow effect. Many of those basins, such as the Collon Cura basin in Neuquen Province, Argentina, present a well-preserved fluvial record (i.e. the Limay Chico Member of the Caleufu Formation). Sedimentological and palaeomagnetic studies have allowed the interpretation of coeval transverse distributary fan and axial mixed-load fluvial systems deposited between 10.6 & PLUSMN; 0.2 and 12.8 Ma. The basin infill arrangement shows that, while the axial mixed-load fluvial system exhibits an aggradational stacking pattern, the transverse distributary fluvial fan system denotes three different orders of stratigraphic patterns: (i) large-scale progradation of the transverse fluvial fan system over a time scale of 106 year; (ii) intermediate-scale progradational-retrogradational transverse intra-basinal fluvial fan episodes over a time scale of 105 year; and (iii) small-scale transverse lobe progradation over a time scale of 105-104 year. These patterns were interpreted as transverse sediment flux variations triggered by variable external forcings. To decouple those forcings, we estimated the Collon Cura basin equilibrium time at 3-5 x 105 year and compared it with the time scale over which different external forcings varied in the Patagonian Andean and foreland regions during Miocene times. Large-scale progradation is linked to an increase in sediment flux triggered by a long-term tectonically driven exhumation forcing associated with the Miocene Patagonian Andean contractional phase. Intermediate-scale progradational-retrogradational episodes are linked to variations in sediment flux due to a mid-term tectonic forcing associated with the western fault system activity. The small-scale fan lobe progradation is related to increases in sediment flux triggered by indistinguishable short-term autogenic processes and/or high-frequency tectonic and climatic forcings. This contribution shows the applicability and limitations of the basin equilibrium time concept to decouple external forcings from the geological record, considering their magnitude, nature and time scale, as well as the basin characteristics.

Anomalous paleomagnetic data have been found worldwide during the Ediacaran period, giving rise to several non-actualistic hypothesis. In order to get more information about this period, paleomagnetic, magnetic fabric and rock magnetic studies were carried out in the Avellaneda Formation (similar to 570-560 Ma) from two drill cores of the Alicia quarry in the Olavarria area of the Tandilia System, in the Rio de la Plata craton (Argentina). Anisotropy of magnetic susceptibility studies indicate a pre-tectonic origin for the magnetic fabric of this Formation. Rock magnetic studies suggest the presence of magnetite and hematite in different proportions as the main ferromagnetic minerals carrying the remanence. After stepwise thermal demagnetization, two different characteristic remanence directions were obtained for the same unit, one corresponding to the marls (''b1") of the lower section of the Avellaneda Formation, and the other from the claystones (''b2") of the upper section of this unit. These results were combined with the remanence directions obtained by Franceschinis et al. (2022) for the same unit at La Cabanita quarry, located 10 km away. This procedure allows the calculation of two paleomagnetic poles for the Avellaneda Formation. The AV1 pole is located at: 2.0 degrees S, 311.1 degrees E, A95: 5.0 degrees, N: 58 while the AV2 pole is at: 3.3 degrees N, 348.9 degrees E, A95: 11.7 degrees, N: 7. These results confirms that the Rio de la Plata craton also presents anomalous paleomagnetic data during the Ediacaran, implying extremely fast movements in very short periods of time. This can be interpreted as evidence of two inertial interchange true polar wander events during this time, as was already proposed by other authors. An alternative possibility suggests a non-actualistic behaviour of the Earth Magnetic Field, switching from axial to equatorial positions, with an intermediate stable position between them. The likelihood and implications of these two hypotheses is discussed. (C) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The Ediacaran apparent polar wander path for the Rio de la Plata Craton was analyzed and a new alternative path is presented. This revised path was constructed considering an opposite polarity for poles older than ca. 590 Ma. This path is more consistent with that recently proposed for West Africa, whose large oscillations were attributed to two events of inertial interchange true polar wander (IITPW). A compilation and selection of Ediacaran paleomagnetic data from the main cratons were analyzed leading to a set of global paleogeographic reconstructions throughout the Ediacaran. This model assumes that a “Clymene Ocean” existed between Central Gondwana and West Africa – Amazonia along this period. All cratons with reliable paleomagnetic information, share similar motions during two time-intervals. The first one (615-590 Ma) can be described by rotation around an Euler pole located in the equator, while the second one (575-565 Ma) by another around an Euler pole on the tropics. Whether these apparent large and fast displacements can be assigned to IITPW events is discussed along with the consistency of considering a large Clymene Ocean during this time.

A paleomagnetic study performed in Plio-Pleistocene volcanic rocks of two localities in the Southern Central Andes is presented. The region corresponds to the transition zone between the Central and the Patagonian Andes. In the latter, deformation is almost exclusively controlled by the dextral-strike slip Liquin tilde e-Ofqui Fault Zone, that extends from-47 degrees S to-38 degrees S and accommodates the deformation generated by the oblique subduction of the Nazca Plate below South America. To the north of-36 degrees S, deformation is mainly contractional. Our study was carried out in the transition zone between both tectonic regimes. Sampling consisted of 31 paleomagnetic sites distributed in two localities: the Loncopue acute accent (-38.0 degrees S, 70.7 degrees W) and Andacollo (-37.2 degrees S, 70.8 degrees W) areas. We sampled Pliocene and Pleistocene volcanic rocks with ages younger than 5 Ma. After stepwise demagnetization and principal component analysis, site mean remanence directions were computed. Both localities show non-significant clockwise rotations of 1.7 degrees +/- 14.4 degrees (Loncopue acute accent ) and 8.1 degrees +/- 8.4 degrees (Andacollo). Although the pres-ently available database does not support significant tectonic rotation of the Andacollo lavas, preliminary results obtained from upper Miocene volcanics in a nearby area indicating-20 degrees of clockwise rotation, encourage further studies to improve the resolution of the paleomagnetic data to determine if crustal block rotations have been, or still are, part of the Andean deformational processes. A revision of previously published paleomagnetic data in the northern Patagonian Andes suggests that, against original claims, no significant tectonic rotations associated to the Liquin tilde e-Ofqui Fault Zone, between-39 and 37.5 degrees S, can be unambiguously demonstrated.

Magnetostratigraphy is a powerful technique for high-resolution stratigraphic correlation and accurate dating of the polarity history of the magnetic field. Up to now, magnetostratigraphic studies have been underutilized in Ediacaran successions. Here, we present a magnetostratigraphy coupled with a carbon isotope study in Ediacaran Avellaneda Formation (similar to 570 Ma), a sedimentary cover sequence in the Tandilia orogenic belt, of the Rio de la Plata craton. Paleomagnetic results and delta C-13 profiles were obtained from three drill cores that cut across the sedimentary record of the Avellaneda Formation. Paleomagnetic results plotted stratigraphically allowed the identification of a prevalent reverse polarity separated by normal polarity interval. Our findings show a coincident correlative polarity transition at each drill core analyzed. delta C-13 values demonstrate that the magnetostratigraphic polarity pattern is laterally consistent. Furthermore, C-isotope curves show a transition from positive to negative values near the top of the Avellaneda Formation. This excursion is likely correlative with the onset of the Shuram excursion (ca. 570 Ma). Our findings suggest that the onset of Shuram excursion took place during a reverse polarity chron. Comparison with other coeval sequences validate this correlation. Geomagnetic polarity reversals pattern in the Avellaneda Formation and its correlative pattern, validates a magnetostratigraphy as a potential method to correlate Precambrian strata. Our new findings shed further light on the possible use of magnetic polarity reversals to correlate Ediacaran successions.

Here, we discuss the role of the main South American cratonic units in the Columbia and Rodinia supercontinents, and Gondwana megacontinent. According to paleomagnetic and geological data Amazonia and West Africa were linked to Baltica, Laurentia and Siberia forming West Columbia at ca. 1.78-1.75 Ga. The 1.78 to 1.42 Ga paleomagnetic data for Amazonia, Baltica and Laurentia suggest either, that West Columbia preserved its integrity, at least, up to 1.42 Ga, or Amazonia/West Africa broke-up from West Columbia at some time between 1.53 and 1.42 Ga.. On the other hand, the Congo/São Francisco, North China, Rio de la Plata, India and proto-Australia formed the East Columbia at ca. 1.78 Ga. However, the presently available Paleo to Mesoproterozoic paleomagnetic data for these cratonic blocks suggest that East Columbia was short-lived. At 1.1 Ga ago, Amazonia/West Africa, Congo-São Francisco, Kalahari and India probably formed a megacontinent that later collided with Laurentia and Baltica forming Rodinia at ca. 1.0 Ga. Most probably, Rodinia broke-up at ca. 750 Ma, when Congo/São Francisco, Kalahari and other smaller blocks rotated ca. 90° counterclockwise, closing the Brasiliano/Clymene ocean and docked against Amazonia/West Africa and Rio de la Plata at ca. 600-570 Ma ago forming West Gondwana.

Clay mineral characterization is a valuable tool for unraveling the evolution of continental sedimentary basins. The Fiambalá basin is a foreland Andean basin located in the Southwest of the province of Catamarca (Argentina), on the flat subduction segment. In order to characterize its paleoenvironment and post-depositional evolution, petrographic, X-ray diffraction (XRD), and scanning microscopy (SEM-EDS) studies were carried out in detrital and volcaniclastic samples from the Tambería, Guanchín, and Rodados de la Puna Fms. Petrographic and XRD analyses show a predominance of phyllosilicates, quartz, plagioclase, and low proportions of feldspar and anhydrite, sporadic calcite, analcime, heulandite, and hematite. In the XRD fraction <2 μm, minerals from the smectite and illite groups dominate, with lower proportions of chlorite and kaolinite. An analyzed tuff level presents smectite solely in this fraction. The textural-compositional analyses of SEM-EDS show that illite and chlorite have a detrital origin. Their preservation would be consistent with the dominance of an arid climate in the region during the erosion and deposition of material from the source areas. The smectites are of the magnesium-rich beidellite-montmorillonite type and, together with the zeolites would be authigenic as a product of the alteration of both the volcanic material and magnesian detrital phases (chlorite and biotite), possibly under the influence of an alkaline environment related to the arid climate. From a thermal point of view, the presence of smectite throughout all stratigraphic succession allows interpreting maximum temperatures that, even in the deepest levels of the basin, inhibit the development of prograde phases (such as smectite/illite and smectite/chlorite mixed-layered) and allow the preservation of smectite. Based on the authigenic clays present in the basin, paleogeothermal gradients of between 13 and 18 °C/km (considered a fill of 4000 m thick) and between 8 and 11 °C/km (considered a fill of 6000 m thick) could be estimated.

A paleomagnetic and rock magnetic study was carried out in the Ediacaran Avellaneda (similar to 570 Ma) and Cerro Negro (similar to 555 Ma) Formations belonging to the La Providencia Group, in the upper part of the Neoproterozoic sedimentary cover of the Tandilia region, in the Rio de la Plata craton. The Avellaneda Formation was studied at outcrop level and in three drill cores, yielding a mean characteristic remanence direction of Dec: 21.4 degrees, Inc: 67.1 degrees, alpha(95): 4.2 degrees, k: 23.9, N: 51 and a paleomagnetic pole at 1.0 degrees S, 313.4 degrees E, A(95): 5.9 degrees. The Cerro Negro Formation yielded a mean characteristic direction of Dec: 22.0 degrees, Inc: 68.5 degrees, alpha(95): 10.3 degrees, k: 20.8, N: 11 obtained from a single drill core, from which a paleomagnetic pole at 3.6 degrees S, 307.8 degrees E, A(95): 16.6 degrees was computed. Rock magnetic data indicates that magnetic remanence is mainly associated with magnetite and hematite. The paleomagnetic information presented here results in a change in the previously accepted Late Ediacaran apparent polar wander path of the Rio de la Plata Craton. The newly obtained poles indicate that Rio de la Plata Craton experienced a rapid drift from a low latitudes location (ca. 19 degrees S) at ca. 600 Ma to moderately higher latitudes (between 50 degrees and 42 degrees S) from around 580 to 550 Ma.

Palaeomagnetic field behaviour within the Triassic is relatively poorly documented in comparison with other periods from across the last ca 250 Ma. Developing a more complete understanding of the Triassic field has important implications for discussion surrounding the Mesozoic Dipole Low (MDL) and the processes that govern field intensity and reversal regimes. We have conducted the first palaeosecular variation study that incorporates Triassic virtual geomagnetic pole (VGP) data, and analysed this data within the context of the average reversal frequency for the period. We observed remarkably similar VGP dispersion patterns from the late Permian, after the Permo-Carboniferous Reversed Superchron, until the onset of the Cretaceous Normal Superchron, despite fluctuating mean reversal rates. We have also completed palaeointensity experiments on samples with a range of lithologies collected from two localities in Argentina as well as pillow basalts from northern Italy. Previously published radiometric ages place our sampled lithologies across all three Triassic epochs, presenting an opportunity to populate the palaeointensity record at multiple ages across the ~50 Ma lacuna. Results were obtained utilizing a range of methods, the IZZI+ thermal Thellier, Shaw, and pseudo-Thellier. Estimates of virtual dipole moment from these experiments will be presented and discussed in the context of their reliability, and importance in better defining the MDL.

The Permian remagnetization belt that affects the southwestern margin of Gondwana has an important geographic extension reaching several South American cratons and terranes. A paleomagnetic pole for the Early Cambrian Guachos Formation in the Eastern Cordillera of Argentina was computed (LG: Lat: 58.1°S, Long: 20.2°E, A95: 6.4°, n: 30), that likely corresponds to a Permian remagnetization and suggests that such belt might extend further north than previously envisaged. We performed several rock-magnetic studies on this succession of laminated fine grain sandstones and siltstones in order to determine the magnetic phases that carry the remanence. Thermomagnetic (k vs. T) curves, field and frequency dependence of bulk susceptibility, hysteresis loops, isothermal remanent magnetization acquisition and back-field curves, three-axis IRM thermal demagnetization, among others, permitted to establish magnetite as the main mineral carrying the remanence. Microscopic observations confirmed a secondary chemical origin for magnetite. Magnetic fabric studies indicate a tectonic fabric, consistent with cleavage developed on these rocks together with low-grade metamorphism. However, a Permian remagnetization, as suggested by the paleomagnetic pole position, cannot be related to Cambrian deformation and metamorphism and might be related to hydrothermal processes.

The Río de la Plata craton is composed by the Piedra Alta and Tandilia terranes that achieved tectonic stability around 2.0 Ga. Paleomagnetic data are available for three short time spans. Nine pole positions for the Piedra Alta terrane in the interval 2.11–2.05 Ga suggest high latitudes with fast drift rates. Comparison with coeval poles from other cratons cast serious doubts on the existence and configuration of the mid-Paleoproterozoic Atlantica continent. A single pole from the 1.79 Ga Florida dyke swarm indicates low paleolatitudes, probably in the northern hemisphere, although its position in the Columbia (Nuna) supercontinent is ambiguous. The late Neoproterozoic is represented by seven pole positions from about 595 Ma to 550 Ma, suggesting fast drift in southern latitudes. Comparison of high quality poles c.575 Ma from West Gondwana cratons suggests that most of this continent was already assembled by middle Ediacaran.

The Special Issue on Paleomagnetism and Magnetic Fabrics in Latin America contains twenty-one original contributions ranging from Paleogeography and Tectonics to Paleosecular variation of the Earth Magnetic Field and Magnetic Fabrics applications, among others. They are good examples of the state-of-the-art of these disciplines applied to a broad range of Earth Sciences subjects in Latin America.