Pub Date : 2025-11-24DOI: 10.1016/j.jsames.2025.105882
Teal R. Riley , Andrew Carter
South Georgia forms one of the most isolated fragments of continental crust on Earth and lies in a remote location in the southern Atlantic Ocean. Its geology is dominated by Early Cretaceous back-arc turbidite successions that are in faulted contact with a late Palaeozoic – early Mesozoic accretionary complex. The accretionary complex includes fragments of a deformed accretionary prism and ophiolite that are intruded by a suite of granitoid plutons that are dated here. Granitoid magmatism has been identified from the Middle Jurassic (c. 163 Ma) and Late Cretaceous (c. 107 Ma, c. 86 Ma), which can be correlated with convergent margin magmatism from the southern (Fuegian) Andes and Cordillera Darwin of southern Patagonia, and the northern Antarctic Peninsula, with the Late Cretaceous magmatism restricted to the western parts of each area. These correlations support earlier findings that established a contiguous relationship between the southeast sector of South Georgia and southernmost Patagonia (south of the Magallanes fault zone) and the northern sector of Graham Land (Antarctic Peninsula).
{"title":"Age of granitoid magmatism in South Georgia and correlations to southern Patagonia and the northern Antarctic Peninsula","authors":"Teal R. Riley , Andrew Carter","doi":"10.1016/j.jsames.2025.105882","DOIUrl":"10.1016/j.jsames.2025.105882","url":null,"abstract":"<div><div>South Georgia forms one of the most isolated fragments of continental crust on Earth and lies in a remote location in the southern Atlantic Ocean. Its geology is dominated by Early Cretaceous back-arc turbidite successions that are in faulted contact with a late Palaeozoic – early Mesozoic accretionary complex. The accretionary complex includes fragments of a deformed accretionary prism and ophiolite that are intruded by a suite of granitoid plutons that are dated here. Granitoid magmatism has been identified from the Middle Jurassic (c. 163 Ma) and Late Cretaceous (c. 107 Ma, c. 86 Ma), which can be correlated with convergent margin magmatism from the southern (Fuegian) Andes and Cordillera Darwin of southern Patagonia, and the northern Antarctic Peninsula, with the Late Cretaceous magmatism restricted to the western parts of each area. These correlations support earlier findings that established a contiguous relationship between the southeast sector of South Georgia and southernmost Patagonia (south of the Magallanes fault zone) and the northern sector of Graham Land (Antarctic Peninsula).</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105882"},"PeriodicalIF":1.5,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145618118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Villarrica volcano is one of the most extensively studied active volcanic systems in the South American Andean range. However, the linkage between the volcano and its surrounding thermal waters remains poorly understood. In this study, we present a comprehensive geochemical investigation based on 52 samples of water and 9 dissolved gas samples collected from 18 sites during three field campaigns. Integrated analyses of physicochemical parameters, major ion species, minor elements, stable isotope ratios, and gas compositions have allowed us to identify and differentiate distinct hydrofacies. Our findings reveal that water-rock interaction, principally through plagioclase dissolution leading to Na enrichment, is the predominant process controlling the hydrochemistry. Furthermore, while the aquifers are heated by a deep magmatic reservoir and by the regional geothermal gradient, interactions with ascending hydrothermal gases are critical to the evolving water composition. In the southern area, the thermal waters are influenced by inputs of both CO2 and H2S, whereas in the northeastern area waters, only CO2 appears to dominate. Structural controls imposed by the Liquiñe-Ofqui Fault System and the Andean Transverse Faults play a predominant role in directing the ascent of gases, and influencing the geochemical signatures of the thermal waters. This study provides an update about the hydrothermal system related to Villarrica volcano, where new sampling sites were analyzed for the first time and new processes were recognized, constraining the hydrogeochemical model of the geothermal system.
{"title":"Hydrogeochemical controls on thermal springs around Villarrica volcano","authors":"Claudia Bucarey Parra , Joaquin Llano , Mariano Agusto , Gabriela Velásquez Vargas","doi":"10.1016/j.jsames.2025.105879","DOIUrl":"10.1016/j.jsames.2025.105879","url":null,"abstract":"<div><div>Villarrica volcano is one of the most extensively studied active volcanic systems in the South American Andean range. However, the linkage between the volcano and its surrounding thermal waters remains poorly understood. In this study, we present a comprehensive geochemical investigation based on 52 samples of water and 9 dissolved gas samples collected from 18 sites during three field campaigns. Integrated analyses of physicochemical parameters, major ion species, minor elements, stable isotope ratios, and gas compositions have allowed us to identify and differentiate distinct hydrofacies. Our findings reveal that water-rock interaction, principally through plagioclase dissolution leading to Na enrichment, is the predominant process controlling the hydrochemistry. Furthermore, while the aquifers are heated by a deep magmatic reservoir and by the regional geothermal gradient, interactions with ascending hydrothermal gases are critical to the evolving water composition. In the southern area, the thermal waters are influenced by inputs of both CO<sub>2</sub> and H<sub>2</sub>S, whereas in the northeastern area waters, only CO<sub>2</sub> appears to dominate. Structural controls imposed by the Liquiñe-Ofqui Fault System and the Andean Transverse Faults play a predominant role in directing the ascent of gases, and influencing the geochemical signatures of the thermal waters. This study provides an update about the hydrothermal system related to Villarrica volcano, where new sampling sites were analyzed for the first time and new processes were recognized, constraining the hydrogeochemical model of the geothermal system.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105879"},"PeriodicalIF":1.5,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-18DOI: 10.1016/j.jsames.2025.105877
Hermann D. Bermúdez , Vivi Vajda , Kajsa G.V. Sigfridsson Clauss , Courtney Jean Rundhaug , Gavin Kenny , Liliana Bolívar , Daniela Bermúdez , Ying Cui
The Chicxulub impact triggered a massive extinction event marked by the Cretaceous-Paleogene boundary (K-Pg ∼66Ma), ejecting vast amounts of dust, molten, and vaporized materials. While impact spherules are interpreted as products of impactor and target lithologies, their precise composition and distribution remain insufficiently constrained. Although previous studies restrict impactor contamination to the condensed spherules from the fireball layer and the K-Pg boundary clay, here we show asteroid contribution to the composition of large spherules from the base of the K-Pg bed. Despite those spherules displaying an apparent immiscible bimodal composition of yellow (Ca-rich) and black (Si-rich) glasses, novel nano-resolution analyses demonstrate enrichment of elements derived from the impactor. By analyzing pristine spherules from the normally-graded sequence of Gorgonilla Island K-Pg site, our results show the presence of metals and platinum group elements (PGEs) in glasses and vesicles within large molten spherules. Furthermore, needle-like and cubic-shaped nanostructures co-localizing Pt, Co, Ni, and Pb, and Cu, Os, and Zn, may represent the first evidence of quasicrystals (quasi-periodic solids, not found in terrestrial rocks, with symmetries forbidden for crystals) in Chicxulub-derived deposits. Those nanostructures challenge the definitions of microtektites and microkrystites, suggesting these classifications are misleading. We recommend abandoning such terminology, preserving the generic term "impact spherules," irrespective of composition, morphology, or size. Our findings contribute to refining the classification and interpretation of impact spherules, advancing our understanding of the processes underlying hypervelocity impacts. Moreover, these insights may hold relevance not only for terrestrial impacts but also for analogous extraterrestrial contexts.
{"title":"Unveiling the nature of glassy impact spherules by analyzing pristine Chicxulub spherules from Gorgonilla Island","authors":"Hermann D. Bermúdez , Vivi Vajda , Kajsa G.V. Sigfridsson Clauss , Courtney Jean Rundhaug , Gavin Kenny , Liliana Bolívar , Daniela Bermúdez , Ying Cui","doi":"10.1016/j.jsames.2025.105877","DOIUrl":"10.1016/j.jsames.2025.105877","url":null,"abstract":"<div><div>The Chicxulub impact triggered a massive extinction event marked by the Cretaceous-Paleogene boundary (K-Pg ∼66Ma), ejecting vast amounts of dust, molten, and vaporized materials. While impact spherules are interpreted as products of impactor and target lithologies, their precise composition and distribution remain insufficiently constrained. Although previous studies restrict impactor contamination to the condensed spherules from the fireball layer and the K-Pg boundary clay, here we show asteroid contribution to the composition of large spherules from the base of the K-Pg bed. Despite those spherules displaying an apparent immiscible bimodal composition of yellow (Ca-rich) and black (Si-rich) glasses, novel nano-resolution analyses demonstrate enrichment of elements derived from the impactor. By analyzing pristine spherules from the normally-graded sequence of Gorgonilla Island K-Pg site, our results show the presence of metals and platinum group elements (PGEs) in glasses and vesicles within large molten spherules. Furthermore, needle-like and cubic-shaped nanostructures co-localizing Pt, Co, Ni, and Pb, and Cu, Os, and Zn, may represent the first evidence of quasicrystals (quasi-periodic solids, not found in terrestrial rocks, with symmetries forbidden for crystals) in Chicxulub-derived deposits. Those nanostructures challenge the definitions of microtektites and microkrystites, suggesting these classifications are misleading. We recommend abandoning such terminology, preserving the generic term \"impact spherules,\" irrespective of composition, morphology, or size. Our findings contribute to refining the classification and interpretation of impact spherules, advancing our understanding of the processes underlying hypervelocity impacts. Moreover, these insights may hold relevance not only for terrestrial impacts but also for analogous extraterrestrial contexts.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105877"},"PeriodicalIF":1.5,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-14DOI: 10.1016/j.jsames.2025.105864
Emmanuel Bustamante-Fernandez, Sarah Woodroffe, Jeremy M. Lloyd
Stratigraphic sequences of coastal wetlands adjacent to active subduction zones permit us to reconstruct past earthquakes and tsunamis, estimate their recurrence intervals, spatial extent, and rupture characteristics, solving the limitations of short instrumental records. This study investigates the stratigraphy of the coastal wetland Estero Potrero Grande, located in the southern segment of the Jalisco subduction zone, in the Mexican Pacific. The stratigraphic sequences reveal eleven abrupt stratigraphic transitions interpreted as proxies for episodic submergence and emergence caused by coseismic land-level changes. Sedimentological and micropaleontological analyses reveal the coseismic origin of only six events, including four episodes of coseismic subsidence and two episodes of coseismic uplift, with half of these events accompanied by tsunami deposition. A Bayesian age-depth model, which integrates radiocarbon (14C) and cesium-137 (137Cs) chronologies, dates these events to 1907–1950 CE, 862–987 CE, 694–796 CE, 679–735 CE, 291–442 CE, and 128–288 CE. Based on the geometry of the megathrust fault, coastal coseismic subsidence is typically associated with shallow earthquakes, with ruptures constrained within the upper portion of the seismogenic zone (<30 km depth). In contrast, evidence of uplift reflects the occurrence of deeper ruptures that can be confined to the deepest portion of the seismogenic zone (up to 40 km depth). Additionally, our records reveal a rupture that very likely extended across the full width of the seismogenic zone, from its shallowest to deepest sections, causing a margin-wide event. These findings highlight the complexity of down-dip rupture segmentation pattenrs over Holocene time scales.
{"title":"Reconstructing coseismic subsidence and uplift from coastal stratigraphic sections in the Jalisco subduction zone, Mexico","authors":"Emmanuel Bustamante-Fernandez, Sarah Woodroffe, Jeremy M. Lloyd","doi":"10.1016/j.jsames.2025.105864","DOIUrl":"10.1016/j.jsames.2025.105864","url":null,"abstract":"<div><div>Stratigraphic sequences of coastal wetlands adjacent to active subduction zones permit us to reconstruct past earthquakes and tsunamis, estimate their recurrence intervals, spatial extent, and rupture characteristics, solving the limitations of short instrumental records. This study investigates the stratigraphy of the coastal wetland Estero Potrero Grande, located in the southern segment of the Jalisco subduction zone, in the Mexican Pacific. The stratigraphic sequences reveal eleven abrupt stratigraphic transitions interpreted as proxies for episodic submergence and emergence caused by coseismic land-level changes. Sedimentological and micropaleontological analyses reveal the coseismic origin of only six events, including four episodes of coseismic subsidence and two episodes of coseismic uplift, with half of these events accompanied by tsunami deposition. A Bayesian age-depth model, which integrates radiocarbon (<sup>14</sup>C) and cesium-137 (<sup>137</sup>Cs) chronologies, dates these events to 1907–1950 CE, 862–987 CE, 694–796 CE, 679–735 CE, 291–442 CE, and 128–288 CE. Based on the geometry of the megathrust fault, coastal coseismic subsidence is typically associated with shallow earthquakes, with ruptures constrained within the upper portion of the seismogenic zone (<30 km depth). In contrast, evidence of uplift reflects the occurrence of deeper ruptures that can be confined to the deepest portion of the seismogenic zone (up to 40 km depth). Additionally, our records reveal a rupture that very likely extended across the full width of the seismogenic zone, from its shallowest to deepest sections, causing a margin-wide event. These findings highlight the complexity of down-dip rupture segmentation pattenrs over Holocene time scales.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105864"},"PeriodicalIF":1.5,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-14DOI: 10.1016/j.jsames.2025.105878
Yellinson de M. Almeida , Henry Montecino C. , George Sand França , Aharon S. Cuevas
The processes responsible for triggering seismicity within intraplate regions remain incompletely understood. One proposed driver of such seismicity is the seasonal variation in hydrological loads, which may influence both the frequency and magnitude of earthquakes in these areas. In Brazil, the Parecis Basin has exhibited persistent seismic activity over recent years, with sporadic occurrences of earthquakes of considerable magnitude. In this study, we analyzed a seismic catalogue spanning from 2014 to 2022 to investigate potential correlations between seismicity and hydrological cycle in this region. We used geodetic data—including GPS positioning and satellite gravimetry—as well as precipitation records. The correlations between these observations and seismicity averaged −0.64 (TWSA-GRACE), 0.61 (VD-GPS), and −0.53 (precipitation), indicating that seismicity tends to increase in the Parecis Basin and adjacent areas at the end of the dry season. Temporal analysis of phase lags between hydrological indicators and seismic events suggests that the modulation of seismicity is driven primarily by the diffusion of pore pressure in the upper crust due to variations in hydrological loading.
{"title":"Can hydrological loads modulate intraplate seismicity in the Parecis Basin, Brazil?","authors":"Yellinson de M. Almeida , Henry Montecino C. , George Sand França , Aharon S. Cuevas","doi":"10.1016/j.jsames.2025.105878","DOIUrl":"10.1016/j.jsames.2025.105878","url":null,"abstract":"<div><div>The processes responsible for triggering seismicity within intraplate regions remain incompletely understood. One proposed driver of such seismicity is the seasonal variation in hydrological loads, which may influence both the frequency and magnitude of earthquakes in these areas. In Brazil, the Parecis Basin has exhibited persistent seismic activity over recent years, with sporadic occurrences of earthquakes of considerable magnitude. In this study, we analyzed a seismic catalogue spanning from 2014 to 2022 to investigate potential correlations between seismicity and hydrological cycle in this region. We used geodetic data—including GPS positioning and satellite gravimetry—as well as precipitation records. The correlations between these observations and seismicity averaged −0.64 (TWSA-GRACE), 0.61 (VD-GPS), and −0.53 (precipitation), indicating that seismicity tends to increase in the Parecis Basin and adjacent areas at the end of the dry season. Temporal analysis of phase lags between hydrological indicators and seismic events suggests that the modulation of seismicity is driven primarily by the diffusion of pore pressure in the upper crust due to variations in hydrological loading.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105878"},"PeriodicalIF":1.5,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-14DOI: 10.1016/j.jsames.2025.105876
Gabriel Legorreta Paulin , Marcus Bursik , Lilia Arana Salinas
Landslides occurring in deep and narrow valleys are common in Mexico because the poorly consolidated volcanic deposits are easily carved by rivers. They have the potential to impact society, disrupt infrastructure, and cause loss of life. This is the case for Ixtaccíhuatl volcano, the third highest stratovolcano in Mexico. This dormant volcano is prone to landslides due to earthquakes and the loose volcanoclastic deposits that are transported by stream floods, flash floods, and lahars during the rainy season. This study assessed and compared three landslide susceptibility models for the Xopanac watershed on the eastern flank of Iztaccíhuatl. In the watershed, unstable areas are mainly along first-order streams that carve deposits, whose stability has further decreased as a result of human activity. The susceptibility was modeled using a pre-existing landform unit model and two Multiple Logistic Regression (MLR) models, using the following variables: elevation, slope angle, aspect, curvature, drainage density, vertical erosion, land use, and with and without landform units. The resultant susceptibility maps were validated according to the Area Under the Curve (AUC) of the Receiver Operating Characteristic and by comparing the inventory map and the model in a contingency table. Both the area under the curve and the statistics from the contingency table indicate that the multiple logistic regression model using landform units has a higher predictive capacity than the multiple logistic regression model not using landform units and the pre-existing landform unit model. However, the multiple logistic regression model not using landform units is preferred over the other two models in areas with sparce information because it obtains a moderate result with fewer significant variables.
{"title":"Comparison of landslide susceptibility assessment in volcanic terrains based on a landform unit model and two multivariate logistic regression models","authors":"Gabriel Legorreta Paulin , Marcus Bursik , Lilia Arana Salinas","doi":"10.1016/j.jsames.2025.105876","DOIUrl":"10.1016/j.jsames.2025.105876","url":null,"abstract":"<div><div>Landslides occurring in deep and narrow valleys are common in Mexico because the poorly consolidated volcanic deposits are easily carved by rivers. They have the potential to impact society, disrupt infrastructure, and cause loss of life. This is the case for Ixtaccíhuatl volcano, the third highest stratovolcano in Mexico. This dormant volcano is prone to landslides due to earthquakes and the loose volcanoclastic deposits that are transported by stream floods, flash floods, and lahars during the rainy season. This study assessed and compared three landslide susceptibility models for the Xopanac watershed on the eastern flank of Iztaccíhuatl. In the watershed, unstable areas are mainly along first-order streams that carve deposits, whose stability has further decreased as a result of human activity. The susceptibility was modeled using a pre-existing landform unit model and two Multiple Logistic Regression (MLR) models, using the following variables: elevation, slope angle, aspect, curvature, drainage density, vertical erosion, land use, and with and without landform units. The resultant susceptibility maps were validated according to the Area Under the Curve (AUC) of the Receiver Operating Characteristic and by comparing the inventory map and the model in a contingency table. Both the area under the curve and the statistics from the contingency table indicate that the multiple logistic regression model using landform units has a higher predictive capacity than the multiple logistic regression model not using landform units and the pre-existing landform unit model. However, the multiple logistic regression model not using landform units is preferred over the other two models in areas with sparce information because it obtains a moderate result with fewer significant variables.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105876"},"PeriodicalIF":1.5,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-11DOI: 10.1016/j.jsames.2025.105867
Victor A. Ramos
This paper examines how the Continental Drift theory quickly gained traction in Argentina, based on evidence discovered by Hans Keidel, which Alfred Wegener utilized to reinforce his hypothesis. The correlation between the Ventania system in Argentina and the Cape system in South Africa was very compelling. Later, tectonics in our country embarked on the Geosyncline Theory, which gained many followers following the teachings of Ángel Borrello. During the 1970s, this theory was in strong dispute with the new basement tectonics theory, which applied the concepts of wrench tectonics. These eventually became dominant and together delayed the introduction of plate tectonics to the country. It was not until the late 1970s that the principles of the new tectonic theory began to be used to analyze the behavior of the Andes. In the early 1980s, it was put into effect through the recognition of different subduction segments with distinct inclinations, which led to the identification of the Pampean flat-slab. This new evidence allowed us to understand the structural characteristics of the Sierras Pampeanas and, based on this, to recognize the development of a broken foreland in central Argentina. Longitudinal variations in subduction allowed us to individually correlate the different Argentine geological provinces with their plate tectonic settings. The discovery of the Cuyania Terrane, an exotic block derived from Laurentia that collided with the Gondwanan margin, allowed us to identify other suspected terranes that slowly took over the Paleozoic tectonic evolution of this sector of Gondwana. These advances in plate tectonics paved the way for understanding the novel processes identified in the mantle, based on new high-resolution seismic tomography, which gave rise to a new revolution in geology known as mantle tectonics.
{"title":"From continental drift to plate tectonics in Argentina: a long journey","authors":"Victor A. Ramos","doi":"10.1016/j.jsames.2025.105867","DOIUrl":"10.1016/j.jsames.2025.105867","url":null,"abstract":"<div><div>This paper examines how the Continental Drift theory quickly gained traction in Argentina, based on evidence discovered by Hans Keidel, which Alfred Wegener utilized to reinforce his hypothesis. The correlation between the Ventania system in Argentina and the Cape system in South Africa was very compelling. Later, tectonics in our country embarked on the Geosyncline Theory, which gained many followers following the teachings of Ángel Borrello. During the 1970s, this theory was in strong dispute with the new basement tectonics theory, which applied the concepts of wrench tectonics. These eventually became dominant and together delayed the introduction of plate tectonics to the country. It was not until the late 1970s that the principles of the new tectonic theory began to be used to analyze the behavior of the Andes. In the early 1980s, it was put into effect through the recognition of different subduction segments with distinct inclinations, which led to the identification of the Pampean flat-slab. This new evidence allowed us to understand the structural characteristics of the Sierras Pampeanas and, based on this, to recognize the development of a broken foreland in central Argentina. Longitudinal variations in subduction allowed us to individually correlate the different Argentine geological provinces with their plate tectonic settings. The discovery of the Cuyania Terrane, an exotic block derived from Laurentia that collided with the Gondwanan margin, allowed us to identify other suspected terranes that slowly took over the Paleozoic tectonic evolution of this sector of Gondwana. These advances in plate tectonics paved the way for understanding the novel processes identified in the mantle, based on new high-resolution seismic tomography, which gave rise to a new revolution in geology known as mantle tectonics.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105867"},"PeriodicalIF":1.5,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145618116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
<div><div>Environmental magnetism methods were applied to surface lake sediments from seven basins located in a climosequence within the Transmexican Volcanic Belt and the Los Tuxtlas Volcanic Field in Central Mexico. The main aims are: 1) to determine the characteristics of magnetic mineralogy, 2) Evaluate the influence of climatic conditions and the geological age of source rocks on these characteristics. 3) Explore the relationship between magnetic mineral properties, climate and catchment age. 4) Integrate existing data from soil and paleosol profiles to provide a broader understanding of environmental and climatic controls on magnetic mineralogy. Results were compared to previous soil environmental magnetism analyses. Five end-members of magnetic components are recognized: 1) detrital partially oxidized Ti-magnetite, 2) pedogenic detrital magnetite, 3) authigenic magnetite formed from both biotic and abiotic processes, 4) detrital and 5) pedogenic hematite. The concentration of magnetic minerals and the distribution of grain sizes are closely linked to climatic regimes and hydrological dynamics. Lakes located in humid regions exhibit the highest concentration of magnetic mineral values, reflecting enhanced detrital input driven by rainfall-induced sediment flux. The observed differences between the magnetic parameters of soils and lacustrine sediments suggest that additional authigenic processes take place within the lakes, expanding the range of magnetic grain sizes and coercivities. This effect is particularly pronounced in warm and humid climates, where maghemitization and the mixing of detrital and authigenic components are more complex. Older basins (>1 Ma) are enriched in fine-grained (SD and SP) pedogenic magnetite and hematite, indicating a substantial soil-derived contribution<strong>.</strong></div></div><div><h3>Abstract</h3><div>Métodos de magnetismo ambiental fueron aplicados a sedimentos superficiales de lagos de siete cuencas ubicadas en una clímosecuencia dentro de la Faja Volcánica Transmexicana y el Campo Volcánico de Los Tuxtlas en el centro de México. Los objetivos principales son: 1) determinar las características de la mineralogía magnética, 2) evaluar la influencia de las condiciones climáticas y la edad geológica de las rocas fuente en estas características. 3) explorar la relación entre las propiedades minerales magnéticas, el clima y la edad de la cuenca. 4) integrar datos existentes de perfiles de suelos y paleosuelos para proporcionar una comprensión más amplia de los controles ambientales y climáticos en la mineralogía magnética. Los resultados se compararon con análisis previos de magnetismo ambiental de suelos. Se reconocen cinco miembros finales de los componentes magnéticos: 1)Ti- magnetita detrítica parcialmente oxidada, 2) magnetita detrítica pedogénica, 3) magnetita autigénica formada a partir de procesos bióticos y abióticos, 4) hematita detrítica y 5) pedogénica. La concentración de minerales magnétic
采用环境磁学方法对墨西哥中部跨墨西哥火山带和洛斯图克斯特拉斯火山田的7个盆地的表层湖泊沉积物进行了研究。主要目的是：1)确定磁性矿物学特征；2)评价气候条件和烃源岩地质年龄对这些特征的影响。3)探讨磁性矿物性质与气候、流域年龄的关系。4)整合现有的土壤和古土壤剖面数据，以更广泛地了解环境和气候对磁矿物学的控制。结果与以往的土壤环境磁性分析结果进行了比较。磁性组分有5个端元：1)碎屑部分氧化钛磁铁矿，2)成土碎屑磁铁矿，3)生物和非生物自生磁铁矿，4)碎屑和5)成土赤铁矿。磁性矿物的浓度和粒度分布与气候制度和水文动态密切相关。位于湿润地区的湖泊显示出最高的磁性矿物值浓度，反映了降雨引起的沉积物通量增加了碎屑输入。土壤和湖泊沉积物磁性参数的差异表明，湖泊内部发生了额外的自生过程，扩大了磁性粒度和矫顽力的范围。这种影响在温暖和潮湿的气候中特别明显，在那里岩浆化和碎屑和自生成分的混合更为复杂。较老的盆地（>1 Ma）富含细粒（SD和SP）成壤磁铁矿和赤铁矿，表明土壤来源的贡献很大。[摘要]磁与环境混合材料的应用与表面沉积技术的研究进展与进展与进展与进展的研究进展与进展与进展与进展的研究进展与进展与进展的研究进展与进展。目标和原则如下：1)确定características关于mineralogía马格里萨的情况；2)评价关于马格里萨的情况的影响climáticas关于马格里萨的情况的影响geológica关于马格里萨的情况的影响características。3)探索la relación中心las proedades minerales magnacticas， el气候la edad de la cuenca。4) integrar拿督存在de perfiles de suelos y paleosuelos对位proporcionar una comprension mas amplia de los还环境y climaticos en la mineralogia magnetica。这些结果可以与análisis以前的磁性和环境性研究进行比较。3)氧化钛（特别氧化钛），2)氧化钛（detrítica聚醚型），3)氧化钛（特别氧化钛），氧化钛（特别氧化钛），3)氧化钛（特别氧化钛），bióticos y abióticos, 4)氧化钛（detrítica y 5）聚醚型)。La concentración矿产资源管理组织与La distribución de los tamaños de grano están矿产资源管理组织与los regímenes climáticos y La dinámica hidrológica。Los lagos ubicados en regios húmedas向市长展示concentración关于矿物学的价值，请向市长汇报detrítico关于矿物学的价值，请向市长汇报。两个不同的观测点分别是：1 .观察点分别是：parámetros大汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织的汇变组织。Este effecto是特别的pronunciado en climas cálidos y húmedos， donde la maghemitización y la mezcla de components detríticos y autig尼科亚斯·más complexas。Las cuencas más antiguas (>1 Ma) están enriquecidas en magnetita y hematita pedógena de grano fino (SD y SP), lo que indica una contribución substance derivative ada del suelo。
{"title":"Magnetic mineral characteristics in lacustrine sediments from a climosequence in central Mexico","authors":"Beatriz Ortega -Guerrero , Sandra García-León , Arnaldo Hernández-Cardona , Daisy Valera- Fernández , Cecilia Caballero-Miranda , Elizabeth Solleiro-Rebolledo","doi":"10.1016/j.jsames.2025.105866","DOIUrl":"10.1016/j.jsames.2025.105866","url":null,"abstract":"<div><div>Environmental magnetism methods were applied to surface lake sediments from seven basins located in a climosequence within the Transmexican Volcanic Belt and the Los Tuxtlas Volcanic Field in Central Mexico. The main aims are: 1) to determine the characteristics of magnetic mineralogy, 2) Evaluate the influence of climatic conditions and the geological age of source rocks on these characteristics. 3) Explore the relationship between magnetic mineral properties, climate and catchment age. 4) Integrate existing data from soil and paleosol profiles to provide a broader understanding of environmental and climatic controls on magnetic mineralogy. Results were compared to previous soil environmental magnetism analyses. Five end-members of magnetic components are recognized: 1) detrital partially oxidized Ti-magnetite, 2) pedogenic detrital magnetite, 3) authigenic magnetite formed from both biotic and abiotic processes, 4) detrital and 5) pedogenic hematite. The concentration of magnetic minerals and the distribution of grain sizes are closely linked to climatic regimes and hydrological dynamics. Lakes located in humid regions exhibit the highest concentration of magnetic mineral values, reflecting enhanced detrital input driven by rainfall-induced sediment flux. The observed differences between the magnetic parameters of soils and lacustrine sediments suggest that additional authigenic processes take place within the lakes, expanding the range of magnetic grain sizes and coercivities. This effect is particularly pronounced in warm and humid climates, where maghemitization and the mixing of detrital and authigenic components are more complex. Older basins (>1 Ma) are enriched in fine-grained (SD and SP) pedogenic magnetite and hematite, indicating a substantial soil-derived contribution<strong>.</strong></div></div><div><h3>Abstract</h3><div>Métodos de magnetismo ambiental fueron aplicados a sedimentos superficiales de lagos de siete cuencas ubicadas en una clímosecuencia dentro de la Faja Volcánica Transmexicana y el Campo Volcánico de Los Tuxtlas en el centro de México. Los objetivos principales son: 1) determinar las características de la mineralogía magnética, 2) evaluar la influencia de las condiciones climáticas y la edad geológica de las rocas fuente en estas características. 3) explorar la relación entre las propiedades minerales magnéticas, el clima y la edad de la cuenca. 4) integrar datos existentes de perfiles de suelos y paleosuelos para proporcionar una comprensión más amplia de los controles ambientales y climáticos en la mineralogía magnética. Los resultados se compararon con análisis previos de magnetismo ambiental de suelos. Se reconocen cinco miembros finales de los componentes magnéticos: 1)Ti- magnetita detrítica parcialmente oxidada, 2) magnetita detrítica pedogénica, 3) magnetita autigénica formada a partir de procesos bióticos y abióticos, 4) hematita detrítica y 5) pedogénica. La concentración de minerales magnétic","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105866"},"PeriodicalIF":1.5,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-08DOI: 10.1016/j.jsames.2025.105863
Leonel Vitório Esteves , Carlos Fabricio Assunção da Silva , José Miguel Reichert , Artur Paiva Coutinho
Coastal areas in the state of Pernambuco in northeast Brazil have numerous records of floods that have worsened over the years, thus requiring hydrological studies to enhance decision-making in water resource management. This study analyzes simulations of the Sirinhaém River Basin (SRB) floodplain, in Pernambuco, under distinct land use conditions for the years 1992, 2002, 2012, and 2022, with return periods (RP) of 20, 50, and 100 years. Additionally, a scenario including the planned Barra de Guabiraba flood-control dam was simulated to evaluate its potential effectiveness in reducing peak discharges and flood extent within the basin. Intense rainfall equations were calculated using the disaggregation method, and the Curve Number (CN) was determined using the interpolation method. Hydrological modeling was performed using the HEC-HMS software, calibrated through the Nash-Sutcliffe Efficiency (NSE) method and Percent Bias (Pbias), while hydrodynamic modeling was conducted using HEC-RAS, with digital elevation models from the three-dimensional PE3d program. Calibration involved two stream gauges: Engenho Bento with an NSE of 0.556 and Pbias of 11.78 %, and Mato Grosso with an NSE of 0.607 and Pbias of −13.73 %. Across the basin, a total of 407 residences were identified as being at risk of flooding across the five studied municipalities. Changes in land use and land cover are contributing to increased flow rates and that the river basin requires the implementation of flood control dams, as occurrences are already reported for return periods above 20 years.
{"title":"Spatiotemporal simulation and analysis of coastal floodplain in Pernambuco, northeast Brazil","authors":"Leonel Vitório Esteves , Carlos Fabricio Assunção da Silva , José Miguel Reichert , Artur Paiva Coutinho","doi":"10.1016/j.jsames.2025.105863","DOIUrl":"10.1016/j.jsames.2025.105863","url":null,"abstract":"<div><div>Coastal areas in the state of Pernambuco in northeast Brazil have numerous records of floods that have worsened over the years, thus requiring hydrological studies to enhance decision-making in water resource management. This study analyzes simulations of the Sirinhaém River Basin (SRB) floodplain, in Pernambuco, under distinct land use conditions for the years 1992, 2002, 2012, and 2022, with return periods (RP) of 20, 50, and 100 years. Additionally, a scenario including the planned Barra de Guabiraba flood-control dam was simulated to evaluate its potential effectiveness in reducing peak discharges and flood extent within the basin. Intense rainfall equations were calculated using the disaggregation method, and the Curve Number (CN) was determined using the interpolation method. Hydrological modeling was performed using the HEC-HMS software, calibrated through the Nash-Sutcliffe Efficiency (NSE) method and Percent Bias (Pbias), while hydrodynamic modeling was conducted using HEC-RAS, with digital elevation models from the three-dimensional PE3d program. Calibration involved two stream gauges: Engenho Bento with an NSE of 0.556 and Pbias of 11.78 %, and Mato Grosso with an NSE of 0.607 and Pbias of −13.73 %. Across the basin, a total of 407 residences were identified as being at risk of flooding across the five studied municipalities. Changes in land use and land cover are contributing to increased flow rates and that the river basin requires the implementation of flood control dams, as occurrences are already reported for return periods above 20 years.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105863"},"PeriodicalIF":1.5,"publicationDate":"2025-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145521110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-07DOI: 10.1016/j.jsames.2025.105865
C. Ferreyra , B. Christofoletti , V. Penzo , G.C. Antunes , L.V. Warren , M.J. Arrouy , D.G. Poiré , L.E. Gómez-Peral
Following the development of the Piedra Amarilla Surface (PAS), where a major karstic unconformity formed during prolonged subaerial exposure, the Tandilia System underwent a profound paleoenvironmental shift in the early Ediacaran. These changes are recorded in the Colombo and Cerro Largo formations, which overlie the PAS and represent a large-scale transgressive–regressive cycle in the Sierras Bayas Group. This cycle begins with post-glacial deposits and culminates in a high-energy, storm-dominated shoreline system, marking a major reorganization of depositional environments in the basin. Sedimentological, stratigraphic, and paleocurrent analyses from eight measured sections identified twelve lithofacies, grouped into four facies associations, arranged in a coarsening-upward pattern from glacimarine deposits (FA-1) to offshore-transition deposits (FA-2), and finally to storm-wave and fair-weather-wave dominated shoreface deposits (FA-3 and FA-4, respectively). Paleocurrent data indicate a NE–SW-oriented paleoshoreline, with deeper marine areas toward the W–NW, in agreement with regional paleogeographic reconstructions. In this high-energy context, microbial mats played a key role in stabilizing substrates and preserving small-scale delicate sedimentary structures. The interpreted depositional model highlights the development of a high-energy overlaying shoreline glacimarine deposits and the dynamic interplay between storm and fair-weather wave processes in shaping early Ediacaran littoral systems.
{"title":"Storm-dominated coastal dynamics in the early Ediacaran record of Argentina","authors":"C. Ferreyra , B. Christofoletti , V. Penzo , G.C. Antunes , L.V. Warren , M.J. Arrouy , D.G. Poiré , L.E. Gómez-Peral","doi":"10.1016/j.jsames.2025.105865","DOIUrl":"10.1016/j.jsames.2025.105865","url":null,"abstract":"<div><div>Following the development of the Piedra Amarilla Surface (PAS), where a major karstic unconformity formed during prolonged subaerial exposure, the Tandilia System underwent a profound paleoenvironmental shift in the early Ediacaran. These changes are recorded in the Colombo and Cerro Largo formations, which overlie the PAS and represent a large-scale transgressive–regressive cycle in the Sierras Bayas Group. This cycle begins with post-glacial deposits and culminates in a high-energy, storm-dominated shoreline system, marking a major reorganization of depositional environments in the basin. Sedimentological, stratigraphic, and paleocurrent analyses from eight measured sections identified twelve lithofacies, grouped into four facies associations, arranged in a coarsening-upward pattern from glacimarine deposits (FA-1) to offshore-transition deposits (FA-2), and finally to storm-wave and fair-weather-wave dominated shoreface deposits (FA-3 and FA-4, respectively). Paleocurrent data indicate a NE–SW-oriented paleoshoreline, with deeper marine areas toward the W–NW, in agreement with regional paleogeographic reconstructions. In this high-energy context, microbial mats played a key role in stabilizing substrates and preserving small-scale delicate sedimentary structures. The interpreted depositional model highlights the development of a high-energy overlaying shoreline glacimarine deposits and the dynamic interplay between storm and fair-weather wave processes in shaping early Ediacaran littoral systems.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"169 ","pages":"Article 105865"},"PeriodicalIF":1.5,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145521111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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