Journal of South American Earth Sciences最新文献

{"title":"Uncertainty analysis of sediment size estimations in gravel-bed reaches in Southern Brazil","authors":"F.C. Zambrano ,&nbsp;Masato Kobiyama ,&nbsp;Gabriel Narváez Campo","doi":"10.1016/j.jsames.2025.105544","DOIUrl":"10.1016/j.jsames.2025.105544","url":null,"abstract":"<div><div>Understanding sediment size distribution is essential for comprehending the hydrogeomorphological dynamics of mountain river systems. Manual and automated techniques for sampling surface sediments in gravel-bed rivers can generate uncertainties naturally. This study aims to comprehend field-walking techniques (manual) and photogrammetric analysis (automation) by estimating uncertainties in sediment size distribution. Measurements were conducted at five sites along the Forromeco River in southern Brazil, including field pebble counting and UAV-based photogrammetry. To calculate the nominal diameter, field measurements provide three axes of the sediment, while photogrammetry only two. A binomial probability distribution model was applied to estimate the percentile confidence interval of sediment size, thus enabling an assessment of the uncertainty between the adopted techniques. Results indicate that 3-axis measurements generally yield smaller sediment sizes compared to 2-axis methods, reflecting the influence of the sediment shape on the shortest axis magnitude. Statistical analysis by site showed no differences between the nominal diameter computed with 3-axis or 2-axis. However, a four sites ensemble revealed discrepancies. Drone-derived measurements, while efficient, tended to overlook finer sediments and overestimate larger sizes, particularly in areas with vegetation obstacles. The present study highlights the importance of considering the sediment shape, sediment configuration and regional lithology when interpreting drone data. Overall, the 3-axis field pebble counting method provides more accurate sediment size characterization in mountain rivers like the Forromeco. This research contributes to the understanding of sediment dynamics in mountainous regions, aiding in the management of water and sediment resources, and mitigating flood-related disasters.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105544"},"PeriodicalIF":1.7,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874313","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}

{"title":"Climatic, anthropogenic and sea level influences on the vegetation landscape of a lagoonal system, over the last 3350 years","authors":"Victor Rocha Carvalho ,&nbsp;Adriana Leonhardt ,&nbsp;Felipe García-Rodríguez ,&nbsp;Andreia Souza Pereira de Ávila ,&nbsp;Silvia Regina Bottezini ,&nbsp;Débora Pimentel Diniz ,&nbsp;Marlon Carlos França ,&nbsp;Paula Dentzien-Dias","doi":"10.1016/j.jsames.2025.105535","DOIUrl":"10.1016/j.jsames.2025.105535","url":null,"abstract":"<div><div>This study explores the influence of dry and wet weather events, sea-level fluctuations, and anthropogenic activities on vegetation dynamics over the past 3,350 cal years BP. Sedimentological and palynological analyses were supported by radiocarbon (¹⁴C) and lead-210 (²¹⁰Pb) dating of a 110 cm sediment core (GAR 1) extracted from the northwest sector of the Garzón Lagoon, Uruguay. Lagoon is an intermittently closed system, periodically opening to the sea, with a maximum depth of 5 m. Two different time windows are presented: part of the late Holocene and the last 150 years. Between 3,350 and 2,345 cal years BP, sea levels were high, and the lagoon maintained a broad connection to the sea, favoring halophytic vegetation, including Amaranthaceae and Poaceae, indicative of a salt marsh environment. After 2,345 cal yr BP, an increase in freshwater algae <em>Botryococcus</em> spp., resulting from a brief eutrophication episode, and a pronounced rise in arboreal taxa, particularly the Moraceae/Urticaceae group, signaled a shift towards a more freshwater-influenced system. The contemporary period (1841–2021 CE) is marked by pronounced climatic variability, alternating wet and dry episodes, and intensified anthropogenic activities, including <em>Pinus</em> spp. afforestation and expanded agricultural practices. These human interventions significantly impacted sedimentation rates and influenced the Garzón lagoon's ecological dynamics.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105535"},"PeriodicalIF":1.7,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877192","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}

{"title":"Unprecedented flooding in Porto Alegre Metropolitan Region (Southern Brazil) in May 2024: Causes, risks, and impacts","authors":"José Roberto Mantovani ,&nbsp;Enner Alcântara ,&nbsp;Cheila Flávia Baião ,&nbsp;Luana Pampuch ,&nbsp;Marcelo Pedroso Curtarelli ,&nbsp;João Vitor Mariano Ribeiro ,&nbsp;Yasmim Carvalho Guimarães ,&nbsp;Luciana Londe ,&nbsp;Klécia Massi ,&nbsp;José Marengo ,&nbsp;Carlos Afonso Nobre ,&nbsp;Arcilan Trevenzoli Assireu ,&nbsp;Cassiano Antonio Bortolozo ,&nbsp;Silvio Jorge Simões ,&nbsp;Javier Tomasella ,&nbsp;Osvaldo Luiz Leal de Moraes ,&nbsp;Edward Park","doi":"10.1016/j.jsames.2025.105533","DOIUrl":"10.1016/j.jsames.2025.105533","url":null,"abstract":"<div><div>On May 2, 2024, Porto Alegre in Rio Grande do Sul, Brazil, experienced a historic flood surpassing the catastrophic 1941 event. The flood's peak water level of 535 cm was 59 cm higher than in 1941, driven by extreme precipitation anomalies and land use changes in the Regional Metropolitan Area of Porto Alegre, with rainfall accumulations up to 500 mm in May 2024. Severe urban flooding impacted riverbanks and low-lying areas, causing significant property damage, displacement, and disruption of essential services. Agricultural lands and grasslands were extensively affected. Detailed maps from May 3 to May 8, 2024, showed floodwaters rising from 5.5 m to 8 m. Validation sample points ensured data accuracy, and flood model validation metrics (NSE = 0.63, R² = 0.71, RMSE = 0.51 m) demonstrated the model's predictive accuracy. Water level fluctuations at Cais Guaíba station revealed rapid rise and recession periods typical of major floods. This study highlights the urgent need for effective flood mitigation strategies, informed by accurate modeling and risk assessment, to protect vulnerable communities and infrastructure. Enhancing resilience through improved urban planning, infrastructure investment, and environmental conservation is crucial to safeguarding Porto Alegre and the broader RMPOA region from future extreme weather events. These findings offer valuable insights for other flood-prone tropical and developing regions, where the combined effects of urban expansion and intensifying climate extremes similarly increase flood risk.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105533"},"PeriodicalIF":1.7,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852006","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}

{"title":"Parameterized models for estimating atmospheric longwave radiation and surface net radiation in the Brazilian semi-arid region","authors":"Delson J.F. Silva ,&nbsp;Tarciana R.B.F. Silva ,&nbsp;Michele L. de Oliveira ,&nbsp;Gabriel de Oliveira ,&nbsp;Manoranjan Mishra ,&nbsp;Celso Augusto Guimarães Santos ,&nbsp;Richarde Marques da Silva ,&nbsp;Carlos A.C. dos Santos","doi":"10.1016/j.jsames.2025.105534","DOIUrl":"10.1016/j.jsames.2025.105534","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study seeks to understand and estimate atmospheric longwave irradiance (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;l&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and surface net radiation (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) using parameterized models applied to semi-arid regions of northeastern Brazil. Studies on surface energy flows are of interest to areas such as environmental and agricultural sciences, and are of great importance in analyzing and managing water resources. Thus, this research could benefit the study region, which constantly experiences periods of water scarcity that affect agricultural activities and the lives of communities. An exploration of data gathered from micrometeorological stations spanning the period from 2014 to 2016 within various caatinga vegetation areas exhibiting distinct levels of preservation. This exploration involved comparative analyses between methods available in existing literature and those proposed by the authors. The biome under study is unique to Brazil and remains relatively underexplored in terms of comprehensive research and studies. In the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;l&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; analysis, parameterizations for days with clear and cloudy skies were considered, and the proposed models presented results that surpassed the results of most of the tested models in the literature. Among the models examined, the Crawford and Duchon (1999) model displayed remarkable efficiency in estimating &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;l&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; within the study area. Furthermore, the models were fine-tuned to estimate the surface &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; for the respective areas of each micrometeorological station. These calibrations factored in both dry and rainy seasons for the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; analyses. The calibration results were satisfactory, with r&lt;sup&gt;2&lt;/sup&gt; values for the proposed models greater than 0.90 for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;l&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; for clear sky conditions and 0.94 for all conditions, and a high agreement was shown with values greater than 0.96 according to the criteria of Willmott et al. (2012). The results for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; show the potential of the models to contribute, for example, to measuring water loss from a vegetated surface, an essential task in agricultural planning. Among the tested models, the one developed by Crawford and Duchon (1999) proved to be very efficient in estimating the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;l&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in the study area. The models were adjusted to estimate the surface &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/msub&gt;&lt;/","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105534"},"PeriodicalIF":1.7,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874312","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}

{"title":"Tectonic geomorphology of mountain relief in the northeast of Mexico. Example of the Santa Rosa, Obayos and Pájaros Azules ranges","authors":"Yuri Almaguer-Carmenates,&nbsp;José Alberto Batista-Rodríguez,&nbsp;Ramón Yosvanis Batista-Cruz,&nbsp;Felipe de Jesús López-Saucedo","doi":"10.1016/j.jsames.2025.105513","DOIUrl":"10.1016/j.jsames.2025.105513","url":null,"abstract":"<div><div>A tectonic geomorphology analysis was carried out in the Santa Rosa, Obayos and Pájaros Azules ranges, with the aim of delving deeper into the regional geological characteristics of northeastern Mexico. The digital processing and interpretation of morphometric maps and geomorphic indices derived from a digital elevation model (DEM) at a scale of 1:50,000 was carried out. Hypsometric, surface drainage, slope, roughness, vertical dissection (VD), isobase, channel gradient and mountain-front sinuosity index maps were interpreted. The analysis reveals, in the Obayos and Pájaros Azules ranges, the development of internal valleys with fluvial drainage to the NE, parallel to the axis of the homonymous anticlines. The Santa Rosa range has a higher altitude and gradient than Obayos and Pájaros Azules. According to the 2nd- and 3rd-order isobases, the Santa Rosa range has higher altitudes (1485 m and 1539 m) than Pájaros Azules (1476 m and 878 m) and Obayos (1163 m and 1085 m), respectively. Morphoalignments with NE-SW directions were identified that are arranged transversely to the axes of the anticlines that form the ranges. In the Santa Rosa SE area, the morphoalignments are radial and coincide with basaltic outcrops; this suggests extensional processes due to the flexure of the anticline axis, which generated fissures and caused the ascent of igneous material. The relief in the Obayos and Pájaros Azules ranges is more evolved, due to a greater structural uplift and denudation. In contrast, the Santa Rosa range exhibits a younger relief. The sinuosity index of the mountain front indicates that the three mountain ranges present a moderate level of tectonic activity, with the Obayos mountain range having the lowest Smf value (1.65) and the greatest tectonic activity. These morphotectonic findings show the relationship between regional tectonic evolution and morphogenic processes in NE Mexico.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105513"},"PeriodicalIF":1.7,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143855407","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}

{"title":"Phrynops Wagler, 1830 (Testudines, Chelidae) in the Late Miocene of Palo Pintado Formation, Salta Province, Argentina, with comments on taxonomy and paleoenvironmental settings","authors":"Marcelo S. de la Fuente ,&nbsp;Carlos A. Luna ,&nbsp;Alfredo E. Zurita ,&nbsp;Claudia I. Galli ,&nbsp;Sofía I. Quiñones ,&nbsp;Juan M. Robledo ,&nbsp;Adriana M. Candela ,&nbsp;Enzo M. Landa Ramírez ,&nbsp;Pablo González Ruiz ,&nbsp;Ricardo N. Alonso","doi":"10.1016/j.jsames.2025.105530","DOIUrl":"10.1016/j.jsames.2025.105530","url":null,"abstract":"<div><div>Pleurodiran chelid turtles are represented from the Late Miocene in northeastern and northwestern Argentina by species assigned to <em>Phrynops sensu stricto</em> = <em>Phrynops geoffroanus</em> complex. In the northeastern region, these turtles include the extinct species <em>Phrynops paranensis</em> (Wieland, 1923) from the Ituzaingó Formation, Entre Ríos Province. On the other hand, from the Late Miocene of northwestern Argentina, <em>Phrynops</em> specimens involve unnamed species coming from El Morterito (Cajon Valley, Catamarca Province) and Andalhualá (Tiopunco, Santa María Valley, Tucumán Province) formations. In this contribution, a new and relatively complete specimen assigned to <em>Phrynops sensu stricto</em> (<em>Phrynops</em> sp.) from the upper levels of the Palo Pintado Formation exposed in Quebrada Salta (Salta Province) is described and compared. The particular morphology of the specimen analyzed, different both from <em>Phrynops paranensis</em>, the only extinct species recognized for the genus, as well as from the current species of the genus, suggests the presence of at least two taxa in the Late Miocene of Argentina, one limited to the northeastern region (<em>Phrynops paranensis</em>) and another as yet unnamed from the northwestern region. Sedimentological analysis and fossil evidence analyzed for the sector strongly suggest the development of a tropical climate during the deposition of the Palo Pintado Formation. Considering that <em>Phrynops sensu stricto</em> spp. currently inhabiting freshwater lowlands in tropical to humid temperate climates, the presence of this aquatic species is consistent with the paleoenvironmental conditions previously interpreted for this unit.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105530"},"PeriodicalIF":1.7,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143838293","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}

{"title":"Freshening processes in a prograding littoral system of the Río de la Plata–sea interaction area","authors":"Maria Paula Leal ,&nbsp;Eleonora Carol ,&nbsp;Santiago Perdomo","doi":"10.1016/j.jsames.2025.105522","DOIUrl":"10.1016/j.jsames.2025.105522","url":null,"abstract":"<div><div>The aim of this study is to evaluate groundwater freshening processes and the development of freshwater lenses in a littoral environment associated with the coastal progradation of beach ridges in the coastal area associated to the interaction zone of the Río de la Plata and the sea. To achieve this, a geomorphological analysis was conducted through the interpretation of satellite imagery, digital elevation models, and field observations, along with sediment sampling and texture analysis. Based on the geomorphology, transects were defined for conducting electrical resistivity tomography (ERT), and a monitoring network for groundwater and surface water was established. In situ measurements of pH and electrical conductivity (EC) were made, and water samples were collected for major ion determination. The geomorphological, sedimentological, geophysical, and hydrochemical studies have identified areas where freshening processes generate freshwater lenses in a littoral environment, initially dominated by saline water. These freshening processes are directly associated with the infiltration of rainwater under humid climate conditions and water surpluses. Infiltration primarily occurs in beach ridge deposits, which are positive landforms with high permeability. Spatially, it was observed that the formation of freshwater lenses mainly occurs in the more continental environments (older within the progradation of the beach ridges), where beach ridges exhibit greater topographic expression and are typically amalgamated deposits. In contrast, in the more coastal zones near the estuary, the development of freshwater lenses is limited by the lower topography of the deposits, which restricts rainwater infiltration and, consequently, reduces freshening processes. A similar situation occurs in the inter-ridge depressions towards the continental zone, where rainwater infiltration is present but limited, resulting in areas of freshwater-saline water mixing. This analysis of the distribution of freshwater lenses demonstrates spatial variation in freshening processes that is controlled not only by geomorphology (presence of beach ridges) but also by the evolutionary sequence of these landforms (progradation). The findings from this study are crucial for the development of sustainable water management and supply strategies in coastal regions, like the one studied, where freshwater resources are scarce.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"159 ","pages":"Article 105522"},"PeriodicalIF":1.7,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820503","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}

{"title":"Reconstructing Paleoproterozoic volcanic environments: Eruptive styles and evidence of phreatomagmatism in the Amazonian Craton's Colíder Group","authors":"André Massanobu Ueno Kunifoshita ,&nbsp;Maria José Mesquita ,&nbsp;Felipe Holanda dos Santos ,&nbsp;Carlos Augusto Sommer","doi":"10.1016/j.jsames.2025.105531","DOIUrl":"10.1016/j.jsames.2025.105531","url":null,"abstract":"<div><div>Paleoproterozoic rocks are essential for understanding Earth's tectonic evolution, particularly in regions where juvenile crust and ore deposits formed. The Amazonian Craton features well-preserved Paleoproterozoic volcanic records, including age ranges linked to the Orocaima, Uatumã, and Colíder Silicic Large Igneous Provinces (SLIPs). Stratigraphic frameworks are supported by the description and interpretation of lithofacies. In the present work, we identify different eruptive styles (effusive and explosive) of the Colíder Group in the Alta Floresta Mineral Province. We have also described, for the first time in Alta Floresta Mineral Province, deposits associated with a phreatomagmatic eruption. The ancient volcanic successions comprises massive hypohyaline rhyolite lavas representing effusive dynamisms, with crystallization ages (U-Pb in zircon) around 1800 Ma, while lapilli tuff and tuffs represent explosive deposits with massive and stratified structures. The pyroclastic rocks compose an ignimbrite deposit. Four types of ash aggregates (ash pellets, coated ash pellets, accretionary lapilli, cored accretionary lapilli) suggest an origin associated with phreatomagmatic deposits. Additionally, epiclastic deposits are characterized by the reworking of primary volcanic rocks and basement rocks. These different eruptive styles allow us to reconstruct a paleoenvironment where water and magma interact during volcanic eruptions. This setting is typical in ancient and recent volcanic calderas, intra-caldera basins, or calderas where there is direct contact with seawater or riverine waters. Our discovery provides new data for the reconstruction of this Paleoproterozoic volcanic terrane and will be valuable for interpreting the geological evolution of this craton in the future.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"159 ","pages":"Article 105531"},"PeriodicalIF":1.7,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143829545","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}

{"title":"Plio-Holocene magmatic evolution during a steepening subduction regime","authors":"Sofía B. Iannelli ,&nbsp;Carina Greco ,&nbsp;Lucía Fernández Paz ,&nbsp;Carlos Pallares ,&nbsp;Vanesa D. Litvak ,&nbsp;Andrés Folguera","doi":"10.1016/j.jsames.2025.105529","DOIUrl":"10.1016/j.jsames.2025.105529","url":null,"abstract":"<div><div>From the late Pliocene to Holocene times, magmatism in the Southern Central Andes (34–38.5 °S) displayed significant geochemical changes that show a systematic variation with both time and location. These changes have primarily been linked to the steepening of the Nazca plate after its shallow subduction configuration in the late Miocene. As a result, Plio-Holocene magmatism developed in three N-S magmatic belts, located within the present-day arc front, the rear-arc, and the back-arc areas. This work presents the compilation of geochemical data (major and trace elements, and Sr-Nd-Pb isotopes) and geochronological data (Ar-Ar, K-Ar, U-Pb) from the Plio-Holocene rear-arc and back-arc magmatic sequences to evaluate the magmatic evolution since the beginning of the Nazca plate steepening in the latest Pliocene.</div><div>The back-arc volcanic sequences show a decrease in arc-like geochemical features and an increase in the concentration of incompatible elements from the northern to the southern back-arc units. This change has primarily been attributed to variations in the mantle source, with southern magmatism associated with an EM-1 OIB type source and northern volcanism related to an N-MORB mantle source. However, other processes, such as changes in the thermal structure of the mantle wedge, along-strike variations in crustal thickness, and forearc subduction erosion, are essential to explain other geochemical features. On the other hand, the geochemistry of the Plio-Holocene rear-arc magmatism slightly reflects the geochemical patterns of the back-arc magmatism, as the northern rear-arc units present arc-like features, while the southern rear-arc shows an incipient intraplate-like signature. Thus, regarding the varying distances to the trench between back-arc and rear-arc units, first-order controls such as heterogeneities in ambient mantle composition and the thermal structure of the mantle wedge have influenced the magmatism of the Southern Central Andes.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"160 ","pages":"Article 105529"},"PeriodicalIF":1.7,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143844752","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}

{"title":"The dynamics of debris-flow events in Southeast Brazil","authors":"Victor Cabral ,&nbsp;Fábio Augusto Gomes Vieira Reis ,&nbsp;Vinicius Queiros Veloso ,&nbsp;Thamiris Costa Basilio ,&nbsp;Claudia Vanessa dos Santos Corrêa ,&nbsp;Christiane Zarfl","doi":"10.1016/j.jsames.2025.105523","DOIUrl":"10.1016/j.jsames.2025.105523","url":null,"abstract":"<div><div>Debris flows are a significant threat in mountain areas in Southeast Brazil. Understanding their dynamics and how a catchment morphology influences an event's magnitude and associated negative impacts is, therefore, relevant. Our goal is to compare the dynamics of debris-flow events (e.g., initiation mechanism, kinematic parameters) in four catchments located in the Southeastern portion of the Serra do Mar Mountain range, highlighting their similarities and differences. We also aim at establishing a general relationship between catchment morphometry and magnitude, based on a Spearman rank correlation analysis. Field campaigns were conducted to investigate the catchments, which were further supported by the acquisition of cartographic and remote sensing data, numerical simulation using RAMMS and rainfall analysis. Our results show that the debris-flow events are characterized by an association between debris flows, debris floods and flash floods, which is directly related to the morphology of the catchments and rainfall intensity. Considering the magnitude of the debris-flow events, Relief ratio is interpreted have a more significant impact among the morphometric parameters, according to the Spearman rank correlation analysis. Moreover, the rainfall accumulated in 48 h prior to an event showed a very strong correlation with the overall magnitude, highlighting the main role that rainfall has in debris-flow initiation and associated damage. Our study highlights the main geodynamic processes that can occur in catchments at Serra do Mar and how both morphometry and rain intensity are directly related to their occurrence.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"159 ","pages":"Article 105523"},"PeriodicalIF":1.7,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143826166","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}