Journal of South American Earth Sciences最新文献

{"title":"Assessment of soil loss and amount of sediment exported and deposited in Upper Grande River Basin (Brazil) considering different scenarios","authors":"R. Cassaro ,&nbsp;J.Z. Lima ,&nbsp;R.R.M. Ferreira ,&nbsp;V.G.S. Rodrigues","doi":"10.1016/j.jsames.2026.105977","DOIUrl":"10.1016/j.jsames.2026.105977","url":null,"abstract":"<div><div>Understanding erosion patterns and drivers of soil in tropical catchments is essential for its effective conservation, especially under increasing climate change uncertainties. In this study, the Integrated Valuation of Ecosystem Services and Tradeoffs – Sediment Delivery Ratio (InVEST-SDR) model assessed soil loss, sediment export, and deposition in the Upper Grande River Basin (UGRB) in Brazil. The model inputs included digital terrain model (30 m × 30 m), 40 years of rainfall data, soil map, land use and land cover data, biophysical table, and calibration parameters. The results showed soil loss varied significantly in response to rainfall erosivity, with the lowest estimated soil loss of 11.29 Mg ha⁻¹ year⁻¹ occurring in 2014, when a severe drought in southeastern Brazil reduced rainfall erosivity to 2734.50 MJ mm ha⁻¹ h⁻¹ year⁻¹. Total soil loss hotspots due to steep slopes and high erosivity were identified in the southern basin region; however, the local soils are shallow and poorly evolved, limiting actual erosion rates. InVEST's reliance on USLE factors such as slope and erosivity leads to an overestimation of soil loss in areas with steeper terrain. Two future land use scenarios were analyzed considering climate change uncertainties. In Scenario 1, the replacement of pastures with temporary crops reduced soil losses from 33.27 Mg ha⁻¹ year⁻¹ (actual use) to 29.76 Mg ha⁻¹ year⁻¹ in 2004–2013, with a slight increase occurring in 2014–2023 (from 25.21 Mg ha⁻¹ year⁻¹ to 27.12 Mg ha⁻¹ year⁻¹). In Scenario 2, replacing pastures with planted forests reduced losses from 6.74 Mg ha⁻¹ year⁻¹ (actual use) to 3.11 Mg ha⁻¹ year⁻¹ in 2004–2013, with stable values in the following decade (2.94 Mg ha⁻¹ year⁻¹). The findings emphasize the potential of land use changes, such as adoption of planted forests, as a sustainable strategy to reduce soil loss, enhance climate change resilience, and keep a profitable activity for farmers. InVEST-SDR effectively assessed soil erosion and sedimentation, offering valuable insights for soil conservation and ecological restoration in tropical regions.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105977"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080256","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":"Geology, U-Pb geochronology, and petrological affinity of peraluminous granitoids in Carajás Province, SE Amazonian Craton","authors":"Heron Silva Bezerra da Costa ,&nbsp;Davis Carvalho de Oliveira ,&nbsp;Bhrenno Marangoanha ,&nbsp;Marco Antônio Galarza ,&nbsp;Williamy Queiroz Felix ,&nbsp;Yury Harrison da Costa Reis ,&nbsp;Ana Carolina Mendes da Silva ,&nbsp;Elizangela de Jesus Vasconcelos","doi":"10.1016/j.jsames.2026.105961","DOIUrl":"10.1016/j.jsames.2026.105961","url":null,"abstract":"<div><div>Peraluminous magmatism records crustal reworking processes and provides important information about the evolution of continental crust. Peraluminous granitoids are uncommon in Archean geology, reflecting the unusual nature of processes at the time. In this context, the Vila Minerasul area in central-western Carajás Province contains a complex geological framework comprised of multiple granitoid plutons with distinct petrogenetic affinities. The main pluton has biotite as its main ferromagnesian mineral and is distinguished by the presence of primary muscovite as a varietal phase. This pluton is elongated in an E-W direction, covering an area of approximately 75 km² and delineated by shear zones. It comprises three lithological facies: muscovite-biotite granodiorite, biotite-muscovite granodiorite, and muscovite-biotite monzogranite. Deformational microstructures reveal the syntectonic character of this pluton, which has zones of low and high strain and deformation temperatures ranging from 300 to 600 °C. The rocks are magnesian, calc-alkaline, and highly peraluminous (A/CNK &gt;1.1). They present low HFSE and high LILE contents and a slight negative Eu anomaly. Compared to the main granitoid units of the Carajás Province, the peraluminous pluton of Vila Minerasul has a stronger affinity for potassic granites, differing by its higher A/CNK values. The crystallization age of this pluton is 2918.5 ± 5.1 Ma, although zircon populations between 2.94 Ga and 3.17 Ga are thought to be inherited. Two younger populations (2888.2 ± 6.7 Ma, 2839 ± 10 Ma) are thought to be rejuvenated metamict ages or regional metamorphic overprints. These rocks are considered to have formed in a collisional environment, with petrogenesis involving partial melting of TTG crust and the incorporation of metasedimentary components.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105961"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001838","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 fate of back-arc basins: a constrained geodynamic model for the Bransfield basin case","authors":"Gonzalo Yanez ,&nbsp;Jorge Sanhueza ,&nbsp;Juan Carlos Parra","doi":"10.1016/j.jsames.2026.105963","DOIUrl":"10.1016/j.jsames.2026.105963","url":null,"abstract":"<div><div>Back-arc basin development is a relatively common and episodic geological process. In all the models proposed subducting slab play a key role. The most common setting is old/cold subducting slabs with island arcs/oceanic overriding plates, and strong corner flow. In contrast, young subducting slabs, continental overriding plates and weak asthenospheric flow is a rare combination for the development of back-arc basins In this particular tectonic setting the driving mechanisms are poorly understood.</div><div>In this communication, we develop a well-constrained thermomechanical geodynamic model to offer insights into the geological processes that allow the development of back-arc basins with a young slab as a driving force. As a case study, we use the Bransfield back-basin in the Antarctic Peninsula. This back-arc basin is a relatively well-constrained case, where independent geophysical proxies can be used to validate the scenarios obtained by the geodynamic model. Geophysical data used for validation purposes include, satellite-derived gravity, regional and local airborne magnetic surveys, natural seismicity, and heat-flow measurements. Geodynamic models, data and information derived from the geophysical proxies offer consistent results.</div><div>The implication of the modelling effort is that, back-arc basins can develop when plate kinematics suddenly stop. In such a particular tectonic setting the subducting slab collapses producing a roll-back effect. The strong corner flow produced drives the upward flow of asthenospheric hot material, enabling the development of a back-arc basin.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105963"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080252","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":"Taxonomic, paleoecological and taphonomic insights on the megafauna of Toca do Angico, Campo Formoso, Brazil","authors":"Clara Maria Oliveira Braga ,&nbsp;João Paulo da Costa ,&nbsp;Gisele Aparecida dos Santos Neves ,&nbsp;André Vieira de Araújo ,&nbsp;Luciano Artemeo Leal ,&nbsp;Gustavo Prado de Oliveira Martins ,&nbsp;Lucas Henrique Medeiros da Silva Trifilio ,&nbsp;Mário André Trindade Dantas","doi":"10.1016/j.jsames.2026.105971","DOIUrl":"10.1016/j.jsames.2026.105971","url":null,"abstract":"<div><div>This study presents new taxonomic records of fossil remains collected from Deposit 1 of Toca do Angico (Campo Formoso, Bahia, Brazil). Deposit 1 corresponds to an extremely poorly sorted sedimentary package characterized by low transport selectivity, moderate reworking, and wind as the primary depositional agent, with water acting as a secondary agent. The negative skewness, with a predominance of coarser grains, indicates higher transport energy or greater proximity to the sediment source area. The identified taxa include toxodonts (<em>Trigodonops lopesi</em>), giant sloths (<em>Valgipes bucklandi</em> and cf. <em>Ocnotherium giganteum</em>), giant llamas (<em>Palaeolama major</em> and Lamini), and felids (<em>Panthera onca</em>). In addition, stable isotope analyses (<em>δ</em>¹³C and <em>δ</em>¹⁸O) were performed to improve the understanding of the diet and paleoenvironment in which this fauna lived. <em>Palaeolama major</em> and <em>Valgipes bucklandi</em> exhibited a mixed diet predominantly composed of C₃ plants (<em>p</em>_<em>i</em> = 78–86 %) and inhabited wooded savanna environments. <em>Trigodonops lopesi</em> and <em>Ocnotherium giganteum</em> occupied the ecotone between wooded and open savannas, showing a mixed diet with similar proportions of C₃ and C₄ plants. The habitat composition of this fauna is consistent with previous reconstructions proposed for the Campo Formoso region during the Late Pleistocene (50–27 ka). Taphonomic analyses indicated that most bones were fractured after fossilization as a result of physical and chemical processes. The predominance of highly transportable skeletal elements suggests an <em>ex-situ</em> preserved assemblage, resulting from the deposition of remains originally exposed on the surface. The corrosion observed on <em>Boa</em> sp. bones may reflect time-averaging or preservation in a more humid section of the cave.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105971"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190544","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":"Tectonometamorphic evolution of the Anicuns-Itaberaí Sequence, Southern Brasília Orogen: Evidence of deep burial and syn-collisional exhumation","authors":"Otávio Passo-Vieira ,&nbsp;Rodrigo Prudente Melo ,&nbsp;Regiane Andrade Fumes ,&nbsp;Gabriel Silveira Brod ,&nbsp;Filipe Altoé Temporim ,&nbsp;Sergio Willians de Oliveira Rodrigues ,&nbsp;George Luiz Luvizotto","doi":"10.1016/j.jsames.2026.105974","DOIUrl":"10.1016/j.jsames.2026.105974","url":null,"abstract":"<div><div>Metamorphic pressure–temperature (P–T) conditions in the Southern Brasília Orogen are relatively well constrained, particularly in its southernmost segments. However, the central and northern portions need further attention, especially regarding the metamorphism affecting the volcano-sedimentary sequences of the Arenópolis Magmatic Arc (AMA). The Anicuns–Itaberaí Sequence (AIS), located in the southern segment of the AMA, comprises a well-exposed metavolcano-sedimentary succession of mafic to ultramafic metavolcanic rocks, metachert, metarhythmite, marble lenses and quartzite. Well-preserved outcrops in the lowlands surrounding the Serra da Jiboia region, located in the central portion of the study area, were used to investigate the structural features and deformation recorded in metasedimentary rocks of the AIS and two samples of metagreywackes were selected for metamorphic modelling. The analyzed rocks correspond to garnet–chlorite–biotite–muscovite schists and were selected for microstructural analysis, quantitative mineral mapping, and thermodynamic modelling based on electron microprobe analyses. The results indicate that the peak metamorphic assemblage (garnet + biotite + plagioclase + muscovite + rutile + ilmenite) was stable at temperatures above 600 °C and pressures exceeding 0.95 GPa. The metamorphic evolution, inferred from compositional zoning in garnet, defines a clockwise P–T path, with initial garnet growth at 525–555 °C and 0.67–0.77 GPa, a metamorphic peak at 660 °C and 1.16–1.30 GPa, followed by decompression between 550 and 585 °C and 0.65–0.79 GPa. These results indicate that the AIS schists reached high-pressure amphibolite-facies conditions, exceeding those typical of the Barrovian metamorphism, and point to a collisional tectonic regime characterized by deep crustal burial and subsequent exhumation. Deformation structures were chronologically classified into four distinct phases (D₁ to D₄). The main deformation event (D₂) is characterized by asymmetric folding, while subsequent reverse faulting and shearing (D₃) are associated with post-burial exhumation during syn-collisional processes. Microstructural evidence suggests that the metamorphic peak likely occurred between the end of D₁ and the onset of D₂, indicating that peak mineral growth was broadly synchronous with early stages of the main deformation phase and burial.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105974"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190542","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 Araçatuba Formation (Upper Cretaceous) as an aquitard in the basalt window: Hydrostratigraphic implications for the Bauru and Guarani Aquifer Systems (SÃO Paulo, Brazil)","authors":"Lívia Freitas ,&nbsp;Claudia Varnier ,&nbsp;Carlos Henrique Gil Marques ,&nbsp;Ricardo Hirata ,&nbsp;André Marconato ,&nbsp;Fernanda Souto Barreto ,&nbsp;Francisco de Assis Negri ,&nbsp;Reginaldo Bertolo","doi":"10.1016/j.jsames.2026.105976","DOIUrl":"10.1016/j.jsames.2026.105976","url":null,"abstract":"<div><div>The Bauru Aquifer System (BAS), the hydrostratigraphic equivalent of the Bauru Group (Upper Cretaceous), serves as the primary source of private groundwater supply for the municipality of Bauru (State of São Paulo, Brazil). The BAS is widely contaminated by nitrate, while the Guarani Aquifer System (GAS) is the primary source of public water supply for the city. Usually, basalts from the Serra Geral Formation hydraulically isolate the BAS from the GAS. However, a local stratigraphic peculiarity—the \"basalt window\"—results in the absence of such basalts, raising concern for possible hydraulic connectivity, especially given the strategic importance of the GAS in the state of São Paulo. This study identified the Araçatuba Formation, a new geological unit in the area, which functions as an aquitard and can confine the GAS even where basalts are absent. The new lithostratigraphy was proposed based on (i) interpretation of geophysical logs from 46 tubular wells, (ii) drilling of a 130 m borehole with geophysical logging (gamma ray, spontaneous potential, resistivity, and sonic) and core description, and (iii) implicit 3D geological modeling using Leapfrog Works®. These combined methods enabled the delineation of the Bauru Group's geological framework (Marília, Adamantina, and Araçatuba formations from top to base). The Araçatuba aquitard, with thicknesses ranging from 8 to 26 m in the study area, provides confirmed confinement for the GAS, even within the \"basalt window\" and under downward hydraulic gradients. Distinct geophysical signatures were defined for each mapped stratigraphic unit, providing a guide for future interpretations in other areas.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105976"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190545","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":"Reassessment of the Holocene eruptive history of atitlán stratovolcano, Guatemala","authors":"Eduard Pico Rodriguez ,&nbsp;Lucia Capra ,&nbsp;Rafael Torres-Orozco ,&nbsp;Daniel Eduardo Secaira Ziegler ,&nbsp;Gustavo Adolfo Chigna Marroquín ,&nbsp;María Moncada Vásquez","doi":"10.1016/j.jsames.2026.105973","DOIUrl":"10.1016/j.jsames.2026.105973","url":null,"abstract":"<div><div>Atitlán volcano, one of the youngest and most active stratovolcanoes in the Central American Volcanic Arc, poses a significant threat to the densely populated regions surrounding Lake Atitlán. Despite its eruptive potential and historic activity, the volcano's recent Holocene stratigraphy and eruptive history remain poorly constrained. This study presents a comprehensive reassessment of Atitlán stratovolcano's eruptive activity through detailed stratigraphic, petrological, and geochemical analysis carried out on 17 new sections across all flanks of the volcano. Field observations, supported by radiocarbon dating, geochemistry, grain-size, componentry, and petrography, allowed us to identify 10 volcanic units spanning from ∼1421 BC to 1856 AD. These eruptive successions reveal a recurring pattern of multi-phase activity comprising fallout, pyroclastic density currents (PDCs), and lava flows. Petrographic and geochemical analyses confirm that the volcano's products display basaltic-andesite compositions (53.03–56.73 SiO₂ wt%) within the calc-alkaline series, showing conspicuous mineralogical variability across eruptive phases. Grain-size and componentry analyses highlight the alternation between explosive and effusive dynamics, and the widespread distribution of deposits across all flanks underscores the volcano's high hazard potential. Volume estimates for the youngest fallout unit (0.01 to 0.12 km³ at a 1σ confidence level) suggest a VEI 3–4 event, consistent with strombolian to sub-Plinian eruptive styles, reaffirming that moderate-magnitude eruptions at Atitlán can produce regionally significant impacts. This work updates the geological map of Atitlán, establishes a robust stratigraphic framework for hazard assessment, and provides new insights into the volcano's eruptive behavior. These findings hold important implications for volcanic risk management at Atitlán and contribute to the broader understanding of stratovolcano evolution and hazards in similar volcanic systems worldwide.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105973"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080254","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":"Evidence of Ediacaran transitional arc magmatism in the pelotas terrane, southernmost Brazil: Insights into the source and magmatic processes of the Pinheiro Machado Complex","authors":"Vivianne Andrade Bastos ,&nbsp;Edinei Koester ,&nbsp;Cristine Lenz ,&nbsp;Carla Cristine Porcher ,&nbsp;Daniel Triboli Vieira ,&nbsp;Rodrigo Chaves Ramos","doi":"10.1016/j.jsames.2026.105962","DOIUrl":"10.1016/j.jsames.2026.105962","url":null,"abstract":"<div><div>The Dom Feliciano Belt in southern Brazil records successive accretionary processes of the Brasiliano/Pan-African cycle that contributed to the assembly of Western Gondwana. This study investigates the Pinheiro Machado Complex (PMC), the main Neoproterozoic unit of the Pelotas Terrane, through whole-rock geochemistry and Sr–Nd isotope analyses. PMC lithotypes range from diorites to granites, with SiO₂ contents of 53.9–73.9 wt% and MgO of 0.6–6.1 wt%, reflecting compositional diversity from mantle-to crust-dominated sources. Trace-element spidergrams show enrichment in LILE (K, Th, Ce) and negative Nb–Ta–Ti anomalies, consistent with subduction-related arc magmatism. Chondrite-normalized REE patterns indicate LREE (Ce/Yb_N = 2.5–55.73) enrichment and subtle negative Eu anomalies. Sr–Nd isotope ratios define a mixed mantle–crustal signature, with ⁸⁷Sr/⁸⁶Sr_(i) = 0.7087–0.7104, εNd_(t) = −6.7 to −4.5, and T_DM ages of 1.4–1.7 Ga, suggesting significant assimilation of Paleoproterozoic orthogneiss basement. Geochemical modeling indicates that PMC magmas evolved predominantly through decoupled assimilation-fractional crystallization (AFC), involving ∼20 % assimilation of gneissic crust. In comparison, the mafic members were generated by 5–10 % partial melting of a spinel lherzolite mantle. These results, discussed in the context of the Pelotas Terrane, demonstrate that PMC magmatism formed in an oblique continental-arc environment during the closure of a V-shaped oceanic basin. The geodynamic model involves subduction, slab failure, and subsequent collision, recorded in the multiple intrusive pulses and structural associations of PMC rocks. This study refines the petrogenetic framework of the Pelotas Terrane and contributes to understanding the Neoproterozoic evolution of Western Gondwana.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105962"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039663","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":"Seismotectonic analysis of the 2017 earthquakes in the Cordón del Plata, Mendoza (33°S): active strike-slip faults oblique to the Andean orogen","authors":"Araceli Tamara Diaz Zapata ,&nbsp;Silvana Liz Spagnotto ,&nbsp;José Francisco Mescua","doi":"10.1016/j.jsames.2026.105952","DOIUrl":"10.1016/j.jsames.2026.105952","url":null,"abstract":"<div><div>We present a seismotectonic study of a sequence of seismic events produced in 2017 in the Frontal Cordillera in Mendoza province, Argentina. The sequence consists of a M_L 5.6 main event that took place on February 3, 2017, west of the Cordón del Plata range and the major aftershocks occurred during February and March. Using seismological data from INPRES and IRIS, we reprocessed the events to obtain improved earthquake locations and to calculate focal mechanisms. Our results indicate that this seismicity was generated by a fault system that we name the Santa Clara fault, a NW-trending sinistral strike-slip structure. Our findings suggest that this fault is capable of producing earthquakes of magnitude greater than 6, with the potential to cause significant damage to populations and infrastructure in northern Mendoza. We also recognize that some of the aftershocks are localized along the ENE-trending nodal plane of this structure, indicating that it was also active during the seismic sequence. This structure can be associated with a fault system inherited from the Triassic extensional event in the region. Field data show that minor faults of this ENE-trending fault system affect Quaternary deposits, documenting its recent activity. We interpret that both fault systems are structures inherited from the pre-Andean history that reactivate in the current stress field as strike-slip faults. The Santa Clara fault is a hazardous structure that should be incorporated in analysis of the seismic hazard and risk in the region. More studies are needed to determine if the ENE-trending fault system is also capable of major earthquakes.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105952"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080257","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":"First palynoflora for the Permian La Golondrina Formation (Santa Cruz Province, Argentina): biostratigraphic and paleoenvironmental implications for the Dos Hermanos Member","authors":"Pedro Raúl Gutiérrez,&nbsp;M. Lucía Balarino,&nbsp;Bárbara Cariglino,&nbsp;Lautaro Ruffo Rey,&nbsp;Sol Noetinger","doi":"10.1016/j.jsames.2026.105951","DOIUrl":"10.1016/j.jsames.2026.105951","url":null,"abstract":"<div><div>We present the first integrated study of the microflora and its associated megaflora from the upper member of the La Golondrina Formation (Dos Hermanos Member) in the La Golondrina Basin, Santa Cruz, Patagonia, Argentina. The microflora is dominated by striate bisaccate pollen (<em>Guttulapollenites, Striatopodocarpites</em>), non-striate bisaccate pollen (<em>Scheuringipollenites, Alisporites/Falcisporites, Platysaccus</em>), trilete spores (<em>Verrucosisporites/Convolutispora, Punctatisporites</em>), and sulcate-plicate pollen (<em>Weylandites</em>). Cluster analysis based on species distribution shows a close affinity with the microflora from the Emakwezini Formation in the Lebombo Basin, South Africa. This correlation supports a Lopingian age for the Dos Hermanos Member, concurring with recent radiometric dating of the unit. The palynological assemblage of the Dos Hermanos Member is consistent with the associated megaflora, which comprises mostly glossopterids and true ferns, alongside sphenophytes and scarce conifers. Both mega- and microfloristic evidence suggest that the flora of the Dos Hermanos Member developed along the margins of the water bodies (lakes, swamps, and marshes) within the floodplains of a low-sinuosity braided river system. The forest was dominated by arborescent Glossopteridales, with an herbaceous-shrub undergrowth composed of true ferns, sphenophytes, lycophytes, and bryophytes. Conifers and seed ferns (other than Glossopteridales), which are scarce or absent in the megaflora but constitute major elements of the palynoflora, likely inhabited the uplands near the deposition area.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"173 ","pages":"Article 105951"},"PeriodicalIF":1.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039672","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}