Journal of South American Earth Sciences最新文献

{"title":"Oral and poster contributions for conferences: Some observations and recommendations","authors":"Wolf Uwe Reimold","doi":"10.1016/j.jsames.2024.105172","DOIUrl":"10.1016/j.jsames.2024.105172","url":null,"abstract":"<div><div>The recent 13th South American Symposium on Isotope Geology (SSAGI) in May 2024 in Buzios (Brazil) was an excellent conference, showcasing the current diversity and high standard of isotope geochemistry and geology at universities and research institutions across Latin America. Three days of oral and poster presentations provided a great forum for scientific and social exchange. This conference, however, also further supported observations made at earlier events that many oral and poster presentations by postgraduate students and docents alike suffer from a number of problems. There is ample scope for improvement, in the interest of more efficient information transfer and better exchange with colleagues. The main problem areas noted (e.g., overloading of powerpoint slides, and of posters, with diagrams and/or text; application of poor color, etc.) are discussed here, and suggestions are made how to avoid these issues and improve our scientific communication.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105172"},"PeriodicalIF":1.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142420363","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":"Microfacies of the San Juan Formation (lower Darriwilian) in the Rio Francia, Central Precordillera, Argentina","authors":"Moreno Florencia,&nbsp;Mestre Ana,&nbsp;Heredia Susana","doi":"10.1016/j.jsames.2024.105169","DOIUrl":"10.1016/j.jsames.2024.105169","url":null,"abstract":"<div><div>In this contribution, we describe and interpret the microfacies of the upper levels of the San Juan Formation in the Río Francia section of the Central Precordillera, Argentina, for the first time. Several studies in this section identified the <em>Lenodus antivariabilis, Lenodus variabilis, Lenodus crassus</em>, and <em>Lenodus pseudoplanus</em> zones, thereby limiting this stratigraphic interval to the early Darriwilian age. Five microfacies were recognized: M1 burrowed bioclastic wackestone, M2 bioclastic mudstone-wackestone, M3 intrabioclastic grainstone, M4 crinoidal wackestone-packstone, and M5 bioclastic wackestone-packstone. These microfacies indicate a shallow subtidal inner platform environment with variations in hydrodynamic energy ranging from low to moderate conditions below the fair-weather wave base level. The vertical arrangement of these sub-environments suggests a gradual transgressive setting during the lower Darriwilian for the carbonate beds of the San Juan Formation. The Baños de Talacasto, Ancha Creek, and Don Braulio sections are correlated with the section studied in this work, where conodont zones were documented, and microfacies analyses revealed shallow subtidal environments with low-energy conditions and occasional high-energy episodes. Differences in redox conditions were observed between the Don Braulio section (anoxic) and the Río Francia section (well-oxygenated), interpreted as the result of a rapid sea-level rise, though diachronic across the platform. Microfacies analysis, combined with precise conodont biostratigraphy, provides a powerful tool for reconstructing the Middle Ordovician carbonate platform.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105169"},"PeriodicalIF":1.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142311435","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":"Low-δ18Ο in mississippian los leones granite (46°S). Tectonic implications for the understanding of late paleozoic evolution in patagonia","authors":"P. Rossel ,&nbsp;M. Suárez ,&nbsp;D. Morata ,&nbsp;R. De la Cruz","doi":"10.1016/j.jsames.2024.105174","DOIUrl":"10.1016/j.jsames.2024.105174","url":null,"abstract":"<div><div>Los Leones Granite represents a calc-alkaline tonalite-granodiorite tabular stock of ∼3 km² intruded within Paleozoic metasedimentary rocks from the Eastern Andean Metamorphic Complex. Two newly obtained zircon SHRIMP U-Pb ages reveal a Middle Mississippian (340-335 Ma) crystallization age, contrasting with previously accepted K-Ar Pennsylvanian age. Isotopic analysis indicate derivation from a depleted source with minimal influence of continental crust contamination (eHf_(i) ∼14), which experienced hydrothermal alteration at high temperatures (δ¹⁸O ∼4.13). New data coupled with contemporaneous subduction-related rocks in Western Patagonia and Antarctica suggest the existence a broader Lower Carboniferous subduction zone extending at least from Northern Patagonia, to Western Antarctica. On the other hand, isotopic signatures depict a tectono-magmatic framework with a thermal configuration of the margin that was modified by the presence of a local slab tear or the progressive horizontalization of the isotherms as result of the ∼20 myr. of magmatic quiescence in the area.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105174"},"PeriodicalIF":1.7,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315947","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":"Geophysical characterization and 2D gravimetric modeling: Application to tectonic control of the Vitória-Trindade Ridge (VTR–ES, Brazil)","authors":"Adilson Oliveira dos Santos ,&nbsp;Webster Ueipass Mohriak ,&nbsp;Alanna Costa Dutra ,&nbsp;Anderson Costa dos Santos","doi":"10.1016/j.jsames.2024.105173","DOIUrl":"10.1016/j.jsames.2024.105173","url":null,"abstract":"<div><div>There are numerous inquiries regarding the origin and development of the Vitória-Trindade Ridge (VTR) in eastern Brazil, a major tectonic feature composed of seamounts, guyots, banks, and islands, prompting extensive studies in the region. These investigations aim to create a more precise crustal model to aid in understanding various geological phenomena, such as the separation of South America from Africa, the interaction between continental and oceanic crusts, and the behavior of oceanic fracture zones. These zones may have served as conduits for magma feeding into the ridge and adjacent areas, or the seamounts could have formed due to a fixed mantle plume related to the West-East trend. This study focuses on exploring the tectonic structure of the region, particularly the subsurface of the VTR, utilizing geophysical data modeling techniques. This includes data from topography, gravimetric and magnetic anomalies, and analysis of reflection seismic lines. The research aims to accurately characterize the geological and geophysical context of the continental margin and some igneous features in the offshore region of the Espírito Santo and Bahia states. The anomalous hotspots correlate with pre-existing fracture zones resulting from the Mesozoic rifting of South American and African continents, which due to later tectonic episodes, have masked traces of deep-seated tectonic structures. The integration of geophysical methods, particularly gravimetry and magnetometry, when combined with reflection seismic data and 2D modeling techniques, offer insights into the geodynamic processes involved in the formation of the volcanic ridge. The results obtained showed the interference generated by magmatism in the oceanic crust and the transition zone. The seismic data allowed the visualization of the approximate geometries and interrelationships of some volcanic edifices that are compared with the Davis Bank, located in the central region of the VTR.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105173"},"PeriodicalIF":1.7,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323432","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":"Unveiling a major strike-slip fault system associated with the Somún Curá Large Igneous Province in central Patagonia, Argentina","authors":"Santiago N. González ,&nbsp;Gerson A. Greco ,&nbsp;Darío L. Orts","doi":"10.1016/j.jsames.2024.105164","DOIUrl":"10.1016/j.jsames.2024.105164","url":null,"abstract":"<div><div>This study presents new evidence of a major, regional strike-slip fault system linked to the emplacement of the Somún Curá Large Igneous Province in central Patagonia, Argentina. Employing a combination of remote sensing techniques and fieldwork, we provide additional insights into the structural complexities underlying this magmatic province, shedding light on its geological evolution. Our findings indicate a compelling correlation between the magmatic products of the Somún Curá Large Igneous Province and the left-lateral strike-slip fault system, resembling similar relationships observed in other magmatic large igneous provinces. Moreover, the strike-slip tectonics delineated in this study likely represent the culmination of the fault system's evolution, possibly originating from a longstanding basement fault and extending beyond the limits of the Somún Curá basaltic plateau.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105164"},"PeriodicalIF":1.7,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315948","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":"Current understanding, knowledge gaps, and challenges of mountain permafrost research in the Chilean and Argentinean Andes","authors":"Hans Fernández-Navarro ,&nbsp;Carla Tapia Baldis ,&nbsp;Claudia Rojas ,&nbsp;Morgane Derrien ,&nbsp;Tania Villaseñor","doi":"10.1016/j.jsames.2024.105165","DOIUrl":"10.1016/j.jsames.2024.105165","url":null,"abstract":"<div><div>Mountain permafrost extends over a vast area throughout the Chilean and Argentinean Andes, making it a key component of these mountain ecosystems. To develop an overview of the current state of knowledge on southern Andean permafrost, it is essential to outline appropriate research strategies in a warmer climate context. Based on a comprehensive review of existing literature, this work identifies eight main research themes on mountain permafrost in the Chilean and Argentinean Andes: paleoenvironmental reconstructions, permafrost-derived landforms inventories, permafrost distribution models, internal structure analysis, hydrogeochemistry, permafrost dynamics, geological hazards, and transitional landscape studies. This extensive review work also highlights key debates concerning the potential of permafrost as a water resource and the factors influencing its distribution. Furthermore, we identified several challenges the scientific community must address to gain a deeper understanding of mountain permafrost dynamics. Among these challenges, we suggest tackling the need to broaden spatial focus, along with the use of emerging technologies and methodologies. Additionally, we emphasize the importance of developing interdisciplinary approaches to effectively identify the impacts of climate change on mountain permafrost. Such efforts are essential for adequately preparing scientists, institutional entities, and society to address future scenarios.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105165"},"PeriodicalIF":1.7,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319184","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":"Trace fossils of incisor marks indicate multiple inhabitants of burrowing systems rodents (Geomyidae) in the Oligocene (Chilapa Formation) of southern Mexico","authors":"Rosalía Guerrero-Arenas,&nbsp;Eduardo Jiménez-Hidalgo","doi":"10.1016/j.jsames.2024.105171","DOIUrl":"10.1016/j.jsames.2024.105171","url":null,"abstract":"<div><p>Trace fossils produced by fossorial mammals are relatively common in the North American fossil record. <em>Yaviichnus iniyooensis</em> consists of a system of chambers and tunnels marked by characteristic paired-groove marks. This text aims to analyze four burrows with well-preserved bioglyphs to determine whether one or more individuals produced them. The burrows were found in the Chilapa Formation (early Oligocene), which outcrops on the outskirts of Santiago Yolomécatl town, northwestern Oaxaca. Bioglyphs are visible on the external surfaces of the tunnel casts. These marks are short, straight, and paired, and are attributable to the incisor marks of <em>Gregorymys</em> spp. They may have been produced during the same ecological period. Analysis of the measurements of the width of these paired marks revealed two distinct groups: one ranging from 2.2 to 3.2 mm (mean 2.95 mm; n = 12) and another ranging from 3.4 to 5.3 mm (mean 3.99 mm; n = 31). A Mann-Whitney U test indicated statistically significant differences between the median widths of the groups. The presence of two different groups of incisor marks within a single burrow system suggests that multiple individuals were the producers. This supports the hypothesis that several individuals of <em>Gregorymys veloxikua</em> and <em>G</em>. <em>mixtecorum</em> were the attributable producers of <em>Yavi</em><em>i</em><em>chnus iniyooensis</em>. The most plausible explanation is that burrows were reused by specimens of both species of <em>Gregorymys</em>, possibly linked to aridity conditions and non-solitary behaviour.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105171"},"PeriodicalIF":1.7,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272861","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":"Taphonomic histories of Quaternary fossil accumulations preserved in Brazilian cave deposits","authors":"Lucas Henrique Medeiros da Silva Trifilio ,&nbsp;Hermínio Ismael de Araújo Júnior ,&nbsp;Kleberson de Oliveira Porpino","doi":"10.1016/j.jsames.2024.105168","DOIUrl":"10.1016/j.jsames.2024.105168","url":null,"abstract":"<div><div>The taphonomic histories of five cave deposits in Brazil were interpreted, focusing on the accumulation and taphonomic modes. These caves, Complexo Suíço, F3, Toca das Onças, Lapa dos Peixes and Gruna das Três Cobras, show evidence of remains being accumulated through entrapping, sheltering, and water transportation. Cluster Analysis revealed a predominance of irregular breaks and low stages of weathering as the primary taphonomic mode, along with lack of corrosion and abrasion. Factor Analysis also indicated that incrustation played a major role in distinguishing between the deposits. The remains in F3, Toca das Onças, Lapa dos Peixes, and Gruna das Três Cobras caves experienced similar preservation conditions, including fragmentation from reworking, block collapses, exposure to acidified rainwater, incrustation and abrasion from water-borne sediments, and corrosion due to bat guano and acidified water.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105168"},"PeriodicalIF":1.7,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319183","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":"Basement reactivation and structural inheritance in the Jurassic to Neogene evolution of the North Patagonian Andes (41° 08’ – 41° 11’ S), Argentina","authors":"Sofía Peltzer ,&nbsp;María Belén Yoya ,&nbsp;Ezequiel Olaizola ,&nbsp;Florencia Bechis ,&nbsp;Daniel Yagupsky ,&nbsp;Pablo D. González ,&nbsp;Miguel A.S. Basei ,&nbsp;Sebastián Oriolo","doi":"10.1016/j.jsames.2024.105170","DOIUrl":"10.1016/j.jsames.2024.105170","url":null,"abstract":"<div><div>Structural inheritance is a major control on the Andean structural architecture and magma emplacement, particularly in Patagonia, where the genesis of sedimentary basins and magmatic arcs has been largely influenced by basement fabrics. Based on new geologic, structural, microstructural and geochronologic data, the aim of this contribution is to evaluate the influence of pre-existing mechanical anisotropies of the Paleozoic basement on the Jurassic-Neogene tectonic evolution in the Paso de las Nubes area (North Patagonian Andes, Argentina). U-Pb zircon data of an orthogneiss yielded an age of 166 ± 2 Ma, which is consistent with the Jurassic batholith reported in the North Patagonian Andes, being thus coeval with retrograde metamorphism and deformation in the metasedimentary wallrock. Fault kinematic data indicate a Jurassic transtensional regime, strongly controlled by basement reactivation. On the other hand, a second kinematic population records a mainly strike-slip solution, associated with partitioned Neogene transpression.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105170"},"PeriodicalIF":1.7,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323412","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":"Geochemistry of fine-grained sedimentary rocks: Implications for source area, paleoweathering, paleoclimate, and provenance of the Santa Maria Formation (Triassic, Paraná Basin, Brazil)","authors":"Isaque C. Rodrigues ,&nbsp;Anderson J. Maraschin ,&nbsp;André W. Borba ,&nbsp;Ana M.P. Mizusaki","doi":"10.1016/j.jsames.2024.105167","DOIUrl":"10.1016/j.jsames.2024.105167","url":null,"abstract":"<div><p>The integration of ICP-OES, XRD, chemical analysis, and scanning electron microscopy was used to investigate the source area, weathering, paleoclimate conditions, and provenance of the siltstones of the Santa Maria Formation (Middle to Upper Triassic, Southern Brazil). This unit is regionally subdivided, from base to top, into the Passo das Tropas Member (Late Anisian–Middle Ladinian) and the Alemoa Member (Middle Ladinian–Carnian). The Chemical Index of Alteration (CIA) was calculated for both members to highlight the weathering processes of primary minerals. The CIA results indicate moderate to extreme weathering of the source rocks for the siltstones. The extreme chemical alteration observed in the Passo das Tropas siltstones (CIA = 76.97–90.83) and in the mid-section of the Alemoa Member (CIA = 87.96–89.63) suggests weathering under more humid conditions, related to an increase in paleorainfall. Paleoclimate was interpreted as semi-arid to arid, with alternating wet and dry seasons. These results align with the geochemical behavior of uranium and thorium. Samples with higher CIA values show higher Th/U ratios, indicating a shift toward a more humid climate. X-ray diffraction analysis of the fine fraction (FF &lt; 2 μm) of the samples identified mixed-layered illite-smectite (I/S) clay minerals with minor amounts of quartz. Regarding provenance, Th/U ratios coupled with Th vs. Sc and La-Th-Sc plots, suggest an upper crustal protolith for the southern Santa Maria siltstones, consisting of uplifted rocks from the crystalline basement of the Sul-Rio-Grandense shield and sedimentary rocks of the Camaquã Basin. The Th/Sc, Sc/Th, Co/Th, and La/Sc ratios, along with the contents of Al₂O₃, SiO₂, TiO₂, Co, V, Ni, and Sc, indicate a more felsic composition for the Passo das Tropas Member. Meanwhile, the source rocks of the Alemoa Member sediments demonstrate a more mafic composition in the mid-section, transitioning to a felsic composition in the uppermost succession.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"148 ","pages":"Article 105167"},"PeriodicalIF":1.7,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272930","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}