Journal of South American Earth Sciences最新文献

Microfacies of the San Juan Formation (lower Darriwilian) in the Rio Francia, Central Precordillera, Argentina 阿根廷前阿尔卑斯山脉中部弗朗西亚河地区圣胡安地层（达里维利系下层）的微地貌

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-21 DOI: 10.1016/j.jsames.2024.105169

{"title":"Microfacies of the San Juan Formation (lower Darriwilian) in the Rio Francia, Central Precordillera, Argentina","authors":"","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":null,"pages":null},"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}

引用次数: 0

Low-δ18Ο in mississippian los leones granite (46°S). Tectonic implications for the understanding of late paleozoic evolution in patagonia 密西西比时期洛斯莱昂斯花岗岩（南纬 46°）中的低δ18Ο。构造对了解巴塔哥尼亚晚古生代演化的影响

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-21 DOI: 10.1016/j.jsames.2024.105174

{"title":"Low-δ18Ο in mississippian los leones granite (46°S). Tectonic implications for the understanding of late paleozoic evolution in patagonia","authors":"","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 km<sup>2</sup> 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<sub>(i)</sub> ∼14), which experienced hydrothermal alteration at high temperatures (δ<sup>18</sup>O ∼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":null,"pages":null},"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}

引用次数: 0

Geophysical characterization and 2D gravimetric modeling: Application to tectonic control of the Vitória-Trindade Ridge (VTR–ES, Brazil) 地球物理特征和二维重力模型：应用于巴西维托里亚-特林达德海脊（VTR-ES）的构造控制

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-20 DOI: 10.1016/j.jsames.2024.105173

{"title":"Geophysical characterization and 2D gravimetric modeling: Application to tectonic control of the Vitória-Trindade Ridge (VTR–ES, Brazil)","authors":"","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":null,"pages":null},"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}

引用次数: 0

Unveiling a major strike-slip fault system associated with the Somún Curá Large Igneous Province in central Patagonia, Argentina 揭示与阿根廷巴塔哥尼亚中部索蒙-库拉大火成岩带有关的主要走向滑动断层系统

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-19 DOI: 10.1016/j.jsames.2024.105164

引用次数: 0

Current understanding, knowledge gaps, and challenges of mountain permafrost research in the Chilean and Argentinean Andes 目前对智利和阿根廷安第斯山脉永久冻土研究的了解、知识差距和挑战

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-19 DOI: 10.1016/j.jsames.2024.105165

{"title":"Current understanding, knowledge gaps, and challenges of mountain permafrost research in the Chilean and Argentinean Andes","authors":"","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":null,"pages":null},"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}

引用次数: 0

Trace fossils of incisor marks indicate multiple inhabitants of burrowing systems rodents (Geomyidae) in the Oligocene (Chilapa Formation) of southern Mexico 门齿痕迹化石表明墨西哥南部渐新世（奇拉帕地层）的穴居系统啮齿动物（Geomyidae）有多种居民

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-19 DOI: 10.1016/j.jsames.2024.105171

{"title":"Trace fossils of incisor marks indicate multiple inhabitants of burrowing systems rodents (Geomyidae) in the Oligocene (Chilapa Formation) of southern Mexico","authors":"","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":null,"pages":null},"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}

引用次数: 0

Taphonomic histories of Quaternary fossil accumulations preserved in Brazilian cave deposits 巴西洞穴沉积中保存的第四纪化石群的堆积史

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-19 DOI: 10.1016/j.jsames.2024.105168

引用次数: 0

Basement reactivation and structural inheritance in the Jurassic to Neogene evolution of the North Patagonian Andes (41° 08’ – 41° 11’ S), Argentina 阿根廷北巴塔哥尼亚安第斯山脉（南纬 41° 08' - 41° 11'）侏罗纪至新近纪演化过程中的基底再活化和构造传承

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-19 DOI: 10.1016/j.jsames.2024.105170

引用次数: 0

Geochemistry of fine-grained sedimentary rocks: Implications for source area, paleoweathering, paleoclimate, and provenance of the Santa Maria Formation (Triassic, Paraná Basin, Brazil) 细粒沉积岩的地球化学：圣玛丽亚地层（三叠纪，巴西巴拉那盆地）的源区、古风化作用、古气候和产地的影响

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-17 DOI: 10.1016/j.jsames.2024.105167

{"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":"","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 < 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":null,"pages":null},"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}

引用次数: 0

Trilobites from the upper middle Cambrian (Miaolingian, Guzhangian) of the Sierra Los Ajos, northern Sonora, Mexico: Biostratigraphic and paleogeographic considerations 墨西哥索诺拉北部洛斯阿霍斯山脉上中寒武统（妙灵统、古丈统）的三叶虫：生物地层学和古地理考虑因素

IF 1.7 4区地球科学

Journal of South American Earth Sciences Pub Date : 2024-09-17 DOI: 10.1016/j.jsames.2024.105163

{"title":"Trilobites from the upper middle Cambrian (Miaolingian, Guzhangian) of the Sierra Los Ajos, northern Sonora, Mexico: Biostratigraphic and paleogeographic considerations","authors":"","doi":"10.1016/j.jsames.2024.105163","DOIUrl":"10.1016/j.jsames.2024.105163","url":null,"abstract":"<div><p>A Cambrian sedimentary sequence with a predominant lithology of limestone, sandy limestone, and quartzite pertaining to the Bolsa and Abrigo formations is exposed in the Sierra Los Ajos to the east of Cananea city (northeastern Sonora, Mexico). Two fossil assemblages from Guzhangian layers of the Abrigo Formation are described herein. The trilobites identified comprise <em>Tricrepicephalus texanus</em> (Shumard), <em>Crepicephalus</em> sp., <em>Coosia ariston</em> (Walcott), <em>Coosia</em> sp., <em>Cedaria</em> cf. <em>eurycheilos</em> Palmer, <em>Coosella</em> sp., <em>Llanoaspis modesta</em> Lochman, and <em>Llanoaspis</em>? sp., representing the <em>Cedaria</em> and <em>Crepicephalus</em> zones (Miaolingian, Guzhangian). The Cambrian rocks of northeastern Sonora (Sierra Los Ajos, El Tule, and Mesteñas hills), southern Arizona, and Texas, were deposited as part of a thick sedimentary sequence on the southwestern margin of Laurentia, associated with an inner shelf marine environment. The distribution of the trilobites identified confirms the existence of a widespread Cambrian faunal province that includes the southeastern United States of America and northwestern Mexico.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272929","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}

引用次数: 0