Journal of South American Earth Sciences最新文献_第3页

The Mesoarchean Algodoeiro Metagranite: a new piece in the Araçuaí Orogen basement inliers puzzle 中太古宙Algodoeiro变质花岗岩：Araçuaí造山带基底地层之谜的新发现

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-12 DOI: 10.1016/j.jsames.2026.105955

Geysianne Morais , Matheus Kuchenbecker , Danilo Barbuena , Lucas Almeida de Souza , Hugo Marques Ascendino Teixeira , Lucília Aparecida Ramos de Oliveira

The Orosirian São Francisco-Congo paleocontinent (SFCP) was one of the crustal segments involved in the Neoproterozoic-Early Paleozoic assembly of the Gondwana supercontinent. During this collisional event, its margins were reworked and fragmented, becoming preserved as basement inliers within the Brasiliano-Pan-African orogenic system. Despite its key role in understanding the processes responsible for the formation of Earth's earliest continental masses, the tectonic evolution and true extent of the SFCP remain poorly constrained. Within the Neoproterozoic Araçuaí Orogen there are several basement inliers, whose Archean and Paleoproterozoic rocks have been valuable to reconstructing SFCP. Here we report the discovery of a small basement inlier in the Southern Espinhaço Range, western domain of the Araçuaí Orogen. Based on integrated field observations, petrography, whole-rock geochemistry and U-Pb zircon geochronology, we characterize the rocks exposed in this inlier and discuss their regional significance. This inlier corresponds to a tectonic slice in which a Mesoarchean (ca. 2.87 Ga) metagranite - herein referred to as the Algodoeiro Metagranite - thrust over the metasedimentary rocks of the Espinhaço Supergroup. The Algodoeiro Metagranite consists of leucocratic, peraluminous, magnesian calc-alkaline metagranites that display moderately to strongly fractionated REE patterns with marked negative Eu anomalies. Petrographic and geochemical similarities, particularly REE slopes and multi-element patterns, combined with geochronological constraints, link these rocks to the gneisses of the Guanhães Complex, exposed in the Guanhães basement inlier, further east. Deformation and metamorphism recorded in the Algodoeiro Metagranite are interpreted as syn-to post-collisional in the context of the Brasiliano-Pan-African orogeny. Taken together, the data indicate that the Algodoeiro Metagranite represents a fragment of the SFCP tectonically reworked within the Araçuaí Orogen during the assembly of West Gondwana. This newly identified inlier therefore adds an important piece to the ongoing efforts to refining the tectonic evolution of eastern South America.

奥陶纪圣弗朗西斯科-刚果古大陆（SFCP）是冈瓦纳超大陆新元古代-早古生代组合的一个地壳段。在这次碰撞事件中，它的边缘被重新加工和破碎，成为巴西利亚-泛非造山系的基底内层。尽管它在理解地球最早大陆块体形成的过程中起着关键作用，但SFCP的构造演化和真实范围仍然很少受到限制。在新元古代Araçuaí造山带内有几条基底地层，其中的太古宙和古元古代岩石对重建SFCP具有重要价值。本文报道了在Araçuaí造山带西域espinharado山脉南部发现的一个小型基底。综合野外观测、岩石学、全岩地球化学、U-Pb锆石年代学等资料，对该区出露岩石进行了特征描述，并讨论了其区域意义。该剖面对应于中太古代（约2.87 Ga）的变质花岗岩（此处称为Algodoeiro变质花岗岩）逆冲在espinhaarso超群的变质沉积岩上的构造片。Algodoeiro变质花岗岩由白晶型、过铝质、镁质钙碱性变质花岗岩组成，REE分馏模式中至强，Eu负异常明显。岩石学和地球化学的相似性，特别是稀土元素斜坡和多元素模式，结合地质年代学的限制，将这些岩石与暴露在更东边的关赫斯基底的关赫斯杂岩的片麻岩联系起来。Algodoeiro变质岩记录的变形变质作用在巴西利亚-泛非造山运动背景下被解释为同向后碰撞作用。综上所述，Algodoeiro变长岩代表了西冈瓦纳组装期间Araçuaí造山带内构造改造的SFCP片段。因此，这个新发现的内层岩为正在进行的提炼南美东部构造演化的努力增添了重要的一环。

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引用次数: 0

Tectono-sedimentary evolution of the western Gondwana margin during the Silurian: Insights from new sedimentological and geochronological analysis of the Villacorta Formation 志留纪冈瓦纳西部边缘构造-沉积演化：来自Villacorta组沉积学和地质年代学新分析的启示

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-12 DOI: 10.1016/j.jsames.2026.105953

D. Milanesio , P. Armas , J. Biddle , A. Edgington , J. Otamendi , J. Fosdick , E. Cristofolini

The Villacorta Formation is a Silurian sedimentary succession exposed in a restricted area in the central-western Famatinian Belt, with its type locality at Los Oitos Creek. This formation represents an exceptional and well-preserved Silurian record. Detailed facies analysis reveals five distinct facies associations that record a progradational trend from subtidal sandbars and tidal channels to a tide-dominated deltaic system. To constrain its provenance, we report U–Pb geochronological analysis of detrital zircon from a sandstone sample collected from the upper portion of the stratigraphic profile. The sample yielded a nearly unimodal age distribution dominated by Lower Ordovician ages, indicating a prevailing source in the Famatinian batholith. This detrital zircon signature resembles the Lower Ordovician age cluster that also occurs in coeval Silurian–Devonian units of the Precordillera (e.g., Los Espejos Formation), supporting the existence of a broader Silurian basin system that stretches from the Famatinian orogen into the Cuyania terrane. These findings suggest that the Silurian Sea extended as far west as the present-day Famatinian batholith. A significant outcome of this study is the recognition of the Villacorta Formation as a synorogenic deposit that predates the collapse of the Famatinian orogen and the exhumation of the Cuyania basement.

Villacorta组是一个暴露在法玛蒂纪中西部有限区域的志留系沉积序列，其类型位置在Los Oitos Creek。这个地层代表了一个保存完好的特殊志留纪记录。详细的相分析揭示了五种不同的相组合，记录了从潮下沙洲和潮汐河道到潮汐主导的三角洲体系的进积趋势。为了限制其来源，我们报告了从地层剖面上部收集的砂岩样品中采集的碎屑锆石的U-Pb年代学分析。样品的年龄分布几乎呈单峰分布，以下奥陶统年龄为主，表明其主要来源为法马纪岩基。这一碎屑锆石特征类似于下奥陶统时代的星系团，这种星系团也出现在前科迪勒拉（Precordillera）的同世志留纪-泥盆纪单元中（例如Los Espejos组），支持了一个更广泛的志留纪盆地体系的存在，该体系从法马梯造山带延伸到Cuyania地体。这些发现表明志留海一直向西延伸到现在的法马蒂纪岩基。这项研究的一个重要成果是承认维拉科塔组是一个同生矿床，早于法马汀期造山带的崩塌和对库亚尼亚基底的挖掘。

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引用次数: 0

First palynoflora for the Permian La Golondrina Formation (Santa Cruz Province, Argentina): biostratigraphic and paleoenvironmental implications for the Dos Hermanos Member 阿根廷圣克鲁斯省二叠纪La Golondrina组第一孢粉植物群：Dos Hermanos段的生物地层和古环境意义

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-09 DOI: 10.1016/j.jsames.2026.105951

Pedro Raúl Gutiérrez, M. Lucía Balarino, Bárbara Cariglino, Lautaro Ruffo Rey, Sol Noetinger

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 (Guttulapollenites, Striatopodocarpites), non-striate bisaccate pollen (Scheuringipollenites, Alisporites/Falcisporites, Platysaccus), trilete spores (Verrucosisporites/Convolutispora, Punctatisporites), and sulcate-plicate pollen (Weylandites). 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.

本文首次对阿根廷圣克鲁斯巴塔哥尼亚La Golondrina盆地上段（Dos Hermanos段）的微生物区系及其相关巨型植物区系进行了综合研究。微生物区系以纹状双孔花粉（Guttulapollenites, Striatopodocarpites）、非纹状双孔花粉（Scheuringipollenites, Alisporites/Falcisporites, Platysaccus）、三孔孢子（Verrucosisporites/Convolutispora, Punctatisporites）和纹状双孔花粉（Weylandites）为主。基于物种分布的聚类分析表明其与南非Lebombo盆地Emakwezini组的微生物区系密切相关。这种相关性支持Dos Hermanos成员的Lopingian年龄，与该单元最近的放射性测年一致。Dos Hermanos成员的孢粉组合与相关的巨型植物群一致，其中主要包括花萼蕨和真蕨类植物，以及叶生植物和稀有针叶树。大型和微型植物区系的证据都表明，Dos Hermanos成员的植物区系是沿着低曲度辫状河系统洪泛平原内的水体（湖泊、沼泽和沼泽）边缘发育的。林内以针叶林为主，草本-灌木林下有蕨类植物、叶生植物、石生植物和苔藓植物。针叶树和种子蕨类（除了光面蕨）在巨型植物区系中很少或没有，但却是孢粉植物区系的主要组成部分，它们可能居住在沉积区附近的高地上。

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引用次数: 0

Paleoenvironmental and paleoclimatic reconstruction of the Lagoa Grande das queimadas archaeological site, Piauí, Brazil Lagoa Grande das queimadas考古遗址的古环境和古气候重建，Piauí，巴西

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-07 DOI: 10.1016/j.jsames.2026.105949

Roberta Maciel Pacheco Valente , Heloisa Helena Gomes Coe , Karina Ferreira Chueng , Aline Gonçalves de Freitas , David Oldack Barcelos Ferreira Machado , Kita Chaves Damasio Macario , Marcelo Alves Ribeiro , José Sebastián Carrión García

The area of this study is the Lagoa Grande das Queimadas archaeological site, located in the southwest of the state of Piauí, in the semi-arid region of Northeast Brazil, a region that is globally recognized for its archaeological and paleontological heritage. The use of biogenic silica (especially phytoliths) as proxies for paleoenvironmental reconstruction aimed to evaluate the paleoenvironment of ancient human occupations. The phytolith assemblages recovered from the sediment record of the Lagoa Grande das Queimadas archaeological site are predominantly composed of Poaceae morphotypes, mainlyBlocky, Bulliform flabellate, Acute bulbosus, and Elongate, with a reduced presence of woody dicotyledons (Spheroid ornate). Arecaceae phytoliths (Spheroid echinate) are also observed throughout the profile, increasing from the oldest to the most recent sample, along with fragments of sponge megascleres and microcharcoals. The results revealed that this region experienced climatic variations during the Greenlandian to Meghalayan, as demonstrated by the phytolith and aquatic bioindicator (sponge spicules and diatom frustules) records. The analyses indicate that between 12,908–12,478 and 4420–4233 cal yrs BP, the temperature and humidity increased progressively, followed by a transition from a more humid climate than at present to drier conditions starting from 4420–4233 cal yrs BP. The qualitative and quantitative results of the phytolith analyses, associated with other proxies studied at this site, contributed to constructing information about the archaeological site and its insertion into the landscape, in addition to understanding the mobility and subsistence models of past human groups during the Holocene in the interior regions of Northeast Brazil.

这项研究的区域是Lagoa Grande das Queimadas考古遗址，位于巴西东北部的半干旱地区Piauí州西南部，该地区因其考古和古生物遗产而享誉全球。利用生物硅（特别是植物岩）作为古环境重建的代用物，旨在评价古人类活动的古环境。从Lagoa Grande das Queimadas考古遗址的沉积物记录中恢复的植物岩组合主要由Poaceae形态类型组成，主要是块状，鳞状，急性球型和细长型，木质双子叶（球形华丽）的存在较少。在整个剖面中也观察到槟榔科植物岩（球状刺状），从最古老的样本到最近的样本，以及海绵大颗粒和微炭的碎片。结果表明，该地区在格陵兰-梅加拉亚时期经历了气候变化，这是植物岩和水生生物指示物（海绵针状体和硅藻体）记录的结果。分析结果表明，在12908 ~ 12478 ~ 4420 ~ 4233 cal年BP之间，温度和湿度逐渐增加，随后从4420 ~ 4233 cal年BP开始由较湿润的气候过渡到较干燥的气候。植物岩分析的定性和定量结果，以及在该遗址研究的其他代用物，有助于构建有关考古遗址及其融入景观的信息，以及了解巴西东北部内陆地区全新世时期过去人类群体的流动性和生存模式。

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引用次数: 0

Paleogeography and stratigraphic correlation of the early rift phase in the northeastern Brazilian basins: Jurassic Aliança formation (Jatobá Basin) and coeval units, Western Gondwana 巴西东北部盆地早期裂谷期古地理与地层对比：西冈瓦纳地区侏罗纪alian<e:1>拉塔组（jatob<e:1>盆地）与同时期单元

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-06 DOI: 10.1016/j.jsames.2026.105950

Leonardo M. De Oliveira , Édison V. Oliveira , Gelson L. Fambrini

This study provides a paleogeographic and stratigraphic synthesis of the early rift phase (Jurassic) along the western margin of Gondwana, focusing on the Aliança Formation (Jatobá Basin) and its correlative units in the Araripe, Sergipe–Alagoas, and Gabon basins. Stratigraphic, sedimentological, and micropaleontological data indicate a regional transgressive shift from ephemeral braided fluvial–aeolian systems (Boipeba Member) to widespread lacustrine deposits (Capianga Member and equivalents), across a basinwide Transgressive Surface (TS). The Capianga Member is interpreted as a balanced-fill playa-lake system with low internal connectivity, dominated by carbonate–evaporitic and fine-grained facies. Facies stacking patterns and taphonomic data reflect tectono-climatic control and seasonal lake dynamics. Correlation with lithostratigraphic and biostratigraphic units—Brejo Santo, Bananeiras, and M'Vone formations—supports a regional model of lacustrine systems along Western Gondwana. Stratigraphic well data suggest that the Boipeba Member correlates with the Candeeiro Formation (SE–AL) and the basal M'Vone Formation; the basal Brejo Santo (well 1-AP-1-CE) records Boipeba-type siliciclastic signatures, although typical fluvial–aeolian sandstones have not yet been documented. These findings support a paleogeographic model of compartmentalized rift basins with limited connectivity, where climatic variability and structural segmentation governed lake evolution, and provide a refined chronostratigraphic framework for the Jurassic of Western Gondwana.

本文以Araripe盆地、Sergipe-Alagoas盆地和Gabon盆地的aliana组（jatob盆地）及其相关单元为研究对象，对Gondwana西缘早裂谷期（侏罗纪）进行了古地理和地层综合。地层学、沉积学和微古生物学数据表明，区域海侵从短暂的辫状河流-风成体系（Boipeba段）到广泛的湖泊沉积（Capianga段及类似物），跨越了整个盆地的海侵面（TS）。Capianga段被认为是一个内部连通性较低的平衡充填湖湖体系，主要为碳酸盐岩蒸发相和细粒相。相叠加模式和地貌学数据反映了构造气候控制和季节性湖泊动态。与岩石地层和生物地层单位（布雷霍桑托、巴纳内拉斯和M’vone地层）的对比，支持了西冈瓦纳湖湖系统的区域模型。地层井资料表明，Boipeba段与candeiro组（SE-AL）和基底M’vone组相对应；基底Brejo Santo （1-AP-1-CE井）记录了boipeba型硅塑性特征，但尚未发现典型的河流-风成砂岩。这些发现支持了一个连通性有限的分区裂谷盆地的古地理模型，其中气候变化和构造分割支配着湖泊的演化，并为西冈瓦纳侏罗纪提供了一个精细的年代地层格架。

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引用次数: 0

Interannual variations in the araruama hypersaline system: Implications for the sedimentological and hydrological characteristics of brejo do espinho lagoon (Rio de Janeiro, Brazil) araruama高盐系统的年际变化：brejo do espinho泻湖沉积学和水文特征的含义（里约热内卢de Janeiro，巴西）

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-03 DOI: 10.1016/j.jsames.2025.105939

Amanda Vilar , Pierre Belart , Joalice de Oliveira Mendonça , Thiago Carelli , Lazaro Laut

This study aims to utilize a multiproxy approach, incorporating physical-chemical parameters, sedimentological, and climate data, to evaluate the trophic status and environmental sediment characteristics of Brejo do Espinho Lagoon during the winter (July 2022) and summer (January 2023). The results revealed significant seasonal and spatial variations, with summer showing lower salinity and higher values for water temperature, total dissolved solids (TDS), and total organic carbon (TOC), indicating a higher inflow of rainfall periods and an increase in primary productivity. In contrast, the BE winter conditions were characterized by higher salinity due to lower precipitation and intensified evaporation. The predominance of fine sediments and high TOC contents in both analysed periods were related to the presence of microbial mats and suggest redox conditions at the bottom. Statistical analyses confirmed that seasonality is a key factor in modulating hydrological and sedimentological dynamics, directly influencing the stability of the different four lagoonal sectors. Sector 4 stood out as the most ecologically stable, while Sectors 2 and 3 exhibited higher seasonal variability. The study emphasizes the lagoon system's sensibility to changes in the hydrological regime, providing essential baseline data to support long-term monitoring and conservation strategies, particularly in the context of ongoing climate change.

本研究旨在利用多代理方法，结合物理化学参数、沉积学和气候数据，评估布雷霍多埃斯皮尼奥泻湖冬季（2022年7月）和夏季（2023年1月）的营养状况和环境沉积物特征。结果显示出明显的季节和空间差异，夏季盐度较低，水温、总溶解固形物（TDS）和总有机碳（TOC）值较高，表明降水周期较长，初级生产力增加。与此相反，BE冬季的特征是由于降水减少和蒸发加剧而导致盐度升高。在这两个分析时期，细沉积物的优势和高TOC含量与微生物席的存在有关，表明底部有氧化还原条件。统计分析证实，季节性是调节水文和沉积动力学的关键因素，直接影响四个不同泻湖区的稳定性。第4区生态最稳定，而第2区和第3区表现出较高的季节变化。该研究强调了泻湖系统对水文制度变化的敏感性，提供了基本的基线数据，以支持长期监测和保护战略，特别是在持续气候变化的背景下。

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引用次数: 0

Relief compartments and forms: Influence on paleoburrow distribution patterns 地形隔室与形态：对古穴居分布格局的影响

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2026-01-02 DOI: 10.1016/j.jsames.2025.105937

Arthur Philipe Bechtel , Jairo Valdati

This article examines the impact of relief compartments and landforms on the distribution of paleoburrows formed by extinct Xenarthra in the Caminhos dos Cânions do Sul UNESCO Global Geopark (CCSUGGP), southern Brazil. The central purpose is to understand how geomorphological and lithological factors have influenced the choice of excavation sites and the preservation of these structures. Twenty-two paleoburrows were analyzed through field surveys, morphological cataloging, and spatial analysis using GIS (QGIS), incorporating altimetric and geological data at various scales. The burrows were mapped and correlated with the relief compartments (Serra Geral Plateau, Serra Geral Escarpments, and Campos Gerais Plateau) and specific landforms (interfluves, convex and rectilinear slopes). The results indicate that paleoburrows are mainly concentrated in inclined reliefs and in sandstone lithologies of the Botucatu Formation, except for one located in weathered basalt. The convex morphology of the sites favors diffuse surface runoff, contributing to the conservation of the burrows by preventing flooding and sediment deposition. A directional pattern was also observed in the tunnels, with 60 % of the tunnels directed towards the southwest/southeast. The paleoburrows' mean altitude ranges between 49 m and 1023 m, being higher on the Escarpments and Plateau. We concluded that the relief compartments and forms may have contributed to both the excavation and preservation of paleoburrows, providing evidence on the behavior of Xenarthra and environmental transformations during the Quaternary. The results contribute to understanding the interaction between geomorphology and the behavior of extinct megafauna, reinforcing the scientific and heritage value of the GMUCCS paleoburrows.

本文研究了巴西南部Caminhos dos cunions do Sul联合国教科文组织世界地质公园（CCSUGGP）中，地形和地形对已灭绝Xenarthra形成的古穴居分布的影响。中心目的是了解地貌和岩性因素如何影响挖掘地点的选择和这些结构的保存。利用地理信息系统（QGIS），结合不同尺度的高程和地质资料，对22个古穴居进行了野外调查、形态编目和空间分析。这些洞穴被绘制出来并与地形区（Serra Geral Plateau、Serra Geral escarments和Campos Gerais Plateau）和特定地形（interfluves、凸坡和直线坡）进行了对比。结果表明，古洞穴除位于风化玄武岩中外，主要集中在坡面起伏和波图卡图组砂岩岩性中。这些地点的凸形形态有利于扩散的地表径流，有助于通过防止洪水和沉积物沉积来保护洞穴。在隧道中也观察到定向模式，60%的隧道朝向西南/东南。古穴居的平均海拔高度在49 ~ 1023 m之间，在陡壁和高原较高。我们的结论是，地形隔间和形态可能对古洞穴的发掘和保存都有贡献，为第四纪时期Xenarthra的行为和环境变化提供了证据。研究结果有助于理解地貌与灭绝巨型动物行为之间的相互作用，增强了GMUCCS古洞穴的科学价值和遗产价值。

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引用次数: 0

Insights on northeastern South America tectonics from local event tomography 局部事件层析成像对南美洲东北部构造的启示

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.jsames.2025.105936

Mariano S. Arnaiz-Rodríguez , Noel Crasto , Ana Jaramillo , Ivan Koulakov , Ana K. Sánchez-Gamboa , Franck A. Audemard , Carlos E. Reinoza , Michael Schmitz

We present results from local earthquake tomography in northeastern Venezuela, where the Caribbean and South American plates meet. The region, dominated by strike-slip faulting, subduction and inhabited by the Paria Seismic Cluster, offers a unique setting for studying the mechanisms of lithospheric tearing, Subduction-Transform Edge Propagator structures and seismic cluster formation. To perform the tomography, we use a compilation of data, including: the ISC catalog, the database of the University of the West Indies, and the data collected by the temporary array of the BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles Arc Region) Project. The combined and revised dataset was composed of 286 stations, 4384 events, 70891 P-wave arrivals and 42532 S-wave arrivals. In our results, the Paria Seismic Cluster appears as a weak region (P-wave low velocity zone) where the lithosphere beneath the active strike-slip system and the subduction slab meet. Hence, the lithosphere tears in response to the dominant shear stress aided by the slab. Furthermore, the cluster appears to be a superposition of the seismicity derived from this process and that of the subducted slab. Crustal-scale high velocities in the Paria Peninsula, associated with the intrusive bodies documented in the area are indicative of subduction-related volcanism active beneath the continent from the Late Miocene to Early Pliocene. Furthermore, we image a high-velocity and seismically active zone beneath Trinidad, which is interpreted as a piece of the Atlantic slab that was torn before subducting underneath the South American lithosphere. Finally, we identify several magmatic chambers beneath the southern Lesser Antilles Arc, as well as an LVZ that we interpret as an upwelling that feeds the volcanism.

我们介绍了委内瑞拉东北部的局部地震断层成像结果，加勒比和南美板块在那里相遇。该地区以走滑断裂和俯冲作用为主，并发育Paria地震群，为研究岩石圈撕裂、俯冲变换边缘传播体构造和地震群形成机制提供了独特的环境。为了进行断层扫描，我们使用了一组数据，包括：ISC目录、西印度群岛大学数据库和BOLIVAR（委内瑞拉和安的列斯弧地区宽带海洋-陆地调查）项目临时阵列收集的数据。合并和修正后的数据集由286个台站、4384个事件、70891个p波到达和42532个s波到达组成。在我们的研究结果中，Paria地震群表现为活动走滑系统下的岩石圈与俯冲板块交汇的弱区（p波低速带）。因此，岩石圈在板块辅助下的主要剪切应力作用下发生撕裂。此外，该群似乎是由这一过程产生的地震活动性与俯冲板块的地震活动性的叠加。帕里亚半岛的地壳高速与该地区记录的侵入体有关，表明晚中新世至上新世早期，该大陆下存在与俯冲有关的火山活动。此外，我们还绘制了特立尼达下面的高速地震活跃带的图像，这被解释为大西洋板块的一块在俯冲到南美岩石圈下面之前被撕裂。最后，我们确定了小安的列斯岛弧南部的几个岩浆室，以及一个LVZ，我们将其解释为为火山活动提供动力的上升流。

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引用次数: 0

A Santacrucian record of Acarechimys minutus (Octodontoidea) from Laguna del Laja (Cura-Mallín Formation, Chile; late Early Miocene) and its biogeographic implications 拉加湖（Cura-Mallín组，智利；早中新世晚期）的Acarechimys minutus（章鱼科）的圣克鲁斯记录及其生物地理意义

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.jsames.2025.105938

Andrés Solórzano , Alfonso Encinas , Mónica Núñez-Flores , Gabriel Carrasco , Karina Buldrini , Jorge Campos-Medina , René Bobe

The fossil record of pre-Quaternary continental mammals from Chile remains less well-documented than that of neighboring Argentina and Bolivia. Among the most promising successions is the Miocene Cura-Mallín Formation at Laguna del Laja (37.5°S), which preserves diverse mammalian assemblages spanning nearly 10 million years. One of the rodents previously reported from this locality is Acarechimys, a small octodontoid widely documented in Late Oligocene to Late Miocene continental deposits of South America. However, records from Laguna del Laja were based exclusively on fragmentary and undescribed material, leaving their taxonomic identity uncertain. Here, we describe a Santacrucian (late Early Miocene) occurrence of a caviomorph rodent from Laguna del Laja, represented by a partial mandible preserving m1–m3 and a fragment of the dp4. Dental traits, including a laterally compressed lower incisor and a developed posterior arm of the metaconid, support referral to Acarechimys minutus. This well-dated record provides a stratigraphically constrained occurrence of the species in south-central Chile and narrows the geographic gap between Chilean localities of Chucal in the north and Aysén in the south. The new evidence supports the hypothesis that the Laguna del Laja assemblage was not fully endemic, but rather integrated into the broader Santacrucian biogeographic continuum, reinforcing its value as a key reference point for Neogene faunal and biogeographic studies in the south-central Andes.

与邻国阿根廷和玻利维亚相比，来自智利的前第四纪大陆哺乳动物的化石记录仍然没有得到充分的证明。最有希望的序列是拉古纳德尔拉贾（37.5°S）中新世Cura-Mallín组，它保存了近1000万年的各种哺乳动物组合。在此发现的一种啮齿类动物是Acarechimys，这是一种小型齿状类动物，广泛记录在南美晚渐新世至晚中新世大陆沉积物中。然而，来自拉古纳德尔拉贾的记录完全基于碎片和未描述的材料，使其分类身份不确定。在这里，我们描述了一种来自拉贾湖（Laguna del Laja）的洞穴形啮齿类动物的圣十字期（早中新世晚期），以部分保存的m1-m3下颌骨和dp4的碎片为代表。牙齿特征，包括侧压下门牙和发达的后髁后臂，支持转介到Acarechimys minuth。这一年代准确的记录提供了该物种在智利中南部地层受限的出现，并缩小了智利北部Chucal地区和南部ayssamin地区之间的地理差距。新的证据支持了拉古纳德尔拉贾组合不是完全地方性的假设，而是融入了更广泛的圣克鲁斯生物地理连续体，加强了它作为安第斯山脉中南部新近纪动物和生物地理研究的关键参考点的价值。

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引用次数: 0

Degassing-driven seismicity and deformation: Evidence from the Cretaceous Alto Paranaíba Igneous Province, southeastern Brazil 脱气驱动的地震活动和变形：来自巴西东南部白垩纪Alto Paranaíba火成岩省的证据

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.jsames.2025.105935

Lucca Martins Franco , Miguel Tupinambá , Emanuele Francesco La Terra , Liliane Paiva Panetto , Rogério Guitarrari Azzone

Here, we provide some structural and mineralogical evidence about what happens below a volcanic field during precursor seismic events. Based on outcrops and borehole material, we analyzed volcanic-related structures within the Cretaceous volcanic sequence of the Alto Paranaíba Igneous Province and the underlying Areado Group sandstones in southeastern Brazil, focusing on the role of magmatic volatiles and magmatic fluid circulation. Structural, petrographic, and geochemical data indicate that magma ascent through subvertical conduits generated overpressure conditions, promoting carbonate-rich hydrothermal activity and widespread deformation. The resulting structural assemblage includes normal faults, deformation bands, localized folding, subhorizontal creeping faults, and soft-sediment deformation structures, particularly concentrated at sandstone–volcanic contacts. Geological profiles highlight the mechanical and hydraulic interaction between alkaline rocks and their sedimentary host. Overall, the results indicate that volatile exsolution during magma ascent was a key driver of fluid-assisted brittle deformation and induced seismicity, exerting first-order control on fault development, sediment destabilization, and hydrothermal alteration.

在这里，我们提供了一些构造和矿物学证据，说明在地震前兆事件期间火山场下面发生了什么。根据露头和钻孔资料，分析了巴西东南部Alto Paranaíba火成岩省白垩系火山层序和下伏Areado群砂岩的火山相关构造，重点研究了岩浆挥发物和岩浆流体循环的作用。构造、岩石学和地球化学数据表明，岩浆通过次垂直管道上升产生超压条件，促进了富含碳酸盐的热液活动和广泛的变形。构造组合包括正断层、变形带、局部褶皱、次水平爬行断层和软沉积变形构造，尤其集中在砂岩-火山接触处。地质剖面突出了碱性岩与其沉积宿主之间的力学和水力相互作用。总体而言，岩浆上升过程中的挥发性析出是流体辅助脆性变形和诱发地震活动的关键驱动因素，对断层发育、沉积物失稳和热液蚀变具有一级控制作用。

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引用次数: 0