Pub Date : 2026-03-01Epub Date: 2026-01-14DOI: 10.1016/j.jsames.2026.105958
Sonia Agostinho , Carlos Alves Moreira Júnior , José Antônio Barbosa , Wilson Rodrigues de Andrade Freitas , Emmanuel Franco Neto , Alcides da Nóbrega Sial
We present an analysis of the ichnofossiliferous content from the Upper Campanian to the Lower Danian, obtained from well 1-PO-01-PE, Paraíba Basin, NE Brazil. The investigation integrated the bioturbation record and lithofaciological changes with δ13C and δ18O isotopic data to understand how variations in depositional environments and climatic conditions affected the benthic community. The analysis of core samples revealed a low diversity ichnological suite, dominated by the generalist ichnogenera Palaeophycus and Planolites, suggesting an ecosystem under ecological stress. The results suggest an intrinsic relationship between the intensity of bioturbation on the carbonate platform and sea-level changes, which controlled substrate oxygenation and energy levels. Reduced bioturbation is observed in periods associated with shallower waters and increased environmental energy (Danian), and also during the high sea-level period which may have reduced substrate oxygenation. The reduction of bioturbation during the Danian was influenced by marine regressive effects and occurred during colder climatic conditions.
{"title":"Ichnological and chemostratigraphic analysis from the K-Pg transition in well 1-PO-01-PE, Paraíba Basin, Northeast Brazil","authors":"Sonia Agostinho , Carlos Alves Moreira Júnior , José Antônio Barbosa , Wilson Rodrigues de Andrade Freitas , Emmanuel Franco Neto , Alcides da Nóbrega Sial","doi":"10.1016/j.jsames.2026.105958","DOIUrl":"10.1016/j.jsames.2026.105958","url":null,"abstract":"<div><div>We present an analysis of the ichnofossiliferous content from the Upper Campanian to the Lower Danian, obtained from well 1-PO-01-PE, Paraíba Basin, NE Brazil. The investigation integrated the bioturbation record and lithofaciological changes with δ<sup>13</sup>C and δ<sup>18</sup>O isotopic data to understand how variations in depositional environments and climatic conditions affected the benthic community. The analysis of core samples revealed a low diversity ichnological suite, dominated by the generalist ichnogenera <em>Palaeophycus</em> and <em>Planolites</em>, suggesting an ecosystem under ecological stress. The results suggest an intrinsic relationship between the intensity of bioturbation on the carbonate platform and sea-level changes, which controlled substrate oxygenation and energy levels. Reduced bioturbation is observed in periods associated with shallower waters and increased environmental energy (Danian), and also during the high sea-level period which may have reduced substrate oxygenation. The reduction of bioturbation during the Danian was influenced by marine regressive effects and occurred during colder climatic conditions.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105958"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978414","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}
Pub Date : 2026-03-01Epub Date: 2026-01-06DOI: 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.
{"title":"Paleogeography and stratigraphic correlation of the early rift phase in the northeastern Brazilian basins: Jurassic Aliança formation (Jatobá Basin) and coeval units, Western Gondwana","authors":"Leonardo M. De Oliveira , Édison V. Oliveira , Gelson L. Fambrini","doi":"10.1016/j.jsames.2026.105950","DOIUrl":"10.1016/j.jsames.2026.105950","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105950"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927673","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}
Pub Date : 2026-03-01Epub Date: 2026-01-02DOI: 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。
{"title":"Relief compartments and forms: Influence on paleoburrow distribution patterns","authors":"Arthur Philipe Bechtel , Jairo Valdati","doi":"10.1016/j.jsames.2025.105937","DOIUrl":"10.1016/j.jsames.2025.105937","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105937"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927676","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}
Pub Date : 2026-03-01Epub Date: 2025-12-12DOI: 10.1016/j.jsames.2025.105912
Beatriz Coira , Suzanne Mahlburg Kay
This paper presents an updated review and discussion of the mining potential of ore and geothermal deposits related to Cenozoic volcanism in the Central Andean Puna. The types and distributions of these systems reflect the volcanic, structural and geophysical conditions at the time of formation. Most are related to volcanism in a thickening continental crust over a shallowing or steepening subduction zone.
The most important Cenozoic mineralization periods were at 33–28.7 Ma, 16-11 Ma and 10-6 Ma. The first produced the early Miocene Cu-Mo-Au porphyries in the southern Puna, the second the middle Miocene Cu-Mo and Au-Cu porphyries related to epithermal systems with Pb and Zn (+Ag ± Sn) in dome complexes in the northern and southern Puna, and the third the base metal Ag-rich veined epithermal deposits in composite volcanoes related to megacalderas with post collapse vetiform epithermal base metals and high Ag/Au ratios and Sb, Sn and Bi anomalies.
Most northern Puna (22°S-24°30′S) ore deposits are in Pb-Zn (+Ag-Sn) epithermal systems whose metallogenetic signatures are like coeval Bolivian Tin Belt deposits. In contrast, most southern Puna deposits (∼24.5°- 27°S) are in porphyry type Cu-Mo, Cu-Au and Pb + Zn ± Ag + Cu ± Au epithermal systems. These differences reflect both tectonic conditions and the nature of the underlying crust.
The most promising geothermal prospects are in the Puna where they are intimately linked with young volcanic centers associated with heat anomalies in the crust related to partial melt zones. Prominent high enthalpy prospects are in the Tuzgle, Tocomar, Cerro Blanco and Cerro Galán regions where Quaternary heat anomalies reflect partial melt zones. Advanced feasibility studies exist in the Tuzgle and Tocomar systems.
{"title":"Relation of Cenozoic volcanism, mineral deposits and geothermal resources in the Puna to the geologic evolution of the Southern Central Andes (22°-28°S)","authors":"Beatriz Coira , Suzanne Mahlburg Kay","doi":"10.1016/j.jsames.2025.105912","DOIUrl":"10.1016/j.jsames.2025.105912","url":null,"abstract":"<div><div>This paper presents an updated review and discussion of the mining potential of ore and geothermal deposits related to Cenozoic volcanism in the Central Andean Puna. The types and distributions of these systems reflect the volcanic, structural and geophysical conditions at the time of formation. Most are related to volcanism in a thickening continental crust over a shallowing or steepening subduction zone.</div><div>The most important Cenozoic mineralization periods were at 33–28.7 Ma, 16-11 Ma and 10-6 Ma. The first produced the early Miocene Cu-Mo-Au porphyries in the southern Puna, the second the middle Miocene Cu-Mo and Au-Cu porphyries related to epithermal systems with Pb and Zn (+Ag ± Sn) in dome complexes in the northern and southern Puna, and the third the base metal Ag-rich veined epithermal deposits in composite volcanoes related to megacalderas with post collapse vetiform epithermal base metals and high Ag/Au ratios and Sb, Sn and Bi anomalies.</div><div>Most northern Puna (22°S-24°30′S) ore deposits are in Pb-Zn (+Ag-Sn) epithermal systems whose metallogenetic signatures are like coeval Bolivian Tin Belt deposits. In contrast, most southern Puna deposits (∼24.5°- 27°S) are in porphyry type Cu-Mo, Cu-Au and Pb + Zn ± Ag + Cu ± Au epithermal systems. These differences reflect both tectonic conditions and the nature of the underlying crust.</div><div>The most promising geothermal prospects are in the Puna where they are intimately linked with young volcanic centers associated with heat anomalies in the crust related to partial melt zones. Prominent high enthalpy prospects are in the Tuzgle, Tocomar, Cerro Blanco and Cerro Galán regions where Quaternary heat anomalies reflect partial melt zones. Advanced feasibility studies exist in the Tuzgle and Tocomar systems.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105912"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886266","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}
Pub Date : 2026-03-01Epub Date: 2026-01-12DOI: 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.
{"title":"Tectono-sedimentary evolution of the western Gondwana margin during the Silurian: Insights from new sedimentological and geochronological analysis of the Villacorta Formation","authors":"D. Milanesio , P. Armas , J. Biddle , A. Edgington , J. Otamendi , J. Fosdick , E. Cristofolini","doi":"10.1016/j.jsames.2026.105953","DOIUrl":"10.1016/j.jsames.2026.105953","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105953"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978413","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}
Pub Date : 2026-03-01Epub Date: 2025-12-24DOI: 10.1016/j.jsames.2025.105933
Luis Gerardo Vázquez-Guevara , René Ventura-Houle , Tomás Alejandro Peña-Alonso , Oscar Guevara-Mansilla , Glenda Nelly Requena-Lara , Elizabeth del Carmen Andrade-Limas , Bárbara Azucena Macías-Hernández
Karst aquifers in northeastern Mexico constitute the primary source of freshwater for more than 900,000 inhabitants, yet the hydrogeochemical functioning of their recharge zones and the mechanisms controlling groundwater evolution remain insufficiently documented. This study examines the origin, circulation, and degree of hydrochemical evolution of groundwater in the Upper Guayalejo–Tamesí Basin, a carbonate-dominated karst system characterized by complex structural controls and seasonal recharge dynamics. Thirteen groundwater samples collected between 2023 and 2024 were integrated with previously reported hydrochemical datasets to evaluate water–rock interaction processes and identify flow components within the local, intermediate, and regional Mifflin framework. Three hydrochemical facies were identified from the results: (1) Ca–Mg–Cl–SO4, associated with evaporation processes and salt dissolution; (2) Ca–Mg–HCO3, typical of recharge zones in carbonate rocks; and (3) Na–K–Cl–SO4, corresponding to evolved waters with high mineralization. Major ion relationships indicate that calcite dissolution predominates (Ca2+ > Mg2+ and HCO3− > Ca2+), with a minor contribution from gypsum dissolution (SO42− > Ca2+), as well as halite dissolution and cation exchange. Flow classification reveals a progression from local to intermediate and regional systems, controlled by increasing residence time, circulation depth, and the influence of structural pathways. These results enhance the understanding of hydrogeochemical processes governing groundwater evolution in a major karst recharge zone of northeastern Mexico and provide a transferable conceptual framework applicable to karst basins worldwide. This contributes to improving regional-scale interpretations of groundwater flow dynamics and supports informed water-resource management in structurally complex carbonate terrains.
{"title":"Groundwater origin and circulation within a karst watershed recharge zone: the case of the Upper Guayalejo-Tamesí River Basin, southern Tamaulipas, Mexico","authors":"Luis Gerardo Vázquez-Guevara , René Ventura-Houle , Tomás Alejandro Peña-Alonso , Oscar Guevara-Mansilla , Glenda Nelly Requena-Lara , Elizabeth del Carmen Andrade-Limas , Bárbara Azucena Macías-Hernández","doi":"10.1016/j.jsames.2025.105933","DOIUrl":"10.1016/j.jsames.2025.105933","url":null,"abstract":"<div><div>Karst aquifers in northeastern Mexico constitute the primary source of freshwater for more than 900,000 inhabitants, yet the hydrogeochemical functioning of their recharge zones and the mechanisms controlling groundwater evolution remain insufficiently documented. This study examines the origin, circulation, and degree of hydrochemical evolution of groundwater in the Upper Guayalejo–Tamesí Basin, a carbonate-dominated karst system characterized by complex structural controls and seasonal recharge dynamics. Thirteen groundwater samples collected between 2023 and 2024 were integrated with previously reported hydrochemical datasets to evaluate water–rock interaction processes and identify flow components within the local, intermediate, and regional Mifflin framework. Three hydrochemical facies were identified from the results: (1) Ca–Mg–Cl–SO<sub>4</sub>, associated with evaporation processes and salt dissolution; (2) Ca–Mg–HCO<sub>3</sub>, typical of recharge zones in carbonate rocks; and (3) Na–K–Cl–SO<sub>4</sub>, corresponding to evolved waters with high mineralization. Major ion relationships indicate that calcite dissolution predominates (Ca<sup>2+</sup> > Mg<sup>2+</sup> and HCO<sub>3</sub><sup>−</sup> > Ca<sup>2+</sup>), with a minor contribution from gypsum dissolution (SO<sub>4</sub><sup>2−</sup> > Ca<sup>2+</sup>), as well as halite dissolution and cation exchange. Flow classification reveals a progression from local to intermediate and regional systems, controlled by increasing residence time, circulation depth, and the influence of structural pathways. These results enhance the understanding of hydrogeochemical processes governing groundwater evolution in a major karst recharge zone of northeastern Mexico and provide a transferable conceptual framework applicable to karst basins worldwide. This contributes to improving regional-scale interpretations of groundwater flow dynamics and supports informed water-resource management in structurally complex carbonate terrains.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105933"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886265","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}
Pub Date : 2026-03-01Epub Date: 2025-12-03DOI: 10.1016/j.jsames.2025.105900
Gabriela A. Gonzalez-Liedtke , Matías M. Morales Cámera , Juan A. Dahlquist , Sebastián Rocher , Juan C. Harasimiuk , Gilmara Santos da Cruz , Pablo H. Alasino , Juan A. Moreno
Felsic microgranitoid enclaves (FMEs) are underexplored components of granitic plutons that preserve key evidence of magma chamber processes. This study examines FMEs and the coexisting fine-grained units in relation to the porphyritic regional granites that host them within the Characato suite of the Achala Intrusive Complex, Argentina, integrating field observations, petrography, whole-rock geochemistry, mineral chemistry, and Nd isotope analyses.
Our main conclusions indicate that the FMEs and associated fine-grained units represent autolithic fragments derived from solidification fronts within granitic magma chambers. Their finer grain size and relatively higher crystallization temperatures (e.g., ΔTZr ≈ 60 °C and ΔTBt ≈ 40 °C) suggest early crystallization under enhanced undercooling conditions near chamber margins.
Field evidence -such as spatial association of FMEs with marginal fine-grained units, gradational contacts, ductile felsic dykes, and magmatic layering and deformation-indicates multiple episodes of solidification front collapse into the host magma. The observed diversity in enclave size, texture, and degree of interaction reflects a continuum of rheological states, ranging from crystal-rich suspensions to partially solidified mushes.
Furthermore, the neodymium isotopic compositions and geochemical trends of the FMEs and marginal fine-grained units are consistent with those of the regional host granites. This supports a cogenetic and crustal origin, with the enclaves and associated lithologies representing more primitive crystallization products.
This study emphasizes the dynamic role of solidification fronts as zones of instability, and magmatic recycling, contributing to the construction and internal evolution of felsic plutonic systems.
{"title":"Felsic microgranitoid enclaves as records of solidification front collapse in silicic magma chambers: Insights from the Devonian Characato suite (Achala Intrusive Complex, Argentina)","authors":"Gabriela A. Gonzalez-Liedtke , Matías M. Morales Cámera , Juan A. Dahlquist , Sebastián Rocher , Juan C. Harasimiuk , Gilmara Santos da Cruz , Pablo H. Alasino , Juan A. Moreno","doi":"10.1016/j.jsames.2025.105900","DOIUrl":"10.1016/j.jsames.2025.105900","url":null,"abstract":"<div><div>Felsic microgranitoid enclaves (FMEs) are underexplored components of granitic plutons that preserve key evidence of magma chamber processes. This study examines FMEs and the coexisting fine-grained units in relation to the porphyritic regional granites that host them within the Characato <em>suite</em> of the Achala Intrusive Complex, Argentina, integrating field observations, petrography, whole-rock geochemistry, mineral chemistry, and Nd isotope analyses.</div><div>Our main conclusions indicate that the FMEs and associated fine-grained units represent autolithic fragments derived from solidification fronts within granitic magma chambers. Their finer grain size and relatively higher crystallization temperatures (e.g., ΔT<sub>Zr</sub> ≈ 60 °C and ΔT<sub>Bt</sub> ≈ 40 °C) suggest early crystallization under enhanced undercooling conditions near chamber margins.</div><div>Field evidence -such as spatial association of FMEs with marginal fine-grained units, gradational contacts, ductile felsic dykes, and magmatic layering and deformation-indicates multiple episodes of solidification front collapse into the host magma. The observed diversity in enclave size, texture, and degree of interaction reflects a continuum of rheological states, ranging from crystal-rich suspensions to partially solidified mushes.</div><div>Furthermore, the neodymium isotopic compositions and geochemical trends of the FMEs and marginal fine-grained units are consistent with those of the regional host granites. This supports a cogenetic and crustal origin, with the enclaves and associated lithologies representing more primitive crystallization products.</div><div>This study emphasizes the dynamic role of solidification fronts as zones of instability, and magmatic recycling, contributing to the construction and internal evolution of felsic plutonic systems.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105900"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886270","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}
Pub Date : 2026-03-01Epub Date: 2025-12-26DOI: 10.1016/j.jsames.2025.105932
Roberto Silva Jr. , Elisabetta Erba , Aristóteles de Moraes Rios-Netto , Silvia Clara Silva , Mauro Daniel Rodrigues Bruno , Lília Dias Sabaraense , Milene Freitas Figueiredo , Leonardo Borghi , João Graciano Mendonça Filho
This study investigates paleoceanographic and paleobiogeographic changes in the South Atlantic Ocean between the late Albian and early Santonian, integrating quantitative analyses of calcareous nannofossil assemblages with new geochemical data from 123 samples collected at Site 356 (São Paulo Plateau). A total of 109 calcareous nannofossil taxa and nine bioevents were identified. Two major hiatuses, corresponding to the late Albian–Cenomanian (∼6.9 Myr) and late Turonian/early Coniacian (∼2.7 Myr), are evident in the calcareous nannofossil record. The integration of nannofossil assemblages, diversity indices, and paleoecological proxies (mTI and mNI) with Total Organic Carbon (TOC) and stable isotope data (δ13C and δ18O) reveals nine distinct paleoceanographic intervals. Notably, the OAE 2 interval is confirmed by a plateau in the positive δ13C excursion and a sharp spike in TOC, reflecting enhanced organic carbon burial, although the onset of this event was truncated by the late Albian–Cenomanian hiatus. The paleoceanographic reconstruction indicates a predominance of warm, oligotrophic surface waters from the late Albian through the Turonian. Subsequently, a distinct positive shift in δ18O values during the late Coniacian signals a transition towards cooler surface waters. The paleobiogeographic affinity of the assemblages shows a dominance of cosmopolitan and mid-to low-latitude taxa, consistent with paleogeographic reconstructions and paleolatitude estimates (24°S–30°S) for the studied section. However, the increased abundance of high-latitude taxa between the late Coniacian and early Santonian appears to reflect a phase of enhanced surface-water connectivity and/or more effective oceanic circulation between the Central and South Atlantic, possibly driven by sea-level rise and/or a reduced influence of geological barriers (e.g., the Rio Grande Rise–Walvis Ridge System).
本研究通过对356 Site （s o Paulo Plateau）收集的123个样品的钙质纳米化石组合的定量分析和新的地球化学数据，研究了南大西洋Albian晚期至Santonian早期的古海洋学和古生物地理变化。共鉴定出109个钙质纳米化石分类群和9个生物事件。在钙质纳米化石记录中，有两个主要的间歇期，对应于晚Albian-Cenomanian （~ 6.9 Myr）和晚Turonian/早Coniacian （~ 2.7 Myr）。综合纳米化石组合、多样性指数、古生态指标（mTI和mNI）、总有机碳（TOC）和稳定同位素（δ13C和δ18O）数据，揭示了9个不同的古海洋层序。值得注意的是，OAE 2的间隔由δ13C正偏移的平台和TOC的急剧上升证实，反映了有机碳埋藏的增强，尽管这一事件的开始被晚Albian-Cenomanian中断所截断。古海洋学重建表明，从晚阿尔比世到Turonian，温暖的、少营养的地表水占主导地位。随后，在Coniacian晚期δ18O值的明显正移标志着向较冷的地表水过渡。这些组合的古地理亲和性显示出世界性和中低纬度分类群的优势，与研究剖面的古地理重建和古纬度估计（24°S - 30°S）一致。然而，在晚Coniacian和早sanantonian之间高纬度分类群的增加似乎反映了一个增强的地表水连通性和/或中大西洋和南大西洋之间更有效的海洋环流阶段，可能是由于海平面上升和/或地质屏障（例如里约热内卢Grande rise - walvis Ridge系统）影响的减少。
{"title":"Paleoceanographic and paleobiogeographic inferences from late Albian to early Santonian calcareous nannofossils at DSDP Site 356, South Atlantic","authors":"Roberto Silva Jr. , Elisabetta Erba , Aristóteles de Moraes Rios-Netto , Silvia Clara Silva , Mauro Daniel Rodrigues Bruno , Lília Dias Sabaraense , Milene Freitas Figueiredo , Leonardo Borghi , João Graciano Mendonça Filho","doi":"10.1016/j.jsames.2025.105932","DOIUrl":"10.1016/j.jsames.2025.105932","url":null,"abstract":"<div><div>This study investigates paleoceanographic and paleobiogeographic changes in the South Atlantic Ocean between the late Albian and early Santonian, integrating quantitative analyses of calcareous nannofossil assemblages with new geochemical data from 123 samples collected at Site 356 (São Paulo Plateau). A total of 109 calcareous nannofossil taxa and nine bioevents were identified. Two major hiatuses, corresponding to the late Albian–Cenomanian (∼6.9 Myr) and late Turonian/early Coniacian (∼2.7 Myr), are evident in the calcareous nannofossil record. The integration of nannofossil assemblages, diversity indices, and paleoecological proxies (mTI and mNI) with Total Organic Carbon (TOC) and stable isotope data (δ<sup>13</sup>C and δ<sup>18</sup>O) reveals nine distinct paleoceanographic intervals. Notably, the OAE 2 interval is confirmed by a plateau in the positive δ<sup>13</sup>C excursion and a sharp spike in TOC, reflecting enhanced organic carbon burial, although the onset of this event was truncated by the late Albian–Cenomanian hiatus. The paleoceanographic reconstruction indicates a predominance of warm, oligotrophic surface waters from the late Albian through the Turonian. Subsequently, a distinct positive shift in δ<sup>18</sup>O values during the late Coniacian signals a transition towards cooler surface waters. The paleobiogeographic affinity of the assemblages shows a dominance of cosmopolitan and mid-to low-latitude taxa, consistent with paleogeographic reconstructions and paleolatitude estimates (24°S–30°S) for the studied section. However, the increased abundance of high-latitude taxa between the late Coniacian and early Santonian appears to reflect a phase of enhanced surface-water connectivity and/or more effective oceanic circulation between the Central and South Atlantic, possibly driven by sea-level rise and/or a reduced influence of geological barriers (e.g., the Rio Grande Rise–Walvis Ridge System).</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105932"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927674","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}
Pub Date : 2026-03-01Epub Date: 2026-01-13DOI: 10.1016/j.jsames.2026.105954
E. Fucks , M.S. Luengo , D. Vera , Y. Rico
The Samborombón River Basin is located in the Pampean plain, in the Pampa Ondulada subregion, at the northeast of Buenos Aires Province, Argentina. Because available information is sparse and fragmented, we integrate geomorphology, stratigraphy, and paleoenvironmental data to reconstruct the basin's late Quaternary evolution. Geomorphological analysis distinguished several basin sectors whose channel forms, slopes, and landforms document the effects of Quaternary climatic fluctuations. The upper basin is characterized by low-sinuosity channels and incision into loessic deposits, whereas the middle basin presents higher sinuosity, meanders, bars, and deflation basins hosting current freshwater lagoons with associated lunettes. The lower basin displays highly sinuous channels, paleochannels, freshwater lagoons, beach ridges, and tidal flats, reflecting strong fluvial-marine interactions related to sea-level fluctuations and avulsion processes. Stratigraphic correlations with dated units in the neighboring Salado River basin allowed the establishment of a regional chronological framework. The characterization of the basin's geomorphological components and their stratigraphic configurations has enabled a more robust interpretation of its Quaternary paleoenvironmental evolution, shaped by the global climatic oscillations that define this interval. During the Late Pleistocene-Early Holocene, humid conditions promoted the onset of drainage network development and the deposition of fluvial and fluvio-lacustrine sediments (La Chumbiada and Gorch Members of the Luján Formation). An arid phase during the Mid-Holocene was marked by eolian activity, deflation processes, and the Holocene marine transgression recorded in the Canal de Las Escobas Formation. After ∼3 ka, renewed fluvial activity under wetter conditions led to the deposition of the Puente Las Gaviotas Member and the reactivation of lagoonal systems, while coastal regression generated beach ridges and paleochannels at the river mouth. Altogether, the sedimentary and geomorphological record of the Samborombón basin constitutes a valuable archive of the late Quaternary climatic and sea-level changes in the eastern Pampean plain.
Samborombón河流域位于潘潘平原，潘帕昂杜拉达次区域，在阿根廷布宜诺斯艾利斯省东北部。由于现有资料的稀疏和碎片化，我们整合了地貌、地层学和古环境资料，重建了盆地的晚第四纪演化。地貌分析区分了几个盆地板块，它们的河道形式、坡度和地貌记录了第四纪气候波动的影响。盆地上部以低弯度河道和切入黄土沉积为特征，而中部则以较高的弯度、曲流、沙洲和泄放盆地为特征，盆地中存在淡水泻湖和伴生月子。盆地下部显示高度弯曲的河道、古河道、淡水泻湖、滩脊和潮滩，反映出与海平面波动和崩解过程有关的强烈的河流-海洋相互作用。与邻近的萨拉多河流域的年代单位进行地层对比，可以建立一个区域年代学框架。对盆地地貌组成及其地层配置的描述，使其第四纪古环境演化得到了更有力的解释，而第四纪古环境演化是由确定这一区间的全球气候波动所塑造的。在晚更新世-全新世早期，湿润条件促进了水系网络发育的开始和河流和河流湖相沉积物的沉积（Luján组的La Chumbiada和Gorch成员）。中全新世的干旱期以风成活动、通货膨胀过程和全新世海侵为标志，记录在Canal de Las Escobas组。在~ 3ka之后，在更湿润的条件下，重新开始的河流活动导致了Puente Las Gaviotas段的沉积和泻湖系统的重新激活，而海岸退缩在河口处产生了海滩山脊和古河道。总之，Samborombón盆地的沉积和地貌记录构成了潘潘平原东部晚第四纪气候和海平面变化的宝贵档案。
{"title":"Late quaternary landscape evolution in the Samborombón River Basin, northeast of Buenos Aires, Argentina: Insights from geomorphology and stratigraphy","authors":"E. Fucks , M.S. Luengo , D. Vera , Y. Rico","doi":"10.1016/j.jsames.2026.105954","DOIUrl":"10.1016/j.jsames.2026.105954","url":null,"abstract":"<div><div>The Samborombón River Basin is located in the Pampean plain, in the <em>Pampa Ondulada</em> subregion, at the northeast of Buenos Aires Province, Argentina. Because available information is sparse and fragmented, we integrate geomorphology, stratigraphy, and paleoenvironmental data to reconstruct the basin's late Quaternary evolution. Geomorphological analysis distinguished several basin sectors whose channel forms, slopes, and landforms document the effects of Quaternary climatic fluctuations. The upper basin is characterized by low-sinuosity channels and incision into loessic deposits, whereas the middle basin presents higher sinuosity, meanders, bars, and deflation basins hosting current freshwater lagoons with associated lunettes. The lower basin displays highly sinuous channels, paleochannels, freshwater lagoons, beach ridges, and tidal flats, reflecting strong fluvial-marine interactions related to sea-level fluctuations and avulsion processes. Stratigraphic correlations with dated units in the neighboring Salado River basin allowed the establishment of a regional chronological framework. The characterization of the basin's geomorphological components and their stratigraphic configurations has enabled a more robust interpretation of its Quaternary paleoenvironmental evolution, shaped by the global climatic oscillations that define this interval. During the Late Pleistocene-Early Holocene, humid conditions promoted the onset of drainage network development and the deposition of fluvial and fluvio-lacustrine sediments (La Chumbiada and Gorch Members of the Luján Formation). An arid phase during the Mid-Holocene was marked by eolian activity, deflation processes, and the Holocene marine transgression recorded in the Canal de Las Escobas Formation. After ∼3 ka, renewed fluvial activity under wetter conditions led to the deposition of the Puente Las Gaviotas Member and the reactivation of lagoonal systems, while coastal regression generated beach ridges and paleochannels at the river mouth. Altogether, the sedimentary and geomorphological record of the Samborombón basin constitutes a valuable archive of the late Quaternary climatic and sea-level changes in the eastern Pampean plain.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"172 ","pages":"Article 105954"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979091","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}
Pub Date : 2026-02-15Epub Date: 2025-12-15DOI: 10.1016/j.jsames.2025.105920
Uilliams Alves de Oliveira Paz , Luis Felipe Ferreira de Mendonça , Arthur Antônio Machado
Topographic irregularities act as mechanisms of flow convergence or divergence, affecting the vertical distribution of motion and creating velocity gradients. In estuarine regions, this process favors the formation of persistent residual structures, which play the role of concentrating or dispersing matter. This study investigates spatial variations in estuarine tidal flow induced by bathymetric variations on scales of 1–70 m, using Acoustic Doppler Current Profilers (ADCP). ADCP results show that in channels near Frades Island, bathymetric deepening generates more intense flows, with velocities reaching 0.6 m/s northward in the meridional component and 0.8 m/s westward in the zonal component, consistent with three-dimensional fluid dynamics. In regions farther from the mainland, bathymetric deepening causes attenuation and reversal of currents. Near to Itaparica Island, bathymetry deepens from 15 m to 50 m over a 2 km stretch, with the meridional component showing a variation from 0.4 m/s northward to 0.7 m/s southward. In the center of BTS, the reversal of the zonal component leads to the formation of cyclonic vortices. The ADCP data show that deepening in confined regions accelerates the flow, while in open areas it decelerates the flow, occasionally creating recirculation zones and localized vorticity. These results corroborate the existing literature on the influence of bathymetry on estuarine circulation and provide in situ evidence, highlighting the importance of incorporating high-resolution bathymetry and stratification to reproduce the complexity of flow in estuarine regions.
{"title":"Influence of bathymetric variation on the flows of Baía de Todos os Santos","authors":"Uilliams Alves de Oliveira Paz , Luis Felipe Ferreira de Mendonça , Arthur Antônio Machado","doi":"10.1016/j.jsames.2025.105920","DOIUrl":"10.1016/j.jsames.2025.105920","url":null,"abstract":"<div><div>Topographic irregularities act as mechanisms of flow convergence or divergence, affecting the vertical distribution of motion and creating velocity gradients. In estuarine regions, this process favors the formation of persistent residual structures, which play the role of concentrating or dispersing matter. This study investigates spatial variations in estuarine tidal flow induced by bathymetric variations on scales of 1–70 m, using Acoustic Doppler Current Profilers (ADCP). ADCP results show that in channels near Frades Island, bathymetric deepening generates more intense flows, with velocities reaching 0.6 m/s northward in the meridional component and 0.8 m/s westward in the zonal component, consistent with three-dimensional fluid dynamics. In regions farther from the mainland, bathymetric deepening causes attenuation and reversal of currents. Near to Itaparica Island, bathymetry deepens from 15 m to 50 m over a 2 km stretch, with the meridional component showing a variation from 0.4 m/s northward to 0.7 m/s southward. In the center of BTS, the reversal of the zonal component leads to the formation of cyclonic vortices. The ADCP data show that deepening in confined regions accelerates the flow, while in open areas it decelerates the flow, occasionally creating recirculation zones and localized vorticity. These results corroborate the existing literature on the influence of bathymetry on estuarine circulation and provide in situ evidence, highlighting the importance of incorporating high-resolution bathymetry and stratification to reproduce the complexity of flow in estuarine regions.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"171 ","pages":"Article 105920"},"PeriodicalIF":1.5,"publicationDate":"2026-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145799274","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}
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