Pub Date : 2025-12-10DOI: 10.1016/j.jsames.2025.105918
C. Montes , C.A. Rosero , F. Lamus , L.C. Perez-Angel , G. Bayona , J.M. Muñoz
A ∼23 km-long, hiking-kayaking, panoramic transect along the Rionegro Canyon in the western flank of the Eastern Cordillera of Colombia reveals two deformed belts with contrasting structural styles separated by a regional fault (La Salina Thrust). East of the fault, a deformed belt is characterized by tight, horizontal and upright concentric and box folds with pervasive axial-planar cleavage within a Lower Cretaceous, mostly sandy sequence. West the fault, the structural style is characterized by thrust sheets with prominent footwall deformation and isoclinal folding in the hanging wall. At least four stacked thrust sheets that repeat Upper Cretaceous sequences define a regional-scale duplex (El Trigo-Bituima anticlinal stack duplex). Immediately west of the anticlinal duplex, a regional syncline (Guaduas) folds a ∼1.5 km-thick, middle Eocene to Oligocene molasse deposit. The western flank of the syncline is thrusted (Cambras Thrust) on to a ∼2 km-thick Miocene molasse deposit repeated by the frontal thrust of the Eastern Cordillera (Honda Thrust). Line-balancing of a 30 km-long cross-section that includes the Honda Thrust results in a shortening value of ∼60 % (∼45 km) not considering layer-parallel shortening. Reconstruction of the original geometry suggests the presence of two rift-fault systems: one to the east, where the thickness of Cretaceous sequence changes from ∼4 to 3 km, and another one ∼50 km to the west, where the ∼3 km-thick Cretaceous sequence thins to nothing. The former is reactivated as the La Salina Thrust and likely contains pre-Cretaceous basement rocks in its hanging wall, and the latter is not reactivated, as previous studies had proposed. All of this is consistent with a main pulse of growth of the Eastern Cordillera and major surface elevation gain starting in middle Eocene times.
{"title":"Panoramic Transect of the Western Flank of Eastern Cordillera Fold and Thrust Belt, Northern Andes, Colombia","authors":"C. Montes , C.A. Rosero , F. Lamus , L.C. Perez-Angel , G. Bayona , J.M. Muñoz","doi":"10.1016/j.jsames.2025.105918","DOIUrl":"10.1016/j.jsames.2025.105918","url":null,"abstract":"<div><div>A ∼23 km-long, hiking-kayaking, panoramic transect along the Rionegro Canyon in the western flank of the Eastern Cordillera of Colombia reveals two deformed belts with contrasting structural styles separated by a regional fault (La Salina Thrust). East of the fault, a deformed belt is characterized by tight, horizontal and upright concentric and box folds with pervasive axial-planar cleavage within a Lower Cretaceous, mostly sandy sequence. West the fault, the structural style is characterized by thrust sheets with prominent footwall deformation and isoclinal folding in the hanging wall. At least four stacked thrust sheets that repeat Upper Cretaceous sequences define a regional-scale duplex (El Trigo-Bituima anticlinal stack duplex). Immediately west of the anticlinal duplex, a regional syncline (Guaduas) folds a ∼1.5 km-thick, middle Eocene to Oligocene molasse deposit. The western flank of the syncline is thrusted (Cambras Thrust) on to a ∼2 km-thick Miocene molasse deposit repeated by the frontal thrust of the Eastern Cordillera (Honda Thrust). Line-balancing of a 30 km-long cross-section that includes the Honda Thrust results in a shortening value of ∼60 % (∼45 km) not considering layer-parallel shortening. Reconstruction of the original geometry suggests the presence of two rift-fault systems: one to the east, where the thickness of Cretaceous sequence changes from ∼4 to 3 km, and another one ∼50 km to the west, where the ∼3 km-thick Cretaceous sequence thins to nothing. The former is reactivated as the La Salina Thrust and likely contains pre-Cretaceous basement rocks in its hanging wall, and the latter is not reactivated, as previous studies had proposed. All of this is consistent with a main pulse of growth of the Eastern Cordillera and major surface elevation gain starting in middle Eocene times.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"171 ","pages":"Article 105918"},"PeriodicalIF":1.5,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145760625","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 : 2025-12-08DOI: 10.1016/j.jsames.2025.105917
María Florencia Ahumada , Marcelo Gonzalez , Franco Clavel Alvarado , Héctor P.A. García , Federico Lince Klinger , Francisco Ruiz
The Guayatayoc salt flat basin, located in the northern sector of the Argentine Puna region (Jujuy province), stands out as one of the most promising areas for in depth geophysical research, focused on brine exploration. This region is considered one of the primary areas hosting several economically important lithium brine deposits. These results were obtained using gravimetry, audio-magnetotelluric (AMT), electrical resistivity tomography (ERT), magnetometry, and refraction seismic techniques. The main objective was to characterize the subsurface properties to infer the presence of clastic and/or evaporitic facies potentially carrying brines, as well as to identify marginal aquifers zones or freshwater sources that contribute to recharge and analyze the structural controls of the basin.
Two 2D geological models were developed, revealing a structurally segmented basin into high and low blocks, with three sub-basins delimited by Paleozoic-Cretaceous basement blocks uplifted by faults. A sedimentary unit with densities and electrical resistivity compatible with saturated sands and gravels, possibly carrying brackish water or clay-rich formation containing brines was modeled.
This work represents one of the few published studies that integrate multiple geophysical methodologies for the characterization of a salt flat basin located in the Puna region of Argentina. The use of multiple geophysical techniques promotes best practices in geophysical exploration and responsible resource management. This methodology can be replicated in other saline regions within the Lithium Triangle.
{"title":"Structural and groundwater exploration in the Guayatayoc salt flat basin (Puna Oriental Jujeña, northwest Argentina), using multiple geophysical techniques","authors":"María Florencia Ahumada , Marcelo Gonzalez , Franco Clavel Alvarado , Héctor P.A. García , Federico Lince Klinger , Francisco Ruiz","doi":"10.1016/j.jsames.2025.105917","DOIUrl":"10.1016/j.jsames.2025.105917","url":null,"abstract":"<div><div>The Guayatayoc salt flat basin, located in the northern sector of the Argentine Puna region (Jujuy province), stands out as one of the most promising areas for in depth geophysical research, focused on brine exploration. This region is considered one of the primary areas hosting several economically important lithium brine deposits. These results were obtained using gravimetry, audio-magnetotelluric (AMT), electrical resistivity tomography (ERT), magnetometry, and refraction seismic techniques. The main objective was to characterize the subsurface properties to infer the presence of clastic and/or evaporitic facies potentially carrying brines, as well as to identify marginal aquifers zones or freshwater sources that contribute to recharge and analyze the structural controls of the basin.</div><div>Two 2D geological models were developed, revealing a structurally segmented basin into high and low blocks, with three sub-basins delimited by Paleozoic-Cretaceous basement blocks uplifted by faults. A sedimentary unit with densities and electrical resistivity compatible with saturated sands and gravels, possibly carrying brackish water or clay-rich formation containing brines was modeled.</div><div>This work represents one of the few published studies that integrate multiple geophysical methodologies for the characterization of a salt flat basin located in the Puna region of Argentina. The use of multiple geophysical techniques promotes best practices in geophysical exploration and responsible resource management. This methodology can be replicated in other saline regions within the Lithium Triangle.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105917"},"PeriodicalIF":1.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737898","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 : 2025-12-05DOI: 10.1016/j.jsames.2025.105898
Camila Loaiza , Benigno Godoy , Nataly Freire , Osvaldo González-Maurel , Inés Rodríguez Araneda , Petrus le Roux , Juan Figueroa
Magmas in the Central Andes have evolved through fractional crystallization and crustal assimilation, operating at different crustal levels during their ascent through the ∼70 km-thick continental crust. Sairecabur stratovolcano, located within the Altiplano–Puna Volcanic Complex (APVC; 21°–24° S) of the Central Andean subduction zone, is stratigraphically divided into three units: Pre-Caldera Lavas (PRECL - Pleistocene), Post-Caldera I Lavas (POCIL - Upper Pleistocene), and Post-Caldera II Lavas (POCIIL - Holocene). These volcanic products range from 55 (basaltic andesite) to 63 (dacite) wt.% SiO2. In particular, Sairecabur shows a negative correlation between SiO2 wt.% and Eu/Eu∗, with Eu/Eu∗ values < 1, indicating the key role of plagioclase during late-stage magma differentiation. A deep-crustal garnet signature - though not prominent - cannot be excluded, which was overprinted by shallow differentiation and assimilation. Over the past 10 Ma, APVC magmas have been affected by significant crustal contamination, linked to crustal thickening during the Andean orogeny and localized processes. This trend is observed in all units of Sairecabur, where 87Sr/86Sr ratios of erupted products range from 0.707057 to 0.708667. This suggests a substantial crustal assimilation of a parental Andean-type magmas (87Sr/86Sr ratio ∼0.705), which was generated by an early stage of magmatic differentiation at lower crustal levels (MASH zone). Petrographic and geochemical data define three main mid-to-upper crustal evolutionary stages occurring afterwards: (1) an AFC stage in mid-to upper-crustal chambers, with 33–47 % AFC-type incorporation of felsic upper crustal material; (2) an intermediate stage of closed-system fractional crystallization involving plagioclase, pyroxene, amphibole, and biotite; and (3) a late-stage episode of magma mixing with shallow crustal melts, evidenced by glomeroporphyritic gabbroic aggregates and by trace-element trends and scatter accompanying advanced differentiation.
{"title":"Petrogenesis of a highly contaminated magmas by ascent through a thick continental crust: The case of Sairecabur volcano, Central Andes","authors":"Camila Loaiza , Benigno Godoy , Nataly Freire , Osvaldo González-Maurel , Inés Rodríguez Araneda , Petrus le Roux , Juan Figueroa","doi":"10.1016/j.jsames.2025.105898","DOIUrl":"10.1016/j.jsames.2025.105898","url":null,"abstract":"<div><div>Magmas in the Central Andes have evolved through fractional crystallization and crustal assimilation, operating at different crustal levels during their ascent through the ∼70 km-thick continental crust. Sairecabur stratovolcano, located within the Altiplano–Puna Volcanic Complex (APVC; 21°–24° S) of the Central Andean subduction zone, is stratigraphically divided into three units: Pre-Caldera Lavas (PRECL - Pleistocene), Post-Caldera I Lavas (POCIL - Upper Pleistocene), and Post-Caldera II Lavas (POCIIL - Holocene). These volcanic products range from 55 (basaltic andesite) to 63 (dacite) wt.% SiO<sub>2</sub>. In particular, Sairecabur shows a negative correlation between SiO<sub>2</sub> wt.% and Eu/Eu∗, with Eu/Eu∗ values < 1, indicating the key role of plagioclase during late-stage magma differentiation. A deep-crustal garnet signature - though not prominent - cannot be excluded, which was overprinted by shallow differentiation and assimilation. Over the past 10 Ma, APVC magmas have been affected by significant crustal contamination, linked to crustal thickening during the Andean orogeny and localized processes. This trend is observed in all units of Sairecabur, where <sup>87</sup>Sr/<sup>86</sup>Sr ratios of erupted products range from 0.707057 to 0.708667. This suggests a substantial crustal assimilation of a parental Andean-type magmas (<sup>87</sup>Sr/<sup>86</sup>Sr ratio ∼0.705), which was generated by an early stage of magmatic differentiation at lower crustal levels (MASH zone). Petrographic and geochemical data define three main mid-to-upper crustal evolutionary stages occurring afterwards: (1) an AFC stage in mid-to upper-crustal chambers, with 33–47 % AFC-type incorporation of felsic upper crustal material; (2) an intermediate stage of closed-system fractional crystallization involving plagioclase, pyroxene, amphibole, and biotite; and (3) a late-stage episode of magma mixing with shallow crustal melts, evidenced by glomeroporphyritic gabbroic aggregates and by trace-element trends and scatter accompanying advanced differentiation.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105898"},"PeriodicalIF":1.5,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737896","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 : 2025-12-05DOI: 10.1016/j.jsames.2025.105911
Micaela García , Joaquín Bucher , Rodrigo Feo , Manuel López , Florencia Milanese , Magdalena Tettamanti , Leandro D’Elia , Andrés Bilmes , Juan R. Franzese
The Patagonian Broken Foreland (PBF) comprises isolated, fault-bounded Neogene basins displaying intricate internal deformation patterns. Although previous studies emphasized reverse faulting along basin boundaries, the role of strike-slip deformation and intra-basin strain partitioning remains poorly constrained. Through a multidisciplinary approach combining structural analysis, paleomagnetic data, and Digital Outcrop Model analyses, this work investigates three key PBF basins: Paso del Sapo, Piedra del Águila, and Collón Cura. Results document widespread distributed deformation characterized by clockwise vertical-axis block rotation controlled by internal oblique-slip faults and inherited basement structures. In the Paso del Sapo Basin, rotations are most pronounced within internal blocks, transitioning to tilting toward basin boundaries. The Piedra del Águila Basin records localized block rotation linked to angular relationships between strata and abrupt dip changes related to tilting of internal structures. The Collón Cura Basin records sustained rotation in fault-bounded blocks that persisted until ∼10 Ma. The magnitude of block rotation decreases upward in stratigraphy, indicating a progressive deformation history. Kinematic data reveal a transpressional regime involving coeval strike-slip and reverse faulting, resulting in spatial variations in strain partitioning across the basins. These findings underscore the value of multidisciplinary approaches to fully characterize retroarc foreland deformation, including the often-overlooked strike-slip components.
巴塔哥尼亚破碎前陆（PBF）由孤立的断界新近纪盆地组成，具有复杂的内部变形模式。尽管以往的研究强调沿盆地边界的逆断裂作用，但走滑变形和盆地内应变分配的作用仍然缺乏明确的认识。通过多学科方法，结合构造分析、古地磁数据和数字露头模型分析，研究了三个关键的PBF盆地：Paso del Sapo、Piedra del Águila和Collón Cura。结果表明，受内部斜滑断层和继承基底构造控制，以顺时针方向块体旋转为特征的大面积分布变形。在Paso del Sapo盆地，旋转在内部块体中最为明显，过渡到向盆地边界倾斜。Piedra del Águila盆地记录了与地层之间的角度关系有关的局部块体旋转和与内部构造倾斜有关的突然倾角变化。Collón库拉盆地记录了断界块体的持续旋转，持续到~ 10 Ma。块体旋转的幅度在地层上逐渐减小，显示出一个渐进的变形历史。运动学数据揭示了一个涉及同期走滑和逆断裂的逆挤压机制，导致了盆地应变分配的空间变化。这些发现强调了多学科方法全面表征弧后前陆变形的价值，包括经常被忽视的走滑分量。
{"title":"Transpressional deformation and block rotation in the Patagonian Broken Foreland: Multidisciplinary approach and future perspectives","authors":"Micaela García , Joaquín Bucher , Rodrigo Feo , Manuel López , Florencia Milanese , Magdalena Tettamanti , Leandro D’Elia , Andrés Bilmes , Juan R. Franzese","doi":"10.1016/j.jsames.2025.105911","DOIUrl":"10.1016/j.jsames.2025.105911","url":null,"abstract":"<div><div>The Patagonian Broken Foreland (PBF) comprises isolated, fault-bounded Neogene basins displaying intricate internal deformation patterns. Although previous studies emphasized reverse faulting along basin boundaries, the role of strike-slip deformation and intra-basin strain partitioning remains poorly constrained. Through a multidisciplinary approach combining structural analysis, paleomagnetic data, and Digital Outcrop Model analyses, this work investigates three key PBF basins: Paso del Sapo, Piedra del Águila, and Collón Cura. Results document widespread distributed deformation characterized by clockwise vertical-axis block rotation controlled by internal oblique-slip faults and inherited basement structures. In the Paso del Sapo Basin, rotations are most pronounced within internal blocks, transitioning to tilting toward basin boundaries. The Piedra del Águila Basin records localized block rotation linked to angular relationships between strata and abrupt dip changes related to tilting of internal structures. The Collón Cura Basin records sustained rotation in fault-bounded blocks that persisted until ∼10 Ma. The magnitude of block rotation decreases upward in stratigraphy, indicating a progressive deformation history. Kinematic data reveal a transpressional regime involving coeval strike-slip and reverse faulting, resulting in spatial variations in strain partitioning across the basins. These findings underscore the value of multidisciplinary approaches to fully characterize retroarc foreland deformation, including the often-overlooked strike-slip components.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105911"},"PeriodicalIF":1.5,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737897","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 : 2025-12-03DOI: 10.1016/j.jsames.2025.105901
Ernesto O. Cristallini , Agostina D'Ascenzo , Renata N. Tomezzoli , Melina E. Gugliotta , Nicolás Braun
Aquí se presenta una interpretación de las principales estructuras geológicas cenozoicas aflorantes en la cuenca de Fiambalá, también conocida como Bolsón de Fiambalá provincia de Catamarca, Argentina. La compresión andina deformó las secuencias sedimentarias neógenas formando una serie de corrimientos dispuestos en sentido ∼ N-S con vergencia hacia el este. A partir de la información relevada en el campo, integrada con estudios geológicos previos e imágenes satelitales, se elaboró una sección estructural balanceada con el fin de caracterizar la deformación del área y se realizó una reconstrucción palinspástica a partir del cual se calculó un acortamiento total de 6.13 km, equivalente al 18 % para la región.
ABSTRACT
We present an interpretation of the main Cenozoic geological structures outcropping in the Fiambalá Basin, also known as Bolsón de Fiambalá, Catamarca Province, Argentina. Andean compression deformed the Neogene sedimentary sequences, forming a series of thrusts arranged in a north-south direction with eastward convergence. Based on own field collected data, combined with previous geological studies and satellite images, a balanced structural section was constructed to characterize the deformation of the area. A palinspastic reconstruction was performed, from which a total shortening of 6.13 km was calculated, equivalent to an 18%, for the studied region.
本文介绍了阿根廷卡塔马卡省Fiambala盆地主要的新世地质构造，也被称为Bolson de Fiambala。安第斯山脉的压缩变形了新近形成的沉积序列，形成了一系列在~ N-S方向上向东倾斜的洋流。信息relevada起地质综合领域,与以前的卫星图像,制定了一个结构平衡的部分,旨在确定区域和变形进行了重建palinspástica从中计算总缩减为6.13平方公里区域,相当于18 %。本文对阿根廷卡塔马卡省菲安巴拉盆地主要的世生代地质结构的解释，也被称为Bolson de Fiambala。这是一个巨大的隆起，形成了一个巨大的隆起，形成了一个巨大的隆起，形成了一个巨大的隆起。根据现场收集的数据，结合以前的地质研究和卫星图像，建造了一个平衡的结构部分，以表征该地区的变形。进行了palinspastic重建，计算出研究区域的总缩短6.13公里，相当于18%。
{"title":"Structural Andean evolution of the western border of the central Fiambalá basin, Catamarca province, Argentina","authors":"Ernesto O. Cristallini , Agostina D'Ascenzo , Renata N. Tomezzoli , Melina E. Gugliotta , Nicolás Braun","doi":"10.1016/j.jsames.2025.105901","DOIUrl":"10.1016/j.jsames.2025.105901","url":null,"abstract":"<div><div>Aquí se presenta una interpretación de las principales estructuras geológicas cenozoicas aflorantes en la cuenca de Fiambalá, también conocida como Bolsón de Fiambalá provincia de Catamarca, Argentina. La compresión andina deformó las secuencias sedimentarias neógenas formando una serie de corrimientos dispuestos en sentido ∼ N-S con vergencia hacia el este. A partir de la información relevada en el campo, integrada con estudios geológicos previos e imágenes satelitales, se elaboró una sección estructural balanceada con el fin de caracterizar la deformación del área y se realizó una reconstrucción palinspástica a partir del cual se calculó un acortamiento total de 6.13 km, equivalente al 18 % para la región.</div></div><div><h3>ABSTRACT</h3><div>We present an interpretation of the main Cenozoic geological structures outcropping in the Fiambalá Basin, also known as Bolsón de Fiambalá, Catamarca Province, Argentina. Andean compression deformed the Neogene sedimentary sequences, forming a series of thrusts arranged in a north-south direction with eastward convergence. Based on own field collected data, combined with previous geological studies and satellite images, a balanced structural section was constructed to characterize the deformation of the area. A palinspastic reconstruction was performed, from which a total shortening of 6.13 km was calculated, equivalent to an 18%, for the studied region.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105901"},"PeriodicalIF":1.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694509","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 : 2025-12-03DOI: 10.1016/j.jsames.2025.105903
M. San Juan , T. Villaseñor , D. Dintrans
Mountain catchments are dynamic sedimentary systems where climate variability significantly affects geomorphic processes and sediment connectivity. This study investigates the processes of sediment generation and transfer in the Volcán River basin in central Chile's semi-arid Andes, a region impacted by a prolonged megadrought since 2010. We combined geomorphological mapping, sediment connectivity modelling using the Index of Connectivity (IC), and sediment geochemistry analysis of suspended sediments collected during spring-summer season of 2022–2023. Geomorphological mapping identified seven distinct morphogenetic environments (morphostructural, volcanic, glacial, fluvial, denudational, glacial ice and anthropogenic), each contributing variably to sediment transfer. IC analysis revealed spatial heterogeneity in sediment connectivity, with higher values in fluvial and denudational domains and lower values in glacial and volcanic areas. Geochemical analysis of rare earth elements (REE) in suspended sediments indicated that Cenozoic volcanic formations, especially from subglacial sources, are the primary sediment contributors under current hydrological conditions, with Mesozoic units contributing episodically during high-magnitude events like debris flows. Under this scheme, surficial glacial and volcanic morphogenetic domains act as sediment buffers due to their distance to the main fluvial channels as well as morphology that promotes sediment accumulation. In contrast, high melt rates of the glaciers in the valley enhance subglacial connectivity to the fluvial network in the context of the megadrought, while mass wasting events act as sources for short-term sediment pulses during high runoff events. These findings highlight how sediment coupling and provenance in mountain basins are modulated by both the current megadrought and extreme hydrometeorological events. The results provide insights for hazard assessment and sediment management in mountainous regions experiencing climatic stress.
{"title":"The megadrought modulation of sediment transfer in the Volcán River basin (33°S), semi-arid Andes","authors":"M. San Juan , T. Villaseñor , D. Dintrans","doi":"10.1016/j.jsames.2025.105903","DOIUrl":"10.1016/j.jsames.2025.105903","url":null,"abstract":"<div><div>Mountain catchments are dynamic sedimentary systems where climate variability significantly affects geomorphic processes and sediment connectivity. This study investigates the processes of sediment generation and transfer in the Volcán River basin in central Chile's semi-arid Andes, a region impacted by a prolonged megadrought since 2010. We combined geomorphological mapping, sediment connectivity modelling using the Index of Connectivity (IC), and sediment geochemistry analysis of suspended sediments collected during spring-summer season of 2022–2023. Geomorphological mapping identified seven distinct morphogenetic environments (morphostructural, volcanic, glacial, fluvial, denudational, glacial ice and anthropogenic), each contributing variably to sediment transfer. IC analysis revealed spatial heterogeneity in sediment connectivity, with higher values in fluvial and denudational domains and lower values in glacial and volcanic areas. Geochemical analysis of rare earth elements (REE) in suspended sediments indicated that Cenozoic volcanic formations, especially from subglacial sources, are the primary sediment contributors under current hydrological conditions, with Mesozoic units contributing episodically during high-magnitude events like debris flows. Under this scheme, surficial glacial and volcanic morphogenetic domains act as sediment buffers due to their distance to the main fluvial channels as well as morphology that promotes sediment accumulation. In contrast, high melt rates of the glaciers in the valley enhance subglacial connectivity to the fluvial network in the context of the megadrought, while mass wasting events act as sources for short-term sediment pulses during high runoff events. These findings highlight how sediment coupling and provenance in mountain basins are modulated by both the current megadrought and extreme hydrometeorological events. The results provide insights for hazard assessment and sediment management in mountainous regions experiencing climatic stress.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105903"},"PeriodicalIF":1.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694606","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 : 2025-12-03DOI: 10.1016/j.jsames.2025.105899
Roberto González-Vidal , Felipe Tapia , Fernando Poblete , Matías Peña , Esteban Salazar , Valentina Ríos
Navarino Island is located in the southernmost part of South America, within the Central Belt of the Fuegian Orogen. The shortening of the geological units observed on the island is believed to be related to a compressional event during the closure of the Rocas Verdes Basin. However, the full extent of this relationship remains unclear due to accessibility challenges and the apparent change in the stratigraphic records both north and south of the Beagle Channel. In this study, we integrate anisotropy of magnetic susceptibility (AMS) with structural observations across turbiditic sandstones and mudstones from the Lower Cretaceous Yahgan Formation. We analyzed thirty new sampling sites located along the northern coast of the island and the Dientes de Navarino mountain group. The AMS data exhibited predominantly oblate magnetic fabrics, with P′ values ranging from 1.02 to 2.22. The ellipsoid orientations correlated well with the structural features, particularly cleavage (S1) and fold axes. High P′ values and tectonic fabric types were concentrated in the western part of the island. A transition from a tectonic fabric with lower anisotropy degrees to a more sedimentary fabric was observed towards the east and south. These findings reflect a W-E deformation gradient consistent with the island's structural features, including an overprinting cleavage family (S2) restricted to the island's northwest. This study highlights the utility of AMS in elucidating strain directions and reconstructing deformation histories in complex orogenic settings.
{"title":"Compressional tectonics related to Fuegian orogeny: Insights from AMS and structural geology in Navarino Island, Chile","authors":"Roberto González-Vidal , Felipe Tapia , Fernando Poblete , Matías Peña , Esteban Salazar , Valentina Ríos","doi":"10.1016/j.jsames.2025.105899","DOIUrl":"10.1016/j.jsames.2025.105899","url":null,"abstract":"<div><div>Navarino Island is located in the southernmost part of South America, within the Central Belt of the Fuegian Orogen. The shortening of the geological units observed on the island is believed to be related to a compressional event during the closure of the Rocas Verdes Basin. However, the full extent of this relationship remains unclear due to accessibility challenges and the apparent change in the stratigraphic records both north and south of the Beagle Channel. In this study, we integrate anisotropy of magnetic susceptibility (AMS) with structural observations across turbiditic sandstones and mudstones from the Lower Cretaceous Yahgan Formation. We analyzed thirty new sampling sites located along the northern coast of the island and the Dientes de Navarino mountain group. The AMS data exhibited predominantly oblate magnetic fabrics, with P′ values ranging from 1.02 to 2.22. The ellipsoid orientations correlated well with the structural features, particularly cleavage (S<sub>1</sub>) and fold axes. High P′ values and tectonic fabric types were concentrated in the western part of the island. A transition from a tectonic fabric with lower anisotropy degrees to a more sedimentary fabric was observed towards the east and south. These findings reflect a W-E deformation gradient consistent with the island's structural features, including an overprinting cleavage family (S<sub>2</sub>) restricted to the island's northwest. This study highlights the utility of AMS in elucidating strain directions and reconstructing deformation histories in complex orogenic settings.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105899"},"PeriodicalIF":1.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694608","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 : 2025-12-02DOI: 10.1016/j.jsames.2025.105896
Nazaré Suziane Soares , José Vidal de Figueiredo , Carlos Alexandre Gomes Costa , Italo Sampaio Rodrigues , José Carlos de Araújo
Transpiration, particularly in dryland forests, plays a major role in the water cycle. The one-million km2 Caatinga Biome is a data-scarce region in the Brazilian Semiarid, where rainy and dry season are clearly distinct. This work aims to measure the natural Caatinga vegetation transpiration using sap flow monitoring (between Feb 2016 and Dec 2017) and to validate the hydrological Distributed Catchment Scale Model (DiCaSM). Measured transpiration in situ was on overall average 0.58 mm.day−1 for rainy and transition seasons. There is evidence that sap flow does not provide a good representation of transpiration in dry seasons: sap flow is high, whereas, according to the Literature, actual evapotranspiration is negligible (<0.01 mm.day−1) due to a very low soil water content, and, thus, transpiration should also be negligible. Transpiration estimated by DiCaSM presented a well-defined seasonal variability, with values close to zero during the driest months, in agreement to previous literature. Overall, the findings contribute to better expertise regarding the transpiration rates in a dryland environment and may be used in water resources management contexts, as the transpiration process gives insight into local water use and availability.
{"title":"Forest transpiration in Brazilian drylands: measurement and validation of a hydrological model","authors":"Nazaré Suziane Soares , José Vidal de Figueiredo , Carlos Alexandre Gomes Costa , Italo Sampaio Rodrigues , José Carlos de Araújo","doi":"10.1016/j.jsames.2025.105896","DOIUrl":"10.1016/j.jsames.2025.105896","url":null,"abstract":"<div><div>Transpiration, particularly in dryland forests, plays a major role in the water cycle. The one-million km<sup>2</sup> Caatinga Biome is a data-scarce region in the Brazilian Semiarid, where rainy and dry season are clearly distinct. This work aims to measure the natural Caatinga vegetation transpiration using sap flow monitoring (between Feb 2016 and Dec 2017) and to validate the hydrological Distributed Catchment Scale Model (DiCaSM). Measured transpiration <em>in situ</em> was on overall average 0.58 mm.day<sup>−1</sup> for rainy and transition seasons. There is evidence that sap flow does not provide a good representation of transpiration in dry seasons: sap flow is high, whereas, according to the Literature, actual evapotranspiration is negligible (<0.01 mm.day<sup>−1</sup>) due to a very low soil water content, and, thus, transpiration should also be negligible. Transpiration estimated by DiCaSM presented a well-defined seasonal variability, with values close to zero during the driest months, in agreement to previous literature. Overall, the findings contribute to better expertise regarding the transpiration rates in a dryland environment and may be used in water resources management contexts, as the transpiration process gives insight into local water use and availability.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105896"},"PeriodicalIF":1.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694604","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 : 2025-12-02DOI: 10.1016/j.jsames.2025.105894
Olga Bohórquez-Orozco , Jhon Restrepo-Berrío , Héctor Mora-Páez
This study characterizes the present-day stress field of northwestern SouthAmerica using 337 focal mechanism solutions compiled from the Colombian Seismological Network, USGS, GEOFON, and GCMT catalogues. Based on seismicity depth, geographic proximity, and tectonic context, 30 stress regions were delineated, and their corresponding stress tensors were determined. The results reveal that compressional regimes dominate north of 5° N, where the maximum horizontal stress (SHmax) trends NW–SE, controlled by the convergence between the Panama–Choco Block and the North Andean Block. Southward, the regime transitions to strike-slip faulting with E–W-oriented SHmax, associated with right-lateral and conjugate fault systems. Along the Nazca Plate subduction front, pre-trench extensional regimes evolve into post-trench compressional settings within the accretionary prism. Intermediate-depth tensors in the Cauca and Bucaramanga sectors reveal an in-slab extensional axis for the former and NW–SE compression for the latter, where seismicity patterns support the presence of a detached Paleo-Caribbean slab. The stress tensor distribution confirms that the Panama–Choco–North Andean boundary is structurally complex, while the Eastern and Central Cordilleras display second-order transpressive regimes consistent with major crustal-scale faults.
Este estudio caracteriza el campo de esfuerzos actual de la esquina noroccidental de Suramérica, utilizando 337 soluciones de mecanismos focales compiladas de los catálogos de la Red Sismológica Nacional de Colombia, USGS, GEOFON y GCMT. Con base en la profundidad de la sismicidad, la proximidad geográfica y el contexto tectónico, se delimitaron 30 regiones de esfuerzo y se determinaron sus respectivos tensores. Los resultados revelan que los regímenes compresivos dominan al norte de los 5° N, donde el esfuerzo horizontal máximo (SHmax) tiene una orientación NW–SE, controlada por la convergencia entre el Bloque Panamá–Chocó y el Bloque Norandino. Hacia el sur, el régimen transiciona a fallamiento de tipo transcurrente con SHmax orientado E–O, asociado a sistemas de fallas dextrales y conjugadas. A lo largo del frente de subducción de la Placa de Nazca, los regímenes extensionales pre-fosa evolucionan hacia configuraciones compresivas pos-fosa dentro del prisma de acreción. Los tensores de profundidad intermedia en los sectores de Cauca y Bucaramanga revelan un eje extensional dentro de la losa para el primero y compresión NW–SE para el segundo, donde los patrones de sismicidad respaldan la presencia de una paleolosa Caribe desprendida. La distribución de los tensores de esfuerzo confirma que el límite entre los bloques Panamá–Chocó y Norandino es estructuralmente complejo, mientras que las cordilleras Oriental y Central exhiben regímenes transpresivos de segundo orden coherentes con fallas corticales de gran escala.
本研究利用哥伦比亚地震网、USGS、GEOFON和GCMT目录汇编的337个震源机制解，描述了南美洲西北部当前的应力场。根据地震活动深度、地理邻近度和构造背景，圈定了30个应力区，并确定了相应的应力张量。结果表明，在5°N以北以挤压体制为主，最大水平应力（SHmax）倾向于NW-SE，受巴拿马-乔科地块与北安第斯地块的辐合控制。向南转变为走滑断裂，东西向的大震区，并伴有右旋和共轭断裂系统。在纳斯卡板块俯冲前缘，增生三棱镜内的前海沟伸展构造演化为后海沟挤压构造。考卡和布卡拉曼加板块的中深度张量显示，前者为板块内伸展轴，后者为北西-东南挤压轴，地震活动模式支持古加勒比板块分离的存在。应力张量分布证实了巴拿马-乔科-北安第斯边界构造复杂，而科迪勒拉斯东部和中部表现出与大地壳尺度断裂相一致的二级逆压机制。哥伦比亚国家地质勘探局、哥伦比亚地质勘探局、哥伦比亚国家地质勘探局、哥伦比亚国家地质勘探局、哥伦比亚国家地质勘探局、哥伦比亚国家地质勘探局、哥伦比亚国家地质勘探局、哥伦比亚国家地质勘探局。Con base en la profunddad de la sismicidad, la proximidad geográfica y el contexto tectónico，通过确定各自的张量，对30个区域进行了划分。洛杉矶resultados revelan,洛杉矶方案compresivos dominan al norte de Los 5°N在el esfuerzo水平maximo (SHmax)这种orientacion -, controlada关于convergencia之间el Bloque Panama-Choco y el Bloque Norandino。在此基础上，我们提出了一种新的解决方案，即解决方案、解决方案、解决方案、解决方案和解决方案。A lo largo del frente de subducción de la Placa de Nazca, los regímenes extensionales pre-fosa evolsion and haacia configuracones compaciones postfosa dentro del prisma de acreción。在考卡省和布卡拉曼加省的两省建立了深厚的媒介关系，并在西北-东南两省建立了广泛的媒介关系，在加勒比地区建立了深厚的媒介关系，在加勒比地区建立了深厚的媒介关系。La distribución de los tensores de esfuerzo confirma que el límite centre los bloques Panamá-Chocó由Norandino es strucalmente complex， mientras que las cordilleras Oriental y Central exhien regímenes透明的de secgundo orden coherentes confallas corticales de gran escala。
{"title":"Stress regime of Colombia from seismological tensor inversion","authors":"Olga Bohórquez-Orozco , Jhon Restrepo-Berrío , Héctor Mora-Páez","doi":"10.1016/j.jsames.2025.105894","DOIUrl":"10.1016/j.jsames.2025.105894","url":null,"abstract":"<div><div>This study characterizes the present-day stress field of northwestern SouthAmerica using 337 focal mechanism solutions compiled from the Colombian Seismological Network, USGS, GEOFON, and GCMT catalogues. Based on seismicity depth, geographic proximity, and tectonic context, 30 stress regions were delineated, and their corresponding stress tensors were determined. The results reveal that compressional regimes dominate north of 5° N, where the maximum horizontal stress (SHmax) trends NW–SE, controlled by the convergence between the Panama–Choco Block and the North Andean Block. Southward, the regime transitions to strike-slip faulting with E–W-oriented SHmax, associated with right-lateral and conjugate fault systems. Along the Nazca Plate subduction front, pre-trench extensional regimes evolve into post-trench compressional settings within the accretionary prism. Intermediate-depth tensors in the Cauca and Bucaramanga sectors reveal an in-slab extensional axis for the former and NW–SE compression for the latter, where seismicity patterns support the presence of a detached Paleo-Caribbean slab. The stress tensor distribution confirms that the Panama–Choco–North Andean boundary is structurally complex, while the Eastern and Central Cordilleras display second-order transpressive regimes consistent with major crustal-scale faults.</div></div><div><div>Este estudio caracteriza el campo de esfuerzos actual de la esquina noroccidental de Suramérica, utilizando 337 soluciones de mecanismos focales compiladas de los catálogos de la Red Sismológica Nacional de Colombia, USGS, GEOFON y GCMT. Con base en la profundidad de la sismicidad, la proximidad geográfica y el contexto tectónico, se delimitaron 30 regiones de esfuerzo y se determinaron sus respectivos tensores. Los resultados revelan que los regímenes compresivos dominan al norte de los 5° N, donde el esfuerzo horizontal máximo (SHmax) tiene una orientación NW–SE, controlada por la convergencia entre el Bloque Panamá–Chocó y el Bloque Norandino. Hacia el sur, el régimen transiciona a fallamiento de tipo transcurrente con SHmax orientado E–O, asociado a sistemas de fallas dextrales y conjugadas. A lo largo del frente de subducción de la Placa de Nazca, los regímenes extensionales pre-fosa evolucionan hacia configuraciones compresivas pos-fosa dentro del prisma de acreción. Los tensores de profundidad intermedia en los sectores de Cauca y Bucaramanga revelan un eje extensional dentro de la losa para el primero y compresión NW–SE para el segundo, donde los patrones de sismicidad respaldan la presencia de una paleolosa Caribe desprendida. La distribución de los tensores de esfuerzo confirma que el límite entre los bloques Panamá–Chocó y Norandino es estructuralmente complejo, mientras que las cordilleras Oriental y Central exhiben regímenes transpresivos de segundo orden coherentes con fallas corticales de gran escala.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105894"},"PeriodicalIF":1.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694507","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 : 2025-12-02DOI: 10.1016/j.jsames.2025.105893
Maria Liceth Cabrera Ruiz, Alessandro Batezelli
<div><div>Understanding carbonate rocks and their geomechanical behavior is essential for optimizing hydrocarbon production. In carbonate reservoir, defining geomechanical facies offers an innovative approach to predict mechanical heterogeneity and supporting hydraulic fracturing design at the field scale. This study aims to classify the Barra Velha Formation into geomechanical facies by integrating mechanical analysis with rock characterization, in order to evaluate how mechanical strength, rock type, diagenetic processes influence the brittleness index and, consequently, reservoir integrity and development. This study utilized a comprehensive database from the Búzios Oil field, including conventional logs, image logs, leak-off tests, repeat formation tests, nuclear magnetic resonance data, mineral spectroscopy, X-ray diffraction, thin section and core photographs, and seismic data. The geomechanical models were developed using dynamic geomechanics and calibrated with well-test data. In addition, a Bayesian classification technique was used to define geomechanical facies. Carbonate rocks were classified according to Gomes et al. (2020). The in-situ stress distribution indicates that the current stress regime in the field is dual, ranging between normal and strike-slip, with a pore pressure gradient greater than the hydrostatic one. The maximum horizontal stress azimuth has two predominant orientations, approximately 80° and 270°. This orientation shows variations compared to the paleo-stress directions, which were aligned with the regional tectonic framework. Four geomechanical facies were defined, with mechanical strength ranging from intermediate to very low (Compacted, Brittle-Reservoir, Ductile-Sealing, and Semiductile-Reservoir), and an overall classification accuracy of 82 %. Compacted facies exhibit the highest mechanical strength and have a high content of quartz, feldspar, and mica due to grainstone texture with a high degree of cementation, very low porosity, and nearly zero permeability. In contrast, Semiductile-Reservoir facies, which displays the lowest mechanical strength, has the highest weight fraction of carbonate and is dominated by in-situ rocks, such as spherulitestones, these exhibit the best porosity and permeability properties, evidence of dissolution processes, and low cementation. Conversely, Ductile-Sealing facies present higher clay fraction values, microporosity, and stylolite development, which coincide with Mudstone lithologies. Regarding brittleness analysis, Compacted facies showed a higher propensity to develop drilling-induced tensile fractures and had the highest IB values. On the other hand, Ductile-Sealing facies were more prone to the development of breakouts, while Semiductile-Reservoir was prone to low amplitude fractures associated with the lowest IB values. In conclusion, this geomechanical study has provided valuable insights into the influence of diagenetic overprinting processes on carbonate rocks, wh
了解碳酸盐岩及其地质力学行为对于优化油气产量至关重要。在碳酸盐岩储层中，定义地质力学相提供了一种创新的方法来预测力学非均质性，并支持现场规模的水力压裂设计。本研究旨在将力学分析与岩石表征相结合，将Barra Velha组划分为地质力学相，以评价力学强度、岩石类型、成岩作用对脆性指数的影响，从而影响储层的完整性和发育程度。该研究利用了Búzios油田的综合数据库，包括常规测井、图像测井、泄漏测试、重复地层测试、核磁共振数据、矿物光谱、x射线衍射、薄片和岩心照片以及地震数据。利用动态地质力学建立地质力学模型，并根据试井数据进行校准。此外，采用贝叶斯分类技术定义地质力学相。碳酸盐岩分类依据Gomes et al.（2020）。地应力分布表明，当前现场应力场为正滑与走滑双重应力场，孔隙压力梯度大于静水压力梯度。最大水平应力方位有两个主要方向，约为80°和270°。与与区域构造格架一致的古应力方向相比，这一方向表现出变化。定义了四种地质力学相，其机械强度从中等到极低（压实相、脆性储层相、延性密封相和半延性储层相），总体分类精度为82%。压实相由于胶结程度高、孔隙度极低、渗透率接近于零的颗粒岩结构，机械强度最高，石英、长石、云母含量高。半枝储层相力学强度最低，碳酸盐岩质量分数最高，以球晶岩等原生岩为主，具有最佳的孔隙度和渗透率，具有溶蚀作用的证据，胶结作用较弱。相反，延性封闭相具有较高的粘土分数值、微孔隙度和柱面岩发育，与泥岩岩性一致。在脆性分析方面，致密相更倾向于形成钻井诱发的张性裂缝，其IB值最高。另一方面，延性—封闭性相更容易发育裂缝，而半延性—储层更容易发育低幅度裂缝，且IB值最低。综上所述，该地质力学研究为研究成岩叠印作用对碳酸盐岩的影响提供了有价值的见解，碳酸盐岩受沉积构造控制。这些因素共同决定了岩石的力学行为。四种地质力学相的地震反演预可行性分析强调了在油田规模上应用这种分类的潜力，从而能够更准确地描述储层特征。这些发现不仅适用于巴西盐下储层，也适用于全球其他具有类似沉积和成岩历史的碳酸盐岩储层。
{"title":"Integrated analysis of geomechanical facies and diagenetic controls on brittleness and reservoir quality in pre-salt carbonates","authors":"Maria Liceth Cabrera Ruiz, Alessandro Batezelli","doi":"10.1016/j.jsames.2025.105893","DOIUrl":"10.1016/j.jsames.2025.105893","url":null,"abstract":"<div><div>Understanding carbonate rocks and their geomechanical behavior is essential for optimizing hydrocarbon production. In carbonate reservoir, defining geomechanical facies offers an innovative approach to predict mechanical heterogeneity and supporting hydraulic fracturing design at the field scale. This study aims to classify the Barra Velha Formation into geomechanical facies by integrating mechanical analysis with rock characterization, in order to evaluate how mechanical strength, rock type, diagenetic processes influence the brittleness index and, consequently, reservoir integrity and development. This study utilized a comprehensive database from the Búzios Oil field, including conventional logs, image logs, leak-off tests, repeat formation tests, nuclear magnetic resonance data, mineral spectroscopy, X-ray diffraction, thin section and core photographs, and seismic data. The geomechanical models were developed using dynamic geomechanics and calibrated with well-test data. In addition, a Bayesian classification technique was used to define geomechanical facies. Carbonate rocks were classified according to Gomes et al. (2020). The in-situ stress distribution indicates that the current stress regime in the field is dual, ranging between normal and strike-slip, with a pore pressure gradient greater than the hydrostatic one. The maximum horizontal stress azimuth has two predominant orientations, approximately 80° and 270°. This orientation shows variations compared to the paleo-stress directions, which were aligned with the regional tectonic framework. Four geomechanical facies were defined, with mechanical strength ranging from intermediate to very low (Compacted, Brittle-Reservoir, Ductile-Sealing, and Semiductile-Reservoir), and an overall classification accuracy of 82 %. Compacted facies exhibit the highest mechanical strength and have a high content of quartz, feldspar, and mica due to grainstone texture with a high degree of cementation, very low porosity, and nearly zero permeability. In contrast, Semiductile-Reservoir facies, which displays the lowest mechanical strength, has the highest weight fraction of carbonate and is dominated by in-situ rocks, such as spherulitestones, these exhibit the best porosity and permeability properties, evidence of dissolution processes, and low cementation. Conversely, Ductile-Sealing facies present higher clay fraction values, microporosity, and stylolite development, which coincide with Mudstone lithologies. Regarding brittleness analysis, Compacted facies showed a higher propensity to develop drilling-induced tensile fractures and had the highest IB values. On the other hand, Ductile-Sealing facies were more prone to the development of breakouts, while Semiductile-Reservoir was prone to low amplitude fractures associated with the lowest IB values. In conclusion, this geomechanical study has provided valuable insights into the influence of diagenetic overprinting processes on carbonate rocks, wh","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"170 ","pages":"Article 105893"},"PeriodicalIF":1.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145694505","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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