Journal of South American Earth Sciences最新文献

{"title":"New occurrences of glacial deposits in the Presidente Figueiredo region, northern margin of the Amazon Basin","authors":"Carmem Nátaly Amorim Franco ,&nbsp;Emílio Alberto Amaral Soares ,&nbsp;Rosemery Rocha da Silveira ,&nbsp;Rodolfo Dino ,&nbsp;Luzia Antonioli ,&nbsp;Mayara Fraeda Barbosa Teixeira ,&nbsp;Rogério Oliveira Barbosa ,&nbsp;Marco Antônio Lima da Silva","doi":"10.1016/j.jsames.2025.105810","DOIUrl":"10.1016/j.jsames.2025.105810","url":null,"abstract":"<div><div>The Paleozoic sedimentary sequence outcropping in the municipality of Presidente Figueiredo, on the northern margin of the Amazon Basin, is bounded to the north by the Paleoproterozoic crystalline basement and to the south by the Cretaceous–Neogene sedimentary cover. Within this sequence, new records of glacial deposits occur associated with shoreface and foreshore sedimentary facies of the Nhamundá and Manacapuru formations (Trombetas Group). Glaciers primarily formed these deposits by sedimenting terminal moraines and depositing material in lakes. They consist mainly of coarse diamictites that contain clasts from igneous, sedimentary, and metamorphic rocks. Glaciers deposited these materials as they moved over marine sedimentary rocks and the underlying crystalline basement. This study highlights the unprecedented record of dropstones embedded in laminated pelite deposited in proglacial lakes from the release of clasts from the base of icebergs. The glacial deposits studied were associated with two events: one positioned in the Early Silurian (Llandovery–Wenlock) based on palynology, and the other corresponding to a newly identified glacial event in this study, placed in the Late Silurian–Early Devonian (Early Pridoli to Early Lochkovian), based on chitinozoans (<em>Angochitina filosa</em>, <em>Angochitina strigosa</em>, <em>Angochitina</em> sp. D, and <em>Lagenochitina</em> cf. <em>L</em>. <em>navícula</em>). In addition to the glaciotectonic deformation identified in some diamictite outcroppings in the Presidente Figueiredo region, the presence of faceted clasts and dropstones also stands out as strong evidence of Silurian–Devonian glacial activity in the Amazon Basin.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"168 ","pages":"Article 105810"},"PeriodicalIF":1.5,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145223048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NW-Amazonian Craton in Colombia: A Paleo-Mesoproterozoic review","authors":"Amed Bonilla ,&nbsp;Thomas Cramer ,&nbsp;Laura Alejandra Hernández","doi":"10.1016/j.jsames.2025.105806","DOIUrl":"10.1016/j.jsames.2025.105806","url":null,"abstract":"<div><div>The geological evolution of the NW-Amazonian Craton in Colombia has been the subject of diverse interpretations over the past decades. In this study, we systematically compare and critically evaluate these contrasting models by integrating published and new field observations and petrographic, geochemical, structural, and geochronological data. The use of advanced digital tools has facilitated the spatial analysis of thousands of datasets—including U-Pb zircon, apatite and monazite, Rb-Sr, K-Ar, and Ar-Ar geochronology of mica and whole-rock samples—enabling a more comprehensive regional perspective. Additionally, recent geophysical studies, including gravimetric and magnetic data interpretations, enriched the discussion and contextualized the results. This study prioritizes a lithological classification of basement units, complemented by geochronological constraints to refine their tectonic evolution and regional correlations. This multidisciplinary approach provides a balanced synthesis of existing viewpoints, highlighting areas of consensus, ongoing debates, and key gaps in our current understanding of the Paleo-to Mesoproterozoic evolution of the NW Amazonian Craton. Eastern and western boundaries of the Rio Negro–Juruena Geochronological Province were also refined, offering new insights and guidelines for future nomenclatural and geological mapping campaigns.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"168 ","pages":"Article 105806"},"PeriodicalIF":1.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145183752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenetic insights of Bezerros and Serra Negra plutons: evidence of syn/post-collisional shoshonitic magmatism in the Caruaru-Arcoverde Batholith, Rio Capibaribe Domain, Northeastern Brazil","authors":"Syllas E.S. Santos ,&nbsp;Alcides N. Sial ,&nbsp;Valderez P. Ferreira ,&nbsp;Charles H.F.S. Neves ,&nbsp;Bianca T.A. Lima ,&nbsp;Diego H. Ardila ,&nbsp;Júlio C. Mendes ,&nbsp;Cláudia R. Passarelli","doi":"10.1016/j.jsames.2025.105799","DOIUrl":"10.1016/j.jsames.2025.105799","url":null,"abstract":"<div><div>Potassic magmatism in the Transversal Zone Domain of the Borborema Province is represented by high-K to shoshonitic granitic suites, commonly associated with syn-to post-collisional settings. The Bezerros (BZP) and Serra Negra (SNP) plutons are located in the eastern portion of the Caruaru–Arcoverde composite Batholith, one of the largest granitic bodies emplaced during the Brasiliano/Pan-African orogeny. They have an elliptical shape oriented NE–SW, controlled by three shear zones. Two of these shear zones, located at the southeastern margin and central part of the intrusions, exhibit dextral kinematics, while the third, situated on the northwestern border, shows sinistral kinematics. These granitoids share a similar mineralogical composition, characterized by potassic feldspar, plagioclase, quartz, and amphibole in varying modal proportions. The BZP is a inequigranular very coarse-grained unit with syenogranitic to monzogranitic composition, whereas the SNP is porphyritic and ranges from quartz-monzonitic to monzogranitic composition. Both plutons host inequigranular enclaves characterized by their finer textures than the host rocks, with biotite-dioritic to biotite-monzonitic compositions. Electron microprobe analyses reveal a edenitic composition of amphibole in both the granitoids and associated enclaves, indicating magma mingling processes, an interpretation further supported by Harker-type variation diagrams. Additionally, biotite compositions reflect a progressive evolution in oxidation state and volatile content (H₂O). The SNP and BZP host granitoids and their enclaves are metaluminous, and show high K₂O contents (4.6–6.4 wt%) and K₂O/Na₂O ratios (1.2–1.8), which confirms their shoshonitic affinity. These rocks are enriched in Ba, Sr, and light rare earth elements and exhibit negative anomalies in Ti, Nb, and P; no negative Eu anomalies were registered. The U–Pb zircon ages of BZP (589 ± 1.4 Ma) and SNP (574 ± 1.4 Ma) are interpreted as crystallization ages. Both plutons exhibit high initial ⁸⁷Sr/⁸⁶Sr ratios (0.709–0.726) and negative εNd(t) values (−16.2 to −14.7), indicating significant contributions from Paleoproterozoic crustal components (Tdm ∼ 2.0 Ga). We propose that the granitic magmas were formed by crustal anatexis induced by K-rich mafic melts derived from a metasomatized lithospheric mantle. The large volume of mafic magma, as evidenced by the numerous enclaves and the various degrees of mixing observed, supports this interpretation. It is possible that some of the chemical signatures observed in the plutons and enclaves were inherited from the mantle source, which was metasomatized during Paleoproterozoic subduction.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"168 ","pages":"Article 105799"},"PeriodicalIF":1.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145223047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New palynological data and paleoenvironmental implications for the Lower Devonian and Lower Cretaceous successions in the Rio do Peixe Basin, Brazil: Sedimentary organic matter analyses","authors":"Lucas Mateus Andrade Lima ,&nbsp;Juan David Vallejo ,&nbsp;Regina Buarque Gusmão ,&nbsp;Mario Ferreira Lima Filho ,&nbsp;Enelise Katia Piovesan","doi":"10.1016/j.jsames.2025.105805","DOIUrl":"10.1016/j.jsames.2025.105805","url":null,"abstract":"<div><div>The Rio do Peixe Basin (RDPB) is recognized for its paleontological significance, due to the presence of dinosaur fossils, as well as traces of invertebrates, such as arthropod and annelid burrows. Additionally are included plant fossils, ostracods, conchostracans, fish scale, and crocodylomorph bones, all from the Lower Cretaceous (Berriasian—Barremian). However, the depositional conditions of the RDPB remain being discussed, considering the presence or not of a Devonian sequence and its limits. The latest proposals indicate two groups for this basin: the Santa Helena Group, from the Lower Devonian and the Rio do Peixe, from the Lower Cretaceous. Between these two units lies a significant depositional hiatus of approximately 265 million years. This study characterizes sedimentary organic matter from Lower Devonian and Lower Cretaceous drill cuttings of the 1-PIL-1-PB well to reconstruct the depositional paleoenvironment, redox conditions and kerogen type. Standard palynological preparation techniques were applied to produce microscope slides and to classify organic matter into groups and subgroups. Based on the analyzed section, the Devonian sequence of the RDPB is interpreted as a closed to semi-closed lagoonal system with marine influence, developed under reducing conditions and generating predominantly Type II kerogen. In contrast, during the Lower Cretaceous, the basin was dominated by a fluvial system characterized input of phytoclast, developed under predominantly oxic conditions. In addition, new miospore occurrences were identified, such as <em>Dictyotriletes emsiensis</em>, <em>Cymbostporites</em> sp., <em>Retusotriletes triangulatus, Retusotriletes</em> sp., <em>Gneudnaspora divellomedia</em> and <em>Diabolisporites</em> sp. Considering the age constraints in this study, we propose a re-evaluation of the Lower Devonian–Lower Cretaceous bounding in this basin.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105805"},"PeriodicalIF":1.5,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphological-textural and chemical study of quartz from the Mocambo and Velho Guilherme Granites – Velho Guilherme intrusive suite (Southeast of the Amazonian Craton): Petrological and metallogenetic implications","authors":"Rubem Santa Brígida Barros Neto ,&nbsp;Claudio Nery Lamarão ,&nbsp;Gisele Tavares Marques","doi":"10.1016/j.jsames.2025.105801","DOIUrl":"10.1016/j.jsames.2025.105801","url":null,"abstract":"<div><div>Quartz crystals from the Mocambo and Velho Guilherme granites, greisenized rocks, and associated veins within the Velho Guilherme Intrusive Suite (Southeast of the Amazonian Craton) are key to understanding magmatic-hydrothermal evolution and Sn-W mineralization in this region. The study aims to characterize the textural and chemical evolution of quartz across magmatic to hydrothermal conditions in these granites, establish a genetic sequence for quartz types, and evaluate their relationship to mineralization using scanning electron microscopy-cathodoluminescence (SEM-CL) imaging and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element analysis. Cathodoluminescence imaging established an evolutionary sequence for quartz in these granites, progressing from magmatic Qz1 (found in less evolved, minimally altered rocks) progressing through Qz2 and Qz3 (common in moderately altered rocks) to Qz4 and Qz5 (dominant in highly evolved and hydrothermally altered rocks, including greisenized rocks and associated quartz veins). These later quartz types serve as markers for cassiterite, wolframite, and sulfide mineralization within the suite. Chemical analyses revealed that quartz types from the Mocambo Granite, source of a significant cassiterite deposit, are more enriched and exhibit greater variability in trace element concentrations. Magmatic quartz is enriched in Ti and displays variable levels of Al, K, P, Na, Fe, and other elements. Hydrothermal quartz is distinguished by higher Al, K, and Li contents. Qz4 in the Mocambo Granite shows frequent and notable concentrations of Al, K, Li, Na, Fe, Sn, W, and Zn, whereas Qz4 in the Velho Guilherme Granite lacks W and contains rare Sn. Ti, Al, and Li concentrations can reach 172, 1841, and 72 ppm, respectively, in the Mocambo Granite, while in the Velho Guilherme Granite, these values can reach 101 ppm for Ti, 1928 ppm for Al, and 117 ppm for Li. Magmatic quartz contains relatively high Al contents in both granites (above 250 ppm), while Al concentrations exceeding 400 ppm occur in quartz veins and greisenized mineralized rocks. The defined quartz sequence and chemistry robustly track magmatic-hydrothermal evolution. Distinct geochemical signatures, particularly the enrichment and presence of Sn and W in Mocambo Granite quartz (Qz4), correlate with its significant cassiterite mineralization potential compared to the Velho Guilherme Granite. Al, Li and K concentration is a key indicator of hydrothermal quartz in veins and greisens.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"168 ","pages":"Article 105801"},"PeriodicalIF":1.5,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145183789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tetrapod tracks and other trace fossils from the Chinches Formation (Andean Precordillera, northern Chile): Indication for Pennsylvanian age and glacial influence","authors":"Sebastian Voigt ,&nbsp;Philippe Moisan ,&nbsp;Gonzalo Sánchez ,&nbsp;Erick Vargas ,&nbsp;Héctor Olivares","doi":"10.1016/j.jsames.2025.105804","DOIUrl":"10.1016/j.jsames.2025.105804","url":null,"abstract":"<div><div>The Chinches Formation is an up to 3000 m thick succession of poorly studied Paleozoic sedimentary deposits cropping out in isolated high mountain areas on the southern edge of the Atacama Desert, northern Chile. During a recent scientific expedition to various outcrops of the formation, an abundant array of trace fossils was discovered that provides new insight into the stratigraphic age and depositional environment of the fossil-bearing sedimentary deposits. The recorded ichnofauna of the Chinches Formation includes invertebrate traces (<em>Cochlichnus</em>, <em>Diplichnites</em>, <em>Glaciichnium</em>, <em>Vagorichnus</em>) and vertebrate traces (<em>Undichna</em>, <em>Dimetropus</em>, <em>Dromopus</em>, <em>Limnopus</em>, <em>Matthewichnus</em>) referred to locomotion and feeding activity of annelids, arthropods, fish and tetrapods. The assemblage combines elements of the <em>Scoyenia</em> and <em>Mermia</em> ichnofacies suggesting fluvio-lacustrine depositional conditions, though a marine influence cannot be ruled out for parts of the sequence. Especially the non-tetrapod trace fossils show similarities with typical glacio-lacustrine late Paleozoic Gondwanan ichnofaunas. Based on the mixed amphibian-early amniote tetrapod ichnofauna, a late Carboniferous (Pennsylvanian) age of the Chinches Formation is proposed. The study area yields the only occurrence of Carboniferous tetrapod tracks in the present-day southern hemisphere and gives evidence that Pennsylvanian land vertebrate faunas of the tropics and mid-southern latitudes were basically similar by comprising temnospondyls, lepospondyls, early synapsids and lacertoid-like sauropsids. The Chinches Formation has great potential to study the effect of the Late Paleozoic Ice Age on continental and maybe shallow marine ecosystems in higher paleolatitudes.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105804"},"PeriodicalIF":1.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of base level change, paleoenvironmental and faciological controls on palynological associations from the final stages of the LPIA in southwestern Gondwana","authors":"Rafael R. Bender ,&nbsp;Paulo A. Souza ,&nbsp;Cristina M. Félix ,&nbsp;Daiana R. Boardman ,&nbsp;Ana Karina Scomazzon","doi":"10.1016/j.jsames.2025.105802","DOIUrl":"10.1016/j.jsames.2025.105802","url":null,"abstract":"<div><div>Insights on paleoenvironmental, faciological and stratigraphic influence in Gondwanan Permocarboniferous glacial and terminal glacial palynofloral successions are provided by new numerical data recovered from drill core sections encompassing the upper Itararé Group, in southwestern Paraná Basin, Brazil. High resolution sampling from a composite section, consisting of four successive boreholes, allows the recognition of the Pennsylvanian <em>Crucisaccites monoletus</em> Zone (CmZ) and the Permian <em>Vittatina costabilis</em> Zone (VcZ). The main quantitative features of spore-pollen assemblages are subject to a high degree of paleoenvironmental, faciological and stratigraphic control, characterizing four distinct palynological intervals. Correlation of palynological and sedimentological data observed along the studied section is tested with the application of multivariate cluster analysis, which suggests that marked shifts in dominance of certain sporomorph genera coincide with stratigraphic surfaces limited by cycles and subcycles of glacier advance and retreat. Oscillations in the quantitative trends of the studied assemblages are interpreted as the result of multiple factors affecting the palynofloral record in the context of a glacio-marine environment from the final stages of the LPIA, which is confirmed by the presence of microplanktonic elements in addition to lithological data. Among the major recognized aspects to exert influence upon the overall composition of palynofloral assemblages are the phytogeographical distribution of particular plant taxa, climate change and sedimentary environments/facies. Gaps in the sedimentary record caused by base level oscillations are directly correlatable to surfaces of sudden palynological change. Additionally, evidence suggests that regressive-transgressive trends could have an effect in the pollen/spore proportions of palynofloral successions.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"168 ","pages":"Article 105802"},"PeriodicalIF":1.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145183788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New fossil evidence of the extinct opossum Lestodelphys juga from the Argentinian Pampas: Implications for species delimitation and morphological diversity","authors":"Catalina Suarez ,&nbsp;Malena Lorente ,&nbsp;Damian Voglino ,&nbsp;José L. Aguilar ,&nbsp;Analia M. Forasiepi","doi":"10.1016/j.jsames.2025.105795","DOIUrl":"10.1016/j.jsames.2025.105795","url":null,"abstract":"<div><div>A new record (specimen MPS 150) of <em>Lestodelphys</em> is described, collected close to the Arrecifes River, San Pedro, Buenos Aires Province (Argentina), from Late Pleistocene deposits (Lujanian Age). It preserves a facial portion of the skull, including dentition. Although its dental measurements overlap with those of the extinct species <em>Lestodelphys juga</em> and the largest specimens of the extant species <em>Lestodelphys halli</em>, the specimen exhibits a distinctive combination of morphological traits that differ from <em>L. halli</em> (i.e., slight decrease in size from I2 to I5, more robust canine and anterior root of P3, P1 oblique, gap between P1 and P2, centrocrista more inflected labially, StC well developed in M1, and metacone anteroposteriorly compressed in M4). In addition, the disproportion between the skull size and its dentition mirrors the mandibular-dental mismatch observed in the holotype of <em>L. juga</em>, reinforcing its assignment to the extinct species as the most parsimonious interpretation. No specimen preserving cranial material has been attributed to <em>Lestodelphys juga</em> (other than specimen MACN-Pv 6408, which preserves a fragmentary maxilla with molars in addition to a fragmentary dentary with m3-4, and was tentatively referred to that species), increasing the relevance of the new material. Finally, in the context of this new record, we analyze the variability of the genus and discuss the diagnostic characters traditionally used to differentiate the two species. Among these, size has often been emphasized. However, we observed an overlap in dental measurements between <em>L. juga</em> and <em>L. halli</em>, indicating that size alone may not constitute a reliable diagnostic feature.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105795"},"PeriodicalIF":1.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cylindrical concentric jointing in lava flows: Description and preliminary ideas on its origin","authors":"John J. Sánchez ,&nbsp;Mariana L. Luna ,&nbsp;Guillermo E. Alvarado","doi":"10.1016/j.jsames.2025.105798","DOIUrl":"10.1016/j.jsames.2025.105798","url":null,"abstract":"<div><div>Studying structures and joint systems in viscous lava flows is important to constrain emplacement and cooling conditions and to decipher the thermal mechanisms acting during solidification of thick felsic lavas. Columnar jointing in basalt lava flows has been extensively studied and the variety of structures and joint systems found is ample. For more viscous flows such as andesites and dacites, however, there are cases that deviate from the classic jointing patterns seen in basaltic flows. Concentric cylindrical and platy jointing in intermediate and silicic lavas is one of such cases that is rarely observed but needs detailed description to draw attention of volcanologists and prompt further research. Based on field data and image analysis, we present a description of three sites, one in Colombia—Machines Quarry, and two in Costa Rica—Virilla River and Zanja Tapada Creek, where intermediate to felsic lavas show unusual jointing systems characterized by pervasive arching joints that form curved slabs surrounding a cylindrical or spindle-shaped massive core with a nearly-circular cross section characterized by concentric joints showing an increase in spacing inwards. Among the three sites we find similarities in tectonic environment (continental arc), age (Lower Pliocene to Middle Pleistocene), lithology (andesites to dacites), dimension (∼5–12 m for the massive core) and jointing styles suggesting comparable sources and emplacement/cooling mechanisms. By comparing the structures and joint systems at the three sites with structures in volcanic rocks elsewhere we discard alternative explanations and conclude that the massive cylindrical or spindle-shaped core surrounded by curved slabs is consistent with either known cleft lavas or the internal structure of ogives, large curved surface ridges common in intermediate to silicic lava flows.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105798"},"PeriodicalIF":1.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the crystalline basement of the Central Cordillera (Colombia): Implications for terrane models and crustal evolution","authors":"Camilo Bustamante","doi":"10.1016/j.jsames.2025.105800","DOIUrl":"10.1016/j.jsames.2025.105800","url":null,"abstract":"<div><div>The crystalline basement of the Central Cordillera of Colombia has traditionally been interpreted within a terrane framework that delineates distinct crustal blocks, such as the Chibcha and Tahamí terranes, separated by major fault zones like the Otú–Pericos fault. This review critically evaluates the validity of this model by integrating U–Pb geochronology, whole-rock Pb isotope geochemistry, and field relationships from key segments of the Central Cordillera.</div><div>New and compiled data challenge the existence of a Proterozoic terrane west of the Otú–Pericos fault and reveal substantial overlap in magmatic ages, metamorphic histories, and isotopic compositions on both sides of the proposed boundary. For instance, the Ibagué and Mariquita plutons intrude basement rocks across the fault and display similar Jurassic–Early Cretaceous crystallization ages and Pb isotopic signatures, undermining the interpretation of a fundamental terrane boundary. In addition, previously assumed Grenville-age exposures, such as the Tierradentro Gneisses and Amphibolites, lack reliable high-grade metamorphic evidence and are better explained as Permo–Triassic mylonitic units.</div><div>These findings suggest that the terrane model, while historically useful, is no longer adequate to explain the complex crustal architecture of the Central Cordillera. Instead, an accretionary-margin framework with lateral crustal growth, punctuated by localized strike-slip displacements, offers a more robust and parsimonious explanation for the tectonic evolution of the northern Andes. This study underscores the need for updated interpretations based on modern analytical datasets and a more integrative tectonic approach.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105800"},"PeriodicalIF":1.5,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158088","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}