Journal of South American Earth Sciences最新文献

{"title":"Maastrichtian to Pliocene dinocyst biostratigraphy of the Lobo X-1 well, Punta del Este Basin, Uruguay","authors":"G. Daners ,&nbsp;C.R. Amenábar ,&nbsp;G.R. Guerstein ,&nbsp;J.P. Pérez Panera ,&nbsp;G. Veroslavsky","doi":"10.1016/j.jsames.2025.105796","DOIUrl":"10.1016/j.jsames.2025.105796","url":null,"abstract":"<div><div>A palynological characterization was conducted on marine sediments from the Lobo X-1 well, drilled by Chevron at the Punta del Este Basin. This basin, situated along the Uruguayan continental margin (UCM)—a passive volcanic margin formed during the breakup of Gondwana—has been the focus of detailed stratigraphic and palynological studies aimed at refining its geological framework. A total of 54 cutting samples collected from depths of 369 to 1869 m yielded moderate to well preserved palynomorphs were analyzed. The samples correspond the following stratigraphic units, from oldest to youngest: Migues, Mercedes, Gaviotín, Fray Bentos, and Camacho formations. The palynological analysis focused primarily on dinoflagellate cyst bioevents allowed to recognize seven stratigraphic intervals. These intervals are: Pliocene; middle to late Miocene; early Miocene; late Eocene; early to middle Eocene; late Maastrichtian to early Danian (tentatively); and early Maastrichtian. The position of the K-Pg transition is also suggested. Some samples were selected to perform calcareous nannofossil analyses and integrate their data with dinoflagellate cyst bioevents to enhance stratigraphic resolution, supporting age interpretations and refining previous stratigraphic frameworks. This multidisciplinary approach, which combines geological and geophysical data—including spontaneous potential (SP) and gamma-ray (GR) logs—with palynological and micropaleontological evidence, strengthens regional correlations within the South Atlantic basins. Moreover, this study presents the first record of calcareous nannofossils in Uruguayan deposits.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105796"},"PeriodicalIF":1.5,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220356","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 Miocene to Pliocene depositional environments of the Llanos Basin: from the decline of the Pebas System to the inception of the Amazon fluvial complex","authors":"Alejandro Beltrán-Triviño ,&nbsp;Andrés Cárdenas-Rozo ,&nbsp;Marcela Jaramillo ,&nbsp;Esteban De Vargas-Mendoza ,&nbsp;Nicolle Rodríguez-Vergel ,&nbsp;Laura Redondo ,&nbsp;Diego Armando Ramírez ,&nbsp;Ricardo Andrés Gomez-Moncada ,&nbsp;José Ricardo Sandoval","doi":"10.1016/j.jsames.2025.105797","DOIUrl":"10.1016/j.jsames.2025.105797","url":null,"abstract":"<div><div>The Guayabo Formation in the Llanos Basin of Colombia is a critical stratigraphic unit for understanding the transition from the Miocene marine-influenced Pebas System to a fluvial-dominated depositional environment. This manuscript examines the sedimentological, mineralogical, and electrofacies characteristics of six intervals (G1 to G6) within the Guayabo Formation, offering insights into the paleoenvironmental evolution from the Middle Miocene to the Pliocene. The analysis reveals a dynamic progression of depositional environments. The G1 interval (Serravallian) exhibits funnel-shaped gamma-ray log patterns indicative of deltaic progradation, marking the transition from marine lagoonal facies to marginal deltaic settings. The G2/G3 interval (early-middle Tortonian) is unified due to similarities in sedimentological patterns, consisting of floodplains and swamp environments that predominated under reducing conditions. The G4 interval (middle-late Tortonian) reflects mixed depositional influences, including tidal flats and fluvial point bars, supported by glauconite pellets and siderite under low-oxygen conditions. The G5 interval (early-middle Messinian) indicates tide-dominated estuarine environments characterized by aggradational sandstone layers, highlighting the influence of marine transgressions and intertidal zones. The G6 interval (late Messinian-Pliocene) exhibits a progradational sequence transitioning from swamps to meandering fluvial channels, driven by climatic changes and sea-level fall. Mineralogical analyses emphasize variations in climatic conditions, depositional dynamics, and diagenetic processes across these intervals. Therefore, our findings suggest that the Pebas System's influence persisted in the Llanos Basin until the Messinian age (ca. 7.2–5.3 Ma), extending beyond its proposed termination in the late Tortonian.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105797"},"PeriodicalIF":1.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158788","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":"Constraining the depositional history of the Maricá group through U–Pb zircon geochronology of tuff, Camaquã Basin, Dom Feliciano Belt, Brazil","authors":"Ricardo Araújo Lemos ,&nbsp;Edinei Koester ,&nbsp;Delia del Pilar Montecinos de Almeida ,&nbsp;Carla Cristine Porcher ,&nbsp;Vivianne Andrade Bastos ,&nbsp;Diego Jaldín ,&nbsp;Luisa Caon ,&nbsp;Daniel Triboli Vieira","doi":"10.1016/j.jsames.2025.105787","DOIUrl":"10.1016/j.jsames.2025.105787","url":null,"abstract":"<div><div>The Maricá Group, located in the Dom Feliciano Belt in southern Brazil, represents the basal unit of the Camaquã Basin; however, its depositional chronology remains a subject of ongoing debate. In this context, a thin layer of intermediate tuff from São Rafael Formation, exposed in the Passo do Salsinho region, was identified and analyzed to constrain the timing of sedimentation. Field observations, petrographic analysis, and X-ray diffraction (XRD) data indicate a thin intermediate tuff layer of andesitic composition, composed predominantly of plagioclase, and K-feldspar, subordinately quartz, embedded in a matrix of devitrified glass now transformed into illite. In situ U–Pb zircon dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded a crystallization/deposition age of 618 ± 4 Ma. Inherited zircon grains with ages ranging from 2.9 to 1.7 Ga were also identified and interpreted as xenocrystal components assimilated during magma ascent, likely derived from deep crustal sources of Archean to Paleoproterozoic age. This new geochronological evidence refines the temporal framework of the Maricá Group, suggesting that volcanism in the region may have provided the material interbedded within the sedimentary succession. A potential source area for this tuff may be associated with the Cordilleran-type arc that evolved between 630 and 605 Ma, linked to the closure of the Adamastor Ocean, specifically the Pinheiro Machado Magmatic Arc.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105787"},"PeriodicalIF":1.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158789","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":"Regional geomorphological and gravimetric analysis of the Gualilán depression: An endorheic basin in the Andean Precordillera, Argentina","authors":"Maria Romina Onorato ,&nbsp;Juan Manuel Alcacer ,&nbsp;Carla Ginesta Torcivia ,&nbsp;Natalia Rios ,&nbsp;Martin Rothis ,&nbsp;Pablo Andrés Blanc ,&nbsp;Federico Haro ,&nbsp;Laura Patricia Perucca ,&nbsp;Nicolas Vargas ,&nbsp;Vicente Mulet","doi":"10.1016/j.jsames.2025.105794","DOIUrl":"10.1016/j.jsames.2025.105794","url":null,"abstract":"<div><div>This study provides the first integrated geomorphological and gravimetric assessment of the Gualilán depression, an endorheic basin located in the Central Precordillera of San Juan, Argentina. The basin covers 1463 km² and is bounded by mountain ranges that strongly influence its hydrological and sedimentary dynamics. Three main morphostructural units were recognized: Mountainous, Piedmont, and Playa. Six river sub-basins were analyzed morphometrically, showing contrasts between the larger, north–south oriented western, northern, and southern sub-basins and the smaller, east–west oriented ones in the eastern sector. Digital elevation models and swath profiles reveal a marked asymmetry, with broader, gently sloping piedmonts in the west and narrower, steeper piedmonts in the east. This morphology reflects tectonic control associated with east-verging thrusts and dominant north–south reverse faults, further segmented by oblique NW–SE and SW–NE structures. Residual Bouguer anomaly analysis (XGM2019e) shows clear correlations between topography and subsurface geometry. Mountainous units are linked to positive anomalies up to +20 mGal, whereas piedmonts display negative values (0 to −20 mGal), indicating lower-density deposits and transitional domains. The Playa unit, with anomalies between −5 and +5 mGal, corresponds to alternating depocenters and areas of limited sediment accumulation. The results support the interpretation of the Gualilán depression as a closed continental piggyback basin that has functioned since at least the Cenozoic as a sediment reservoir. The integration of geomorphology, morphometry, and gravimetry highlights the role of inherited basement structures and neotectonic activity in shaping drainage patterns, sediment storage, and overall basin evolution within an actively deforming compressional orogen.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105794"},"PeriodicalIF":1.5,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096531","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":"Geophysical characterization of the different heterogeneities that subduct with the Nazca Plate beneath the central Andes","authors":"Federico Lince Klinger ,&nbsp;Orlando Alvarez ,&nbsp;Silvina Nacif ,&nbsp;Mario Gimenez ,&nbsp;Agustina Pesce ,&nbsp;Walter Báez ,&nbsp;Rubén Filipovich ,&nbsp;Andrés Folguera","doi":"10.1016/j.jsames.2025.105792","DOIUrl":"10.1016/j.jsames.2025.105792","url":null,"abstract":"<div><div>Using information from the Earth magnetic anomaly model (EMAG2), gravity (global vertical gravity gradient), Geoid (Eigen6C4), and heat flow, complemented with seismological data (NEIC), we were able to analyze sublithospheric and lithospheric processes beneath the South American plate in the Central Andes where the Nazca Plate experiences a strong transition from horizontal, from the Chilean-Pampean flat subduction zone in the south to steep in the north beneath the southern Altiplano, a region characterized by delamination. This section of the Nazca Plate presents several heterogeneities, such as the transform Challenger Fault Zone, and three aseismic volcanic chains originated in hot spots, the Juan Fernández Ridge, Copiapó Ridge, and Taltal Ridge that were signaled as sources for subducted plate tearings, abnormal heat flow, volatile injection and asthenospheric upwellings from tomographic and volcanological studies. Besides, associated sub-lithospheric viscosity drop has been linked to lithospheric delamination. Geoid residuals confirm the existence of thinned sectors of the over-thickened southern Altiplano crust, in coincidence with low seismicity and high heat flow zones at the site of subduction of the Challenger fault zone and Copiapó and Taltal aseismic Ridges, which supports former proposals of subducted slab tearings at these heterogeneities controlling lithospheric drippings and retro arc volcanism.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105792"},"PeriodicalIF":1.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096532","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":"K-Bentonite deposits in the argentine Precordillera: Characterization and new findings from the eastern Precordillera of San Juan","authors":"Julian D. Rolan ,&nbsp;Jonatan A. Arnol ,&nbsp;Fernando E. Lopez ,&nbsp;Francisco I. Lugo ,&nbsp;Norberto J. Uriz ,&nbsp;Juan M. Drovandi ,&nbsp;Osvaldo A. Conde ,&nbsp;Miguel A.S. Basei","doi":"10.1016/j.jsames.2025.105780","DOIUrl":"10.1016/j.jsames.2025.105780","url":null,"abstract":"<div><div>The rifting, drifting and eventual accretion of the Cuyania Terrane to the southwestern margin of Gondwana represents one of the most well-documented cases of the accretion of an allochthonous lithospheric fragment. Among the key lines of evidence supporting the proximity of Cuyania Terrane to the paleomargin of Gondwana is the occurrence of numerous K-bentonite levels interbedded with Ordovician sedimentary successions in both the Precordillera and the Famatina System. These volcanic ash fall deposits are interpreted as the result of Famatinian arc volcanism during the pre-collisional stage of Cuyania, when the remnant ocean separating the two lithospheric fragments was gradually closed. This contribution presents the first zircon U-Pb geochronological results from a K-bentonite level in the Eastern Precordillera of San Juan, specifically within an olistolith of limestone that was resedimented into the Rinconada Formation (Silurian-Early Devonian?). This discovery documents the first known occurrence of K-bentonite in the Sierra de La Rinconada, and the second within the Eastern Precordillera. The results yielded an age of 475 ± 8 Ma (Floian). The new information obtained is compared with the current knowledge of the spatial and temporal distribution of the Famatinian volcanism as well as with the existing biostratigraphic framework. Thus, the new age recorded for this K-bentonite level is broadly congruent with the temporal extent of Famatinian volcanism (<em>ca.</em> 479-463 Ma), and concordant with existing biostratigraphic information.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105780"},"PeriodicalIF":1.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096535","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":"Review and update of the benthic paleocommunities of the Malvinoxhosan Bioregion, a case study in the Paraná Basin, Brazil","authors":"Iniwara Kurovski ,&nbsp;Elvio Pinto Bosetti","doi":"10.1016/j.jsames.2025.105791","DOIUrl":"10.1016/j.jsames.2025.105791","url":null,"abstract":"<div><div>In 1971, Arthur James Boucot proposed the first paleocommunities for Devonian benthic marine invertebrates of the Malvinokaffric Realm: <em>Lingula</em>, <em>Australospirifer</em>, <em>Eocoelia</em>, and <em>Notichonetes</em>. However, since taphonomy was not widely applied at the time, some aspects were not considered. This work aims to revise these paleocommunities, taking those factors into account. Based on field observations, laboratory sample analysis, and literature review, the following paleocommunities are proposed: a) “<em>Australospirifer</em>”; b) “Infaunal Lingulids” (a provisional name until a taxonomic revision of <em>Lingula</em> is conducted); and c) “<em>Pleurochonetes</em> + <em>Australocoelia</em>”. These are positioned within the following paleoenvironmental settings: Lower Shoreface (first two) and Lower Shoreface to Offshore Transition (last one). These changes are justified by: (1) The <em>Australospirifer</em> Paleocommunity is retained, as it was identified both in the field and laboratory, except for some transported material previously interpreted as in situ. (2) The so-called <em>Lingula</em> paleocommunity is a thanatocoenosis, and the genus <em>Lingula</em> is no longer considered Paleozoic, making it unsuitable as a representative taxon. (3) The <em>Eocoelia</em> and <em>Notichonetes</em> paleocommunities may represent a single group, as they are often found together in the same paleoenvironment and sometimes in life position. Boucot's paleocommunities are a reference for the Devonian of the Paraná Basin but require updates due to numerous recent discoveries and the integration of new fields such as taphonomy and ichnology. Therefore, this work presents an updated arrangement of the Devonian paleocommunities in the Paraná Basin, based on field evidence and recent studies.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105791"},"PeriodicalIF":1.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096536","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":"Spatio-temporal analysis of soil loss and sediment export using GIS and the InVEST-SDR model: application in the Rio Pardo Basin, Brazil","authors":"Donizeti Aparecido Pastori Nicolete,&nbsp;Edson Luís Piroli","doi":"10.1016/j.jsames.2025.105793","DOIUrl":"10.1016/j.jsames.2025.105793","url":null,"abstract":"<div><div>Identifying areas with high erosion rates and sediment source is essential for effective natural resource management and land use and land cover (LULC) planning in river basins. This study applied the Revised Universal Soil Loss Equation (RUSLE), integrated with the Sediment Delivery Ratio (SDR) module of the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, to estimate water erosion and sediment transport rates in the Rio Pardo Basin (RPB), located in southeastern Brazil. This basin has experienced changes in LULC in recent years, which have affected soil loss and sediment delivery. From 2003 to 2023, results showed an increase in the classes of highest erosion intensity (slight/moderate, moderate, moderate/high, high, very high and severe), with a 17.4 % reduction in the slight class, evidencing the intensification of surface erosion processes in the RPB, mainly driven by LULC changes. The average SDR values were 0.033 and 0.034 for the years analyzed, while the average sediment export rate for 2023 was 0.22 Mg ha⁻¹ yr⁻¹, higher than the average in 2003, which was 0.16 Mg ha⁻¹ yr⁻¹. To refine the spatial analysis, the RPB was divided into four sub-basins, with the sub-basin called Baixo Pardo presenting the highest erosion rates, SDR, and sediment export. Hotspot analysis further confirmed critical erosion areas in Baixo Pardo and the headwaters of other sub-basins. This study provides a useful tool and methodological approach for decision-makers to implement conservation practices, supporting water security in the RPB and similar areas.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105793"},"PeriodicalIF":1.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145118955","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":"Amorphous inorganic materials and mineralogy of tropical mountainous topsoils in the Atlantic Forest southeastern Brazil","authors":"Caio Rocha de Moura Silva,&nbsp;William Zamboni de Mello,&nbsp;Manuel Moreira,&nbsp;Carla Semiramis Silveira","doi":"10.1016/j.jsames.2025.105790","DOIUrl":"10.1016/j.jsames.2025.105790","url":null,"abstract":"<div><div>Inorganic amorphous materials influence soil physical and chemical properties, with the potential to reflect the environmental conditions, contributing to processes such as nutrient cycling, water retention capacity, and carbon capture and stabilization. This study aimed to evaluate the content and composition of amorphous inorganic material and the mineralogy of the silt-clay fraction in mountainous topsoils of the Atlantic Forest, associating these attributes with indicators of soil weathering. Topsoil samples were collected from two sites in Serra dos Órgãos, RJ (continental slope - BM and oceanic slope - SB), and one site in Serra do Caparaó, ES (SM). Mineralogy was quantified using powder X-ray diffraction (XRD), while total chemical composition was determined by X-ray fluorescence (XRF). The amorphous material content was quantified using the internal standard method, and its composition was assessed through mass balance calculations. Molar ratios indicate the direct dissolution of K-feldspar and plagioclase, forming gibbsite as the main weathering reaction at all sites. Amorphous material constitutes the dominant fraction in all topsoils, ranging between 27 % and 44 %, composed mainly of forms of SiO₂ (100–230 g kg⁻¹) and Fe₂O₃ (30–70 g kg⁻¹). Analyses of molar compositions between primary and secondary minerals and variations in the composition of the amorphous fraction revealed the following trend in weathering degree: SM &gt; SB &gt; BM. The relative SiO₂ content in the amorphous fraction was explained by the rate of feldspar decomposition into gibbsite, which acts as an indicator of the weathering process at the sampling sites.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105790"},"PeriodicalIF":1.5,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145118956","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":"Hydrological implications of agricultural expansion on natural and degraded lands in Northeastern Brazil","authors":"Kaline Muriel de Figueiredo Gomes ,&nbsp;Sandra Isay Saad ,&nbsp;Jonathan Mota da Silva","doi":"10.1016/j.jsames.2025.105785","DOIUrl":"10.1016/j.jsames.2025.105785","url":null,"abstract":"<div><div>Unplanned agricultural expansion puts pressure on natural ecosystems and harms water resources. In Brazil, agricultural growth continues to threaten natural ecosystems despite the availability of extensive degraded areas. This study examines the hydrological impacts of agricultural expansion using modelling under two land use and land cover (LULC) change scenarios in the Maxaranguape watershed, in Northeastern Brazil: an Optimistic scenario (S1), where agriculture replaces degraded pasturelands, and a Business-as-usual scenario (S2), where expansion encroaches upon natural vegetation. We projected agricultural expansion through 2034 based on the trend observed between 2000 and 2020, which showed an average increase of 5.8 km² per year. The Business-as-Usual scenario (S2) resulted in more pronounced hydrological impacts: surface runoff increased by 11.8 % in S1 and 13.2 % in S2, while groundwater flow decreased by 0.6 % and 1.1 %, respectively. These changes led to reductions in minimum streamflow (Qmin) of up to 2.4 % in S1 and 5.2 % in S2, and increases in maximum streamflow (Qmax) of up to 4.4 % in S1 and 2.7 % in S2. The greater decline in Qmin under S2 highlights a more severe impact on water availability—an especially critical concern in drought-prone regions like Northeastern Brazil. These findings underscore the importance of prioritizing agricultural expansion over degraded pasturelands rather than natural ecosystems, as this approach helps prevent further deforestation while promoting long-term water security.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"167 ","pages":"Article 105785"},"PeriodicalIF":1.5,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096533","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}