Revista de la Asociación Geológica Argentina

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Leticia Lescano, Micaela NAVARRO, Constanza BOURNOD, Jorge SFRAGULLA — Thu, 30 Jul 2026 00:00:00 +0000

The 25 de Mayo mine, currently abandoned, is located in the south-central portion of the Sierras Pampeanas of Córdoba, within the Calamuchita Department in the 25 de Mayo mining district. Based on systematic sampling at open-pit exposures, mineralogical and morphological analyses were carried out using optical microscopy, phase contrast, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Serpentinized rocks containing veinlets of asbestiform chrysotile were identified. The fibers exhibit length-to-width ratios greater than 400 and diameters below 3 μm in at least 50% of cases, qualifying as hazardous to human health according to international standards. Partial pseudomorphic replacement of chrysotile by carbonates was observed, although this does not eliminate its potential health risk. The mineralogical and textural evolution suggests at least two serpentinization events, including one associated with retrograde metamorphism. These findings highlight the importance of assessing the environmental impact of asbestiform minerals in abandoned mines, due to their biopersistence and ease of disaggregation. The results contribute to the regional geological understanding and to preventive environmental management in response to the presence of hazardous minerals in abandoned open-pit mines from Córdoba Province’s mining past.

Diffuse recharge in the unconfined aquifer of the coastal dune barrier in southwestern Buenos Aires Province, Argentina: assessment using independent methods

Andrés Gabriel Ruffo, Matías REY, René ALBOUY — Thu, 30 Jul 2026 00:00:00 +0000

Quantifying the volume of water entering the aquifer is essential for the sustainable management of the resource, particularly in semiarid regions such as the southwestern sector of Buenos Aires Province. The study area features a sandy barrier of dunes that hosts an unconfined freshwater aquifer within an arid–semiarid environment, which constitutes the main water supply for local populations. This study quantifies natural aquifer recharge resulting from precipitation-driven water surplus using two independent methods: a daily-step Soil Water Balance (SWB) and the chloride mass balance approach. The former was applied using two daily precipitation series (2001–2018 and 2013–2024) and two independent estimates of potential evapotranspiration. The chloride mass balance method was implemented based on 20 precipitation events and chloride concentrations measured in six wells located in preferential recharge zones of the dune system. The annual mean recharge rate estimated for the study area using both methodologies ranged between 27% and 39% of mean annual precipitation, with maximum values of 61% and minimum values of 18%, highlighting its temporal variability. These results are consistent with recharge estimates reported by other authors for the study area and for similar regions.

Forzantes climáticos, costeros y antropogénicos de los peligros geomorfológicos en una ciudad costera patagónica de alto relieve: Comodoro Rivadavia, Argentina

JOSE PAREDES, Silvina Mariela OCAMPO, Mauro Nicolás VALLE, Fabián SUÁREZ — Thu, 30 Jul 2026 00:00:00 +0000

Comodoro Rivadavia, en la costa atlántica patagónica de Argentina, es una ciudad de alto relieve con clima semiárido, cuencas efímeras de fuerte pendiente, sucesiones sedimentarias cenozoicas poco competentes y dinámica costera macromareal, condiciones que interactúan con el uso urbano e industrial del suelo. Este estudio presenta una evaluación integrada de inundaciones, deslizamientos, erosión costera, sedimentación portuaria y disrupción de la conectividad urbana, basada en estudios previos, registros meteorológicos actualizados, mapeo geomorfológico, observaciones de campo, topografía derivada de drones, imágenes multitemporales y datos batimétricos. El registro de precipitaciones de 1956–2022 confirma la magnitud excepcional de la tormenta de marzo–abril de 2017, con 399,4 mm de precipitación acumulada y 232 mm en un solo día, mientras que un evento extremo de 82 mm/día ocurrido en 2022 indica una exposición persistente a tormentas de alta magnitud. Los impactos de las inundaciones incluyen erosión por cárcavas, ensanchamiento de canales, obstrucción del drenaje, sedimentación urbana y aporte
de sedimentos a la costa; sin embargo, la mitigación permanece incompleta, con solo un dique de retención de los 4 planificados actualmente operativo. La estabilidad de laderas está controlada por contrastes litológicos, disparadores subterráneos o marinos y modificaciones antrópicas, incluyendo alteración del drenaje, riego, excavación del pie de taludes y urbanización sobre depósitos de
deslizamientos previos. La reactivación del deslizamiento del Cerro Chenque en 2023, desencadenada por marejadas que intensificaron
la erosión basal, involucró aproximadamente 70.425 m³ y provocó el cierre de la Ruta Nacional 3 durante 35 días.

Hydrosedimentological controls on bedform development in a mesotidal environment

AGUSTINA ANDREOLI, SILVIA SUSANA GINSBERG, SALVADOR ALIOTTA — Thu, 30 Jul 2026 00:00:00 +0000

The Bahía Blanca Estuary, located in the southern sector of Buenos Aires Province (Argentina), exhibits a wide variety of bedforms generated by the interaction among hydrodynamic and sedimentary processes. The aim of this study is to analyze these geomorphic features by identifying their sedimentary characteristics, their spatio-temporal evolution, and their relationship with the prevailing hydrodynamic conditions within the estuary. To this end, data acquired in the outer sector of the estuarine inlet were integrated, including side-scan sonar records, high-resolution seismic profiles, surface sediment samples, and hydrodynamic information. The identified bedforms include sand ribbons, with and without superimposed dunes, comet marks with different geometries, and asymmetric dunes of various dimensions. The distribution and type of bedforms reflect the interaction between sediment supply and the dominant hydrodynamic regime. The availability of sediment transported as bedload constitutes the main factor controlling their morphological configuration, spatial distribution, and dynamic behavior. Dunes develop in sectors where sandy thicknesses exceed 1 m, whereas intermediate thicknesses (0.5–1 m) allow the formation of sand ribbons with superimposed dunes and smaller-scale dunes. In contrast, sediment thicknesses below 0.5 m are associated with sand ribbons without dunes and comet marks. The morphological characteristics of the recorded bedforms, together with the measured current velocity patterns, indicate a marked dominance of the ebbrent, with values exceeding 1 m/s.