Revista de la Asociación Geológica Argentina

The parent material in soil development in southern Tierra del Fuego.

2025-04-23T20:48:11+00:00

Six soil profiles were analyzed in an area undergoing urban expansion on the southeastern slope of Mount Susana (Ushuaia, southern
Tierra del Fuego). Fieldwork included detailed descriptions of soil morphology and the lithological characterization of parent materials.
Laboratory analyses determined particle-size distribution, organic matter (by loss-on-ignition), pH, and electrical conductivity. These
data were integrated to assess soil genesis, pedogenic processes, and to propose a preliminary classification. Results indicate that
parent material exerts a dominant control on soil diversity across the southern Isla Grande of Tierra del Fuego. Glacial deposits, the
most widespread parent material, prevail in piedmont areas and are often overlain by mass-wasting deposits on steeper slopes. Their
high textural heterogeneity results in multiple lithological discontinuities within the soil profiles. The predominant soil order is Inceptisols,
featuring umbric epipedons. In more permeable substrates (glaciofluvial sands and gravels), podzolization is incipient (pH < 5.5),
marked by Bs, Bh, and/or Bhs horizons, occasionally E horizons, indicating transitions toward Spodosols. In less permeable materials
(compact tills), histic Inceptisols develop, with pH near 6 and no illuvial horizon. Where bedrock occurs near the surface, lithic soils
form. Along coastal areas, calcareous parent materials (shell-rich deposits) favor Mollisols with alkaline pH (7–8) and no illuvial horizon.
These findings highlight the strong lithological control on pedogenesis in subantarctic environments and provide a baseline for
evaluating soil evolution under anthropogenic and climatic influences.

Morphological and morphometric characterization of the Tul Tul, Pocitos, and Del Medio Volcanoes. Puna, Central Andes

2025-04-30T19:32:53+00:00

The morphology of volcanoes reflects the interplay of constructive and destructive processes acting over time. The morphometric characterization of the Tul Tul, Del Medio, and Pocitos (TUMEPO) volcanoes, located in the Puna region near the Calama–Olacapato–El Toro lineament, reveals a complex volcanic evolution. Digital Elevation Models (DEMs) derived from ALOS PALSAR data (12.5 m resolution) enabled identification of key features such as craters, lava flows, and domes, supporting a detailed morphological analysis. The current form of these volcanoes results from the combined influence of eruptive behavior, structural controls, and post-eruptive processes, including erosion and gravitational collapse. All three centers classify as sub-cones, though with distinct morphologies: Tul Tul retains a regular conical shape with radial drainage; Del Medio shows a more complex structure shaped by a large summit crater and nearby volcanic centers; and Pocitos presents a more degraded morphology linked to intense erosion. These variations reflect both the eruptive histories of each volcano and their spatial and temporal interactions. Evidence within the TUMEPO chain suggests that partially synchronous activity among adjacent centers contributed to their present morphologies. Post-eruptive domes at Del Medio and the preservation of youthful forms at Tul Tul support this interpretation. This study underscores the usefulness of DEMs for geomorphological and geodynamic analysis of volcanic systems, while highlighting the need for higher-resolution datasets, field-based validation, and improved geochronological constraints. Overall, the results provide a robust framework for understanding the evolution of the TUMEPO volcanic chain and contribute to broader volcanic research in the region.

Reclassification and chemical revision of iron meteorites from the La Plata Museum

2025-06-02T15:07:47+00:00

The La Plata Museum houses a significant meteorite collection established in 1884, comprising 91 specimens from Argentina and
abroad. As part of the first stage of a broader reclassification project, eight iron meteorites from this collection—previously lacking conclusive
chemical data—were analyzed using instrumental neutron activation analysis (INAA). The new results confirm the classification
of six specimens and lead to the reclassification of two as pallasites. This study also corrects historical misidentifications, such as
the Otumpa meteorite, provides the first chemical classifications for the Dadin (IIIAB) and Huaytiquina (IIAB) meteorites, and expands
the chemical database for Caperr, Ñorquin, and El Sampal. The updated information will be submitted to the Nomenclature Committee
of the Meteoritical Society. Overall, this work underscores the importance of applying modern analytical methods to reassess historical
collections and update meteorite classifications according to current standards.

Morphosedimentary models of urban drainages in the coast of Vicente López applied to environmental management.

2025-04-08T17:59:12+00:00

Coastal systems are highly dynamic, and when modified by human activities, their behavior becomes difficult to predict. Morphodynamics and ecology are closely interconnected; therefore, effective management requires a comprehensive understanding of both aspects. This study analyzes the geomorphology and sedimentary dynamics of the fluvial channels formed by the progradation of the
Vicente López coast in the late 1990s. The results show that the sediments in these channels are mostly muddy sands with a high organic matter content and display sedimentary grading toward the mouth (estuary). Water quality varies seasonally: during summer, anoxic conditions, low oxygen levels, and high concentrations of nitrates and ammonium are recorded, whereas aerobic environments prevail during the rest of the year. During the extreme drought of 2023, no cyanobacterial blooms were observed; however, high levels of ammonium, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were detected, possibly linked to treated wastewater discharges. This study provides insights to support environmental management and promote the sustainable development of the Vicente López coastal corridor. The findings highlight the need to: (a) reduce effluent discharge into the channels, particularly during summer; (b) preserve riparian forests and stream systems that have developed over the past two decades; (c) regulate fishing activities at stream mouths; (d) implement management policies grounded in the geomorphological and ecological functions of the
streams; (e) prevent disturbance of bottom sediments; and (f) enhance public awareness of the ecological value of urban green spaces and their associated ecosystems.

Descifrando migmatitas cámbricas a través de sus texturas de fusión y deformación: el caso de las diatexitas La Totorilla, Macizo San Carlos, Sierras Pampeanas de Córdoba, Argentina

2025-06-18T15:15:01+00:00

El cuerpo anatéctico La Totorilla se ubica en el Macizo Migmático de San Carlos, parte de la Faja Granulítica Central, eje térmico regional de las Sierras Pampeanas de Córdoba, Argentina. Consiste en un cuerpo elipsoidal (~3 km × 0,5 km) compuesto por diatexitas porfiroblásticas foliadas, ricas en feldespato potásico y cordierita, con claras evidencias de fusión y deformación. Está rodeado por las migmatitas Pichanas, que exhiben una estructura tipo schollen. Ambas unidades contienen schlieren y xenolitos derivados de esquistos bandeados Tuclame y gneises biotíticos. Venas graníticas turmaliníferas y pegmatíticas atraviesan las litologías, evolucionando localmente desde boudines hasta pliegues. La evolución metamórfica de las diatexitas se divide en tres etapas: (1) una etapa prógrada asociada al equilibrio estaurolita–biotita (~600 °C); (2) un pico metamórfico de 788 ± 15 °C a presiones medias (≤ 6 kbar), caracterizado por la generación de cordierita, feldespato potásico y fundido por deshidratación de biotita; y (3) una etapa retrógrada marcada por deformación progresiva, enfriamiento e hidratación. La foliación penetrativa S2 (N 300°) domina el área y se originó por aplastamiento en régimen de cizalla pura. Estructuralmente, el cuerpo se encuentra boudinado dentro de las migmatitas Pichanas, reflejando un fuerte contraste litológico y reológico. La edad U–Pb en circón de 532.1 ± 1.7 Ma indica que las diatexitas se formaron durante la orogenia Pampeana, en niveles de corteza media (≤ 22 km). La Totorilla constituye un ejemplo destacado de roca anatéctica que registra la interacción entre metamorfismo, deformación y fusión parcial durante el Cámbrico temprano en las Sierras Pampeanas.

Geoenvironmental assessment of the Ctalamochita fluvial system, Córdoba, Argentina.

2025-05-26T13:54:50+00:00

Geoenvironmental analysis is based on planetary transformation processes and involves human beings as agents. In the Central Fluvioeolic Plain (Córdoba, Argentina) there are environmental problems by changes in soil use. The objective is to analyze rural and periurban geopedological environments. The Cenozoic sedimentation of the Ctalamochita River extends from the foothills of the Sierra Los Cóndores-Las Peñas in paleochannels covered by loess, controlled by compressional neotectonic deformations. Cartographic analyses and measurements enabled the identification of five representative geotaxa and pedotaxa at the Subfamily level. The Depression
Geotaxa with udic Haplustols, in the northeastern periurban area of Villa María, has problems of waterlogging, compaction and urbanization advancement over the agricultural sector. The Paleocauce Geotaxa with typical Natracualfs corresponds to relicts of native forest, vulnerable by the hydric dynamics, hydromorphism and halomorphism. Although the Ordinance declares some sectors
as a Protected Natural Reserve, it lacks a detailed management plan. The Manto Loéssico Geotaxa, interfluves with typical Haplus-tols, is stable to fluvial dynamics, but vulnerable to eolian and agroecosystemic intensification. The Floodplain Paleollanura Geotaxa with typical Haplustols evidences the advance of the agricultural frontier over the riparian forest. The Geotaxa Faja Fluvial with typical Ustipsamments, vulnerable to flooding and bank erosion, presents conflicts related to conservation and riparian boundary. The progressive pedogenesis: Entisols-Mollisols-Alfisols, base that relates processes and geoenvironmental degradation according to paleo and actual fluvioeolian dynamics, would allow legislating and verifying land use. Consequently, vulnerability depends on geopedological characteristics and socio-environmental problems.