The Vargeão Dome, also known as the Vargeão crater, is a complex, partially eroded impact structure in western Santa Catarina, southern Brazil. It is about in diameter and extends across parts of the municipalities of Vargeão, Faxinal dos Guedes, and Passos Maia. The town of Vargeão lies inside the crater, close to its southern rim.
Access to the structure is mainly via BR-282, which crosses western Santa Catarina; Chapecó, the main regional urban centre and the location of the nearest airport, Chapecó Airport, lies about from Vargeão.
The structure formed mainly in volcanic rocks of the Serra Geral Formation, which overlie sandstones of the Botucatu Formation and Pirambóia Formation in the Paraná Basin. The impact uplifted these sedimentary units in the centre of the crater and produced features of shock metamorphism, including shatter cones, shocked quartz, and impact breccias. These features confirm its impact origin.
The age of the impact has not been securely established. U–Pb dating yielded an age of , which has been proposed as the age of the crater, but later studies regard only the maximum age imposed by the volcanic target rocks—approximately 134 million years—as secure.
Geology In the Vargeão area, the Serra Geral Formation consists of a volcanic sequence about one kilometre thick, composed mainly of basalts. Beneath it lie sandstones of the Pirambóia and Botucatu formations. The Botucatu Formation sandstones were deposited by wind-blown dunes in an extensive desert environment before being covered by the Serra Geral lava flows.
The crater is approximately circular, with a well-defined rim and concentric and radial fractures in its interior. It is classified as a complex impact structure, characterised by uplift of the central region during crater formation. At Vargeão, this process brought sandstone blocks to the surface that would normally remain buried beneath the volcanic sequence.
Geophysical modelling indicates a central uplift about wide and a vertical displacement of the sandstones of about . The original structure may have been about in diameter before erosion removed approximately of rock.
Evidence of shock metamorphism includes shatter cones in sandstone and basalt, planar deformation features in quartz and plagioclase, diaplectic glass in feldspars, and several types of impact breccia. Geophysical surveys have also identified a magnetic anomaly in the core of the structure, associated with intensely deformed rocks and pseudotachylytic breccias.
Formation and age Numerical simulations indicate that the structure may have been produced by an impactor about in diameter, striking the region at approximately . The model reproduces a crater formed in a thick basaltic sequence over sandstone and is consistent with the uplift observed in the centre of Vargeão.
Researchers used U–Pb dating on zircon crystals in veins interpreted as being related to the impact and obtained an age of . This age was proposed for the event but remains debated. The secure chronological constraint is that the impact postdates the Serra Geral volcanic rocks affected by the crater, which are approximately 134 million years old.
Research history The circular structure was recognised in 1978 on radar images produced by the RADAMBRASIL survey. Early studies described the anomalous occurrence of older sedimentary units within the volcanic sequence and named the feature the Vargeão Dome.
In the early 1980s, surveys associated with oil and gas exploration considered volcanic and tectonic hypotheses for its origin. An impact origin was proposed in 1982 and was subsequently confirmed by the identification of shock-metamorphic features.
Since the 2000s, geophysical, petrographic, geochronological and numerical-modelling studies have refined understanding of the crater's geometry, internal structure and impact-related processes.
Research and geoconservation Vargeão is one of the few known impact structures on Earth formed predominantly in basaltic rocks. It is therefore used in studies of impact cratering in volcanic terrains, which are common on other bodies in the Solar System.
Recent research has also examined hydrothermal alteration associated with the structure. Analyses published in 2026 identified two main stages of vein formation and indicated that the impact reactivated a pre-existing hydrothermal system. Vargeão is therefore studied as a terrestrial analogue for hydrothermal systems associated with impact craters on Mars.
The Vargeão Dome is included in the geodiversity-site inventory of the Geological Survey of Brazil. The inventory assesses the site as being at high risk of degradation and identifies agricultural land use and the extraction of sandstone for construction sand among the principal pressures on the site.
See also
Araguainha crater Vista Alegre crater Cerro do Jarau crater List of impact structures on Earth
References
External links "Curiosidades do Oeste de SC: a história da queda de meteorito em Vargeão" – Balanço Geral Oeste Vargeão Dome at the Impact Earth database