The Colônia structure,São Paulo,Brazil |
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| Authors: | Claudio RICCOMINI Alvaro P CRÓSTA Renato L PRADO Marie‐Pierre LEDRU Bruno J TURCQ Lucy G SANT’ANNA José A FERRARI W Uwe REIMOLD |
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| Institution: | 1. Institute of Geosciences, University of S?o Paulo, Rua do Lago 562, 05508‐080 S?o Paulo, SP, Brazil;2. Institute of Geosciences, University of Campinas, R. Pandiá Calógeras 51, Cidade Universitária Zeferino Vaz, 13081‐970 Campinas, SP, Brazil;3. Institute of Astronomy, Geophysics and Atmospheric Sciences, University of S?o Paulo, Rua do Mat?o 1226, 05508‐090 S?o Paulo, SP, Brazil;4. ISEM/Paléoenvironnements, CNRS UMR 5554, Université de Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France;5. IRD, Centre de Recherche d’Ile de France, 32 Avenue Henry Varagnat, 93143 Bondy Cedex, France;6. School of Arts, Sciences and Humanities, University of S?o Paulo, Av. Arlindo Béttio 1000, 03828‐000 S?o Paulo, SP, Brazil;7. Instituto Geológico do Estado de S?o Paulo, Secretaria Estadual do Meio Ambiente, Av. Miguel Stefano 3900, 04301‐903 S?o Paulo, SP, Brazil;8. Museum für Naturkunde, Leibniz‐Institiute for Evolution and Biodiversity Research, Humboldt University Berlin, Invalidenstrasse 43, D‐10115 Berlin, Germany |
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| Abstract: | Abstract– The near‐circular Colônia structure, located in the southern suburbs of the mega‐city of São Paulo, Brazil, has attracted the attention of geoscientists for several decades due to its anomalous character and the complete absence of any plausible endogenous geologic explanation for its formation. Origin by impact cratering has been suggested repeatedly since the 1960s, but no direct evidence for this has been presented to date. New seismic data have been recently acquired at Colônia, providing new insights into the characteristics and possible layering of infill of the structure, as well as into the depth to the underlying basement. We review the current knowledge about the Colônia structure, present the new seismic data, and discuss the existing—as yet still indirect—evidence for a possible origin by an impact. The new data suggest the existence of a sedimentary fill of approximately 275 m thickness and also the presence of two intermediate zones between sediment and basement: an upper zone that is approximately 65 m thick and can be interpreted as a possible crater‐fill breccia, whereas the other zone possibly represents fractured/brecciated basement, with a thickness of approximately 50 m. Although this depth to basement seems to be inconsistent with the expected geometry of a simple, bowl‐shape impact structure of such diameter, there are a number of still unconstrained parameters that could explain this, such as projectile nature, size and velocity, impact angle, and particularly the current erosion depth. |
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