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Journal Articles Meteoritics & Planetary Science Year : 2022

Nova Colinas, Maranhão State: A newly confirmed, complex impact structure in Brazil

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Wolf Uwe Reimold
  • Function : Author
Ludovic Ferrière
  • Function : Author
Álvaro Penteado Crósta
  • Function : Author
Manfred Gottwald
  • Function : Author
Mauricio da Silva Borges
  • Function : Author
Fernando Lessa Pereira
  • Function : Author
Ana Maria Goés
  • Function : Author
Natalia Hauser
  • Function : Author
Mark Jessell
  • Function : Author

Abstract

The Nova Colinas structure is an approximately 7 km wide, nearly circular feature centered at 07°09'33″S/46°06'30″W in Nova Colinas municipality in southwestern Maranhão State, Brazil. The area has been investigated for 40 yr and it has been suggested repeatedly that the structure could be of impact origin—without proof having been furnished. Magnetic anomaly maps depict the structure clearly with a strong, positive magnetic anomaly over the apparent rim zone. The central area is characterized by significant positive K and Th radiometric anomalies. Fieldwork showed that the structure has annular features along the outside and some prominent, structurally dissected hills in the interior. Thirty-three arenite samples were collected for petrographic analysis, mostly from within the structure. Microdeformation, in the form of cataclasis; concussion fractures related to compaction, and presence of planar fractures, feather features, and planar deformation features in quartz are reported. Three samples with a multitude of quartz grains with these microdeformations were analyzed by universal stage to determine the crystallographic orientations of planar fractures and planar deformation features. The results provide robust evidence that these microdeformation features represent shock metamorphism, with low (approximately 5-10 GPa) to moderate (10-16 and 10-20 GPa) shock levels. Thus, the Nova Colinas structure is now confirmed as a bona fide meteorite impact structure. The structure is moderately eroded, as shown by the absence of stronger shock deformation. The still limited available structural geological field evidence, paired with remote sensing and geophysical data, indicates that the innermost part of the structure may have a sizable remnant of a central uplift. The Nova Colinas impact age is only poorly constrained from stratigraphic inference to an upper limit of about 200-250 Ma.
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Dates and versions

insu-03867006 , version 1 (23-11-2022)

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Wolf Uwe Reimold, Ludovic Ferrière, Álvaro Penteado Crósta, Marcos Alberto Rodrigues Vasconcelos, Manfred Gottwald, et al.. Nova Colinas, Maranhão State: A newly confirmed, complex impact structure in Brazil. Meteoritics & Planetary Science, 2022, 57, pp.1519-1541. ⟨10.1111/maps.13833⟩. ⟨insu-03867006⟩
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