Título:	Geological and morphostructural analysis of the Araguainha impact structure, Brazil
Outros títulos:	Análise geológica e morfoestrutural da estrutura de impacto Araguainha, Brasil
Autor(es):	Bernardes, Renato Borges
Orientador(es):	Reimold, Wolf Uwe
Coorientador(es):	Gibson, Roger L.
Assunto:	Crateramento por impacto Geologia estrutural Soerguimento central
Data de publicação:	26-Mai-2026
Data de defesa:	27-Out-2025
Referência:	BERNARDES, Renato Borges. Geological and morphostructural analysis of the Araguainha impact structure, Brazil. 2025. vi, 193 f., il. Tese (Doutorado em Geologia) — Universidade de Brasília, 2025.
Abstract:	The Araguainha impact structure (AIS) is the ~40-km-wide erosional remnant of South America's largest confirmed impact structure. It was formed in a mixed crystallinesedimentary target in the north-northwest part of the Paraná Basin, Central-West Brazil, at 259–252 Ma. Geological and structural mapping, especially the analysis of new, extensive exposures from roadworks on the MT-100 state road in and around the AIS, has been conducted. Combined with a multi-methodological investigation using airborne geophysics, remote sensing, lineament analysis, and modeling of the (apparent) crater rim trace shape, this has provided an updated geological map, expanded the structural inventory, and allowed the investigation of the influence of the preexisting regional structural framework on the development of the first-order morphostructure of the AIS. The formation of the most prominent morphological and structural features in the different sections – i.e., outer rim region, intermediate section, and central uplift – of the AIS is associated with the excavation and modification stages of cratering. Large, faultbounded blocks dominate the outer domains of the AIS, with the Passa Dois Group Blocks (PDGBs) in the outer rim region resembling gravity-driven complex slumps. The AIS is unlikely to be of the peak-ring type, as previously suggested. The northern core of the central uplift can be divided into a structurally diverse megablock zone, with rare injections of impact melt rock and occurrences of at least three types of impact breccia (suevite and polymict lithic breccia), which in turn overlies a seemingly coherent but folded and faulted crater floor formed by (meta)sedimentary basement. The AIS and its central uplift, the latter of which may be up to ~20 km wide, are (structurally) asymmetric features. The development of the structure’s morphostructural asymmetry was fundamentally controlled by the pre-impact anisotropy of the target. A contribution from oblique impact to the observed asymmetry, however, cannot be ruled out. The preexisting structural fabric of the target is primarily characterized by lineaments prominently trending in the NE-SW and NW-SE directions, which can be linked principally to structures related to the Paraguay Belt and, to a lesser extent, the Transbrasiliano Lineament beneath the NNW Paraná Basin. This pre-impact structuration of the target yielded an apparent rim trace shape that is not circular, but best represented by an irregular nine-sided polygon (enneagon). Therefore, the AIS is recognized as the eroded remnant of a polygonal impact crater. These results highlight new aspects of the intricate processes involved in the formation of large, complex impact structures in heterogeneous targets, including the importance of the target's anisotropic features – including layering and/or fractures and faults – in shaping the main morphostructural aspects of these structures.
Unidade Acadêmica:	Instituto de Geociências (IG)
Informações adicionais:	Tese (doutorado) — Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2025.
Programa de pós-graduação:	Programa de Pós-Graduação em Geologia
Licença:	A concessão da licença deste item refere-se ao termo de autorização assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
Aparece nas coleções:	Teses, dissertações e produtos pós-doutorado

Os itens no repositório estão protegidos por copyright, com todos os direitos reservados, salvo quando é indicado o contrário.