Araguainha Dome, Brazil: A polygonal impact structure due to a complex pre‐impact regional structural framework

Abstract

Abstract We investigated the structural framework of the north–northwestern Paraná Basin in Brazil to test whether the pre‐impact structures in this region may have had any influence on the first‐order formation and morphostructure of the Araguainha impact structure (AIS). The AIS—an ~40‐km‐diameter, erosional remnant of the largest confirmed, complex impact structure in South America—was formed approximately 259–252 Ma in a mixed sedimentary‐crystalline target. We employed a multi‐method approach, including airborne geophysics, remote sensing, lineament analysis, fieldwork, and modeling of the shape of the (apparent) outer rim trace. This approach reveals that prominent NE–SW‐ and NW–SE‐trending lineaments characterize the AIS region. Much of this fabric can be linked to regional structures associated with the Paraguay Belt and, to a lesser extent, the Transbrasiliano Lineament—both of which influenced the NNW Paraná Basin during its pre‐impact evolution. We present evidence that this preexisting regional structural framework partially controlled the formation and shape of the AIS. The AIS and its central uplift are asymmetric features, with the asymmetry of the central uplift evident from the time of its formation. Our results suggest that the shape of the AIS rim trace is consistent with a polygonal structure. At the analyzed scale, the AIS rim trace is best described as an irregular nine‐sided polygon. This polygonal shape was likely formed during the modification stage, when crater collapse was influenced by the regional pre‐impact structural fabric. Our findings improve understanding of the cratering process in structurally heterogeneous targets and provide valuable insights into the target region's subsurface structural framework.