Abstract:Santa Marta is a 10 km wide, reasonably well preserved, complex impact structure located in southwestern Piauí state, northeastern Brazil, with a central uplift of 3.2 km diameter. The Santa Marta structure was recently recognized as the sixth confirmed impact structure in Brazil, based on widespread occurrence of shatter cones and the presence of shock deformation features in quartz. The latter includes planar deformation features (PDF), planar fractures (PF), and feather features (FF). The structure was form… Show more
“…In the Dhala structure, the area occupied by this annular moat (ring syncline) is covered with post-impact sediments of the Dhala Formation. Similar features have been observed at many other impact structures worldwide (e.g., Dypvik et al, 1996;Schmieder et al, 2011;de Oliveira et al, 2017). The dug well sections observed in the annular moat of the Dhala structure comprise various sedimentary units (sandstone, pebbly sandstone, siltstone, sandy shale, and shale) that contain dropstones, convolute bedding, and related soft-sediment deformation structures (Pati, Reimold, et al, 2008;Pati et al, 2010Pati et al, , 2019.…”
Section: Discussionsupporting
confidence: 72%
“…The annular moat is the area between the crater rim and central uplift/elevation, also termed a ring syncline (Kenkmann et al, 2014;de Oliveira et al, 2017). In the Dhala structure, the area occupied by this annular moat (ring syncline) is covered with post-impact sediments of the Dhala Formation.…”
Geomorphological study of some of the just more than 200 known terrestrial impact structures has demonstrated that despite extensive degradation, important geomorphological keys, such as drainage pattern, topographic signatures, erosional landforms, and depositional features, can still be assessed. They can provide possible indicators to assist in the recognition of further impact structures, especially on Precambrian shields and cratonic landmasses. This study documents the surface features and landforms of the Paleoproterozoic, about 11 km diameter Dhala impact structure in India. The Dhala structure has an estimated age that is constrained stratigraphically between 1.7 and 2.5 Ga. This structure is deeply eroded, and barely has a morphological resemblance to other known terrestrial or extraterrestrial impact structures.We have analyzed the operative surface-forming processes for the Dhala area.We demand to continue the in-depth study of all terrestrial impact structures, especially the pre-Paleozoic ones, so that geomorphological criteria can be rigorously constrained and applied in conjunction with a priori remote sensing and field data to support the identification of new structures prior to their ultimate confirmation using diagnostic evidence of shock metamorphism.
“…In the Dhala structure, the area occupied by this annular moat (ring syncline) is covered with post-impact sediments of the Dhala Formation. Similar features have been observed at many other impact structures worldwide (e.g., Dypvik et al, 1996;Schmieder et al, 2011;de Oliveira et al, 2017). The dug well sections observed in the annular moat of the Dhala structure comprise various sedimentary units (sandstone, pebbly sandstone, siltstone, sandy shale, and shale) that contain dropstones, convolute bedding, and related soft-sediment deformation structures (Pati, Reimold, et al, 2008;Pati et al, 2010Pati et al, , 2019.…”
Section: Discussionsupporting
confidence: 72%
“…The annular moat is the area between the crater rim and central uplift/elevation, also termed a ring syncline (Kenkmann et al, 2014;de Oliveira et al, 2017). In the Dhala structure, the area occupied by this annular moat (ring syncline) is covered with post-impact sediments of the Dhala Formation.…”
Geomorphological study of some of the just more than 200 known terrestrial impact structures has demonstrated that despite extensive degradation, important geomorphological keys, such as drainage pattern, topographic signatures, erosional landforms, and depositional features, can still be assessed. They can provide possible indicators to assist in the recognition of further impact structures, especially on Precambrian shields and cratonic landmasses. This study documents the surface features and landforms of the Paleoproterozoic, about 11 km diameter Dhala impact structure in India. The Dhala structure has an estimated age that is constrained stratigraphically between 1.7 and 2.5 Ga. This structure is deeply eroded, and barely has a morphological resemblance to other known terrestrial or extraterrestrial impact structures.We have analyzed the operative surface-forming processes for the Dhala area.We demand to continue the in-depth study of all terrestrial impact structures, especially the pre-Paleozoic ones, so that geomorphological criteria can be rigorously constrained and applied in conjunction with a priori remote sensing and field data to support the identification of new structures prior to their ultimate confirmation using diagnostic evidence of shock metamorphism.
“…), and Santa Marta (Oliveira et al. , ). However, it still has not been completely ascertained whether comparable features may be formed by other tectonic processes although the lack of such reports from both the impact and the tectonic communities strongly speaks out for FFs being characteristic impact deformation.…”
Section: The Search For Shock Deformationmentioning
Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30o12′S and 56o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.