Search Results (2)

A possible impact crater at Mahout in Oman was recently proposed by Nasir et al. (2023 [¹]). They alleged that “crater” morphology, shatter cones, shock metamorphic evidence in quartz, plagioclase, and calcite, as well as initial geochemical information and geophysical data supported this proposal. Their conclusion was that “All current analyses suggest the impact origin of the Mahout structure” (p. 20 of the article). In this Comment, their evidence is critically discussed and largely refuted. It is demonstrated that the basis to consider the Mahout structure a possible impact structure is very limited and that further detailed, state-of-the-art analyses of the mesoscopic and microscopic de-formation features are required to obtain credible evidence. Beyond the discussion of the article by Nasir et al., this Comment emphasizes the general need for careful and comprehensive analysis of the geological structures that might, a priori, suggest a possible impact origin if, ultimately, a new impact structure can be successfully confirmed. Full article

The present work reports on the first evidence of a possible hypervelocity impact crater in the Sultanate of Oman. The impact origin of the structure is determined based on field observations, microscopic observations of shatter cones, planar fractures (PFs) and feather features (FFs) in quartz, calcite, and feldspar, and melt-bearing polymict breccias with various types of melts. The structure consists of an elliptical bowl-shaped ridge 750 m long and 550 m wide, oriented roughly north-northeast to south-southwest. The elliptical shape and relief asymmetry indicate an oblique collision. The precursor target lithologies include local late Proterozoic Masirah Bay siliciclastic formations, carbonate and acidic volcanic rocks of the late Precambrian Halfayn Formation, and basement rocks. The crater rim, up to 15–20 m above ground, is composed of quartzite, jasper, agate, monomict siliceous and hematite breccia, and metamorphosed shale (hornfels). An ejecta blanket composed of target rocks covers the floor, outer rim, and the area extending to the immediate northeast and east of the structure. Quaternary aeolian sand covers most of the crater surface, including the 1 to 2 m thick melt-rich polymict breccia found in the crater center. The planar fractures (PFs) and feather features (FFS) in quartz and feldspar suggest a low shock pressure between 5 and 14 GPa. Our observations are consistent with set criterions for impact crater identification, confirming the possible impact origin of the Mahout structure. Full article