Geological and geophysical investigation of Kamil crater, Egypt

Abstract

Abstract-We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45°. Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050-1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t.

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater, Egypt

“…; Urbini et al. ). The pristine state of preservation is in agreement with the young age of the crater (<5000 yr; Folco et al.…”

“…and a), a depth of approximately 10 m, an upraised rim about 3 ± 0.7 m above the pre‐impact surface as modeled by Urbini et al. (). In situ, uplifted sandstone strata are observed along the upper part of the crater walls (e.g., Fig.…”

“…Due to the high depth‐to‐diameter ratio of the transient cavity, Urbini et al. () suggested that Kamil formed by the impact of a single iron mass (or a tight cluster of fragments). Based on the geometry of the crater and asymmetries in shrapnel and ejecta distribution Folco et al.…”

“…(), and Urbini et al. () concluded that the Gebel Kamil iron meteorite arrived from the NW with an impact angle between 30° to 45°. The minimum projectile mass inferred from systematic meteorite search and geomagnetic data is approximately 5 t (Urbini et al.…”

“…; Urbini et al. ). During this campaign a series of target rock samples representing the crater wall and ejecta were collected with the aim of investigating the shock metamorphism and impact melting induced in the local rocks by the impact of the small (5–10 t) Gebel Kamil Ni‐rich ataxite (D'Orazio et al.…”