Endogenous and non-impact origin of the Arkenu Circular Structures, al-Kufrah Basin (SE Libya)

The twin Arkenu Circular Structures (ACS), located in the al-Kufrah basin, SE Libya, were previously recognized as double impact craters (the “Arkenu craters”) and were included in the terrestrial impact crater list. The Arkenu Circular Structures consist of a NE (Arkenu 1) and a SW structure (Arkenu 2), with approximate diameters of about 10 km. They are characterized by two shallow depressions surrounded by concentric circular ridges and silica-impregnated sedimentary dikes cut by local faults. Our field, petrographic and textural observations definitely exclude that the ACS have been originated by the collision of two cosmic bodies.