The target peneplain of the Lockne impact

Abstract

The Lockne impact crater in central Sweden, with a diameter of about 7 km, formed in the mid-Ordovician in a marine environment that was deeper than present shelf seas. The present dip of the so-called sub-Cambrian peneplain in the target area of the impact is about 0.85° toward the northwest. The peneplain is cut by a set of northwest-striking, nearly vertical faults with a throw of up to just over 100 m, collectively. The identification of the peneplain and its deformation by faulting allows us to infer that the part of the crater that is exposed to the east of Lake Locknesjön has been lowered by about 100 m relative to parts exposed to the west of the lake and that it has, therefore, been spared from significant erosion. Therefore, the preservation of the whole crater is even better than was assumed in previous work. The peneplain extends to 600-700 m from the rim of the inner crater. Hence, the structural uplift of the rim is quite subdued compared to the craters that formed on land.