A large array of inselbergs on a continuation of the sub-Cambrian peneplain in the Baltic Basin: evidence from seismic data, Western Lithuania

The sub-Cambrian peneplain is well-known in Scandinavia, out cropping in Finland, Sweden and Norway. This peneplain is thought to have formed within the Baltic Sea region in Cryogenian and Ediacaran/early Cambrian time, when Baltica, a part of Rodinia for most of that time, experienced tectonic stability, strong sheet-wash weathering and glaciations. While the peneplain outcrops in the Baltic Shield region, it continues beneath Phanerozoic strata of the Baltic Basin. This buried part of the sub-Cambrian peneplain is known to have several isolated inselbergs. We interpret newly acquired 2D and 3D seismic data and show that the sub-Cambrian peneplain extends at least to Western Lithuania where the palaeotopography of the Precambrian basement changes its character from peneplain-like flat to hilly terrain with a large array of inselbergs. Even though some of the largest features of this palaeotopography have been known before, they are here demonstrated for the first time within the regional context of the sub-Cambrian peneplain.