Insights into the structural geology and sedimentary succession of the Baltic Basin, Western Lithuania

The geological structure of the sedimentary cover of the Baltic Basin has been investigated since the 1960's. In Western Lithuania, seismic data were acquired during 1995–2015; however, the interpretation results have remained largely unpublished. In this work, the relatively newly acquired 2D and 3D seismic data have been incorporated into a single seismic interpretation. Detailed depth maps for the key seismic reflection horizons, an updated presentation of fault traces, as well as a few representative seismic profiles are made to illustrate the geological structure of the study area, which is in Western Lithuania and spans nearly 360 km². This area includes Late Caledonian structures, such as the Gargždai Elevation, which contains some of the Lithuanian hydrocarbon fields, and is limited by the Gargždai Fault. This study demonstrates that the Gargždai Fault is not a single continuous fault, but rather it comprises a system of faults. Moreover, the Gargždai Elevation itself contains small-scale structures that are either fault-related, cross-faults, drape structures or combined types. In addition to previously known large separated Precambrian palaeo-topographical features, additional features are mapped as a result of this study. They are interpreted as erosional remnants (inselbergs) on the sub-Cambrian peneplain surface, and form a large group of inselbergs, which is not typical of the Baltic Basin. Several structural features related to Zechstein Basin are mapped as well: the northern edge of Zechstein evaporites and, possibly, Permian reefs.