Closure of the Tornquist sea: Constraints from MONA LISA deep seismic reflection data

Deep seismic reflection profiles west of Denmark across the suture between Baltica and Eastern Avalonia reveal weak, southward-dipping reflectors within the crystalline basement. These reflectors are interpreted as thrusts resulting from emplacement of Eastern Avalonia onto the southern edge of Baltica. North of these reflectors are the remains of a dissected Silurian foredeep. The presence of this foredeep and the 440 Ma age of metamorphism in rocks recovered from boreholes into Eastern Avalonian rocks suggest that closure of the Tornquist sea occurred in the Late Ordovician, which is consistent with paleobiogeographic data and paleomagnetic apparent polar wander paths for Eastern Avalonia and Baltica. The similarity between these reflection data and the BABEL AC profile permits correlation of reflectors beneath Denmark into the southern North Sea.