Caledonian deformation upon southwest Baltica and its tectonic implications: Alternatives and consequences

The continuation of the basement of the southwestern Baltic Shield toward the SW is of major interest for the Caledonian evolution in the southwestern Baltic Sea and northern Germany. A reinterpretation of various marine seismic data suggests a reconsideration of the Caledonian collision pattern. The Sorgenfrei Tornquist Zone forming the northwestern extension of the Tornquist Zone is regarded as the northeasterly boundary fault and the Elbe Lineament is regarded as the southwestern limit of an area which suffered from the docking of East Avalonia to Baltica. It shows many northwestsoutheast striking structures, anomalies, and fault patterns. From our studies, two alternative models emerge: one which considers the Caledonian Deformation Front as the northeastern limit of East Avalonia and a zone of major transpression, collision, and subduction of the Tornquist Sea. Another model considers the Elbe Lineament in Schleswig‐Holstein (NW Germany) as a major (dextral) strike‐slip fault which is interpreted as the northeasterly limit of East Avalonia and the southwest boundary of the Baltic Shield. Along the Elbe Lineament the Tornquist Sea plus rotating Avalonia were displaced to the northwest. A large part of the area to be studied might have developed into a passive margin toward the Upper Ordovician. A decision which of the two models is to be prefered has to be the major goal of future geophysical experiments.