Crustal structure and tectonic evolution of the Tornquist Fan region as revealed by geophysical methods

Abstract

Crustal structure derived primarily from geophysical investigations reveals fea-tures that may be related to the complex tectonic evolution of the Tornquist Fan region. This northwestwards widening splay of Late Carboniferous - Early Per-mian fault zones in the Danish region emanates from the Teisseyre-Tornquist Zone in northern Poland. Seismic reflections and velocity anomalies image collisional fault zones that formed during the Proterozoic and Palaeozoic amal-gamation of the crust. Re-equilibration of Moho appears to have taken place before late Palaeozoic rifting and magmatism initiated the main phase of basin formation that continued into the Mesozoic. The resulting, strong Moho topog-raphy, with variation between depths of 26 and 48 km, has been practically fro-zen in since then, although the late Cretaceous - early Cenozoic inversion tec-tonics may have formed a crustal keel underneath part of the Sorgenfrei-Torn-quist Zone which cuts across the Proterozoic crust of the Tornquist Fan region.