Vendian-Cambrian subsidence of the passive margin of western Baltica - application of new stratigraphic data from the Scandinavian Caledonian margin

Stratigraphic information from the Neoproterozoic to Cambrian cover sequenc es at the Caledonian margin in central Scandinavia has been compiled from t he literature and our own data. Four flooding events can be recognized in t he autochthonous cover rocks and parts of the eastern Caledonian Lower Allo chthon: one, at the base of the Vendian at 590 Ma, two Early Cambrian event s (540 and 530 Ma), and the fourth at the base of the Mid Cambrian and the alum shales (518 Ma). Stratigraphic successions of the western Baltica marg in from northern Sweden to southern Norway are correlated using these flood ing events. Based on these correlations, depth and time sections are constr ucted and subsidence curves calculated. Although Early Cambrian flooding ev ents lead to temporarily higher sedimentation rates. the subsidence appears to have decreased through time. Such a decrease is consistent with models of lithospheric stretching and subsequent thermal subsidence. A review of a vailable age data on tectonic events suggests a transition from continental rifting to ocean-floor formation off western Baltica at ca. 600 Ma ago. Ac cordingly, the Vendian to Cambrian evolution of the western Baltica contine ntal margin is interpreted as a stage of post-rift subsidence showing the ' steer's head' geometry characteristic of sequences onlapping from an older zone of active rifting and of ocean-floor formation farther west The gradua l decrease in thermal subsidence through Cambrian time also shows that the Baltica lithosphere was essentially thermally re-equilibrated prior to earl iest Caledonian tectonic activity in Early Ordovician time.