Ro. Greiling et al., Vendian-Cambrian subsidence of the passive margin of western Baltica - application of new stratigraphic data from the Scandinavian Caledonian margin, NORSK GEOL, 79(3), 1999, pp. 133-144
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.