Reappraisal of deep seismic reflection Profile VIII across the Pripyat Trough

Two, deep (24 s), multi-channel seismic reflection profiles, each >200 km in length, were shot across the Pripyat Trough, a Late Devonian rift basin in Belarus, in the 1980s by the Polessian Geophysical Expedition of the former Soviet Union. Additional post stack processing and migration on one of these, Profile VIII, has been applied at Uppsala University and allows a re-evaluation of the crustal structure of the Pripyat Trough with particular focus on the deeper parts. Previous interpretations showed numerous steeply dipping faults extending from the surface to depths of 30-40 km and sometimes penetrating into the mantle, which was defined to be located at the top of a reflective zone beginning at about 10 s TWT. This reflective zone, recorded to depths of 16 s TWT, was interpreted as a mixture of crustal and mantle rocks. Based on the original stacked section and the further processing the reflective zone is reinterpreted to be reflective lower crust, not upper mantle, and the Moho is identified to be at 45-50 km labour 15 s TWT). The major basin bounding faults appear to be listric at depth and sole into the top of the reflective lower crust rather than be truncated by it. The newly interpreted crustal structure is consistent with a model of continental rifting involving brittle failure in a thick upper crustal layer and ductile shear in the lowermost crust with some degree of detachment between crust and mantle within the lower crustal ductile layer.