Syn-rift evolution of the Pripyat Trough: constraints from structural and stratigraphic modelling

Abstract

The Pripyat Trough is a Late Devonian rift basin. It forms part of the larger Pripyat-Dniepr-Donets rift system which has a length in excess of 800 km and separates the Ukrainian Shield from the Voronezh Massif. The Pripyat Trough contains a well resolved stratigraphic sub-division within the syn-rift basin fill sequence which allows the duration and rate of rifting to be determined using 2-D forward and reverse structural and stratigraphic modelling. The analysis shows that rifting was extremely rapid. Sequential decompaction and flattening of 2-D cross-sections has been applied to six syn-rift time horizons between top Upper Devonian (364 Ma) and top Middle Devonian (377 Ma) and used to quantify the syn-rift development of basin cross-sectional area in time. The evolution of basin cross-sectional area shows that some initial rifting had occurred prior to the Middle Frasnian (369 Ma); however, most rifting occurred in the Famennian (367-364 Ma). Forward syn-rift modelling using the flexural cantilever model of rift basin formation has also been applied to quantify the magnitude of extension within the Pripyat Trough in time. Forward syn-rift models are constrained by the intra syn-rift flattened and decompacted cross-sections and the observed evolution of the cross-sectional area. Most rapid rift basin formation is shown to have occurred in the Famennian with over 66% of basin cross-sectional area forming in less than 5 Myr, and with approximately 80% or more of total extension occurring in less than 3 Myr. This period of most rapid extension during the Famennian coincides with the most active period of volcanicity. Total Devonian extension across the Pripyat Trough is estimated to be of the order of 11–14 km with a maximum β stretching factor of approximately 1.12. Extensional strain rates are estimated to be of the order of 0.8 × 10 −15 s −1.