Zusammenfassung
We have analysed 129 stratigraphic sections from the Timan-Pechora
basin, from its adjacent continental shelf and from the South Barents
Sea basin, in order to determine whether existing models of extensional
sedimentary basin formation can be applied to these intracratonic
basins or whether new mechanisms of formation need to be invoked.
The subsidence history of each section has been calculated using
standard backstripping techniques. An inverse model, based on finite-duration
lithospheric stretching, has then been used to calculate the distribution
of strain rate as a function of time required to fit each subsidence
profile. Results demonstrate an excellent fit between theory and
observation. By combining our analysis with independent field-based
and geophysical observations, we show that the Timan-Pechora basin
underwent at least four phases of mild lithospheric stretching during
the Phanerozoic (beta<1.2). These phases occurred in Ordovician,
Late Ordovician-Silurian, Middle-Late Devonian and Permian-Early
Triassic times. Growth on normal faults, episodes of volcanic activity
and regional considerations provide corroborative support for the
existence of all four phases. Although less well constrained, subsidence
data from the South Barents Sea basin are consistent with a similar
Early-Middle Palaeozoic history. The main difference is that Permian-Early
Triassic extension is substantially greater than that seen onshore.
This similarity implies structural connectivity throughout their
respective evolutions. Finally, subsidence modelling demonstrates
that rapid foreland basin formation, associated with the Uralian
Orogeny, was initiated in Permo-Triassic times and is confined to
the eastern margin of the Timan-Pechora basin. Coeval foreland subsidence
does not occur on the eastern margin of the South Barents Sea basin,
supporting the allochthonous nature of Novaya Zemlya. The most puzzling
result is the existence of simultaneous lithospheric extension and
foreland loading in Permian-Early Triassic times. This juxtaposition
is most clearly seen within the Timan-Pechora basin itself and suggests
that convective drawdown may play a role in foreland basin formation.
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