Effects of lithosphere buckling on subsidence and hydrocarbon maturation: A case-study from the ultra-deep East Barents Sea basin

- We evaluate the conditions for lithosphere buckling to form long-lasting basins.
- We evaluate the implications of buckling on the maturation of hydrocarbons.
- The EBB may result from buckling and densification of a crustal mafic body.
- We test an explanation for non-extensional sedimentary basins.

Lithospheric extension is proposed as one of the most common mechanism to explain the formation of intra-continental sedimentary basins. However, extension is an unlikely mechanism for the formation and preservation of certain intra-continental basins as for example the East Barents Sea basin (EBB), whose origin remains unexplained. An alternative basin-formation mechanism is buckling accompanying lithosphere shortening. Here we evaluate the conditions for lithospheric shortening/buckling as a mechanism to form deep and isostatically compensated sedimentary basins. We use a forward thermo-mechanical finite element technique to evaluate this mechanism for the EBB, where a very large and compensated subsidence is observed. The lower crust is modeled with petrologic consistent densities that depend on pressure and temperature taking into account de-hydration at high P-T conditions. Various models are tested, characterized by different compositions for the lower crust. Results show that lithospheric shortening/buckling may result in compensated ultra-deep basins like the EBB provided the presence of crustal heterogeneities such as a mafic underplate. The implications of buckling for the maturation of source rocks are evaluated. Results show that maturation of kerogen in a contractional basin takes much longer time compared to a basin formed by extension, owing to the significantly lower temperatures in the initial stages of basin formation. In the case of the EBB, buckling predicts better preservation of hydrocarbons as potential Triassic source rocks may enter the oil and gas window after deposition of Middle Jurassic reservoir rocks and formation of Late Jurassic-Early Cretaceous traps.