Salt tectonics in the Bend Zone segment of the Carpathian fold and thrust belt, Romania

Abstract

The Carpathian Bend Zone is part of the Eastern Romanian Carpathians. The stratigraphic profile contains two levels of salt: Lower Miocene (Lower Burdigalian) and Middle Miocene (Badenian). The studied segment of the fold belt was deformed during the Middle Miocene (Badenian-to-Middle Sarmatian phase) and during the Late Miocene to present (Wallachian phase). During this latter phase, the Lower Burdigalian salt was remobilized and reached the surface on several locations piercing through 2–3 km-thick post-tectonic deposits. The salt outcrops and contractional structures now form a 30 km long, NE–SW lineament at the surface. This contribution proposes kinematic models for the Lower Burdigalian salt movement during both tectonic phases. The lineament was a detachment fold in the Middle Miocene phase. Thickened Burdigalian salt and Oligocene s.l. duplex filled the core of the detachment fold. The detachment fold was subsequently peneplained with the Burdigalian salt exposed on the paleo-surface that locally redeposited during the Badenian. The Wallachian evolution is less clear and we propose two viable kinematic models. It is possible that the salt rise kept up with sedimentation and halokinetic sequences formed at the salt–sediment interface. Alternatively, the area was reactivated in a thin-skinned, right-lateral strike–slip manner with local pull-apart basins (1–2 km across) providing space for salt plugs. Currently available data do not allow us to pick a preferred model for the kinematics during the Wallachian phase. Both kinematic models are novel and are in contrast with earlier ideas.