Olistostromes in the Miocene salt-bearing folded deposits at the front of the Ukrainian Carpathian orogen

Abstract

The origin of the olistostromes at the front of the Ukrainian Carpathian orogen is related to Miocene synsedimentary thrust movements of the Carpathian accretionary prism and to erosion of uplifted areas of the Boryslav-Pokuttya Nappe in the front of the accretionary prism. There are two olistostrome complexes. The first is the Lower Miocene Polyanytsya-Vorotyshcha Olistostrome with clasts of molasse and flysch deposits formed in a piggy-back basin on the inner part of the Boryslav-Pokuttya Nappe at the top of the accretionary wedge. This olistostrome is associated with the Sloboda Conglomerate derived from the fore-bulge at the foreland of the Boryslav-Pokuttya Nappe. The second one is the Middle Miocene Lanchyn Olistostrome with olistoliths of strongly deformed molasse deposits. These olistoliths were slid from the uplifted front of the Boryslav-Pokuttya Nappe. The Lanchyn Olistostrome was deposited at front of this nappe in a foredeep basin.