An Oligocene olistostrome with exotic clasts in the Silesian Nappe (Outer Ukrainian Carpathians, Uzh River Basin)

Abstract

In the Ukrai nian part of the Silesian Nappe (Outer Carpathians, Uzh River Basin) the ex otic clast-bear ing Uzhok Olistostrome (up to 60 m thick) oc curs within the Oligocene Krosno For ma tion and un der lies the Pikui Sand stone (Otryt Sand stone in Poland). The Uzhok Olistostrome con sists of de bris/grain/mud flow de pos its with clasts of schist and bioclastic lime stone. These de pos its con tain re de pos ited pe lagic sed i ments with plank tonic foraminifers in clud ing Parogloborotalia pseudocontinuosa (Jenkins), Ciperoella ciperoensis (Bolli), Globoturborotalita woodi (Jenkins), Chiloguembelina adriatica Premec Fucek, Hernitz Kucenjak and Huber. The age of the Uzhok Olistostrome based on plank tonic foraminifers cor re lates with the mid dle Oligocene within the mid dle O2-O5 zones. The source area for the Uzhok Olistostrome and Pikui Sand stone was a mid-Oligocene intrabasinal palaeouplift (the Pikui Ridge) in ter preted as the fore-bulge lo cated in the Silesian Sub-basin ahead the emerg ing Outer Carpathian accretionary prism (in clud ing the Dukla Nappe and other West Carpathian in ner flysch nappes).

Characteristics structures of the mélange zones in the Ukrainian Carpathians

“…In the Uk rainian Carpathians, most of the best-expres sed olistostromes are identified in seve ral zones related to the frontal parts of the great nappes [Hnylko, 2011a]. They have been described in the Marmarosh Klippen Zone [Kruglov, 1965] and at the front of the Marmarosh [Byzova, 1965], Chornohora [Gruzman, Smirnov, 1985], Dukla [Glushchenko, 1972;Glushchenko et al, 1980;Hnylko et al, 2021], Silesian [Astakhov, 1989] and Boryslav-Pokuttya nappes [Kulchitskiy, 1977;Hnylko, 2014].…”

“…1. Main tectonic units of the Ukrainian Carpathians [Hnylko, 2011b, Hnylko et al, 2021 and location of the photographs (a) (see . Tectonic setting of the Ukrainian Carpathians, position of the terranes and main geological boundaries after [Săndulescu, 1988[Săndulescu, , 2009Kováč et al, 2016Kováč et al, , 2017Csontos, Vörös, 2004;Horvath, Galacz, 2006;Oszczypko, 2006;Schmid et al, 2020] simplified and partly modified (b).…”