Mid-Cretaceous turnover in the Oravic segment of the Pieniny Klippen Belt (Western and Eastern Carpathians): New data and synthesis

Abstract

The Oravicum provides a crustal ribbon, whose deposits recently form a major part of the Pieniny Klippen Belt being a mélange zone between the Carpathian internides and externides. The Hauterivian–Albian turnover completely changed its character. The paper brings synthesis of old and new data that reveals processes which had taken place at that time. The Hauterivian–Albian uplift and tilting resulted in shallowing, emersion and karstification of the elevated part of the Oravicum for about 20 Ma. It caused slumping and redeposition in the basinal part. An Urgonian-type platform occurred on the basin margin. Subsequent Albian collapse caused the drowning of the Oravicum to neritic/bathyal depths with deposition of oceanic red beds, black shales, and flysch deposits. The new data elucidate some phenomena: 1) Karstification is evident despite that isotopes show no evidence of purely fresh-water speleothems. 2) A newly found block of Urgonian-type limestone with basal breccia is a rare example of the presence of Oravic material in the exotic flysches. 3) Slumping of sediments in the deeper parts of the Oravicum might lead to local unroofing of the older, Aalenian black shales with subsequent deposition of Cretaceous black and red shales on them, thereby explaining the frequent tectonic mixing of these two types of lithostratigraphic units. The final synthesis indicates that the Oravicum lost at least a part of its basement during the Albian when it was likely in contact with the Carpathian internides. Subcrustal erosion by a subducting mid-oceanic ridge beneath the Carpathian plate is the most plausible explanation.