Czorsztyn Ridge was not uniform: new data from the Ukrainian part of the Pieniny Klippen Belt (Eastern Carpathians)

摘要

The Czorsztyn Ridge was the shallowest part of the continental crust ribbon called Oravicum. It originated due to the Jurassic opening of the Ligurian-Penninic-Vahic Ocean. Because of its shallow-water nature, depositional record of the Czorsztyn Succession, which was closest to the ridge top, displays considerable variability. Inventory of lithostratigraphic units and specific developments of this unit lasts since 19th century and is still incomplete. This paper deals with three new localities in the western Ukraine which are different from previously described klippen of this succession: Veliky Kamenets 2, Vilki Dil, and Mala Ugolka. They show some features, which are unique and atypical of the Czorsztyn Succession, and allow us to envisage spatial variability in depositional environments along the Czorsztyn Ridge. The Veliky Kamenets 2 represents a locality with most condensed sedimentary succession ever registered in the Czorsztyn Unit, capturing multiple emergence periods with erosion and karstification, evidenced by numerous sedimentary gaps resulting in very condensed sedimentary record with uneven, bizarre voids, omission surfaces, microstalactitic and meniscus cements. After Bajocian deposition of the crinoidal limestones (Smolegowa and Krupianka limestone formations) there was a karstification period followed by deposition of greenish quartz sandstone with carbonate cement. This sandstone has no analogue with so far known lithostratigraphic units. The Middle Jurassic crinoidal limestones also contain pyroclastic material which manifests one of the earliest volcanic phase in the Pieniny Klippen Belt. The locality probably represents a megabreccia formed by the pre-Albian emersion which is also unique as it was not registered so far at other localities. The Vilki Dil locality is unique by very late onset of marine transgression, where only thin beds of the crinoidal limestone (Smolegowa and Krupianka limestone formations), or locally even the first beds of nodular limestone (Czorsztyn Limestone Formation) rest on terrestric pale sandstones and quartzites. Pale quartz sandstones are typical of the Czorsztyn Succession in the Ukrainian sector of the Pieniny Klippen Belt. They resemble Gresten Beds from the Eastern Alps, but they differ in their heavy-mineral contents. They also differ from other Jurassic sediments of all Oravic units known so far. The sandstones are mostly dominated by ultrastable trinity tourmaline, zircon, and rutile, with the dominance of tourmaline. The Gresten Beds and previously analysed Oravic units are dominated by garnet and the ultrastable trinity is strongly dominated by zircon. This difference may be a reflection of longitudinal variability of the Oravic crustal segment (Czorsztyn Ridge). Siliciclastic admixture is ubiquitous at the examined localities and reaches up to the Berriasian. Therefore, the eastern localities were situated much closer to the source of siliclastics on the emerged portions of the Czorsztyn Ridge than those occurring more westward and that emersion persisted much longer in the eastern part, even after the Bathonian-Callovian sea-level rise. The Mala Ugolka locality is unique by Late Berriasian breccia with cement-coated clasts which represents the first manifestation of post-Tithonian shallowing that preceded the Hauterivian-Aptian emersion of the Czorsztyn Ridge.