ГЕОЛОГІЯ СУБСІЛЕЗЬКОГО ПОКРИВУ В БАСЕЙНІ Р. РІКА (УКРАЇНСЬКІ ЗОВНІШНІ КАРПАТИ, ГОЛЯТИНСЬКА СТРУКТУРА)

Abstract

Listen

Translate article

The author's detailed geological mapping works suggest that the Holyatyn Structure (located near the villages of Holyatyn and Maidan in the Rika River basin, Ukrainian Carpathians, Transcarpathian administrative region) is a destructured fragment of the Sub-Silesian Nappe located in the Outer Carpathians between the Silesian and Skyba nappes. Within this structure, Lower Cretaceous–Oligocene deposits are developed among the Oligocene flysch of neighboring tectonic units. The stratigraphic succession of these deposits is represented by: dark to black flysch (Shypot Formation, Barremian–Albian); green shales with cherts; red and green shales and marls (Holyatyn Beds, Upper Cretaceous–Paleocene); greenish and dark to black flysch (Soimy Formation, Eocene); black shales, cherts and sandstones (Menilite Formation, Oligocene) and gray flysch with layers of black shales (Verets or Transitional Formation, Oligocene). The limestone blocks (unknown age) is developed in front of the thrust-sheet. According to sedimentological features (typical hemipelagites), age and microfauna content, the Holyatyn Beds correspond to the Weglowka Marls of the Subsilesian Unit in the Polish Carpathians, while the Weglowka Marls are a “diagnostic lithofacies” for the Subsilesian Unit. The Holyatyn Structure is probably an “extruded lens”, the anticline core of which is composed of deformed Lower Cretaceous flysch and ductile Upper Cretaceous clay-marly Holyatyn Beds. This extrusion apparently occurred after nappe structure forming and was caused by transpressive movements. In result, the relatively thin and ductile Subsilesian Nappe was stretched into separate tectonic lenses (large boudins ?) placed between the rigid flysch of neighboring tectonic nappes. One such lens is the Holyatyn Structure, which is similar to the transpressive “flower structure”. A ductile-type melange is exposed in the thrust zone of the Silesian/Sub-Silesian nappes. It suggests that the initial thrust stage occured in poorly consolidated water-saturated sediments.