POTOK JANOSKA (JANOSKA STREAM)



Commune: Milówka (pow. żywiecki, woj. śląskie)

Framework element or context represented:
Lithostratigraphy of flysch formations of the Silesian Unit – Outer Carpathians.

Primary geological/geomorphological interest:
The long, standard sequence of Silesian Unit, Upper Cretaceous – Palaeogene.

Comparative assessment justification:
The most representative and very well exposed sequence of the Silesian Unit, important for training and comparative research.

Protection status and accessibility:
The area is proposed as a nature reserve. The tourist trail runs along the valley.

Character of site: Natural outcrops along the stream.

Area: ca. 15 ha

Altitude: 500 – 750 m a.s.l.

Lithology: sandstones, conglomerates, breccias, shales, silstones, claystones

Discipline: Palaeobiology, Geomorphology, Palaeoenvironment, Stratigraphy of Phanerozoic

Process Age: Holocene, *all periods

Bedrock Age: Paleogene, Cretaceous, *all periods




Description of primary interest:
The nearly complete sequence of flysch formations of the Silesian Unit crops out at the bottom and on steep slopes of the Janoska Stream valley. The valley is asymmetrical, running consequently in relation to dipping of beds. Formations from the youngest to oldest ones crop out along the stream at the stretch of 3 km. These are: Krosno Beds (Oligocene) – thin bedded and thin-grained sandstones intercalated with marly shales; Variegated Shales (Upper Eocene) – strongly folded on the tectonic contact with Krosno Beds; Hieroglyphic Beds (Middle Eocene) – shales and thin-bedded sandstones with mica and glauconite; Ciężkowice Sandstones (Lower Eocene) – lenses of thick-bedded and thick-grained sandstones with traces of ichnofossils; Upper Istebna Beds (Paleocene) – thick-bedded sandstones rich in pebbles of exotic rocks, passing upward into black mudstones with thin layers of siderites and numerous distinctly visible foraminifers of the genus Batysiphon; Lower Istebna Beds (Upper Senonian) – thick-bedded sandstones and conglomerates gradually laminated, interbedded with black mudstones containing the plant detritus. The Janoska Valley is rocky, deep and narrow like a small canyon with steps of downstream inclined waterfalls. The highest of them (3 m) is developed within sandstones of the Upper Istebna Beds.

Literature:

ALEXANDROWICZ Z. 1994–Geologically controlled waterfall types in the Outher Carpathians. Geomorphology 9: 155-165.     ALEXANDROWICZ Z. 1997–Waterfall conservation in the Polish Carpathians (English sum.). Chrońmy Przyr. Ojcz. 53, 4: 39-57.     BURTON J., KONIOR K., KSIĄŻKIEWICZ M. 1937–Mapa geologiczna Karpat Śląskich (Polish only). PAU Kraków.     UNRUG R. 1969–Przewodnik geologiczny po zachodnich Karpatach fliszowych (Polish only). Wycieczka 5: 79-86.