Nove poznatky o stratigrafii podslezske jednotky v jablunkovske brazde: potok Kopytna

Subsilesian Unit, Silesian Unit, Carpathian Flysch Belt, Cretaceous, Paleogene, stratigraphy, Foraminifera Summary: In the northern part of the Jablunkov Furrow the Subsilesian Unit is exposed in a tectonic half-window surrounded by the Silesian Unit. The Frýdek Formation is believed to be the oldest part of the Subsilesian succesion at the Czech part of Carpathians (Menčík et al.. 1983). According to Polish authors, the succession starts with the Lower Cretaceous equivalents of the Hradiště Formation (a. o. Huss 1957, Ślączka et al.. 2006). Eliáš (1998) believed that Cretaceous strata assigned to the Subsilesian Unit in Polish Carpathians are in fact a part of the Kelč Development (Eliáš 1979), which is the slope facies of the Silesian Unit. Outcrops in Kopytná Stream (table 1, Fig. 1) brought new insight into this topic. Foraminifer biostratigraphy allowed distinguishing of following stratigraphic levels (referring to zones of Berggren and Pearson 2005):
1) Barremian-Aptian black grey claystones of the Hradiště Fm. accompanying a body of amygdaloid vulcanite of the teschenite association (sample MB127, Fig. 3a).
2) Cenomanian black clay with Plectorecurvoides irregularis Geroch and Bulbobaculites problematicus (Neagu), sample MB129D (Fig. 3b).
3) Turonian-Coniacian green silty claystones with Marginotruncana pseudolinneiana Pess., Uvigerinammina jankoi Majzon and Bulbobaculites problematicus; sample MB129E.
4) Upper Campanian-Lower Maastrichtian light grey marly claystones with Globotruncanella petaloidea (Gand.), Globotruncana linneiana (Orb.) and Macroglobigerinelloides bollii (Pess.), samples MB128A (Fig. 3c) and MB016.
5) Upper Maastrichtian light grey clay with Globotruncanella petaloidea and Rzehakina fissistomata (Grzyb.), sample MB131A (Fig. 2).
6) Paleocene (Thanetian?) calcareous sandstones intercalated with dark grey silty claystones with Hormosina? velascoensis (Cush.) and Pseudonodosinella elongata (Grzyb.), sample MB015.
7) Uppermost Thanetian-lower Ypresian light grey claystones, foraminifer zone P5-E4, sample MB133A.
8) Uppermost Ypresian grey and greenish mottled claystones (samples MB131C and MB133B) and variegated claystones (MB129A and MB130B), foraminifer zone E7.
9) Upper Lutetian greenish grey marlstone, foraminifer zone E9, sample MB131D.
10) Uppermost Lutetian to basal Bartonian light grey and green grey clays intercalated with glauconitolite, zonal interval E10-E11 (sample MB130A).
11) Priabonian dark grey claystones, foraminifer zone E15, sample MB131B.
12) Lower Kiscellian dark grey brown marly claystones with Tenuitellinata angustiumbilicata (Bolli), Tenuitella gemma (Jenkins), T. brevispira (Subb.) and Cibicides amphisyliensis (Andreae), Menilite Fm., samples MB129B and MB132A.
Campanian-Maastrichtian to Priabonian strata can be assigned to the Frýdlant Formation. Cenomanian and Turonian-Coniacian claystones were observed at the area for the first time. They seem to be part of the Subsilesian Unit based on their position and lithology. The claystones may be compared with the Węglówka Marls (Huss 1957) rather than Kelč development of Eliáš (1979). Węglówka Marls differ in more oligotrophic variegated facies.
The Subsilesian Unit in Kopytná possesses character of tectonic lenses in outcrop scale and tectonic slices in section scale. Strong tectonic reduction is apparent at outcrop MB131 (Fig. 2), showing a contact of Maastrichtian, Ypressian, Lutetian and Priabonian rocks on 2 m of thickness. Bedding planes in the whole section are dipping predominantly in directions between East and South under the average angle 50°.

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