Early Stages of the Polish Carpathian Foredeep Development

136 Slovak Geol. Mag. 6, 2-3(2000), 136-138

Early stages of the Polish Carpathian foredeep development

NESTOR OSZCZYPKO & ANNA LUCTNSKA-ANCZKIEWICZ

Jagiellonian University, Institute of Geological Sciences, Olcandry 2a, 30-063 Krak6w, Poland

Abstract: The flysch olistoplaque from the W part of Polish Carpathian Foredeep could be correlated with the Old Styrian overthrust of the Moravo-Silesian Carpathians. This nappe load caused the development of the Karpatian flexural depression which was filled with coarse clastic sediments.This subsidence was followed by the intra-Karpatian uplift and erosion of the Cieszyn-Slavkov Ridge. The new Late Karpatian/ Early Badenian subsidence was connected with development of extensional grabens at the front of the Old Styrian thrust, and accompanied by the Early Badenian regional transgression Key words: Mioceneflysch olistoplaque, Old Styrian nappe front, Karpatian foredeep, of theWestern Car- pathians

Introduction quartzites, fragments of metamorphic rocks and granites which derived from both the Carpathian flysch as well as The Early to Middle Miocene Polish Carpathian from the Paleozoic basement. These conglomerates pass Foredeep (PCF) developed as a peripheral foreland basin into the upper part of the Stryszawa Fm. This part of the in front of the moving Carpathians (Oszczypko, 1998). formation is composed of variegated, conglomerate- The outer foredeep is filled with Badenian and Sarmatian sandy-mudstone strata. The Stryszawa Fm. contains a marine deposits which are up to 3500 m thick. The inner relatively frequent microfauna from the Lower Cretaceous foredeep is located beneath the Carpathian nappes and - Early Miocene age recycled from the Carpathian flysch composed of Lower to Middle Miocene autochthonous (Oszczypko, 1998). From this formation, Karpatian cal- deposits. The Lower Miocene strata are mainly terrestrial careous nannoplanktom (NN 4) has also been reported in origin, whereas the Badenian and Sarmatian ones are (Garecka et al., 1996). The upper part of the Stryszawa marine. Fm. resembles features of the alluvial fan deposits. In the Sucha IG-l(SIGl) borehole (Fig. 1) this formation passes Results upwards into Lower Badenian Skawina Fm. In the Cieszyn area the flysch olistoplaque (Zamarski In the inner part of PCF (Fig. 1) the flysch derived Mb.) has been preserved in the central part of paleo-val- olistoplaque (Sucha Fm., Slaczka, 1977) has been docu- ley beneath the frontal part of the Carpathian overthrust mented in a few deep boreholes (Moryc, 1989, (Fig. 1, Bula & Jura, 1983). The Zamarski olistoplaque, Oszczypko, 1998). This formation overlaps both a few which overlapped both the Upper Carboniferous base- dozen metres of the Lower Miocene polimictic conglom- ment as well as the Lower Miocene Zebrzydowice erates as well as the Paleozoic basement. The olisto- Fm.(Bula & Jura, 1983), is 25-150 m thick, reaches at plaque, which is 79-267 m thick, is composed of Lower least 50 sq. km and is composed of elements of the Sub- Cretaceous to Paleocene flysch and is connected with the silesian Unit. The Zebrzydowice Fm. (Fig. 1) is com- Subsilesian/Silesian successions (Laskowicz, 1997, Gedl, posed of pelitic grey-greenish deposits of the Early 1997). The olistoplaque is covered by the Stryszawa Fm. Burdigalian (N5/N6) age (Garecka et al., 1996). Early which, itself, reaches a thickness of 360-566 m Burdigalian (NN2-NN3) marine deposits were also dis- (Oszczypko, 1998). The Lower portion of the formation covered in NE Moravia (Jurkova et al., 1983). In the is represented by polimictic conglomerates of the Sta- Bielowicko IG-1 (BIG1) borehole, polimictic pebbly chor6wka Mb.(Sla.czka, 1977, Moryc, 1989) up to 650 m mudstones, 23 m thick, have been found (Jaworska, 1998) thick (Slemieh 1,SL1). In the Zawoja-1 borehole, the Sta- at the base of the flysch olistoplaque (Fig. 1). The olisto- chorowka Mb., 180 m thick, is composed of conglomer- plaque is covered by a 10-110 m thick layer of variegated ates and coarse to fine-grained arenites. This matrix of conglomerates composed of flysch-derived clasts. These conglomerates changes from clay minerals to a sandstone conglomerates resemble the Stryszawa Fm. from the type, with a dominance of quartz (medium to coarse- Sucha-Zawoja area. In the Cieszyn area the upper part of grained, poorly rounded and poorly sorted), whereas the the sub-thrust molasse sequence is represented by a 40-90 cement is composed of changing proportions of carbon- m thick complex of transgressive Debowiec conglomerate, gypsum and anhydrite. The conglomerate clasts are ates, which are composed of Upper Carboniferous clasts. dominated by: sandstones, mudstones, carbonates, These conglomerates pass upwards into the Skawina Fm. N. Oszczypko and A. Lucinska-Anczkiewicz: Early stages of the Polish Carpathian 137

Fig. 1. Distribution of the Miocene autochthonous deposits in the Valasske Mezifici-Ostrava and Cieszyn-Bielsko Biala-Zawoja areas (after Jurkova, 1971, Jurkova et al., 1983, Oszczypko et al, 1989, Palensky et al., 1995 and new boreholes). Platform basement: 1 — Proterozoic-Lower Paleozoic, 2- Upper Paleozoic, 3 - Mezozoic, Carpathian Foredeep: 4 - Karpatian, 5 - Lower-Middle Badenian, 6 - boundary of the Zebrzydowice Fm. (Early Burdigalian), 7 - northern boundary of the Karpatian deposits, 8 - northern boundary of the Old Stryrian overthrusts, 9 - present-day front of the Outer Carpathians, 10-fault, 11 - northern boundary of the Paleogene autochtonous deposits, 12 - borehole. Abrevations: CSR-Cieszyn- Slavkov (Pribor) Ridge, PKB-Pieniny Klippen Belt, 1C- Inner Carpathians.

According to Garecka et al. (1996) both the Debowiec The flysch olistoplaque (Sucha and Zamarski fms.) congl. as well as the lowermost portion of the Skawina from the W part of PCF could be correlated with the Old Fm. belong to the Late Karpatian. An isolated fragment of Styrian overthrust in marginal part of the Moravo-Silesian the Subsilesian Unit has also been found in a sub-thrust Carpathians. In the PFibor area, the front of the Old Sty- position in borehole K-3 near Bielsko-Biala (Fig. 1). This rian nappe, composed of the Sub-Silesian sequence, is 112 m thick olistoplaque was discovered in conglomer- located 1 -3 km north of the present-day margin of the ates of a Debowiec type. In our opinion the Subsilesian Carpathians (Fig. 1). In a few places the erosional outliers fragments (Zamarski Fm.) found at the base of the Bade- of this nappe are even preserved in the Badenian pa- nian subthrust sequence in the Cieszyn - Bielsko-Biala leodepresion 10 km north of the Carpathian margin. Close area could belong to the same flysch olistoplaque in the to the Polish-Czech border, the Old Styrian nappe is pres- Sucha-Zawoja area (Sucha Fm.). In the area between ently overlapped by a margin of the Carpathians. Mean- Bielsko-Biala and Zawoja this olistoplaque was removed while East of Cieszyn this nappe has been described by erosion. In the more uplifted part of the Cieszyn above as the Zamarski and Sucha Fms. Slavkov Ridge (CSR), both the flysch olistoplaque as well as Miocene deposits are absent (Fig. 1, Oszczypko et al., Interpretation 1989). The westernmost fragment of the CSR is covered by Karpatian deposits, which are a few dozen metres In our opinion, all buried fragments of the Sub-Sile- thick (Palensky et al., 1995). In the South-West of sian unit are erosional remnants of the Old Styrian ValaSske Mezifici, the thickness of these strata are more nappe, which was at least 25 km wide. According to than 300 m (Palensky et al., 1995). In NE Morava, the Jurkova (1971), the Old Styrian overthrust was formed Karpatian foredeep was at least 40 km wide (Fig. 1). This after the Karpatian age and before the deposition of foredeep extended to the East - Zawoja-Sucha area „basal Badenian elastics", which are synonimous with (Poland) and also towards the Sambor-Rozniatov basin the Debowiec congl. in Poland. However, if we accept (Ukraine). Beneath the Polish Carpathians, the axes of the the new biostratigraphic data (Garecka et al., 1996), Karpatian foredeep is manifested by the magnetotelluric then the age of Old Styrian thrusting should be regarded depression and a gravimetric low (Oszczypko, 1998). as intra-Karpatian. Slovak Geol. Mag, 6, 2-3(2000),136-138 138 On this basis, we are able to propose the following Gedl, P 1997: Palynological study of an olistolith from the so-called Sucha Formation, Zawoja IG-1 borehole (Flysch Carpathians, scenario for the Early/Middle Miocene evolution of the Poland) age and palaeoenvironment Ann Soc. Geol Pol, 67, inner western part of PCF: After the Ottangian compres- 16-28. sive event, the front of the Outer Carpathians overrode the Jaworska, J. 1998: Sedimentological features of the autochthonous platform and the thin-skinned Sub-Silesian nappe (NE Miocene deposits in the Bielowicko area. MsC theses, Jagiellonian Moravia and S Silesia) reached more or less the present- University, Institute of Geological Sc, Krakow, 97 pp Jificek, R. 1995 Stratigraphy and geology of the Lower Miocene sedi- day position of the Carpathians. The load of this nappe ments of the Carpathian Foredeep in South Mooravia and adjacent caused the development of the Karpatian flexural depres- par t of Lower Austria In: HamrSmid (Ed): New results in Tertiary sion (foredeep), which was filled with coarse clastic, ter- of West Carpathians II, Knohovnicka ZPN, 16, 37-65, Hodonin restrial sediments from both the Carpathians as well as the Jurkova, A 1971: Die Hntwicklung der badener Vortiefe im Raum der Mahnschen Pforte und Gebie von Ostrava (German Summary) emerged platform. This event was further followed by an Geol. Prace, 57, 155-160. intra-Karpatian uplift and an erosion of the CSR (EliaS & Jurkova, A., MolCikova, V., Ctyroky, P & Policky, J. 1983: New Eg- Palensky, 1997), which could be correlated with the dis- genburgian finds in NE Moravia (English Summary) Geol. Prace, cordance below the terminal Karpatian strata in Southern 79, 153-168. Laskowicz, I 1997 Miocene sediments under the Carpathian overthrust Moravia (Jiricek, 1997). The new period of the Late Kar- in the Sucha Beskidzka are (Carpathian Foredeep) (English patian/ Early Badenian subsidence was characterised by Summary) Biuletyn Paiistwowego Instytutu Geologicznego, 376, the development of SW-NE and NW-SE trending grabens 61-74. at the front of the Old Styrian thrust (Fig. 1). This subsi- Moryc, W 1989: Miocen przedgorza Karpat Zachodnich w strefie Biel- sko-Krakow. 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