in Jurassic and Cretaceous Stratigraphy

Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321
Jurassic Evolution of the Oravic Crustal Segment (Pieniny Klippen
Belt, Western Carpathians) and Its Importance for the Tethyan
Paleogeography
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R. Aubrecht 1,2 , J. Schlögl 1 , D. Reháková 1
1. Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina - G, 842 15 Bratislava,
Slovakia (E-mail: aubrecht@fns.uniba.sk; schlogl@fns.uniba.sk; rehakova@fns.uniba.sk)
2. Geophysical Institute, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 28 Bratislava, Slovakia
Pieniny Klippen Belt (PKB) is a strongly com-
pressed mélange zone between the Inner and Outer
Western Carpathians. The mélange consists of Jurassic
and Cretaceous sediments. Paleogeographic reconstru-
ction of this zone (summarized by Birkenmajer, 1977)
showed that most of the mélange components came
from the paleogeographic zone called Oravicum
(foormerly known as Pieninicum); smaller part was of
the Inner Carpathian origin. The Oravic segment re-
presented a segment of the continental crust with
crystalline basement and Mesozoic sedimentary cover.
Only Jurassic and Cretaceous sediments were preserved
as tectonic blocks and matrix of the mélange; the
basement with Triassic part of the sedimentary cover
was detached and probably underthrust below the Inner
Western Carpathians. The known sedimentary record
of the Oravic successions is mostly with Aalenian black
shales, which served as a detachment horizon during
the deformation. Jurassic evolution can be then recon-
structed solely on the basis of Middle to Upper Jurassic
sedimentary record (Liassic sediments are present but
detached and their attribution to the the units which
were individualized in the Middle Jurassic is proble-
matic). It is supposed that the Oravic segment prior to
the Middle Jurassic rifting was a part of the North
European Platform shelf. The exact position of the
segment is difficult to reconstruct as the older rocks
were not preserved. However, heavy mineral analysis
of the clastic admixture in the Jurassic sediments
showed predominance of pyrope-almandine garnets
from granulitic and eclogitic source rocks. As the best
matching position for the Oravic crustal segment, the
Moldanubian Zone of the Bohemian Massif was
inferred (Aubrecht and Méres, 2000). Howerver, recent
research in the Bathonian–lower Callovian clastics in
the Cracow-Wieluń Upland (Polish Platform) showed
predominance of similar garnets from an unknown
source (Aubrecht et al., 2009). This stretched the possi-
ble provenance of the Oravic segment as far as the
Polish Platform. The rifting caused block tilting which
resulted in rising of the central part is called Czorsztyn
Ridge, which became a site of shallow-marine deposi-
tion (Czorsztyn Succession). The first signs of the ridge
uplift are visible already in the Aalenian sediments,
otherwise dominated by black shales, in form of local
olistolites (Aubrecht et al., 2004), intercalations of
crinoidal limestones (Schlögl et al., 2004), local
turbidites, passing to siliciclastic flysch (Szlachtowa
Formation – Birkenmajer, 1977). In the west Ukrainian
part of the PKB sandy to coarse-clastics dominate the
Aalenian sediments of the Czorsztyn Succession. In
Bajocian, sedimentation of shallow-marine crinoidal
limestones started (Krobicki and Wierzbowski, 2004),
locally preceded by coral limestones in the western part
of the PKB (Schlögl et al., 2006). In deeper parts of the
Oravic Zone (Kysuca-Pieniny Succession), deposition
of spotted limestones occurred, with distant crinoidal
calciturbidites coming from the Czorsztyn Ridge.
Extensional synsedimentary tectonic on the Czorsztyn
Ridge is expressed by presence of breccias to
megabreccias (Krasín Breccia – Aubrecht and Szulc,
2006). At the Bajocian/Bathonian boundary, a sea-level
rise caused deepening of the sedimentary area which
resulted in deposition Ammonitico Rosso facies on the
Czorsztyn Ridge and radiolarites in the Kysuca-Pieniny
Trough. The continuing synrift extension is expressed
by numerous neptunian dykes in the Czorsztyn Suc-
cession (Aubrecht and Túnyi, 2001) with pre-
dominantly NE-SW orientation (indicating NW-SE
extentsion). Paleomagnetic investigations showed that
the oceanic spreading increased rapidly during Callo-
vian, when the Oravic crustal segment was shifted
rapidly towards south for almost 1000 km (Lewan-
dowski et al., 2004). In Oxfordian, the spreading
stopped and the segment slowly returned to higher
latitudes. At the end of the Jurassic (after Kim-
meridgian), the Ammonitico Rosso facies was replaced
by Calpionella limestones in the trough, with organo-
detritic admixture on the Czorsztyn Ridge forming even
various sorts of coquinas.
The Callovian rapid oceanic spreading registered
in the PKB should also concern other Tethyan crustal
segments but their sediments are often remagnetized.
Moreover, the time span of the event is relatively short
and the corresponding facies are often condensed which
makes paleomagnetic detection very difficult.
Acknowledgements: The research was supported
by the APVV Grant Agency (grants No. APVV-0280-
07 and APVV-0465-06).