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Palaeomagnetism of the Pieniny Klippen Belt (Carpathians): evidence for low-latitude origin and palaeogeographic dispersion of the Upper Jurassic carbonates

Lewandowski M., Aubrecht R., Krobicki M., Matyja B., Reháková D., Schlögl J., Sidorczuk M., Wierzbowski A.

Volumina Jurassica

2006

Vol. 4, no. 1

56-58

Palaeomagnetic studies on the Middle and Upper Jurassic carbonates were recently carried out along the Pieniny Klippen Belt from Ukraine (Veliky Kamenets, Lewandowski et al. 2005), through Poland to Western Slovakia (Fig. 1A). More than 200 oriented cores and hand samples were collected from lithologies considered representative for the Czorsztyn Succession (Birkenmajer 1976, 1986), cropping out from the East to the West of PKB in Slovakia. Laboratory work aiming at recognizing the natural remanent magnetization structure, involving thermal and alternating field demagnetizations, magnetic measurements using 2G SQUID magnetometer and employing principal component analysis revealed a multicomponent nature of NRM (Fig. 1B-C). Rock magnetic studies have shown that Ti-poor magnetite is the main magnetic carrier of NRM. In turn, EMS and SEM analysis confirmed the presence of magnetite grains of both detrital and autigenic origin (Fig. 1E-F). Low coercivity/unblocking temperature components are considered post-tectonic and genetically interpreted as an orogeny-related overprint. An overall direction is proximal to the Tertiary directions from cratonic Europe, pointing to only minor individual block rotations after the Pieniny Klippen Belt was formed (Fig. 1). Characteristic, high blocking temperature components (ChRM) show dual-polarity distribution (reversal test statistically positive at B and C levels) and are considered primary. Palaeomagnetic declinations differ among the localities, testifying tectonic rotations of individual blocks after acquisition of ChRMs, supposedly exerted due to transform faults systems, active during Late Jurassic-Cretaceous time. Palaeomagnetic inclinations for the Oxfordian point to palaeolatitude positions ranging from (assuming North) 28° in Veliky Kamenets (Ukraine, see Lewandowski et al. 2005), 17° at Kyjov Pusté Pole, 12° at Milpoš, and 9° in Babina (all in Slovakia), an average error of the oval of 95% confidence being 8° (Fig. 1D). Interestingly, the Milpoš section yielded ca. 10° inclination shift between Bajocian and Oxfordian rocks, indicating southward migration of the host basin in the time concerned. This conclusion is in line with the data obtained for the Kamenets section (Lewandowski et al. 2005). On the other hand, Callovian radiolarites of Butkov, the Inner Carpatians unit situated today in the vicinity of Babina, yielded palaeolatitudes of ca. 22°. It is worth also to note that palaeomagnetic studies of the uppermost Jurassic carbonates from the Brodno Klippe of the Kysuca (equivalent of Branisko) Succession (Houša et al. 1999) also point to low latitudes of deposition. These new data evidence wide palaeogeographic separation of currently neighbouring sedimentary rocks and their host basins in Late Jurassic time, the southernmost of them being in the proximity of Northern Africa. This outcome suggests that Pieniny Klippen Belt is composed of Tethyan microblocks (terrains), witnessing an evolution of Jurassic basins at relatively distant areas of the Tethys domain. Alternatively, the latitudinal dimension of the Czorsztyn Ridge, the host structural unit for the Czorsztyn Succession, would have been 2000±900 km during mid-Oxfordian time.

Fast palaeogeographic changes of the Pieniny Klippen Basin from palaeomagnetic data of the Bajocian-Berriasian section in the Veliky Kamenets (Carpatians, West Ukraine)

Lewandowski M., Krobicki M., Matyja B., Wierzbowski A., Sidorczuk M.

Volumina Jurassica

2006

Vol. 4, no. 1

58-59

A 40 m thick carbonate succession of the Bajocian to Berriasian age from the Veliky Kamenets quarry (Novoselica area, Pieniny Klippen Belt, Ukraine) resembles both the Czorsztyn and Niedzica successions of the Pieniny Klippen Belt, traditionally considered ridge slope-related deposits. 176 individually oriented cores have been collected for palaeomagnetic purpose from the bottom to the top of the sequence, with sampling density dependent on inferred sedimentation rates. Unblocking temperature spectra and results of the Lowrie test, as well as electron microscope analyses, point to a Ti-poor magnetite as a main magnetic carrier. Thermal demagnetization revealed two main components of the natural remanent magnetization (NRM). A low-blocking temperature component S of normal polarity is considered of post-tectonic, probably thermoviscous origin due to overheating by Neogene volcanics. A stable, high-blocking temperature NRM component P shows dual polarity distribution and is considered primary. Since two significant sedimentary gaps occur at 422 cm and 860 cm (the main hiatus - H) from the base, the latter comprising the Late Callovian - Early Oxfordian time span (6-8 Ma), the pattern of magnetic reversals presented in this study can not be considered complete. A palaeolatitude of 41° ±5° is calculated for the mid-Jurassic part below H, similar to that expected for the European Craton at the Kamenets locality. The mid-Oxfordian limestone, directly overlying H, has palaeolatitudes around 28° ±6°. This implies a relatively fast opening of the oceanic domain to the North of the Kamenets block. Palaeomagnetic declinations suggest 100° counterclockwise rotation of the whole section before the Neogene.