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Magnetic, paleomagnetic and palynologic studies of Paleolithic depositions of the Akhshtyrskaya cave (Russia)

Pospelova G.A., Król E., Levkovskaya G.M., Kruczyk J., Kądziałko-Hofmokl M., Kulakov S.A.

Acta Geophysica

2007

Vol. 55, no. 4

619-639

The paper presents the results of experimental rock-magnetic, paleomagnetic and palynologic study of Paleolithic sediments sampled along two profiles in the Akhshtyrskaya cave, situated in the vicinity of Black Sea shore. In the upper part of profiles, some magnetite was observed; in the middle and lower parts, strongly oxidized non-stoichiometric magnetite and hematite prevail. Thin maghemite covers on the surface of fine magnetite grains are present in the majority of specimens. Natural remanence has one characteristic component (CHRM), mostly of chemical origin, although in few specimens containing magnetite it may be sedimentary. Directions of CHRM obtained by standard paleomagnetic methods revealed anomalous pattern only in layer 3/2, which is slightly older than the overlying layer 3/1 whose age was established as (35š2)×103 years BP by the U-Th method. This suggests that this paleomagnetic anomaly (PMA) can be correlated with Kargapolovo excursion dated on about (45-39)×103 years BP. In the remaining overlying and underlying layers, directions of CHRM are grouped around the present geomagnetic field. Depth distributions of scalar magnetic parameters generally coincide with the lithological division of the profiles. Palynologic study revealed the presence of 22 pollen zones. Five thermomers separated with colder periods were found in the middle and lower parts of profile. The non-magnetite composition of magnetic fraction of the majority of studied sediments – oxidized nonstoichiometric magnetite and hematite – resulted in the lack of correlations between paleoclimatic and scalar magnetic characteristics.

Paleomagnetic study of Middle-Upper Jurassic sediments from the Polish segment of the Pieniny Klippen Belt

Kruczyk J., Kądziołko-Hofmokl M.

Acta Geophysica

2006

Vol. 54, no. 2

205-224

Middle-Upper Jurassic carbonates exposed in 7 separate fragments of three tectonic units were sampled in the Polish segment of the Pieniny Klippen Belt in 1981, before construction of the Niedzica-Czorsztyn dam. Demagnetization experiments performed about 20 years ago and analyzed lately with modern program package revealed the presence of Middle Miocene overprints acquired in the normal and reversed geomagnetic field, and pre-folding components of natural remanence acquired during the Middle-Upper Jurassic. A paleolatitude of 36Nš7° was obtained for the studied area for this time on the basis of 3 normal and 1 reversed components. Three pre-folding pole positions are situated between pole positions of the normal and reversed Stable European Middle Jurassic field. The obtained pa-leomagnetic results imply several prefolding (pre-Upper Miocene) and postfolding (post-Upper Miocene) episodes of rotations of the studied fragments.