UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-23 18:13

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Conference: Bucharest University Faculty of Physics 2014 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
Estimating superparamagnetic particles grain size distribution from Romanian loess/paleosol deposits by frequency dependent magnetic susceptibility


Authors:
C. NECULA(1), C.G. PANAIOTU(1), Victor KUNCSER(2)


Affiliation:
1)Faculty of Physics, Paleomagnetic Laboratory, University of Bucharest, Bucharest, Romania

2)National Institute of Material Physics, Bucharest-Magurele, Romania


E-mail
c3necula@yahoo.com


Keywords:
Romanian loess, frequency dependent magnetic susceptibility, superparamagnetic grain size distribution


Abstract:
We report the first reconstruction of grain size distribution (GSD) of the superparamagnetic particles for two Romanian loess deposits (Costinesti located at the Black Sea shoreline and Mircea Voda located in the central Dobrogea Plateau) using wide-band frequency spectrum of magnetic susceptibility (FSMS) All paleosol samples display relatively narrow, unimodal GSD pattern with almost the same maximum diameter in all paleosols of about 17 nm. In addition we found an almost uniform GSD both within sites as well as between them proving that the GSD in paleosols is independent of pedogenesis. Loess GSDs on the other hand are slightly broader with maximum diameters shifted to slightly higher value (~18nm). Moreover the shape of loess GSDs differs from paleosols. For example Mircea Voda loess shows a bimodal distribution with a second maximum at about 20 nm diameters suggesting that pedogenesis modifies the GSDs of parent material. The concentration of SP particles in loess is one order of magnitude smaller than in paleosols. Of the two loess-paleosol sections studied Costinesti section displays the highest concentrations of superparamagnetic particles. The highest concentration of fine-grained pedogenic particles was found in S3 paleosol consistent with the magnetic enhancement observed for Romanian paleosol. All these suggest that magnetic susceptibility variations recorded in the Romanian loess deposits mainly reflect changes in concentrations of ultrafine pedogenic particles.