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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:29 |
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Conference: Bucharest University Faculty of Physics 2015 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Magnetic properties of Costinesti loess-paleosol deposit (western Black Sea shore, Romania)
Authors:
Cristian NECULA (1), Daniela DIMOFTE (2), Cristian PANAIOTU (1)
Affiliation:
1)Faculty of Physics, University of Bucharest, Paleomagnetic Laboratory, 010041 Bucharest, Romania
2)Faculty of Geology and Geophysics, University of Bucharest, Paleomagnetic Laboratory, 010041 Bucharest, Romania
E-mail
c3necula@yahoo.com
Keywords:
Rock and mineral magnetism, loess-paleosol, paleoclimate, Pleistocene
Abstract:
The aim of this study is to derive new information on the Middle – Late Pleistocene paleoenvironment from a high resolution multi-proxy assessment of the iron mineralogical composition at the Costineşti loess-paleosol sequence located on the western Black Sea shore. It is the easternmost loess section in the Romanian loess region studied and its distinct pattern of the proxy records can be used to correlate the lower Danube loess to other key sites of the Moldavia and Ukraine loess regions. To investigate the climatic control on soft and hard ferromagnetic minerals we used several types of rock magnetic properties: magnetic susceptibility and its frequency dependence, anhysteretic remanent magnetization, isothermal remanent magnetization, hysteresis properties and FORC distributions, an unmixing model for isothermal remanent magnetization curves, and high field (up to 8T) isothermal remanence measurements. Our results show that the paleosol horizons, formed during interglacials , experienced pedogenic alteration, resulting in high amounts of superparamagnetic, single domain and pseudosingle domain magnetite /maghemite grains and hematite. The loess layers, formed during glacial periods, are mainly dominated by multidomain and/or pseudosingle domain oxidized magnetite and some hematite, all probably of aeolian origin. Goethite contribution is probably minor and constant both in loess and paleosol horizons suggesting an Aeolian origin. Our new results can be interpreted as a support for the transition of a Mediterranean type climate to a steppe type climate in the last two interglacial periods in the western Black Sea. Changing pattern of magnetic susceptibility from the lower Danube basin with distance from the Black Sea shore probably reflects the local influence of the Black Sea on continental scale climatic oscillations during the last 600 ka. The values of background magnetic susceptibility of the Romanian loess-paleosol sections indicate that the main source area of the dust changed during this climatic transition.
Acknowledgement:
Daniela Dimofte was supported by the project POSDRU/159/1.5/S/133391. This research was funded by CNCS - UEFISCDI Grant PCCE_ID 31/2010.
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