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Paleoclimatic significance of the mineral magnetic record of the Chinese loess and paleosols.

Maher, Barbara A. and Thompson, Roy (1992) Paleoclimatic significance of the mineral magnetic record of the Chinese loess and paleosols. Quaternary Research, 37 (2). pp. 155-170. ISSN 0033-5894

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Abstract

The origins of the magnetic susceptibility variations of the Chinese loess and paleosols are explored by scanning and transmission electron microscopy of magnetic extracts, and by magnetic modeling of magnetic hysteresis data, to provide quantified estimates of the major magnetic components. Microscopy identifies several distinct size and shape characteristics in the magnetic carriers. Lithogenic magnetites, intact and abraded, dominate the coarse-grained magnetic fraction. The smallest of the coarse grains is 2 μm. The remaining magnetic materal is ultrafine in size, with two types of magnetite particles present. Type A particles strongly resemble soil magnetites produced by inorganic precipitation. Type B particles, which occur rarely, are probably bacterial in origin. Quantitative modeling of these magnetic assemblages shows that over 90% of the susceptibility variations is accounted for by the superparamagnetic magnetite component. Compared to the loess units, the paleosols are richer in magnetite, particularly of superparamagnetic size, and have a threefold higher ratio of magnetite to hematite. We identify pedogenic formation of magnetite as the major contributor to the loess magnetic record. Matching this record against other paleoclimatic records, we find an extremely high correlation with the standard 18O record. The Chinese loess sequences record a very high resolution magnetic stratigraphy directly related to changing climate.

Item Type: Article
Journal or Publication Title: Quaternary Research
Uncontrolled Keywords: Loess magnetism ; Quaternary palaeoclimate ; single domain magnetite ; superparamagnetic magnetite ; Chinese loess and palaeosols
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 302
Deposited By: Professor Barbara A Maher
Deposited On: 06 Nov 2007
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 16:48
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/302

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