Unmixing hysteresis loops of the late Miocene–early Pleistocene loess-red clay sequence

Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresi...

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Bibliographic Details
Published in:Scientific reports 2016-07, Vol.6 (1), p.29515-29515, Article 29515
Main Authors: Zhang, Rui, Necula, Cristian, Heslop, David, Nie, Junsheng
Format: Article
Language:English
Subjects:
704/106/413
704/2151/412
Archives & records
Clay
Humanities and Social Sciences
Loess
Mathematical functions
Mineralogy
Miocene
multidisciplinary
Pleistocene
Science
Sediments
Soils
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Summary:Magnetic paleoclimatic records often represent mixed environmental signals. Unmixing these signals may improve our understanding of the paleoenvironmental information contained within these records, but such a task is challenging. Here we report an example of numerical unmixing of magnetic hysteresis data obtained from Chinese loess and red clay sequences. We find that the mixed magnetic assemblages of the loess and red clay sediments both contain a component characterized by a narrow hysteresis loop, the abundance of which is positively correlated with magnetic susceptibility. This component has grain sizes close to the superparamagnetic/stable single domain boundary and is attributed to pedogenic activity. Furthermore, a wasp-waisted component is found in both the loess and red clay, however, the wasp-waisted form is more constricted in the red clay. We attribute this component to a mixture of detrital ferrimagnetic grains with pedogenic hematite. The abundance of this component decreases from the base to the top of the red clay, a pattern we attribute to decreased hematite production over the Chinese Loess Plateau (CLP) due to long-term climate cooling. This work demonstrates the potential of hysteresis loop unmixing to recover quantitative paleoclimatic information carried by both low and high coercivity magnetic minerals.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep29515