Advances in Earth Science ›› 2014, Vol. 29 ›› Issue (3): 369-380. doi: 10.11867/j.issn.1001-8166.2014.03.0369

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Anisotropy of Magnetic Susceptibility Response to the Regional Stress Variation in Aeolian Red Clay Sequence

Xinbo Gao 1, 2, Xiaoke Qiang 1, Hui Zhao 1, 2, Ting Chen 1, 2   

  1. 1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710075
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2013-09-16 Revised:2013-01-29 Online:2014-03-20 Published:2014-03-10

Xinbo Gao, Xiaoke Qiang, Hui Zhao, Ting Chen. Anisotropy of Magnetic Susceptibility Response to the Regional Stress Variation in Aeolian Red Clay Sequence[J]. Advances in Earth Science, 2014, 29(3): 369-380.

The Aeolian sediment sequences from the Chinese Loess Plateau record abundant paleoclimatic and paleoenvironmental information, while little is known about whether there were any stress effect during the sedimentary period. In terms of tracking stress variation, anisotropy of magnetic susceptibility(AMS) has some particular advantages in comparison with other traditional methods. Systematic magnetostratigraphy, rock magnetism and anisotropy of magnetic susceptibility analysis were carried out on Shuiluo Aeolian red clay profile, which is located at the western Liupan Mountain. In the field, there are not any obvious tectonic traces that can be observed, which indicates the primitive deposit, but AMS results have many distinct differences between Shuiluo aeolian red clay profile and other typical aeolian sediment sequences(loess/paleosol, red clay). These differences mainly manifest from the following aspects. Firstly, abundant magnetic ellipsoid is located in the prolate area; Secondly, the stereonet projections of the κmax and κmin principle axes of AMS ellipsoids show that the κmax axes are well grouped in an approximately east-west direction, while the κmin shows a slight girdle in an approximately north-south direction; and in addition, the Pj-T diagram shows that the magnetic ellipsoid is being transition from oblate to prolate magnetic ellipsoid. These characteristics listed above suggested that Shuiluo red clay profile had gone through a weakly stress effect, and comparing with previous research we infer that these AMS characteristics be correspondent to the incipient deformation with a weaker stress intensity and the moderate deformation with a stronger stress intensity. After further classification, comparison and using a variety of analysis methods, we find that from 14.8 Ma to 11.0 Ma, the stress state is accompanied by three stress increase and decrease alternately, and these stress effects may correspond to the stress from the northwest Tibetan plateau. In about 11.0~8.7 Ma, AMS shows a strong stress effect, and almost all AMS ellipsoid is located in the prolate magnetic ellipsoid area. At the same time, the κmin axes shows a strong girdle in an approximately north-south direction and it should be in response to the stress increasing in the local area.

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