TY - JOUR
T1 - AC magnetic susceptibility studies of Chinese red clay sediments between 4.8 and 4.1 Ma
T2 - Paleoceanographic and paleoclimatic implications
AU - Nie, Junsheng
AU - King, John
AU - Jackson, Mike
AU - Fang, Xiaomin
AU - Song, Yougui
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2008/10/4
Y1 - 2008/10/4
N2 - Recent studies show that measuring AC magnetic susceptibility (with in-phase X′ and quadrature X″ components) versus temperature provides an effective way to map the grain-size distribution of pedogenic maghemite. Applying this method, we mapped the pedogenic maghemite grain-size distribution of samples of the red clay sediments deposited on the Chinese Loess Plateau (CLP) during the interval 4.8-4.1 Ma, during which the validity of magnetic susceptibility as an East Asian summer monsoon precipitation intensity proxy has been questioned. The results show that the pedogenic maghemite grain-size distribution is the same as in the overlying loess-paleosol sequence and in the other intervals of the red clay sequence, suggesting similar pedogenesis mechanisms and marked precipitation seasonality on the CLP between 4.8 and 4.1 Ma compared with the other intervals. We argue that the seasonal position shift of the polar westerlies produces the required precipitation seasonality and thus produces a uniform pedogenic grain-size distribution during this time interval. Reconstructing paleo-rainfall on the central CLP on the basis of surface calibration results suggests that the intensification of the East Asian summer monsoon might be a key trigger for the subsequent significant ocean and cryosphere adjustments during the Pliocene.
AB - Recent studies show that measuring AC magnetic susceptibility (with in-phase X′ and quadrature X″ components) versus temperature provides an effective way to map the grain-size distribution of pedogenic maghemite. Applying this method, we mapped the pedogenic maghemite grain-size distribution of samples of the red clay sediments deposited on the Chinese Loess Plateau (CLP) during the interval 4.8-4.1 Ma, during which the validity of magnetic susceptibility as an East Asian summer monsoon precipitation intensity proxy has been questioned. The results show that the pedogenic maghemite grain-size distribution is the same as in the overlying loess-paleosol sequence and in the other intervals of the red clay sequence, suggesting similar pedogenesis mechanisms and marked precipitation seasonality on the CLP between 4.8 and 4.1 Ma compared with the other intervals. We argue that the seasonal position shift of the polar westerlies produces the required precipitation seasonality and thus produces a uniform pedogenic grain-size distribution during this time interval. Reconstructing paleo-rainfall on the central CLP on the basis of surface calibration results suggests that the intensification of the East Asian summer monsoon might be a key trigger for the subsequent significant ocean and cryosphere adjustments during the Pliocene.
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U2 - 10.1029/2008JB005654
DO - 10.1029/2008JB005654
M3 - Article
AN - SCOPUS:57649188042
SN - 2169-9313
VL - 113
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 10
M1 - B10106
ER -