TY - JOUR
T1 - Magnetic properties of the tertiary red clay from Gansu Province, China and its paleoclimatic significance
AU - Liu, Xiuming
AU - An, Zhisheng
AU - Rolph, Tim
AU - Qiang, Xiaoke
AU - Hesse, P.
AU - Lu, Huayu
AU - Zhou, Jie
AU - Cai, Yanjun
PY - 2001
Y1 - 2001
N2 - The study on magnetic properties of the red clay indicates that the red clay and loess-paleosol sequence have a common magnetic mineralogy, with magnetite, maghemite, hematite (and possibly goethite) contributing to the magnetic behavior. The red clay magnetic susceptibility is also found to have a positive relation with extrafine superparamagnetic grains. This suggests that, like the Quaternary loess-paleosols, an ultrafine ferrimagnetic component produced during pedogenesis in the red clay under humid conditions also plays an important role in susceptibility enhancement in the soil units. This is supported by the correlation between Rb/Sr ratio and magnetic susceptibility. This signifies that, like the above loess-paleosol sequence, the magnetic susceptibility of the red clay can be used as a general proxy paleoclimatic indicator, although whether its susceptibility in the red clay is comparable to pedogenesis intensity and requires further investigation. Magnetic susceptibility variation in the red clay thus also provides an eolian/pedogenic record of paleoclimatic evolution. Study of the background susceptibility indicates that, on average, the absolute scale of the paleoclimatic shift from red clay development to Quaternary loess deposition is similar to the climatic shift from stage 5 (S1) to stage 2-4 (L1). This may suggest that during the Quaternary there is an evident strengthening of the absolute wind intensity to bring more (about double) coarser and less weathered (non-SP fraction) eolian magnetic input from the source regions to the Loess Plateau than during the Pliocene. The presence of eolian red clay since 7.5 Ma BP in central-northern China implies an important environmental change from the underlying Cretaceous red sandstone. The red clay development was closely related to global drying and climate cooling since the Cretaceous and closely associated with the abrupt uplift of the Qinghai-Xizang Plateau at about that time. This uplift of the plateau intensified the East Asia monsoon system and started red clay deposition.
AB - The study on magnetic properties of the red clay indicates that the red clay and loess-paleosol sequence have a common magnetic mineralogy, with magnetite, maghemite, hematite (and possibly goethite) contributing to the magnetic behavior. The red clay magnetic susceptibility is also found to have a positive relation with extrafine superparamagnetic grains. This suggests that, like the Quaternary loess-paleosols, an ultrafine ferrimagnetic component produced during pedogenesis in the red clay under humid conditions also plays an important role in susceptibility enhancement in the soil units. This is supported by the correlation between Rb/Sr ratio and magnetic susceptibility. This signifies that, like the above loess-paleosol sequence, the magnetic susceptibility of the red clay can be used as a general proxy paleoclimatic indicator, although whether its susceptibility in the red clay is comparable to pedogenesis intensity and requires further investigation. Magnetic susceptibility variation in the red clay thus also provides an eolian/pedogenic record of paleoclimatic evolution. Study of the background susceptibility indicates that, on average, the absolute scale of the paleoclimatic shift from red clay development to Quaternary loess deposition is similar to the climatic shift from stage 5 (S1) to stage 2-4 (L1). This may suggest that during the Quaternary there is an evident strengthening of the absolute wind intensity to bring more (about double) coarser and less weathered (non-SP fraction) eolian magnetic input from the source regions to the Loess Plateau than during the Pliocene. The presence of eolian red clay since 7.5 Ma BP in central-northern China implies an important environmental change from the underlying Cretaceous red sandstone. The red clay development was closely related to global drying and climate cooling since the Cretaceous and closely associated with the abrupt uplift of the Qinghai-Xizang Plateau at about that time. This uplift of the plateau intensified the East Asia monsoon system and started red clay deposition.
KW - red clay
KW - magnetic property
KW - magnetic susceptibility
KW - Rb/Sr ratio
KW - paleoclimatic significance
UR - http://www.scopus.com/inward/record.url?scp=0035385423&partnerID=8YFLogxK
U2 - 10.1007/BF02875337
DO - 10.1007/BF02875337
M3 - Article
AN - SCOPUS:0035385423
SN - 1006-9313
VL - 44
SP - 635
EP - 651
JO - Science in China, Series D: Earth Sciences
JF - Science in China, Series D: Earth Sciences
IS - 7
ER -