Loess magnetic susceptibility flux: A new proxy of East Asian monsoon precipitation. (1st October 2020)

• Record Type: Journal Article
• Authors: Kong, Xianghui; Zhou, Weijian; Beck, J. Warren; Xian, Feng; Qiang, Xiaoke; Ao, Hong; Wu, Zhenkun; An, Zhisheng
• Is Part Of: Journal of Asian earth sciences. Volume 201(2020)
• Publication Date: 2020-10-01
• Subjects: Pedogenic magnetic susceptibility flux -- Chinese loess -- Monsoon precipitation proxy -- Orbital forcing; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2020.104489
• Languages: English
• ISSNs: 1367-9120

Abstract

Highlights: Pedogenic MS (χ) flux in loess is a better proxy of EASM precipitation than χ. Pedogenic χ-flux in loess shows clear eccentricity, obliquity and precession periods. Precession signal strength in loess χ-flux is modulated by eccentricity. Abstract: Magnetic susceptibility (χ) of loess-paleosol sequences on the Chinese Loess Plateau (CLP) has been widely used as a proxy for East Asian summer monsoon (EASM) precipitation variability. Such records typically show strong climate forcing in the ~100 ka orbital eccentricity band, but exhibit weak precessional (~23 ka) forcing relative to that seen in oxygen isotopes from marine sediments. This is puzzling as monsoons should be highly sensitive to precession variations. We assert that this lack of precessional signal is because χ is a concentration, which is strongly affected by the dilution effect of dust sedimentation rate superimposed on rainfall rate. χ-flux on the other hand corrects for dust accumulation rate and bulk density effects to better reveal pedogenic mineral ingrowth rates associated with rainfall. In this study, we compare three 600 ka records of loess pedogenic χ-flux from the CLP with Chinese speleothem δ 18 O records and a 550 ka loess-paleosol 10 Be flux record from Baoji which has also been used as a monsoon precipitation proxy record. Pedogenic χ-flux exhibits clear signals of orbital precession, whereas χ (-concentration) does not.