Loess magnetic susceptibility flux: A new proxy of East Asian monsoon precipitation

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 δ¹⁸O records and a 550 ka loess-paleosol ¹⁰Be 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.