Weathering history indicated by the luminescence emissions in Chinese loess and paleosol

Abstract

In the past several decades, luminescence emissions from quartz and feldspar grains have been used mainly for optical dating of detrital sediments. Here we extend the luminescence application field, with variations in luminescence emissions being introduced to reflect weathering degree and recover its potential paleoclimate information in the Chinese loess–paleosol sequence. Four wavebands (320–340, 405–425, 465–495 and 545–575 nm) of infrared stimulated luminescence (IRSL) from polymineral grains (4–11 μm) are presented, and IRSL intensities show distinct variation between the well-developed paleosol, weakly developed soil and typical loess in the last glacial-interglacial cycle. Based on the facts that IRSL signal originates from feldspars and optically stimulated luminescence (OSL) after long duration of Infrared stimulation from quartz grains, referred to as [post-IR] OSL signal, the IRSL/[post-IR] OSL ratios were proposed to represent the relative abundance of feldspar and quartz. This ratio was linked to the degree of weathering in Chinese loess and paleosol units. In addition, the ratios between the four IRSL emissions may also show the relative abundances of four corresponding feldspar groups. Compared to the magnetic susceptibility record, the IRSL/[post-IR] OSL ratios are more sensitive to the degree of weathering in Chinese loess. Convenient to measure and available as a byproduct of routine optical dating, such ratios may act as potential proxies of paleoclimate in Chinese loess.