Aeolian process and pedogenesis under the influence of the East Asian monsoon: A statistical approach to particle-size distribution variability

The grain size of Chinese loess has been widely regarded as a sensitive proxy for the intensity of the wind strength associated with the winter component of the East Asian monsoon. The majority of papers concerned with loess particle size examine variations in moments of the particle size distribution. However, in coastal geomorphological research parametric models have been used and the samples represented by resulting parameter estimates. Here we investigate the use of log-hyperbolic and log-skew-laplace models to distinguish between loess, loess subgroups and palaeosols in a particularly high accumulation rate profile from the NW Chinese loess plateau area. The aim is to define narrow units of 'pristine' loess that may indicate brief returns to dust storm conditions. With this approach, units within the loess, previously ascribed to Heinrich events, can be seen to have a particular particle size distribution signature, thus allowing them to be stratigraphically and environmentally constrained. Parametric models applied to grain-size distribution data in Chinese loess make a useful addition to previously used particle size techniques that have demonstrated cyclicity on a scale similar to that of Dansgaard-Oeschger events in ice cores and those designed to determine the degree of loess pedogenesis such as micromorphology and magnetic enhancement. The aim of our work is to make full use of particle size distribution data in the wider context of palaeoenvironmental reconstruction.