<p>Mean size and sorting are the main statistical parameters of grain size distributions and are traditionally used to interpret sediment sources and transport processes. Recent studies have shown that these parameters vary systematically under increasing velocity of the bottom current in mud-sand contourites. However, the influence of sediment sources on this trend, and whether it exists in other deep-sea facies, has not been studied in detail. In this paper, the grain size data of polyfacial Late Quaternary sediments of contourite drifts of the Charlie-Gibbs Fracture Zone are studied. The results reveal ascending and descending sorting trends with increasing mean grain size within the same ranges as in previous studies. In the mineral subfraction, sorting increases (worsens) from 2.2 to 7.3 as the mean size rises from 2.2 to 18&#xa0;μm. Sorting improves (values decrease from 7.5 to 1.8) as the mean size further increases to 110.2&#xa0;μm. Unmixing of grain size distributions by end-member modelling and genetic analysis of grain-size subpopulations demonstrates the following reasons for this trend. The very poorly sorted sediments consist of mixture of three and four grain-size subpopulations. Sediment sources changed from coarse-grained ice-rafted debris in Late Pleistocene hemipelagites to a suspension load of silt–clay components in Holocene contourite-hemipelagite facies. A deficiency of the silt fraction is registered, likely due to low bottom-current velocities and a large distance from the sediment source. The observed trends in mean grain size and sorting may be more universal than previously found.</p>