Long-range transport of 'giant' aeolian quartz grains: linkage with discrete sedimentary sources and implications for protective particle transfer

Several articles have documented the presence of large particles (> 62.5 mu m) that have been transported great distances (> 1000 km) through the atmos phere. At present, we do not understand the mechanisms that lead to mineral grains being carried aloft far beyond the limits imposed by conventional g ravitational settling models. Typically, marine geologists refer to ice raf ting and/or advective transport by ocean currents as the dominant transport processes that deliver large mineral grains to deep sea sediments. Textura l analyses of 'giant' quartz grains from six sedimentary deposition events collected from various sources, including a single site in the North Pacifi c Ocean and sites in the British Isles and France, strongly support the ide a that in each case all of the grains were initially eroded from a discrete sediment type, and often a discrete point source, and subsequently transpo rted via the atmosphere to our sampling sites up to 10 000 km away. These f indings suggest that at least at times erosional events fuelling long dista nce atmospheric transport are exceedingly specific and operate upon geologi cally distinctive assemblages; and are able to effect long distance transfe r of large grains with no grain-to-grain collisions. This work also suggest s that atmospheric transport should be included as a possible means of deli very for significant quantities of 'giant' sedimentary particles to remote marine sites such as the Lord Howe Rise. (C) 2001 Elsevier Science B.V. All rights reserved.