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 mum) that have been transported great distances (> 1000 km) through the atmosphere. At present, we do not understand the mechanisms that lead to mineral grains being carried aloft far beyond the limits imposed by conventional gravitational settling models. Typically, marine geologists refer to ice rafting and/or advective transport by ocean currents as the dominant transport processes that deliver large mineral grains to deep sea sediments. Textural analyses of 'giant' quartz grains from six sedimentary deposition events collected from various sources, including a single site in the North Pacific Ocean and sites in the British Isles and France, strongly support the idea that in each case all of the grains were initially eroded from a discrete sediment type, and often a discrete point source, and subsequently transported via the atmosphere to our sampling sites up to 10 000 km away. These findings suggest that at least at times erosional events fuelling long distance atmospheric transport are exceedingly specific and operate upon geologically distinctive assemblages; and are able to effect long distance transfer of large grains with no grain-to-grain collisions. This work also suggests that atmospheric transport should be included as a possible means of delivery 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.