Monitoring of Saharan dust fallout on Crete and its contribution to soil formation

A series of 6 dust traps was established in 1988 distributed over the island of Crete (Greece). Eolian dust has been collected in the traps each year and in each season during the 4 years of investigation which is still going on. The mean deposition rate for the 6 stations and 4 years was calculated as 21.3 g m^-2 yr^-1. Using the highest and lowest values, the deposition can be extrapolated to 6.6-21.4 mm for 1000 years, which is in agreement with other researchers' findings. The trapped dust shows a homogeneous grain-size distribution. Its mineralogy is similar to what characterizes soil samples from Psiloritis on Crete and source areas in southern Tunisia. In the fine fraction of the soil (particles < 10 µ), the contents of the clay mineral kaolinite and of quartz are high. In addition, the oxygen isotope composition of the 3 types of substrate is similar but differs from the weathering products of the limestone bedrock. Statistics of dust episodes covering the period c. 1955-1990 from 10 meteorological stations in Greece revealed that long-distance transport of dust in combination with winds from a southerly sector is common in the Aegean area during spring.