Mineralogy of atmospheric microparticles deposited along the Greenland Ice Core Project ice core

The mineralogical composition of atmospheric dust particles changes along the Greenland Ice Core Project (GRIP) ice core in phase with other paleoatmospheric records, showing that climatic changes affect the location, the relative extent, and the surface characteristics of the dust source areas. Fifty GRIP ice samples from the Eemian to the last glacial maximum were analyzed using a scanning electron microscope coupled with X ray energy dispersive system microprobe. More than 20 mineral types or groups were identified and their relative abundance was evaluated. A different mineralogical composition was systematically observed in cold and warm time periods. Quartz, illite, chlorite, micas, and feldspars prevail in the mineral assemblage associated with cold stages or phases (marine isotope stage (MIS) 4, MIS 2, cold part of MIS 3 fast variations), while kaolinite and Fe (hydr)oxides dominate in warm episodes (MIS 5e5, warm parts of fast variations). The first dust mineral assemblage is related mainly to the mechanical weathering prevailing in arid and cold mid-high-latitude areas, while the second dust mineral assemblage is related mainly to deep chemical weathering in warm and humid low-latitude areas. K/C and O/Q ratios may be assumed as indicative of the relative importance of low-latitude versus arid and mid-high-latitude source areas. It is worthwhile to mention that the first warmer part of Eemian (5e5) differs in dust mineralogy from the second part (5e4-5e1) and that also the fast variations are accompanied by clear mineralogical changes of the dust microparticles. The changes of the atmospheric dust mineral background are possibly related to changes of the atmosphere dynamics (meridian pressure gradient, polar front shift, storm track changes, etc.) and or to changes in the relative extent of the deflation source areas.