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| Titel |
Aeolian dust in Europe: African sources and European deposits |
| VerfasserIn |
J.-B. W. Stuut, I. S. Smalley, K. O'Hara-Dhand |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025625
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| Zusammenfassung |
| Here we present a conceptual model for the provenance and dispersal patterns of small dust
that falls on Europe. Generally its sources are in North Africa, and it is distributed across all
Europe. Several key sources can be distinguished: ‘Sahelian’ dust comes largely from the old
Lake Chad region- this is a clay-rich unimodal material; ‘Saharan’ dust comes from the great
sand sheets- it contains small monomineralic particles and may have a bimodal size
range.
Three simple deposition zones can be recognised; a D1a zone where sufficient dust is
deposited to form a discrete soil layer (not well classified as a Rendoll), in the extreme south
of Europe; a D1b zone where the airborne dust simply provided a silty admixture to soil
systems- across Middle Europe; and a northern zone D1c where the dust is a fugitive cloud,
but very occasionally forms noticeable deposits.
Two particle formation methods can be noted; particle control in Sahelian dust is via the
sedimentation in the original lake. This gives an open structure which can be modelled using
a simple Monte Carlo approach. The open structure ensures that only small particles are
produced; size control is via particle packing. A chipping mechanism can produce fine quartz
particles from sandy deserts. The aeolian energy is, by and large, not sufficient to cause major
impact fracturing but small mineral chips can be produced in the small dust size (fine
and very fine silt) which go into high level suspension and travel to Europe and
beyond.
The Saharan material can have a wider, more variable size distribution than the
Sahelian material. The Canary Islands ‘loess’ is largely Sahelian material; the Cape
Verde Islands deposits, from the nearby sandy regions, are Saharan deposits. Large
dust has fallen on Europe, and produced widespread loess deposits. Large dust is
essentially an ‘in-continent’ deposit; small dust comes from outside- from Africa. |
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