Aeolian dust deposits can be considered as one of the most important archives of past
climatic changes. Alternating loess and paleosol strata display variations of the
dust load in the Pleistocene atmosphere. By using the observations of recent dust
storms, we are able to employ Late Pleistocene stratigraphie datasets (with accurate
chronological framework) and detailed granulometric data for making conclusions on
the atmospheric dust load in the past. Age-depths models, created from the absolute
age data and stratigraphie interpretation, allow us to calculate sedimentation rates
and dust fluxes, while grain-size specifies the dry-deposition velocity, i.e. the
atmospheric residence time of mineral particles. Thus, the dust concentration can
be expressed as the quotient of the dust flux and gravitational settling velocity.
Recent observations helped to clarify the mechanisms behind aeolian sedimentation
and the physical background of this process has nowadays been well established. Based
on these two, main contrasting sedimentary modes of dust transport and deposition
can be recognised: the short suspension episodes of the coarse (silt and very fine
sand) fraction and the long-range transport of a fine (clay and fine silt) component.
Using parametric curve fitting the basic statistical properties of these two sediment
populations can be revealed for Pleistocene aeolian dust deposits, as it has been
done for loess in Hungary. As we do not have adequate information on the magnitude
and frequency of the Pleistocene dust storms, conclusions could only be made on the
magnitude of continuous background dust load. The dust concentration can be set in
the range between 1100 and 2750 ug/m3. These values are mostly higher than modern
dust concentrations, even in arid regions. Another interesting proxy of past atmospheric
conditions could be the visibility, being proportional to the dust concentration.
According to the known empirical dust concentration - visibility equations, its value
is around 6.5 to 26 kilometres.