Subaquatic Dust Deposits - Mineral Dust: A Key Player in the Earth System - page 438

settling, there is a part of the wind-blown sediment fraction that is washed out of the
atmosphere by rain or snow. These processes were synthesised for the north African
dust sources by Stuut et al. ( 2009 ) and are described in this topic in Chap. 8 .

17.3 Wind-blown Dust in Subaqueous Sedimentary

Archives: A Recorder of Environmental Changes

17.3.1 Lacustrine Dust Archives

As opposed to the more regional character of dust deposited in marine sedimentary
archives, lacustrine archives contain a more local signal of environmental conditions
leading to dust generation, entrainment and finally deposition. Early recognition of
the potential of lake deposits as archives of dust deposition dates back to the studies
of,e.g.Grove( 1972 )andBowler( 1976 ). Well-established palaeo-environmental
records derived from lacustrine deposits include the southern German Alpine lakes
(Niessen et al. 1992 ), the German Maar records (Zolitschka et al. 2000 ; Sirocko et al.
2005 ), the Patagonian crater lakes (Mayr et al. 2007 ), the central North American
lakes (Dean 1997 ) and the central Saharan Ounianga lakes (Kröpelin et al. 2008 ).
Another advantage of lake sediments is that often they are varved, which is the result
of seasonal differences in environmental conditions. For example, high-latitude
lakes may be frozen over during winter, which leads to a seasonal banding of the
sedimentary deposits on the lake floor.
Especially the Maar records are examples of lakes where wind-blown material is
the only terrigenous input and thus where the dust can relatively simply be isolated
from the biogenic sedimentary fraction that is produced in both the lake waters and
on the lake floor. Sirocko et al. ( 2005 ) argue that the sediments that were retrieved
from the various Maar lakes in central Germany are a two-component mixture of
dark biogenic material produced in the lake and light-coloured quartz particles
blown into the lake. The authors argue that during warm periods, organic-rich
sediments are deposited as opposed to colder periods when deposition of wind-
blown particles dominates. Thus, the greyscale of these sediments can be used to
reconstruct variability in the input of the two individual components (Fig. 17.3 ).
The advantage of recording mere local environmental conditions may turn into
a disadvantage in the case of small lake basins where very local conditions (like a
nearby field of sand dunes) potentially dominate the depositional system. It is hard
to say what the appropriate lake size should be in order to avoid such artefacts.

17.3.2 Marine Dust Archives

Marine sediment archives containing dust most likely record integrated signals
from a larger dust-producing region, especially when the source-to-sink distance is