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| Titel |
Dating sedimentation in the Belgian loess region |
| VerfasserIn |
Bastiaan Notebaert, Gert Verstraeten, Dimitri Vandenberghe, Jean Poesen, Gerard Govers |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035852
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| Zusammenfassung |
| In many catchments in temperate regions, soil erosion and sediment deposition has varied
largely during the Holocene as a result of variations in climate and land use. In order to
identify the relative importance of these driving forces, an accurate dating control of the
sedimentary archives is necessary, which is not straightforward. The objective of this
study is to identify the driving forces for Holocene sediment dynamics in the Dijle
catchment (central Belgium), based on dating results. Individual colluvial and alluvial
sedimentation units were dated using AMS radiocarbon and optical dating. For
each individual site a sediment deposition curve was constructed. These curves
represent the evolution of sediment mass accumulation through time, corrected for
the presence of organic material and bulk density. Apart from this, a database was
constructed with all available radiocarbon ages of the catchment. Analysis of this
database allows to identify catchment wide patterns in the sedimentation history.
First, it was analyzed using cumulative probability functions (CPFs) of calibrated
ages, grouped by the geomorphological activity phase they represent (active/stable
floodplain). In addition, sediment mass accumulation rates were calculated. These rates
were normalized in order to allow a comparison between sites with different total
accumulated volumes. OSL dating results for the floodplain show some stratigraphic
inconsistencies, caused by incomplete bleaching of the sediments upon deposition.
The results indicate that for most sites an increase in sediment deposition starts
between 4000 BCE and 500 BCE for colluvial sites and around 2000 BCE for alluvial
sites and. Before this first increase, floodplain deposition was low with mainly
peat growth, while there remain no traces of colluvial sedimentation. Between ca
4000 BCE and 1000 CE, the relatively larger part of the sediments were deposited
as colluviums compared to the previous or subsequent period. The major part of
the Holocene deposits, both colluvial and alluvial, has been deposited in the last
1000 a. Sedimentation curves vary between individual sites, and even sites located
close to each other may vary largely. The CPFs of the radiocarbon ages contains
peaks in active colluvial deposition ages from 4000 BCE on, while most peaks are
situated in the last 3000 a. Peaks in the CPFs of active floodplain deposition are
mainly situated in the last 1000a, while ages of stable floodplains and peat growth are
spread over the Holocene. The analysis of mass accumulation rates indicates that
colluvial sedimentation increased from ca 1000 BCE on, while alluvial sedimentation
has on average increased in the last 2000 a. Using these three methods, the results
indicate that the sedimentation history shows an important correlation with the
catchments land use history, while there is no field evidences for an influence of climatic
variations. There is, however, some variation between the individual sites, indicating
that single site studies are not valid to reconstruct the sedimentation history of a
catchment. |
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