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| Titel |
A potential record of Late Holocene natural environmental changes in a cultural landscape |
| VerfasserIn |
Niels Emil Søe, Bent Vad Odgaard, Jesper Olsen, Søren Munch Kristiansen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097245
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| Publikation (Nr.) |
 EGU/EGU2014-12804.pdf |
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| Zusammenfassung |
| The Late Holocene period is in most of Europe characterised by fast developing culture and
agricultural techniques with associated changes in land-use, land-cover and landscape
processes. Therefore, European Late Holocene natural environmental changes are often
difficult to document. A core from Lake Ilsø, Denmark, was obtained to investigate
environmental changes in the lake and its catchment during the Late Holocene.
This record suggests an environment little disturbed by humans during the Iron
Age.
Lake Ilsø, situated in the central Jutland, is a small (0.005km2) and wind-protected lake
in an east-west directed tunnel valley. The lake has an outlet, now channelised, and its
topographical catchment area is 0.2km2. The morphology and size of Lake Ilsø gives it
the potential of recording local-scale hydrological, environmental and climatic
changes.
Five radiocarbon dates on terrestrial material constitute an age-depth model of the 7m
core, which was obtained in the central part of Lake Ilsø at maximum water depth (2.5m).
The core covers the time interval from 2750 cal yr BP until the present. The core was
analysed on an Itrax XRF-core scanner and sampled in 5cm increments for analysis of pollen
and isotopes.
The XRF-counts of titanium are expected to reflect the amount of detrital material
entering the lake and thereby a proxy of the erosion from the catchment. This interpretation is
supported by a high correlation between titanium and potassium. The titanium counts indicate
a significant and rapid increase in erosion at 1000 cal yr BP, which continues to be high
towards the present. Prior to 1000 cal yr BP organic rich sediment was deposited in the lake
with short intervals of minor detrital input. The sedimentation rate was approximately
2.3mm/yr, which increased slightly to approximately 2.9mm/yr after 1000 cal yr
BP.
The marked change in the lake sediment is interpreted to be caused by human induced
changes in the catchment during the early medieval period. The significant increase in
catchment erosion could be due to forest clearance and intensified agriculture, e.g. the heavy
wheeled plough was implemented in Denmark at this time.
The low detrital input before 1000 cal yr BP indicates low erosion in the catchment and
preliminary pollen data does indicate dense beech forest cover during this period. This record
can potentially provide a proxy of natural changes in the environment during the Iron Age in
Denmark. Changes in hydrology, primary productivity, lake conditions or carbon source will
be targeted through analysis of δ13C and δ15N of the organic fraction. Furthermore δ18O
and δ13C of the carbonate fraction and of cellulose is expected to provide a climate signal. |
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