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Titel |
Lake Biel Holocene sediment record before and after the Aare river deviation (1878 AD) |
VerfasserIn |
Alice Jeannet, Juan Pablo Corella, Katrina Kremer, Stéphanie Girardclos |
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 |
250087740
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Publikation (Nr.) |
EGU/EGU2014-1798.pdf |
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Zusammenfassung |
Lake sediments are excellent archives of environmental and climate changes as well as
human impact on lake- and river-systems. Lake Biel is a medium-sized peri-alpine lake in
Switzerland, with a maximum depth of 74 m, and lies at an altitude of 429 m a.s.l. Lake Biel,
which formed during the Pleistocene by glacial erosion, is part of the Aare river system. Our
study focuses on the south-west part of the lake basin where the lake sedimentation
was originally (i.e. naturally) mainly controlled by autochthonous sedimentation.
This area is currently under a strong influence of water and sediment input from
this river catchment since the Aare river deviation through the Hagneck canal in
1878.
A 10.05 m long composite sediment sequence, cored from a 52 m water depth in
September 2011, was built from two long cores retrieved with the ETH Zurich/Eawag Uwitec
system. A radiocarbon age model indicates that the retrieved sedimentary sequence spans the
last 7500 years. The upper sediments were correlated to previous short core radionuclide
stratigraphy for the 1.5 m upper part (Thevenon et al., 2013). Magnetic susceptibility and
density were measured by Geotek MultiSensor Core Logger at 0.5 cm resolution.
Granulometry was measured with a CILAS grain sizer every 10 cm, and X-ray fluorescence
(XRF) was carried out using an Avaatech core scanner at 1-cm resolution. This technique
provides semi-quantitative information of the sediment elemental composition and shows
how runoff and river input (Ti, Al, Si) or redox conditions (Fe/Mn) vary through
time.
Lake Biel sediment record suggests marked environmental changes with runoff decrease
linked to climate and vegetation change during Atlantic chronobiozone, as well as a complex
climate-human impact during the ‘La Tène’ and Roman cultural times. The most
prominent recorded feature is the 10-times increase of sediment rate that occurred
after the Aare river deviation through the Hagneck canal into Lake Biel in 1878.
This artificial new river input is also linked to a massive and sudden Ti increase,
and inversely abrupt Ca decrease in XRF data. This record reveals the significant
alteration in the sediment dynamics, and the lake oxygenation changes that the lake
experienced when it shifted from a relatively closed basin to a river and delta-influenced
basin.
Thank you to Flavio S. Anselmetti, Christine Guido and Frédéric Arlaud for help coring
on the field and Stefanie Wirth for help at Limnogeology Laboratory. This study, undertaken
as a Master thesis, was financed by the Swiss National Foundation projects 121666 and
146889.
Reference
Thevenon F. et al. 2013. Human impact on the transport of terrigenous and anthropogenic
elements to peri-alpine lakes (Switzerland) over the last decades. Aquatic Sciences 75:
413-424. |
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