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| Titel |
Large-scale landslide-induced liquefaction and transport of valley-fill deposits in the Vorderrhein River Valley, Graubunden, Switzerland |
| VerfasserIn |
Nancy Calhoun, John Clague, Andreas von Poschinger |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072555
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| Zusammenfassung |
| The Flims landslide, located in the canton of Graubunden in the eastern Swiss Alps, is
one of the largest Holocene mass movements in the world. About 10-12 km3 of
Helvetic carbonate rocks slid away from the north side of the Vorderrhein valley
8900 years ago and crashed onto the valley floor, blocking the Vorderrhein. An
important secondary effect of the landslide was the liquefaction and mobilization of
about 1 km3 of valley-fill sediments, which resulted in the emplacement of the
Bonaduz gravels. The Bonaduz gravels were deposited by a mass flow in front of the
Flims rockslide debris, to the east down the Vorderrhein valley, and to the south
up the Hinterrhein valley, up to 16 km away. The unit, which is more than 60 m
thick and stands in near-vertical faces, consists of upward-fining, well-rounded,
poorly sorted gravels that grade into pebbly silt and, locally, silt. Characteristic
sedimentological features include “Pavoni pipes” – sub-vertical, tube-shaped dewatering
pipes – and large (up to multi-meter) rip-up clasts of lacustrine clayey silt. The
mass flow that deposited the Bonaduz gravels rafted masses of rockslide material
(“Toma hills”) up to 260 m long and 70 m high for distances of several kilometers.
Generations of scientists have explored diverse aspects of the Flims landslide, but
questions remain about the emplacement of the Bonaduz gravels and how liquefied
valley-fill sediments can travel so far with so much power. We are attempting to better
understand the Bonaduz gravels and the sequence of events that produced them through
stratigraphic and sedimentological observations, particle-size analysis, and analysis of
Lidar imagery. We are incorporating these observations into GIS-based maps of the
Vorderrhein and Hinterrhein valleys. Of particular interest are several key field
sites within and near the base of the Flims rockslide debris, where atypical facies
of the Bonaduz unit interfingering with Flims rockslide debris have been found. |
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