HR: 0800h
AN: C41B-0472    [Abstracts]
TI: Evidence for catastrophic outbursts and tunnel valley formation in northern Denmark during the last deglaciation
AU: * Larsen, N K
EM: nicolaj_krog.larsen@geol.lu.se
AF: Lund University, Department of Geology, Solvegatan 12, Lund, 22362, Sweden
AU: Auken, E
EM: esben.auken@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Knudsen, K
EM: karenluise.knudsen@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Krohn, C
EM: charlotte.krohn@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Kronborg, C
EM: geolck@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Murray, A
EM: andrew.murray@risoe.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Nielsen, O B
EM: ole.bjoerslev@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AU: Sandersen, P
EM: peter.sandersen@gmail.com
AF: Grontmij-Carl Bro, Dusager 12, Aarhus, 8200, Denmark
AU: Westergaard, J
EM: jaw@geo.au.dk
AF: University of Aarhus, Hoegh-Guldbergs Gade 2, Aarhus, 8000, Denmark
AB: A series of buried valleys was mapped in northern Denmark using SkyTEM and conventional TEM. The valleys are 2-13 km long, 0.5-2 km wide and up to 170 m deep, and their distribution can be linked to former ice margins. Exploration wells were drilled in the centre and on the flanks of representative valleys in order to understand the environmental development and to establish a chronological framework for their genesis. The recovered samples were analysed using a wide range of sedimentogical and biostratigraphical proxies and the chronology is based on OSL and AMS 14C age determinations. Most of the tunnel valleys turned out to be incised into Eemian to Late Weichselian marine or lacustrine clays, and they have been refilled with silty and sandy sediments containing a mixed, redeposited Eemian and Weichselian fauna. Based on lithostatigraphic correlation and absolute datings, as well as the biostratigraphy of wells drilled through the flanks, the age of the valleys can be constrained to ~18 ka BP at which time northern Denmark was deglaciated, and they have been refilled within a few centuries in a sub- or proglacial environment. This implies that much of the meltwater from the Scandinavian Ice Sheet was drained along systems of tunnel valleys formed during catastrophic flood events and not by steady state drainage.
DE: 4540 Ice mechanics and air/sea/ice exchange processes (0700, 0750, 0752, 0754)
SC: Cryosphere [C]
MN: 2007 Fall Meeting