The Deglaciation History of Trondheimsfjorden and Trondheimsleia 415
NORWEGIAN JOURNAL OF GEOLOGY The deglaciation history of Trondheimsfjorden and Trondheimsleia 415 The deglaciation history of Trondheimsfjorden and Trondheimsleia, Central Norway Leif Rise, Reidulv Bøe, Harald Sveian, Astrid Lyså & Heidi A. Olsen Rise, L., Bøe, R., Sveian, H., Lyså, A. & Olsen, H.A.: The deglaciation history of Trondheimsfjorden and Trondheimsleia, Central Norway. Norwegian Journal of Geology, Vol. 86, pp. 419-438. Trondheim 2006. ISSN 029-196X. A dense grid of seismic data and core data from several boreholes up to 70 m deep, have been studied to determine the Quaternary stratigraphy in Trondheimsfjorden and Trondheimsleia. In the outer part of Trondheimsfjorden with water depths of 600 m, the basement rocks were glacially eroded to nearly 1300 m below sea level, and up to 750 m of sediments are present. Most of the sedimentary succession is acoustically stratified and was deposited during the last deglaciation when ice and water from a large sector of the Scandinavian ice sheet drained into the fjord. Chaotic seismic reflection patterns show that mass-wasting processes were common in some areas. At 13-12.5 ka 14C BP, the ice margin was located near the coastline west of Trondheimsfjorden, and up to 360 m of stratified sediments were deposited in the northern part of Trondheimsleia. The ice calved and receded rapidly in the deepest part of Trondheimsfjorden, and glaciomarine conditions were established near Trondheim around 12 ka 14C BP. The maximum sedimentation rate was probably 0.5-1 m/year both in Trondheimsleia and between Trondheim and Agdenes. During Allerød time the ice recession continued east- and southwards from Trondheim, and glaciomarine sediments were also trapped in the inner basin west of Skogn.
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