Late Glacial and Holocene sedimentary processes .....

Late glacial and Holocene sedimentary processes and environments, Ranafjorden, Nordland – preliminary results

1Martha K. Stalsberg, ¹Astrid Lyså, ¹Eiliv Larsen, ¹Oddvar Longva, ²Hans Petter Sejrup and ²Inge Aarseth

^{1 Geological Survey of Norway, Postbox 3006 – Lade, 7491 Trondheim, Norway
^{2 Department of Geology, University of Bergen, Allegt. 41, 5007Bergen,
Norway

The purpose of the present study which is a subproject within the NORPAST project (Past
Climates of the Norwegian region) is to develop better knowledge on fjords as sedimentary
basins and how these respond to and reflect climatic changes by obtaining a detailed
stratigraphy and a detailed sedimentology of the outer and inner fjord basins. A cruise
with Håkon Mosby, in October 1999 will hopefully give interesting seismic data as well as
sediment cores covering the late glacial-deglacial and Holocene record in Ranafjorden.

The area of Ranafjorden is located within the catchment area of Svartisen,
Høgtuvbreen, and Okstindbreen. The fjord is approximately 70 km long and comprises three
basins separated by moraine thresholds. The moraines represent the Tjøtta event (Younger
Dryas, 11200-10400 BP), The Nordli event (10200-10100 BP) and the Narvik II event (9600±
200 BP) (Andersen et al., 1982;1995). The outer fjord basin (max. 430 m deep) is located
in-between the Nordli and the Tjøtta event and is covered by 40-50 m of stratified
sediments. The middle fjord basin (max. 440 m deep) is situated in-between the Narvik II
and the Nordli event. More than 50 m of sediments are deposited within the middle basin
where avalanche deposits overlying stratified glacimarine sediments are often found below
stratified sediments (tentatively of late Holocene age). The inner fjord basin (max. 510 m
deep) is situated inside the Narvik II event and 40-50 m of stratified sediments is
deposited within this basin. According to existing Boomer seismics the Holocene sediments
in Ranafjorden are relatively undisturbed which should favour a high resolution study of
the record.

Preliminary results to be presented: MST data (density, p-wave velocity,
susceptibility), x-ray images of sediment cores, seismic data.

References:

Andersen, B.G., Bøen, F., Rasmussen, A., Rokoengen, K., & Vallevik,P.N 1982. The
Tjøtta glacial event in southern Nordland, North Norway. Norsk geol. Tidsskr.62,
39-49

Andersen; B.G., Mangerud, J., Sørensen, R., Reite, A., Sveian, H., Thoresen, M., &
Bergstrøm B. 1995. Younger Dryas ice-marginal deposits in Norway. Quat. int. 28,
147-169

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