GEOMORFOLOGI

There has been some discussion concerning classification and definition of
rapid mass movements and related deposits. There seems to be a need for a
clearer systematization and division of the processes and deposits. Vi have
thus developed a classificiation system for rapid mass movements and related
deposits in alpine areas. The system is divided into four groups after the
type process involved: (1) Rockslide/rockfall; (2) Snow avalanche; (3) Debris
flow; and (4) Flash flood. The different processes result in deposits with
characteristic surface features. Knowledge about these features is important
during general mapping projects, because these can point out which slope
processes act in different areas. We have made suggestions as to how symbols
can be used on maps. These data will be of practical use in natural-hazard
mapping projects for land-use planning.

The superficial deposits within the area of map-sheet Asker, southeastern
Norway, are classified and described. The areas above the upper marine limit
(c. 220 m a.s.l) are dominated by exposed bedrock or a thin and discountinuous
cover of till. In the main valleys, below the upper marine limit, fine-grained
sediments dominate. These are commonly overlain by sandy and gravelly marine
shore deposits. Only small glaciofluvial deposits exist, mostly near the heads
of the main valleys. Weathering material overlies most of the Cambro-Silurian
bedrock along the inner part of Oslofjorden. Ice movements and the course of
the deglaciation have been reconstructed. The oldest ice movement was towards
south-east (with Oslofjorden as the confluence area). During the deglaciation
of the mapped area, there was only one main glacial event (the Aker Moraine
event) marking advance or half of the ice-front. The Aker Moraine is dated to
c. 9800 years B.P. Short accounts are given on shorelines, shorelevel displacem
nt and pollen analyses.

The superficial deposits within the area of map-sheet Siljan, southeastern Norway, are classified and described. Most of the hilly areas are dominated by exposed bedrock or a thin and discontinuous cover of till. In the main valleys, beow the marine limit (c. 160-180 m a.s.l.), fine-grained marine sediments and fluvial deposits dominate. Glaciofluvial deposits exist in Siljandalen and Lågendalen as well as in the tributary valley Hærlandsdalen. Ice movements and the course of deglaciation are reconstructed. The oldest ice movements were towards the south, later turning towards SSE and SE. Features associated with gacial events marking small advances or halts of the ice-front during the deglaciation in late Younger Dryas and early Preboreal time have been detected within map-area. The Geiteryggen Ice-marginal deposits are correlated with the Ski Ice-marginal deposits in the Oslofjord region and dated to c. 10 000 years B.P. The mapped area was ice-free 9,850-9,800 years B.P. Short accounts are given on shorelines and shore-level displacement. The potential for different utilization of the superficial deposits is also briefly discussed.

The superficial deposits and their morphological features within the area of map-sheet Nordfjordeid, western Norway, are classified and described. Ice movements and the course of the deglaciation are reconstructed. The oldest ice movements had a flow direction towards N and NNW almost independent of the underlying topography. Younger ice movements were directed by the fiords and valleys with flow directions mainly towards W. The deglaciation of the area took place in Allerød and Younger Dryas (11,800-10,000 B.P.), interrupted by two readvances: the Vardehaug moraines (10,700-10,600 B.P.) and the Nor moraines (10,500-10,000 B.P.). Outside the area covered by the inland ice cirque glaciers and glacier caps developed in Y. Dryas, indicating a glacial level limit 650 m lower than today. The Nor level is the most distinct marine level in the area having a dip of 1,4 m/km towards WNW. Tills are subdivided according to thickness and occur mostly where metwater reached the sea at the time of deposition, c. 40-70 m a.s.l. Fluvial deposits are found along rivers and mainly as reworked glaciofluvium in the area between the glaciofluvial deposits and the present sea-level. Marine deposits, mainly found in Eidsdalen and along the sides of the fiords, are deposited in areas which were submerged during the deglaciation. Weathered material is present mainly in areas higher than 1000 m a.s.l. Fluvial deposits are found along rivers and mainly as reworked glaciofluvium in the area between the glaciofluvial deposits and the present sea-level. Marine deposits, mainly found in Eidsdalen and along the sides of the fiords, are deposited in areas which were submerged during the deglaciation. Weathered material is present mainly in areas higher than 1000 m a.s.l., and rapid mass-movement deposits found at the base of the steep hills and valley sides.

The superficial deposits within the map-sheet Kilebygd, southeastern Norway, are classified and described. Most of the area is dominated by exposed bedrock or a thin and discontinuous cover ot till. In the Nordsjø-Vollsfjorden and Skien basins, below the marine limit(c. 145 m a.s.l), fine-grained marine sediments dominate. A large glacifluvial deposit, Geiteryggen, exists at the eastern end of Nordsjø. Ice movements and the course of deglaciation are constructed. The oldest ice movement was towards SSE, later turning towards SE and ESE. Features associated with glacial events marking small advances or halts of the ice-front during the deglaciation in late Younger Dryas and early Preboreal time have been detected within the map-area. The Geiteryggen frontal deposit with the Ski Moraine in the Oslofjord region and dated to c. 10,000 years B.P. The mapped area was ice-free about 9,850-9,900 years B.P. Short accounts are given on shorelines, shorelevel displacement and pollen analysis. The potential for different utilization of the superficial deposits is also briefly discussed.

The superficial deposits within the area of map-sheet Reisadalen, 1734 III, in nothern Troms, North Norway, are classified according to their genesis and described. Ice movements and the course of deglaciation are reconstructed. The Reisafjord moraines are correlated with the Tromsø-Lyngen or the Ra moraines of Younger Dryas age. The younger Storbakken, Bergmo and Sappen moraines are of Preboral age, formed 9900-9800 B.P., 9700-9500 B.P. and 9400±250 B.P., respectively. Short accounts are given on shorelines, shore-level displacement and pollen analyses. Till and weathering material cover large areas of the mountainous regions. The bottom of the valley is filled with loose deposits with thicknesses up to 200 m. Large deposits of glaciofluvial and fluvial material represent valuable sand and gravel resources in the area. The potential for different utiliziation of the superficial deposits is also briefly discussed.

The superficial deposits within the map-sheet Nordatugu, southeastern Norway, are classified and described. Most of the mountainous areas are dominated by exposed bedrock or a thin and discontinuous cover of till. In the main valleys, below the marine limit (c. 150 m a.s.l.) fine-grained marine sediments dominate. Large glaciofluvial deposits exist in the valley of Saua, north of Nordsjø. Chemical analyses have been carried out on samples from the superficial deposits. Ice movements and the course of deglaciation have been reconstructed. The oldest ice movement was towards the south, later turning towards SE and ESE. During the deglaciation of the mapped are, there were three glacial events marking advances or halts of the ice-front. The Geitryggen event is correlated with the deposition of the Ski Moraine in the Osdlofjord region and dated to c. 10 000 years B.P. Most of the Nordagutu area was still covered by ice at this time. The younger Akkerhaugen and Nordagutu events have been dated to c. 9800-9750 years B.P., respectively. Short accounts are given on shorelines, shorelevel displacement and pollen analyses. The potential for different utilization of the superficial deposits is also briefly discussed.