ISAVSMELTING

The superficial deposits within the map-sheet are classified genetically and described. The ice-marginal line "Tingvolltrinnet" is reconstructed from the positions of terminal moraines in the fjord areas. Radiocarbon dating of these moraines shows that the readvance occurred some 12 000 years ago. Short accounts of the distribution of glaciofluvial deposits are given. Diverse technical tests have been carried out on the gravel samples and are summarized in the "Grusregister".

The superficial deposits ocurring within the map-sheet area are classified according to their genesis and described. Till is the dominationg sediment, but considerable glacifluvial deposits also occur. Glacier movement directions have been recounstructed in eight phases and subphases. The three youngest subphases correlate with events during the deglaciation. The older phases are considered to span most of Weichselian time. Of the eight glacial events known form the Porsangerfjord area, four occur within the map-area: the Repparfjord event (Older Dryas?), the Gaissa and the Main events (mainly Younger Dryas?) and the Rotnes event (early Preboral?). Extensive deposits, mainly glacifluvial, are related to the Main event. Radiocarbon datings are lacking and suggested ages are based on correlation with dated events in Troms.

The superficial deposits occurring within the map-area are described and classified according to their genesis. In the mountains, till and organic deposits dominate. In the lowland areas glaciofluvial and glaciomarine sediments were deposited at a sea-level situated c. 175 m above the present one. During the shoreline displacement these sediments were strongly influenced by fluvial erosion and slides. The ice recession was interrupted by a glacial advance which took place dUring the first half of the Younger Dryas Chronozone, reaching just to the north of the map-area. Another glacial advance can be traced from the southwestern part of the map towards Reinsfjell and possibly to the western part of the lake Selbusjøen. These marginal moraines were deposited during late Younger Dryas. Short accounts are given on the potential for different utilization of the superficial deposits.

The superficial deposits occurring within the area of this map-sheet are classified according to their genesis and described. Based on glacial striae and till stratigraphy 3-4 regional and one (youngest) local icemovement directions are reconstructed. During deglaciation the meltwater was ice-directed. Three phases in the deglaciation are distinguished on the basis of changing meltwater drainage routes.

The superficial deposits within the area of the map-sheet Askvoll, in western Norway are classified and described. Ice movements and the course of deglaciation are reconstructed. The thin and discontinous cover of till and the weathering material are the most extensive deposits in the area. The bogs and the marine deposits are of some economic importance, being used for cultivation. Two glaciation phases are reconstructed on the basis of glacial striae. Ice movement during the older phase was towards the west; this must have been of the pre-Younger Dryas age. The younger phase corresponds well with the Younger Dryas end moraines. Grain-size and lithological analyses have been carried out on the superficial deposits. The tills are dominated by material from the local bedrock, and their predominant grain sizes are those of sand and gravel. Geochemical analyses have also been carried out on superficial deposits.

The superficial deposits occurring within the map-sheet are described and classified according to their genesis. Short accounts are also given on sand and gravel resources and groundwater resources. Ablation till and sandy basal till are the dominant deposits. The till cover is mostly continous and thick. The biggest glaciofluvial and fluvial deposits are situated at the mouths of the main valleys. There are also concentrations of these sorted, sandy and gravelly deposits along the main meltwater drainage routes at Hunder in Gudbrandsdalen, and south of Sjusjøen. A fine-grained bluish grey basal till, named the Jørstad till, dominates at 2 m and more below surface througout the area, but mainly in the valleys. The ice flow direction during the initial part of the last glaciation followed the main valleys.
Subsequently the ice movements were directed to the SE. In the next phase the
ice movement were to the SSE-S and locally to the SSW. During the course of
deglaciation the ice movements gradually turned towards lake Mjøsa both
from the west and from the north. The last local ice movements followed the
main valleys. There are indications of a water level at about 180 m a.s.l.
near Lillehammer and at Vingrom 6 km south of Lillehammer. The water level
in lake Mjøsa at Lillehammer sank below 130 m a.s.l. prior to 8.200 years B.P.

The superficial deposits occurring within the map-sheet are classified and described according to their genesis. The ice-marginal lines - Repparfjord- trinnet and the younger Hovedtrinnet - are reconstructed and it is suggested that these events belong to the Older Dryas and Younger Dryas chronozones, respectively. Till and weathering material (blockfield) dominate the superficial material. Glaciofluvial and fluvial deposits occur mostly in the main valley, Repparfjorden. Several well-defined meltwater channels are present in the Skaidi area. These channels might indicate that meltwater runoff increased when the front of the glacier reached this point of the valley. Seismic profiles have been used to calculate the volume of some of the glaciofluvial deposits. Various geotechnical tests have been carried out on some of these sediments in order to classify them for technical purposes.

The map-sheets Lønsdal and Graddis, 2128 III and 2128 II, cover parts of the area of a Quaternary mapping programme carried out by NGU in the Saltfjellet district of Nordland, north Norway. The superficial deposits are classified according to their genesis and described. The directions of ice movements have been reconstructed mainly on the basis of glacial striae and drumlins, and the coarse of deglaciation established based on ice movements, marginal moraines, meltwater drainage and the distribution of glacial deposits.

The map-sheet Bjøllådal, 2028 II, covers a part of the area of a Quaternary mapping programme carried out by NGU in the Saltfjellet district of Nordland. The superficial deposits are classified according to their genesis, and described. The directions of ice movements have been reconstructed mainly on the basis of glacial striae and drumlins, and the course of deglaciation established based on ice movements, marginal moraines, meltwater and the distribution of glacial deposits. The ice movements can be divided intor three main phases: 1) The oldest observed movement direction, towards the west. 2) A younger movement directed towards the northwest. 3) At the end of the deglaciation all the high mountains were ice-free, but glacier tongues flowing from the inland ice further east still occupied the valleys. During the deglaciation c. 9000 yrs. B.P. there were readvances of the inland ice, each one depositing marginal moraines, glaciofluvial and glacio- lacustrine deposits. At the end of the deglaciation extensive ice-dammed lakes developed, especially in Bjøllådalen where ice movements and meltwater drainage were directed towards the north, opposite to the present drainage of Bjøllådalen. The last ice remnants were located in the main valley. Dunderlandsdalen were the ice front receded towards the east. Till is the most common deposit, thick deposits occurring mainly in the valleys.

The superficial deposits within the map-sheet Hølonda were formed during the Late Weichselian and Holocene. At the time of deglaciation the sea-level was situated ca. 175 m above the present one, and fine-grained marine sediments were deposited distal to ice-marginal glaciofluvial deposits. In the central part of the map area the superficial deposits are dominated by till and glaciofluvial sediments. In the mountainous areas the till cover is generally thin and discontinous. The ice recession occurred during the Allerød (12 000-11 000 years B.P.), but remnants of glacier may still have remained in the central part of Hølonda during an early Younger Dryas glacier advance, taking place 10 800-10 500 years B.P. Short accounts are given of geological processes during the Late Weichselian and Holocene. The potential for different utilization of the superficial deposits is also briefly discussed.