REGIONAL KARTLEGGING

The superficial deposits within the map sheets are discribed and classified according to their genesis. Within map sheet Brattvåg both land and sea areas are mapped. The dominant deposits are tills, marine sediments, weathering material and bogs. The area has been glaciated at least three times during the Weichselian with intervening interstadial periods. The last deglaciation occured some time before 12,300 years B.P., and several moraines were deposited. During Younger Dryas the ice front was situated far to the east of the area, but several cirque moraines were formed within map sheet Brattvåg. The regression was very rapid just after deglaciation and up to 9000 years B.P., but levelled off during Younger Dryas. The Holocene transgression maximum was reached at about 6000-7000 years B.P.

Petrographic and structural descriptions are presented of the different rock-types occurring within the area of map-sheet Arstaddal. The area investigated is situated in the Breiarn Nappe Complex in the Caledonides of Nordland. The rocks are divided into five units: Govddestinden Nappe, the Habresåga (Stabben) Nappe, the Sokumfjell Group, the Gråtådalen Group and the Stabbursdalen Group. The data show that there must be significant differences in age between the various units in the map-area and also that the units have different early deformational and metamorphic histories.

The superficial Quaternary deposits occuring within the map-sheet area have been classified and mapped according to their genesis. Fine-grained marine deposits dominates in the main valley below the highest postglacial sea-level. c. 1973 m a.s.l. Numerous glaciofluvially ice-contact deposits are situated in the main valley too, but only the nothernmost was built up to the sea level (true deltas). During the postglacial isostatic uplift, the rivers retransported the glaciofluvial deposits and most of this material was deposited as regression-deltas at lower levels. Above the highest sea level quaternary deposits are almost lacking except for scattered till.
Løsmasse og arealbruk: The utilization and evaluation of the superficial deposits with regards to cultivation, forestry, waste disposal, engineering, groundwater, sand and gravel resources and nature conservation, are discussed. A field trip guide to the area is presented.

The superficial deposits occuring within the mapped area are classified according to their genesis. Finegrained marine sediments are the dominating deposits. The map covers one of the biggest Preboreal glaciofluvial icefront deltas in Norway - the Hauerseter deposit. A silt layer - The Romeriksmjele - covering maine sediments, has been found to be a flood deposit settled during a Preboreal catastrophic flood. Iceflow direction has varied from SE to SV most likely being SV during maximum glaciation and during a late stage of deglaciation. Sealevel was 205 m a.s.l. during the Hauerseter event c. 9,500 BP and 150-160 m a.s.l. approx 9,200 BP. The clay deposits are severely dissected by river- and creek erosion and quick clay slides.

The superficial quaternary deposits occurring within the map-sheet area have been classified and mapped according to their genesis. Till dominates in the lower part of the area. Considerable weathering has taken place at heights above 900-1000 m a.s.l. The steepest hillsides are often covered with talus and other mass-movement deposits derived mostly from weathered material. Glaciofluvial deposits and a large number of glaciofluvial erosion channels occur in the main valleys. The ice flow direction in the area was towards the WNW during the Weichselian maximum. During the course of deglaciation the ice flow direction became more northerly, especially in the northern part of the area. The ice sheet was dynamically active in the main valleys during the entire deglaciation period. Melting features of various kinds indicate rapid melting after last (pre-Boreal) readvance. The entire area was probably ice-free between ca. 9300 and 9000 YBP.

Beskrivelse i NGU Skrifter nr 93

Beskrivelse i publikasjonen "En vandring i tid og rom, geologien i Narvik" (NGU, 1995)