STRATIGRAFI

Kartet er bilag til doktoravhandlingen til Terje H. Bargel, Quaternary geoogical mapping of Central Fennoscandia and Nordland : deglaciation, deposition, stratigraphy and applications, NTNU Dr.Ing.thesis 2003:40

Kartet er fra Mid-norden project som er et samarbeid mellom GTK; NGU; og SGU i perioden 1989-1996. og viser midtnorden. Norge fra Ålesund i Møre og Romsdal til Mosjøen i Nordland, Østersund til Haparanda i Sverige, og Vaasa til Tornio i Finland

The eugeoclinal rocks of the Sulitjelma region occup a large depression in the Norwegian Caldonodrd betwwen the Nasafjell tectonic window of Precambrian rocks in the south and the Tysfjord window in the north. The age of the rocks is thought to be Cambro-Silurian. The regionl metamophism is mainly in greenschist facies in the lower units, amphibolite facies in the Gasak Nappe and greenschist to amphibolite facies in the Fauske Nappe. Some of the largest sulphide deposits in Norway are located near Sulitjelma. The different types of mineralizations occurring in the region are briefly described.

The principal geological and tectonostratigraphic divisions of the bedrock within the area of mapsheet Mosjøen are: (1) Precambrian basement rocks with minor occurrences of possible Cambrian cover sediments, (2) the Susendalen Nappe, (3) the Seve-Køli Nappe Complex, (4) the Rødingsfjell Nappe, and (5) the Helgeland Nappe Complex. Short accounts of economic geology (ores and industrial minerals) are given.

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.

The map-sheet Båtsfjord covers an area belonging geologically to the Barents Sea Region. Two major lithostratigraphic units occur within the confines of the map-sheet: the Lokvikfjellet and the Barents Sea Groups, with the former overlying the latter along an angular unconformity. The age of both groups is Late Proterozoic. The rocks in the area were metamorphosed at a very low grade during the Caledonian orogeny. The tectonic structure of the area is comparatively simple, characterized by Ne-SW trending folds with approximately vertcal axial planes.

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 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.

Three principal geological and tectonostratographic divisions of the bedrock can be recognised within the are of map-sheet Nordkapp: 1) the Kalak Nappe Complex, 2) the Magerøy Nappe, and 3) the Skarsvåg Nappe. All three nappe units form part of the Caledonian fold belt, but their internal strucutral deformation and thrusting occurred at different times during the protracted Caledonian orogenic cycle. The tectonic structures and metamorphic parageneses occurring in the different nappes are described in some detail, and short accounts are given on fossil occurrences, radiometric age determinations and aspects of economic geology. Aeromagnetic and gravity anomalies are present within the map-area, both on land and offshore, and the posiible sources of these anomalies are discussed in relation to the known geological and structural features of the region.

The main tectonostratigraphic units within the Melvær and Askvoll map-areas are: Precambrian basement rocks, allochthonous Precambrian charnokitic- mangeretic rocks of the Dalsfjord Nappe; allochthonous mainly Cambro-Silurian rocks of the Stavfjord Nappe; Devonian sedimentarty rocks. A description of the different rock types are given. Brief descriptions are also given of the tectonic structures occurring in the area and of the metamorphism of the different units. The Dalsfjord Nappe was thrust towards the south-east, probably in Early Ordovician time, and was strongly eroded before thrusting of the Stavfjord Nappe took place in the Late Silurian. The Stavfjord Nappe was thrust towards the south-east as a major asymmetric anticline - the Stavfjord Anticline - with an axial plane dipping about 40 degrees towards the north-west. A general description is given of some ore and building- stone occurrences.

Forkortet. Jæren in southwestern Norway is covered with a sheet of Late Weichselian glacial deposits which in places overlies rather thick units of older glacial and marine deposit. Younger Late Weichselian and Holocene marine sediments, eolian sand and peat cover parts of the Late Weichselian sheet. The distribu- tion of the surficial deposits was mapped, and numerous analyses of grain size, fabric, clastic roundness and pebble counts were used to characterize the depositional environments. On the basis of lithostratigraphical, bio- stratigraphical and cronostratigraphical studies, including datings by differ- ent methods, a stratigraphical model is presented for the Late Weichselian and older deposits. The model is preliminary, since the dating and correlation of deposits older than 25 000-30 000 years B.P. remain uncertain. All units in the model are mentioned in stratigraphical order.