FOSSIL

The Ordovician successions of the Oslo Region are subdivided in terms of a modern lithostratigraphical scheme. Twenty-nine formations are defined; some of which are subdivided into stratigraphical or geographical members. Type localities (including hypostratotypes) are designated and many illu- strated by measured sections. Provisional correlations with the standard British and the Baltic chronostratigraphical schemes are made but highlight the lack of good bio- stratigraphical controls at several levels. The Tremadoc to Llanvirn litho- stratigraphy shows considerable uniformity over the Oslo Region but the remainder of the Ordovician shows some marked lithofacies contrasts between, and even within, districts.

The Ranafjorden area in northern Norway is a region of increased seismicity and
anomalous land uplift. There is evidence for recent movements in the bedrock;
1) A total of 0.89 m uplift of a bladder wrack mark from 1894 to 1990 in
Hemnesberget; 2) Anomalous low uplift of the islands of Hugla and Tomma in the
outer Ranafjorden area (0,0 0.06 and 0.07 m from 1894 to 1990 compared to 0.25-
0.30 m in the area to the north and the south); 3) Associated with the 1819
magnitude 5.8-6.2 earthquake in the Ranafjorden area, an uplift of a shallow
sea floor above sea level during an aftershock was reported in the bay Ut-
skarpen. During the main earthquake a major land slide occurred at the same
location. This earthquake is the largest North European near-shore earthquake
recorded in historical time; 4) An uplift of approximately 1 metre of a farm-
house in the 1870's at Båsmoen. The observation has been made relative to the
two neighbouring mountains Snøfjellet and Høgtuva. 5) Approximately 0.5 m
uplift of a boathouse in the bay Straumbotn during the last 50 years.
There are, consequently, indications of recent faulting in the Ranafjorden area
It is, however, difficult to find conclusive evidence for postglacial and
present-day movements along specific faults. We have therefore established
a Global Positioning System (GPS) network designed to measure the active
geological strain in the area.

Denne rapporten gir en oversikt over de viktigste kalksteinsprovinsene med tilhørende forekomster innenfor GEOS-området. Det er 4 områder med forekomst av kalksteiner der det har vært drift tidligere: Totenområdet, Lunnerområdet, Oslo-Drammen-Holmestrandområdet og Skien-Langesundområdet. 4 forekomster er i drift: Steens kalkbrenneri ved Furuberget nord for Hamar, Franzefoss Hole ved Bøverbru, Ringerike kalkverk ved Steinsfjorden og Kjørholt og Bjørntveig gruver ved Norcems sementfabrikk ved Brevik. Følgende formasjoner i Oslofeltets kambro-silur lagrekke har kalksteiner i interessante mengder, Hukformasjonen, Steinvikformasjonen, Mjøsaformasjonen, Kalvsjøformasjonen, Rytteråkerformasjonen og Steinfjordformasjonen. Ett utvalg av kjemiske analyser viser at alle forekmostene har en sammensetning som tilsvarer kalkstein, dolomitt er ikke påvist. Ingen av kalksteinene inneholder skadelige nivåer av tungmetaller eller skiller seg ut ved uvanlig sporelementinnhold, den kjemiske variasjon er imidlertid stor.
(Forkortet)