DEVON

This is a review of the structural and tectonic evolution of the Old Red Sandstone (ORS) of Svalbard put into the context of current regional geological understanding. The Svalbardian Orogenic Event, starting in the late Famennian and culminating in the Tournaisian, is emphasized and discussed in the regional context of the Ellesmerian Orogeny.

Kartlegging på Frøya og Froøyane har vist at berggrunnen for det meste er samansatt av kaledonske intrusivar som i nokre område innheld xenolittar av metasedimentere bergarter med ukjend alder. På Frøya og i ein del område i Froan er bergartene sterkt folierte og har ein gneissliknande tekstur. Elles ser ein primære magmatiske teksturar i bergartane. Tonalittar og granodio- rittar på Frøya er kalk-alkaline, medan høg-K kalk-alkaline monzodiorittar, kvartsmonzonittar og grandodiorittar med jamnkorna eller porfyrisk tekstur dominerer på Froøyane. Fleire av bergartane har høgt innhald av Sr og Ba, og (87 Sr/86 SR)0-veridiar ligg stort sett mellom 0.705 og 0.710. Bergartane utgjer den nordlege delen av Smøla-Hitra-batolitten, og undersøkingane så langt tyder på at dei høyrer til same typen som ein finn i sørlege delen av denne batolitten og i delar av Bindalsbatolitten i Helgeland. Eit område med devonsk konglomerat dekker eit ca 10 km2 stort område ved Vingleia Fyr. Bergarten er dominert av svært grove konglomerat med bolletypar som viser at dei granittiske bergartane i aust mest truleg har vore kjelde for avsetjingane.

In July 1996, a team of researchers visited the "Troll" and "Jotun" springs of northern Svalbard to carry out mapping and sampling activities. The main conclusions of the hydrochemical survey will be reported in scientific articles in the journals "Geothermics" and "NGU Bulletin". This report serves to document the data used in these articles and to present an unpublished assessment of analytical techniques applied to the trace element geochemistry of solid (rock and travertine) samples.

In the first part of the report, a synopsis is presented of the general geology and tectonostratigraphy of this part of Central Norway, with a slightly more detailed account given of the geology of Fosen Peninsula. The second part comprises an excursion guide, spanning 3 days, covering the southern district of Fosen from Rørvik to Ørland and to the outer coast near Sandnes; and then continuing along the Verran Fault (Møre-Trøndelag Fault Complex) via Verrabotn and Beitstadfjorden to Steinkjer. The last day of the excursion takes in selected localities along the southeastern side of Trondheimsfjorden, finishing at Storvika close to Trondheim airport Værnes. The excursion aims to show the variety of rock-types at different tectonostratigraphic levels in this part of the Caledonides, and demonstrates the significance of faulting and diversity of fault trends, fault rocks and vein systems of a variety of ages in this onshore region adjacent to the Mid-Norwegian continental shelf. A preliminary version of this report and guide was distributed to participants during the actual excursion, 2-4 September 1998 - days blessed by warm, sunny weather. The excursion was the first in the project "Basin analysis and applied thermochronology on the Mid-Norwegian Shelf", otherwise known as the "BAT project".

Many modern accounts of Devonian rocks of western Norway, which emphasise the extensional phenomena affecting them, tend to ignore or gloss over the deformation and metamorphism which these rocks have suffered during contractional deformation. The present account describes extensive ductile folding, penetrative cleavage formation and low-grade metamorphism developed in the Devonian rocks of the Scandinavian Caledonides share a common tectonothermal development. In summary, the bulk observations support a regional contractional event which, conceptually, may relate either to a Mid-late Devonian arc-continent collision, or to a transpressional strain regime.