Skip Navigation LinksEXCURSION NO 34 > Programme

Scientific Outline and General Schedule:  Following is a brief scientific outline of the geology to be covered.  In addition to the principal leaders, we have enlisted others to provide local leadership on specific days, and/or to contribute important scientific information pertinent to the trip (b). Under a) we include Arne Solli, Per Terje Osmundsen, Tor Grenne, Herman van Roermund, Hans Vrijmoed, and Michael Terry.   Under (b) we include Kurt Hollocher, Tom Krogh and Robert D. Tucker,

Day 0 (Thursday): Arrive in Östersund. Evening presentation on maps and tectono-stratigraphy. 

Day 1 (Friday): The orogenic front and detailed stratigraphy of Cambrian autochthon and Cambrian-Ordovician-Silurian Lower Allochthon near Östersund. Demonstration of the Ordovician Lokne Impact structure.

Day 2 (Saturday):  Stratigraphy and tectonics of the Offerdal, Särv and Seve Nappes. The Offerdal consists of mylonitized metasediments and Precambrian granites, the Särv of Late Neoproterozoic sandstones including Vendian glacials cut by diabase dikes intruded during opening of Iapetus, and the Seve of medium- to high-grade metamorphic rocks with a pre- to early Scandian evolution. 

Day 3 (Sunday): Nappes and basement windows toward the Norwegian border area with evidence of forward and backward extensional detachments. Metamorphism and deformation of high-grade rocks in the Seve Nappe, Handöl ophiolite and Köli Nappes.  Weather permiting, we will take a cable car high up and far above tree line on the mountain Åreskutan to hike over garnet-bearing migmatitic gneisses and migmatitic mafic pyroxene granulites.

Day 4 (Monday): From the Swedish border across the enormous Trondheim Nappe in the upper part of the Upper Allochthon, with emphasis on Ordovician stratigraphy with turbidites and volcanics under low-grade conditions, especially large exposures beside Trondheimsfjord.

Day 5 (Tuesday): A traverse from Trondheim to Brekkstad and return with two ferry crossings.  Emphasis will be on the deep infolding of nappes into the Precambrian basement of the hinterland, on the extensive orthogneissic units in the Upper Allochthon composed of Ordovician arc plutons, on the Agdenes ductile extensional detachment, on the Høybakken ductile to brittle extensional detachment and associated Devonian sandstone basin, and on the contribution of zircon and titanite geochronology to deciphering tectonics. 

Day 6 (Wednesday): The first part of this day will be occupied in the Upper Allochthon with the Ordovician (Llanvirn) stratigraphy and paleontology with Laurentian affinities near Holonda,  with the overlying Caradocian section, and with the Løkken volcanic-hosted massive sulfide deposit located in inverted position in the early Ordovician Løkken ophiolite.  The end of the day will involve the classic Oppdal flagstone and augen gneiss localities of the Middle Allochthon on the east side of the Trollheimen window, and then a quick traverse across the Trollheimen basement antiform via the deep Driva Valley to the fjord at Sunndalsøra.

Day 7 (Thursday): The morning will be occupied with travel through fjord scenery to Molde and ferry to Otrøya.  In the afternoon we examine the Uglevik Garnet Peridotite/Pyroxenite made famous by the discovery of pyroxene exsolution from garnet, indicative of pressures in the Mid-Proterozoic mantle up to 80 kbar.  These rocks may have been tectonically interleaved into Western Gneiss Region basement by processes involving Late Neoproterozoic continental extension during the formation of Iapetus and basement imbrication during continental collision, including imposition of UHP metamorphic conditions.  Two more ferries follow to our overnight location on Lepsøy.  Eclogites may be seen at any time on Days 7, 8 & 9.

Day 8 (Friday):  Late morning ferry to mainland and day along coast to view extreme attenuation and extreme strain partitioning of nappes of the Upper, Middle and Lower Allochthons in the Moldefjord and Helleneset belts in a zone of orogen-parallel sinistral constrictional deformation and related mylonites.  Note that days 8 and 9 can be switched depending on weather.

Day 9 (Saturday): Morning ferry to Haramsøya-Flemsøya to examine superbly exposed eclogite-facies structural and metamorphic features with orogen transverse shear zones and tubular folds, and superimposed later amphibolite-facies orogen parallel constrictional deformation in top west and sinistral shear.  Stops include eclogite-facies shear zones in pristine 1466 Ma Haram Gabbro, Åkre amphibolite-facies mylonite, Ullaholmen world-class subhorizontal late extensional tubular folds, Flem Gabbro transformed into eclogite with 410 Ma metamorphic zircons, Kvalvika garnet peridotite - pyroxenite preserving a P-T path to 750oC, 40 kbar with eclogite envelope, eclogite-facies tubular folds, and Nogva UHP kyanite eclogite.

Day 10 (Sunday): A) Water taxi from Lepsøy to Ålesund Vigra Airport for travel to Oslo, Trondheim, Bergen or Stavanger and out of Norway; B) Ride back to Molde Årø Airport for afternoon flight to Oslo, Trondheim, Bergen or Stavanger, or C) Ride back in vans by a different route to Trondheim , including 2-3 geologic stops and the Atlantic Highway, arriving in evening.  One of the stops near Bud, if not reached already on Day 7, an ultramafic lens containing micro-diamonds, and with a phase assemblage suggesting equilibration at 55 kbar.