Major tectonic processes illustrated with examples from the

Major tectonic processes illustrated with examples from the Geology of Norway • • • Intro and overview of the Late Proterozoic to Permian tectonic evolution Baltica becomes a tectonic entity The margins of Baltica Early deformation along the Caledonian margin Ophiolites and island arcs Towards continental collision and the Scandian orogeny Late to post-orogenic tectonic processes Late Palaeozoic continental rifting Start of a new Wilson cycle

1 WHERE DO WE FIND EVIDENCE FOR EARLY-CALEDONIAN (PRE-SCANDIAN) TECTONIC EVENTS ALONG THE CALEDONIAN MARGIN OF BALTICA? 1) W- Finnmark/E-Troms (pre-490 Ma) 2) Central Sweden-Nordland (pre-490 Ma) 2 3) Otta-Foldal-Røros (pre-470 Ma) 4) Atløy (pre 450 Ma) 4 3 6 5 5) Jæren (? ) 6) Cromite in Seds in foreland ca 470 The telescoped Caledonian margin of Baltica

Seiland Igneous Province 650 Ma + 525 Ma 608 ± 1 Ma Otta Atløy From: Modified from Rehnström et al. 2002 From Svenningsen et al. 1993

Well documented pre-Silurian orogenic event at ca 450 Ma W-Norway From: Andersen et al. 1990

MAJOR EVENTS DOCUMENTED FROM BALTIC TERRANES (deformation/metamorphism in rocks belonging to the Caledonian margin of Baltica) From: Andersen et al. 1998

OUTBOARD ACTIVITY: From the Ægir Sea to the Iapetus and Tornquist Oceans The oldest supra-subduction zone ophiolites and island-arc complexes in the Scandinavian Caledonides (`Group 1´) formed in this time-span in the Early to Middle Ordovician (495 to 465 Ma) while Baltica started to drift northwards with velocities up to ~10 cm/yr

Plate-tectonic velocities of Baltica quantified by pal-mag. data (Torsvik & coworkers) Timanian From: Torsvik & Rehnström 2002

`Group 1´ type ophiolites and island-arc complexes: • Situated within the Upper Allochton between Karmøy in the south and Lyngen in the north • Ages spanning 495 to 465 Ma (within uncertainty) with the Leka, Karmøy ophiolites as the oldest and arc-plutons and volcancs as the youngest • Both spreding axis and arc-magmatism have geochemical subduction zone signatures Lyngen Narvik Leka Gjersvik Trondheim area Otta-Foldal Roberts et al. 2002 Subduction polarity away from Baltica, eventually build-up of mature arcs Bergen Bømlo/Stord Karmøy

Arc-related plutons AGE OF GROUP-1 OPHIOLITES/ISLAND -ARCS From: Pedersen 1992 From: Roberts et al. 2002

Closure of the Tornquist Ocean “Soft docking” of Avalonia before the Late Ordovician ?

MATURE ISLAND-ARC VOLCANIC AND COMPOSITE PLUTONIC COMPLEXES BUILD DURING THE MIDDLE TO LATE ORDOVICIAN Bindal-Helgeland Smøla-Hitra Up Hovind Gp. Sunnhordland

INTRA-ARC INCONFORMITIES BELOW MID-LATE SILURIAN OR DEVONIAN CONGLOMERATES (UCF-3) IN SUNNHORDLAND

IAPETUS IS CLOSING AND CONTINENTAL COLLISION TAKES OVER FROM THE WENLOCK

THE LATE-SILURIAN FULL SCALE COLLISON BETWEEN BALTICA AND LAURENTIA