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

The start: Short overview of the main age provinces of Fennoscandia (Baltic shield) Super-continent cyclisity? Main events of the Late Proterozoic: • Late Proterozoic Timanian (Baikalian/Cadomian) deformation in Arctic Norway • Rifting along the future Caledonian margin of the Fennoscandian shield, major igneous complexes, diatremes and dykes • The palaeocontinent of Baltica becomes an tectonic entity • The Vendian glaciation (before 595 Ma, at ca 620 Ma? ) • The Seve transitional continental - oceanic crust • The sedimentary basins and establishment of a rift margin • Sparagmites to the Cambro-Silurian foreland sequence

The main geological layout of the Baltic Shield > 2. 5 Ga 2. 0 -1. 8 Ga 1. 75 -1. 5 Ga 1. 2 - 0. 93 Ga

Supercontinent cyclisity? From Rodinia to Pangea? Does the earth´s continental lithospheric plates assemble and rift apart in longer term cycles? ≈ 500 myr. cycle? A speculative Rodinia reconstruction, ca 750 Ma Supercontinent PANGEA in the late Permian ca 255 Ma

TIME: 600 -570 Ma NB! Notice uncertain position of Laurentia The story is more complicated than a simple break-up of the supercontinent! F. example: In the Mid- to Late Vendian, we have the Timanian Orogeny; (prev. referred to as the Baikalian) in the now Arctic Norway. This reconstruction correlates the Timanian orogeny in time and space with the Cadomian of Europe, Eastern US and Canada From: Roberts & Siedlecka 2002

From Torsvik and Cox, for further explanation see: http: //www. geodynamics. no/platemotions/500 -400/ BALTICA CERTAINLY A SEPARATE CONTINENT AT 550 Ma Notice the Gondwana-wide Cadomian Pan-African deformation belts, also affecting the margin of Baltica (Timanian)

MAGMATIC ROCKS ASSOCIATED WITH RIFTING OF BALTICA Northern Scandianvia: Seiland Igneous Province: Ultramafics, gabbros syenites etc Gabbros 570 -560 Ma (Unpubl. data R. J. Roberts; pers com. 2003) Nefeline-syenite-pegmatite: 531 and 523 ± 2 Ma (Pedersen et al. 1989) Kalak nappe complex dyke complex(es) (not yet dated) Central Scandinavia: Sarek sheeted dykes: 608 ± 1 Ma (Svenningsen 1999) Ottfjellet dykes: 665 ± 10 Ma (Ar, Claesson & Roddick 1983) Southern Scandinavia: Lavas within the Hedemark “sparagmite” basin (not yet dated) Atløy dykes: (pre 450 Ma, not yet dated) Hunnedalen dykes: ~850 Ma (Ar, Walderhaug et al. 1999) Egersund dykes: 616 ± 3 Ma (Bingen et al. 1997) Fen complex: ~585 Ma (Ar, Meert et al. 1999)

Fen 585 Ma Egersund dykes 616 Ma Hedemark lava ? Atløy dykes ? Sarek dykes 608 Ma Ottfjallet dykes 665 Ma Seiland IC 570 -560 Ma Fen complex ~585 Ma From Meert et al. 1999

Second stage w nefelinesyenites U/Pb z. 531 -523 Ma

600 -570 Ma Varanger Glaciation older than 595 Ma, ~ 620 Ma? VARIOUS VENDIAN CAMBRIAN RECONSTRUCTIONS

Southern hemisphere, major (~ 900) anticlockwise rotation Cambrian - Ordovician

Late-Proterozoic to Cambrian stratigraphy in Scandinavia ~545 Ma older than 595 Ma ca 620 Ma?

Traditional 2 -D conseptual model From: Kumpulainen and Nystuen 1985

ca 620 Ma ca 610 -545 Ma, nb! remember Timanian def in the north From: Kumpulainen and Nystuen 1985

First signs of collision: Eclogite facies metamorphism, Seve Nappe complex; arc-collision? From Torsvik and Cox, for further explanation see: http: //www. geodynamics. no/platemotions/500 -400/

Transitional continental - oceanic crust preserved in the Seve nappe complex 608 ± 1 Ma Present day Norwegian Sea analogue to a Seve nappe complex

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