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 Ga Ga Ga Supercontinent cyclisity? From Rodinia to Pangea? Does the earths 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 From: Roberts & Siedlecka 2002 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 TIME: Ma NB! Notice uncertain position of Laurentia From Torsvik and Cox, for further explanation see:Notice the Gondwana-wide Cadomian Pan-African deformation belts, also affecting the margin of Baltica (Timanian) BALTICA CERTAINLY A SEPARATE CONTINENT AT 550 Ma MAGMATIC ROCKS ASSOCIATED WITH RIFTING OF BALTICA Northern Scandianvia: Seiland Igneous Province: Ultramafics, gabbros syenites etc Gabbros 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) Atly 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) From Meert et al Fen complex ~585 Ma Hedemark lava ? Atly dykes ? Sarek dykes 608 Ma Ottfjallet dykes 665 Ma Seiland IC Ma Egersund dykes 616Ma Fen 585 Ma Second stage w nefeline- syenites U/Pb z Ma Ma VARIOUS VENDIAN CAMBRIAN RECONSTRUCTIONS Varanger Glaciation older than 595 Ma, ~ 620 Ma? Southern hemisphere, major (~ 90 0 ) anticlockwise rotation Cambrian - Ordovician older than 595 Ma ca 620 Ma? Late-Proterozoic to Cambrian stratigraphy in Scandinavia ~545 Ma Traditional 2-D conseptual model From: Kumpulainen and Nystuen 1985 ca 620 Ma ca Ma, nb! remember Timanian def in the north First signs of collision: Eclogite facies metamorphism, Seve Nappe complex; arc-collision? From Torsvik and Cox, for further explanation see: 608 1 Ma Present day Norwegian Sea analogue to a Seve nappe complex Transitional continental - oceanic crust preserved in the Seve nappe complex The telescoped Caledonian margin of Baltica WHERE DO WE FIND EVIDENCE FOR EARLY-CALEDONIAN (PRE-SCANDIAN) TECTONIC EVENTS ALONG THE CALEDONIAN MARGIN OF BALTICA? 1 1) W- Finnmark/E-Troms (pre-490 Ma) 2 2) Central Sweden-Nordland (pre-490 Ma) 3 3) Otta-Foldal-Rros (pre-470 Ma) 4 4) Atly (pre 450 Ma) 5 5) Jren (?) 6 6) Cromite in Seds in foreland ca 470