Transcript Major tectonic processes illustrated with examples from the Geology

Major tectonic processes illustrated with
examples from the Geology of Norway
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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
B
Archaean
Svecofennian
A
Transscandinavian
Igneous Belt
Sveconorwegian
Paleozoic
> 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 616Ma
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
600-570Ma 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
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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)
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3) Otta-Foldal-Røros
(pre-470 Ma)
4) Atløy
(pre 450 Ma)
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5) Jæren (?)
6) Cromite in Seds in foreland
ca 470 The telescoped
Caledonian
margin of Baltica