Major tectonic processesillustrated 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 telescopedCaledonian margin of Baltica

WHERE DO WE FIND EVIDENCE FOREARLY-CALEDONIAN (PRE-SCANDIAN)

TECTONIC EVENTS ALONG THE CALEDONIAN MARGIN OF BALTICA?

11) W- Finnmark/E-Troms (pre-490 Ma)

2

2) Central Sweden-Nordland (pre-490 Ma)

3

3) Otta-Foldal-Røros (pre-470 Ma)

4

4) Atløy (pre 450 Ma)

5

5) Jæren (?)

6

6) Cromite in Seds in foreland ca 470

608 ± 1 Ma

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

From: Modified from Rehnström et al. 2002 From Svenningsen et al. 1993

Atløy

Otta

Seiland Igneous Province 650Ma + 525Ma

Well documented pre-Silurian orogenic event at ca 450 Ma W-Norway

From: Andersen et al. 1990

MAJOR EVENTSDOCUMENTED FROM BALTIC TERRANES

(deformation/metamorphismin rocks belonging to the

Caledonian margin ofBaltica)

From: Andersen et al. 1998

OUTBOARD ACTIVITY:From the Ægir Sea to the

Iapetus and Tornquist Oceans

The oldest supra-subduction zoneophiolites and island-arc complexesin the Scandinavian Caledonides(`Group 1´) formed in this time-spanin the Early to MiddleOrdovician (495 to 465 Ma) whileBaltica started to drift northwardswith velocities up to ~10 cm/yr

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

From: Torsvik & Rehnström 2002

Timanian

Plate-tectonic velocitiesof Baltica quantified by pal-mag. data (Torsvik & coworkers)

`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

Karmøy

Bømlo/Stord

Bergen

Trondheim area

Otta-Foldal

Leka

Narvik

Lyngen

Gjersvik

Roberts et al. 2002

Subduction polarityaway from Baltica, eventuallybuild-up of mature arcs

From: Roberts et al. 2002

From: Pedersen 1992

AGE OF GROUP-1 OPHIOLITES/ISLAND -ARCS

Arc

-rel

ated

plu

ton

s

“Soft docking” of Avaloniabefore the Late Ordovician ?

Closure of the Tornquist Ocean

MATURE ISLAND-ARCVOLCANIC AND COMPOSITEPLUTONIC COMPLEXESBUILD DURING THE MIDDLETO LATE ORDOVICIAN

Smøla-Hitra

Up Hovind Gp.

Sunnhordland

Bindal-Helgeland

INTRA-ARC INCONFORMITIESBELOW MID-LATE SILURIAN

OR DEVONIAN CONGLOMERATES(UCF-3) IN SUNNHORDLAND

IAPETUS IS CLOSING AND CONTINENTALCOLLISION TAKES OVER FROM THE WENLOCK

THE LATE-SILURIANFULL SCALE COLLISON

BETWEEN BALTICA AND LAURENTIA