The Wilson Cycle - Episode 3 - Ocean's Closing
Channel: PHAB Outreach
Date: 2022-07-08

The third of four episodes of "The Wilson Cycle" series.  This is Episode 3: Closure of Major Oceans by Subduction. 

In this episode, we look at computer simulation of oceanic closure, island-arc and back-arc-basin formation by subduction and at the field-evidence for the initial intra-oceanic subduction-related formation of island-arc magmatism. We visit a large granodiorite formed by partial melting and intrusion in an island-arc above an intra-oceanic subduction zone. This island-arc magmatism took place in late Ordovician at 445 million years ago, shortly before the final closure of the Iapetus Ocean in the Middle Silurian. We study the evidence for how the granodiorite was exhumed to the surface during and after the Caledonian continental collision. We also look at the structural and stratigraphic evidence for how parts of the former Oceanic Crust, the Solund Stavfjord Ophiolite, was pushed up onto the margin of Baltica in the final stages of the closure of the Iapetus Ocean in the  Middle Silurian around 430 to 428 million years ago.

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Join us to discover the Wilson Cycle, one of the most fundamental concepts in geology. The “Wilson Cycle” explains the process of orogeny, which related to the formation of the world's large-scale mountain belts by a series geological events. The various elements of Wilson Cycle (and the Supercontinent Cycle, more broadly) have underpinned and inspired many of the research undertaken over the last 10 years at CEED. 

Production, financial support and acknowledgements:
The Centre for Earth Evolution and Dynamics (CEED) at the University of Oslo (UiO), Norway. 
License: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Professor Torgeir B. Andersen (CEED, UiO) and his former PhD students/Post Doc at CEED, Dr Hans-Jørgen Kjøll (now at IG-UiO) and Dr Johannes Jakob (now at NGU) guide us through the geotraverse and explained details of the geological observations.

Dr Valentina Magni (CEED, UiO) shows and explains some computer simulations to illustrate elements of Wilson Cycle Tectonics, such as subduction and Island-arc formation and eduction.

Dr Dougal Jerram (CEED, UiO) is the narrator, asks all the important questions and introduces and summarise explanations underway.

Assistant Professor Owen Anfinson (Sonoma State University, U.S.A) helped with skilful drone-piloting under the instruction of main photographer Andrew Blix, who together with Dougal Jerram have edited and produced the final four clips of our Wilson Cycle movie.

Norwegian Research Council's financial support to CEED and the Fri-Nat Project “Hyper-extension along the Pre-Caledonian margin of Baltica” together with the INTPART NOR-R-AM and NOR-R-AM2 "Changes at the Top of the World through Volcanism and Plate Tectonics: Arctic Norwegian-Russian-North American collaboration" project financed the film project.

SGC (Sunnfjord Geo-Centre) with Einar Alsaker is thanked for help and guidance during visit to the Staveneset copper mine. Knutholmen A/S w/Svein Fosse provided the boats used during filming.

We hope you enjoy the series!