Bergen Tectonics and Thermochronology

PhD defence (press release)

"The supercontinent which was not superb enough"

Kosuke Ueda defends on friday 11. mars 2011 for the PhD-degree at the University of  Bergen with the thesis:

“Orogenic decay from collision to rifting – characteristics and implications of delamination illustrated by a case study of the East African-Antarctic Orogen in NE Mozambique”

The majority of the present continents formed a contigous supercontinent, Gondwana, around 500 million years ago. Gondwana was transected by a number of mountain belts that could be compared to the Himalaya today. Much later, rifting between East Africa, India, and Antarctica led to the formation of new oceans. Remarkably enough, this rifting took place accurately where mountains had been formed before.

The thesis investigates changes in orogenic systems which can lead to partial melting and crustal weakening following removal of mantle lithosphere. When tectonic plates delaminate in such a way, orogenic collapse is one potential consequence. The latest phases in the life cycle of an orogen are therefore characterised by large amounts of granitoid melts, slow cooling, and associated extension that can result in rifting.

For the main part, the thesis discusses the geological evolution of Northern Mozambique from mountain belt to ocean. It is shown that the transition was accompanied with initial high temperatures, extension, and subsequent slow cooling which continued for about 100 million years after the formation of the mountain chain.

In addition, numerical models show that crustal weakening of this type fades slowly and can last for even up to 300 million years, and that delamination can start while orogeny is still ongoing. It is argued that Gondwana broke up into its fragments also as a heritage of its own growth.

Kosuke Ueda was born in 1980 in Tokyo and grew up in Germany. He took a diploma (natural sciences) degree at ETH Zurich (Switzerland) in 2007, with specialisation in structural geology and tectonics. From 2007 to 2010, he worked on his PhD project at the Department of Earth Science, University of Bergen.

Time and place of trial lecture:

21.02.2011,  10:15h. Given topic: “The role of channel flow/ductile extrusion during continent-continent collision”
Place: Auditorium 5, Realfagsbygget, Allégaten 41

Time and place for public defence:
11.03.2011, 10:15h, Aud. 5, 3rd floor. Realfagsbygget, Allégaten 41

Kosuke Ueda, tlf 55 583 516, e-mail: kosuke.ueda@geo.uib.no
Media contact Gudrun Sylte, tlf. 55 58 91 70 (a),
e-mail: gudrun.sylte@uib.no

The thesis can be borrowed from the Library of Natural Sciences. For a purchase/order of the thesis, contact the candidate directly.