Tectonic evolution of continental rifts. Inference from numerical modelling and fission track thermochronology
Résumé
The primary goal of the studies reported in this thesis was to incorporate the thermo-tectonic evolution of rifted basins and their margins, as recorded by fission track thermochronological data, into numerical models for rifted basin formation and evolution. Such data provide an additional constraint on these models, enabling a further discrimination between geologically feasible and unrealistic hypotheses. To this end, numerical modelling studies were performed, based on published (Chapter 2) as well as newly collected (Chapters 3-5) fission track data. As the objective of these studies is to incorporate observations on vertical motions into tectonic models, a kinematic modelling approach is employed throughout. The kinematic modelling results are interpreted by comparing them with predictions of rheological and dynamic models of extension. Chapter 2 introduces the role of different uplift mechanisms in creating the currently observed topography and erosion patterns at rifted continental margins. In Chapter 3 mechanisms of rift flank uplift are studied in more detail by looking at topography and erosion adjacent to two young intracontinental rifts: the Baikal rift (SE Siberia) and the Malawi rift (East Alrica). Chapter 4 discusses mechanism of post-rift 'passive' margin uplift, as exemplified by the morphotectonic evolution of southem Norway. In Chapter 5 the focus is turned towards the thermo~tectonic evolution of a magmatic continental rift. Finally, in Chapter 6 the main conclusions of this study are brought together and their implications for rheologieal models of the lithosphere and dynamlc models of extension are discussed.
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