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Title: The thermotectonic development of southern Norway: constraints from low-temperature thermochronology
Author: Leighton, Callum Alexander
ISNI:       0000 0001 3607 9070
Awarding Body: Imperial College London (University of London)
Current Institution: Imperial College London
Date of Award: 2007
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Abstract:
This project aims to test ideas, and propose new ideas where appropriate, about the topographic development ofsouthern Norway by studying the thermal and erosional history of the region. To this end apatite fission-track (AFT) analyses from 77 samples, as well as zircon fission-track and apatite (U-Th)/He analyses are reported. All apatite fission-track ages are mid Cretaceous to late Permian. It is demonstrated that southern Norway can be separated into crustal blocks with distinct AFT ages, bound by major Caledonian structures. Inverse modelling methods are used to extract cooling histories through the upper crust for all AFT data using individual and joint-modelling strategies. Cooling is interpreted in terms of denudation chronologies which are established for each crustal block. Rapid denudation (30-100 m Ma-l ) is inferred for the whole region in the late Permian and Triassic which is linked to a period of extension, faulting and relief development w~ich may have caused accelerated erosion. In most crustal blocks this is followed by a drop in denudation rate (to <10 m Ma-l ) in the Jurassic which lasts until the latest Cenozoic when rates are highest (although poorly constrained). Local deviations from these trends indicate periods of fault reactivation in the Mesozoic and Neogene. Theories that have been proposed as ex'planations ofthe present-day topography of southern Norway· . are assessed in light ofthe new data. Mantle based mechanisms oftopographic support are a poor explanation for observed AFT ages and the data is more compatible with long-term survival (since the end-Silurian) ofa Caledonian crustal root, buoyantly supporting the present-day topography. It is argued that this latter model is both simpler and consistent with all the available data and is therefore preferable. This interpretation has implications for understanding the topographic history of Palaeozoic orogens and high elevation passive margins worldwide.
Supervisor: Not available Sponsor: Not available
Qualification Name: Imperial College London, 2007 Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.487533  DOI: Not available
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