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Title: Early Cenozoic denudation of the British Isles : a quantitative stratigraphic approach
Author: Clarke, B.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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The early Cenozoic sedimentary rocks which lie offshore northern Britain have been divided using a regional stratigraphy with the highest possible resolution, as a framework in which to describe them quantitatively. Only when quantified can meaningful comparison of the sedimentary record with possible controls be made. Up to twenty coarsening-fining sequences are recognised and correlated regionally using high-resolution biostratigraphy. The duration of each sequence can be calculated by relating this regional biostratigraphy to published chronostratigraphies, which are modified in the light of new isotopic age estimates of key stratigraphic levels in the early Cenozoic. The sequences are bounded by armine condensed horizons representing extremely low sedimentation rates and have durations of between approximately 150 ka and 1.4 Ma. The depositional rates vary within each sequence by up to two orders of magnitude. Sedimentation rates increase from 50 m/My to over 100m/My at 62 Ma and reach peak values of about 300m/My at 59 Ma, which decrease during the late Palaeocene and early Eocene. The similarity between the timing of peak offshore sedimentation rates and the acme of onshore igneous activity is compelling, although perhaps circumstantial, evidence for them being signatures of a common control. Episodicity in both thermal and underplated uplift, resulting in pulsed sediment supply, are possible controls on the sub million year coarsening-fining cycles represented by each sedimentary sequence. There is little evidence of global synchroneity in transgressive-regressive cycles, and so eustatic sea level variation is unlikely to be a control. The high frequency cyclicity in British early Cenozonic sedimentation may alternatively be explained by dramatic changes in erosion rates controlled by fluctuating climate, independent of variations in uplift.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available