Quantitative analysis of the tectonic evolution of the North Sea has tended to concentrate on the Mesozoic and Cenozoic rifting phases (Sclater & Christie, 1983; Barton & Wood, 1984; Latin & White, 1993). A Permo-Triassic phase of lithospheric extension has been recently interpreted from tectonic subsidence data from the northern North Sea (Hellinger <I>et al</I>., 1989; White & Latin, 1993; Roberts <I>et al</I>., 1995) and speculative suggestions on the influence of this phase on estimates of successive phases of rifting have been made (Hendrie <I>et al</I>., 1993). The aim of this dissertation is to examine the late Palaeozoic/early Mesozoic geological history of the southern North Sea. 631 one-dimensional stratigraphic sections were modelled by backstripping and strain rate inversion. A model of lithospheric extension accounts successfully for the observed tectonic subsidence. No previous study has undertaken a comprehensive quantification of Permo-Triassic lithospheric extension within the North Sea. Six phases of lithospheric extension in the southern North Sea, Danish Basin, Wessex Basin and East Irish Sea basin have been interpreted by modelling of water-loaded subsidence data: (i) Late Carboniferous (approximately 320 to 296 Ma), (ii) Late Permian-Early Triassic (256 to 240 Ma), (iii) Early Jurassic (208 Ma), (iv) Mid-Jurassic-Early Cretaceous (180 to 155 Ma), (v) Late Cretaceous-Early Tertiary (90 to 50 Ma) and (vi) Late Tertiary (25 to 2.5 Ma). Lithospheric stretching in the Late Permian-Early Triassic commenced at 256 Ma, and shows an acceleration in tectonic subsidence at 245 Ma. The average duration of rifting is 15 Ma and the average stretching factor, β, is 1.15. In localised areas, such as the Sole Pit Basin, β=1.16 to 1.20. In this work it has been shown that the lithospheric plate model is a valid approximation for the structure of continental lithosphere. Inverse modelling of observed subsidence data from the southern North Sea is used to estimate (i) the lithospheric thickness; (ii) the linear coefficient of thermal expansion and (iii) the basal plate temperature. The values obtained (120 ± 5 km, (3.65 ± 0.25) x 10<SUP>-5</SUP> °C<SUP>-1</SUP> and 1425 ± 125°C, respectively) are consistent with those of Parsons & Sclater, (1977).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:605068 |
| Date | January 1996 |
| Creators | Jarvis, E. L. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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