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Title: The rise and fall of diapirs during regional extension and its influence on the deposition of a net-transgressive coastal-plain-to-shallow-marine succession, Middle-to-Upper Jurassic, Norwegian Central Graben
Author: Mannie, Aruna
ISNI:       0000 0005 0734 4217
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2014
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Regional extension in salt basins can initiate and drive salt tectonics, which may influence sediment routing systems and reservoir distribution. Structural controls on the deposition of Middle-to-Upper Jurassic, net-transgressive, shallow-marine strata preserved on the eastern flank of the North Sea Central Graben have been studied using an integrated subsurface dataset (3D and 2D seismic reflection, wireline-log, core and biostratigraphic data) in order to: (i) characterise the main structural styles in a salt-influenced rift basin; (ii) describe the sedimentology and stratigraphic architecture of the Middle-to-Upper Jurassic succession; and (iii) investigate the role that rift-related salt tectonics had on the thickness and facies distribution of the Middle-to-Upper Jurassic, syn-rift succession. Early Triassic rifting initiated reactive diapir rise of Late Permian salt, which influenced the geometry of Triassic rafts between salt walls. Middle-to-Late Triassic differential loading and density-driven subsidence resulted in further passive diapir growth, until a depletion of salt supply led to the formation of salt welds below Triassic rafts and burial of salt diapirs. A second phase of extension in the Middle-to-Late Jurassic resulted in either diapir collapse, providing accommodation for diachronous deposition of shallow-marine reservoirs, or reactive diapir rise, which influenced the depositional thickness of these reservoirs along salt wall flanks. Sedimentological core analysis of the Middle-to-Upper Jurassic in combination with biostratigraphic and wireline-log data has identified offshore, offshore transition, lower shoreface, upper shoreface and coastal-plain deposits. These deposits are arranged into upward-shallowing parasequences bounded by flooding surfaces. The timing of transgression is diachronous, with flooding and shoreline retreat controlled by the underlying rift topography. The resulting facies architecture reflects the balance between fault- and halokinesis-driven accommodation creation, and intra- and extra-basinal sediment supply. This thesis highlights the key role that salt has in modifying the tectono-stratigraphic evolution of rift basins.
Supervisor: Jackson, Christopher ; Hampson, Gary Sponsor: Commonwealth Commission ; Centrica Energi
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral