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Title: A global analysis of igneous sill dimensions and their effect on sedimentary basins and petroleum system : statistics and modelling of seismic observations
Author: Hoggett, Murray
ISNI:       0000 0004 8499 6713
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2019
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Igneous sill intrusion majorly impacts sedimentary basins, causing forced folding of host rocks, thermal maturation of source rocks, and basinal fluid flow changes. However, the detail of these effects has received little study. Similarly, the mechanisms by which sills are emplaced in basins are poorly understood, and emplacement mechanism may influence the aforementioned basinal impacts. The key that ties impacts and mechanisms together is that models explaining both have not been tested due to a lack of data on sill dimensions. Seismic reflection data presents a unique opportunity to collect detailed measurements on sill dimensions. Work presented in this thesis suggests that the number, shape and dimensions of sills have significant differences between sedimentary basins, having major implications for palaeoclimate modelling. Comparing theoretical sill models with measurements of actual sills undermines many models based around linear elastic fracture mechanics. However, intrusion models which incorporate an overlying elastic plate predict far more accurate sill geometries in comparison with seismic measurements. Additionally, several authors have noted that there is a discrepancy between the amplitude of forced folds and the thickness of their underlying sills. This thesis shows that a large proportion of this discrepancy can be explained by compaction of the fold after sill emplacement. While collecting data on forced folds, a seismic reflector in the Northeast Rockall Trough was mapped which displays undulose topography. Multiple observations point to this reflector being an opal A - opal CT transition. Numerical modelling and kinetic parameterization of the opal A-CT indicates that this topography can arise from local lateral temperature variations. Finally, a recently published model for hydrocarbon prospectivity based on fluid flow arising from sill tips is investigated. It is demonstrated that the original study shows no evidence for the validity of the model, prompting new questions on the scale at which intrusions could affect fluid flow. This thesis therefore shows that current paradigms of sill intrusion mechanisms, palaeoclimate model parameterizations, opal A-CT formation mechanisms and intrusion related fluid flow all need to be reexamined.
Supervisor: Not available Sponsor: NERC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QE Geology