| Summary: | This thesis investigates the origin of large-scale sandstone intrusions. A new approach combining seismic, well data, core and outcrop observations with numerical modelling has been undertaken. Two possible end members of saucer-shaped, seismic-scale sandstone intrusions from the North Sea were identified on the basis of seismic data and core observation. Diagnostic criteria were proposed to differentiate between fully and only partially injected sand bodies. Outcrop and core data presented in this thesis provide a direct example and analogue for seismic and sub-seismic scale sandstone intrusions, highlighting the brittle nature of the host rock deformation at all levels within the examined intrusion complexes. On this basis, the rheological behaviour of the host strata at the time of sand injection is inferred to be elastic with brittle fracturing. This outcome is used as an input condition for Finite Difference and Finite Element modelling that aim to test hypotheses describing triggering mechanisms and estimate their regional extent, depth and overpressures present during sand injection. The results of numerical modelling indicate that formation of the North Sea sandstone intrusions could potentially be triggered by catastrophic event(s) such as a meteorite impact or earthquakes, leading to sand liquefaction and remobilization. It has also been shown that depths at which sand injection can take place reach 1 km. Only supra-lithostatic pressures generate bodies composed of lower, bedding concordant part of intruded or depositional origin feeding inclined dykes at its marginal parts resembling those observed today on seismic data from the North Sea and in outcrops.
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