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Title: 3D seismic analysis of the Silverpit structure
Author: Wall, Mostyn Leonard Thomas
ISNI:       0000 0004 2746 7663
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2008
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This thesis uses industry 3D seismic reflection datasets to investigate the Silverpit structure, a proposed impact crater located in the southern North Sea, UK. The principal aim of this thesis is to investigate the origin of the Silverpit structure. Research has focused on constraining the age of the Silverpit structure, investigation into regional magmatic activity in the southern North Sea study area and structural analysis of the Silverpit structure. The Silverpit structure is a multi-ringed circular structure 20 km in diameter found within Cretaceous and Eocene age marine sediments. The Silverpit structure is composed of a 3 km diameter excavated cavity is surrounded by a series of concentric listric faults. The outer rings of the structure are composed of extensional grabens and concentric folds. Within the excavated cavity, a series of localised uplifted reflections, termed the central uplift, can be identified. A boundary marks a common upper limit of deformation. Undeformed reflections above this boundary have parallel onlapping geometry onto the underlying cavity and are an indication of instantaneous creation of accommodation space. This boundary between undeformed and faulted reflections has been interpreted to be the crater floor and has been dated to be Middle Eocene in age. A tertiary dyke swarm, 54 Ma old, has been identified and mapped 20 km to the North of the Silverpit structure. The dykes are characterised by a linear seismic disturbance and linear coalesced depressions at the upper limit of the seismic disturbance. The depressions above the dyke tips formed during the release of volatiles from the intruding magma. The dykes and coalesced depressions are new Earth analogues for Martian pit chain craters. No magnetic anomaly can be identified over the Silverpit structure, ruling out an igneous origin. The age of the Silverpit structure is older than the onset of regional folding, therefore ruling out a folding/salt withdrawal origin. The circular Silverpit structure is unrelated to the underlying elongate salt geometry. Any fault growth associated with salt movement would trace the underlying salt body we would therefore expect any faults related to salt movement to be elongate, not circular. The morphology of the Silverpit structure is characteristic of an impact crater. The features mapped, central uplift, excavated crater, multi rings and folds, are all diagnostic features of an impact crater. Bolide impact is the most likely origin for the Silverpit structure as all the alternative origins can be ruled out. Importantly further diagnostic evidence is still needed to confirm the Silverpit structure as an impact crater. Until such evidence is found the Silverpit structure is classified as a probable impact crater.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available