Interactions between sedimentation and deformation in deepwater fold and thrust belts

Clark, Ian Richard 2009. Interactions between sedimentation and deformation in deepwater fold and thrust belts. PhD Thesis, Cardiff University.

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Abstract

The progress of modern hydrocarbon exploration into increasingly deepwater settings has led to a renewed interest in deepwater fold and thrust belts. Deepwater fold and thrust belts often form as a result thin-skinned compression above a ductile substrate, such as overpressured shale or salt. The compression driving deformation in these settings accommodates up-dip extension due to gravitational collapse of passive margin deltaic systems. Deformation in these settings is accompanied by a range of coeval sedimentary processes which interact with the deforming seafloor topography both at large scales to form kilometre-thick growth sequences, and at smaller scales involving individual flow events. Thus, in order to fully understand how these systems evolve, it is necessary to link structural and sedimentary processes when developing conceptual models which may then be applied to predicting facies distributions in these settings. Imaging of deepwater fold and thrust belts using three-dimensional (3D) seismic data permits detailed investigations to be carried out into the development of, and interactions between, features such as folds, growth sequences and submarine channel levee systems. Although such data has already been used to advance our understanding of many deepwater depositional systems, it has not been fully utilised to study the interactions between deformation and sedimentation in these settings. The aim of this study is to utilise 3D seismic data volumes from the Eastern Nile Foldbelt and the deepwater western Niger Delta to study the interactions between sedimentation and deformation, and to extract some general principles which can be applied to other deepwater fold and thrust belts. The scale of investigation ranges from growth sequences - which are up to two kilometres thick, to more detailed interactions between smaller scale (c. 500m in width) submarine channel levee systems and fold growth. For the first time, a coherent set of end-member interactions between submarine channel systems and evolving seafloor structures is presented. These interactions form a descriptive framework and serve as a basis for comparing submarine channel responses to deformation from various deepwater fold and thrust belt settings. Transitions between these interactions is controlled by factors such as relative timing and rates of deformation compared to sedimentation, and recognition of these interactions allows more accurate inferences to be made regarding the evolution of seafloor relief during folding. The interactions between submarine channel development and folding also depends on the fold structural style which is critical in controlling the nature of localised accommodation space adjacent to the fold. Changes in accommodation space associated with folding can result in dramatic spatial variations in channel morphology over less than a hundred metres. This study also documents the strong control on growth sequence development and internal architecture as a result of variations in structural style along strike. Relationships such as overlap and onlap can be used to predict submarine channel responses to folding, given a knowledge of the fold structural style. The internal architecture of growth sequences is also dependant on compensational stacking relationships, and the case study from the Niger Delta shows an important example of how mass transport deposits play a key role in filling local accommodation space and influencing subsequent sedimentation pathways. The results presented in this thesis demonstrate that 3D seismic data can be a powerful tool in our understanding of deepwater fold and thrust belt systems, and that linking structural and stratigraphic investigations can provide new insights into the interactions between deformation and sedimentation.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
ISBN:	9781303215353
Date of First Compliant Deposit:	30 March 2016
Last Modified:	09 Jan 2018 23:45
URI:	https://orca.cardiff.ac.uk/id/eprint/54907

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