3D seismic analysis of sedimentary processes on deepwater continental margins

Heinio, Paivi Tuuli 2007. 3D seismic analysis of sedimentary processes on deepwater continental margins. PhD Thesis, Cardiff University.

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Abstract

Two 3D seismic reflection datasets from the West African and Brazilian continental margins were analysed to determine their architectural elements and to further the understanding of the sedimentary processes that control their morphology. The results suggest a strong influence of local slope variations on the sedimentary processes and depositional and erosional products within these complex deep water settings. The Niger Delta dataset is characterised by large channel-levee systems and thrust-related folds. The folds degrade by channel erosion and slope failure, which creates laterally discontinuous erosional surfaces on the crests and flanks of the anticlines and chaotic deposits at their bases. The type of slope failure depends on the length and morphology of the local slope, sediment properties and the presence of anisotropics, such as faults. The location and morphology of the channel-levee systems on the Niger Delta are affected by topographical effects associated with thrust-related folding. Fold-induced local changes in gradient cause turbidity currents to deposit sediment upstream of the folds and erode the seafloor downstream of them. This results in the formation of knickpoints along the present- day thalweg of a channel-levee system. A model for the formation and evolution of the knickpoints predicts that they migrate upstream and leave internal erosion surfaces and terraces with coarse sediments in the sedimentary record. They may be an important process by which channels cut through uplifting fold belts. The Espirito Santo Basin dataset is characterised by salt diapirs, slope failures, channels and canyons. Interaction of turbidity currents with variations in topography has led to the formation of large depressions, which occur above abrupt breaks in slope and in trails that follow underlying erosional channels. They are inferred to form by Froude-supercritical currents that become unstable as they encounter topographical irregularities, such as scarps and knickpoints. This leads to the formation of erosional scours and deposits similar to sediment waves, which, when confined within channels, appear as roughly circular depressions.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
ISBN:	9781303219344
Funders:	Cardiff University, Finnish Cultural Foundation, Helsingin Sanomat Centennial Foundation
Date of First Compliant Deposit:	30 March 2016
Last Modified:	10 Jan 2018 02:41
URI:	https://orca.cardiff.ac.uk/id/eprint/55059

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