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Title: The influence of confinement on turbidite sheet systems depositional architecture
Author: Liu, Qun
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2019
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Turbidite sheet systems have various depositional architectures, whose differences are likely to be the result of variations in flow efficiency and degree of confinement. Recent depositional models on turbidite sheet systems have been built up largely based on unconfined sandy systems. A more comprehensive framework is needed to encompass all turbidite sheet systems. The research is fieldwork-based and focuses on comparing depositional architecture differences of five contrasting units that exhibit deposits of flows with differing flow efficiency and confinement. Four of these occur in the Mississippian/Pennsylvanian Paganzo Basin in NW Argentina and one occurs in the late Cretaceous age Magallanes Basin in Chile. The thesis established a semi-quantitative way of assessing the degree of confinement in turbidite sheet systems by dividing the flow efficiency by the maximum preserved basin dimensions. Individual beds are found to obey power law decay in highly confined turbidite sheet systems, whereas they obey a logarithmic decay in unconfined and loosely confined systems. In highly confined settings, individual beds stack vertically, whereas in unconfined systems, individual beds stack compensationally. Five facies associations (axis, off-axis, lateral fringe, distal-fringe and frontal fringe) have been identified in unconfined systems and they follow linear transitions from axis to distal fringe; only one facies association has been identified in confined turbidite sheet systems and does not show spatial variation. The preexiting 'lobe' model and terminologies only apply to unconfined sheet systems. Below the hierarchical level equivalent to lobe complex, degree of confinement is the dominant controlling factor of turbidite sheet systems. The number of beds are much less in confined systems than that in unconfined systems at a same hierarchical level, which may indicate that less frequent flows allow the larger flows. A comprehensive framework combing flow efficiency, degree of confinement, types of facies association and rate of facies associations has been established.
Supervisor: Kneller, Ben C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Turbidites ; Basins (Geology) ; Geology