Quantification of tectonic controls on the distribution and architecture of deep-water facies during the growth of the toe-thrusts region of the Niger Delta
File(s)
Author(s)
Pizzi, Marco
Type
Thesis
Abstract
Using 3D seismic data, the deep-water fold and thrust belt of the southern lobe of the Niger Delta has been investigated over an area of 4500 km2 to document, for the first time, the detailed growth history of a thrust array and how it controlled the distribution and architecture, through time, of the coeval deep-water sedimentary systems. Quantification of the growth of each structure has been achieved using line-length balancing and yielded measures of cumulative shortening and strain, and their evolving rates, along and across strike and through time. This has enabled a new model for thrust growth to be proposed and linked to the observed change in stratigraphic architecture. The results show that all thrusts nucleated coevally in the study area as small segments, deforming at low strain rates, which caused the deflection of early leveed channels. The progressive lateral propagation and linkage of the segments, along with an increase in strain rates, caused the spatial restriction of the slope channels, until it induced the deposition of ponded lobes and the alteration of the channel architectures into erosional forms. The later decrease in strain rates and smoothing of the topography linked to the deposition of channelized sheets within shallow-ponded basins. These observations lead to the development of a predictive facies model where the occurrence of a specific facies (the architecture) is explained depending on when and where (along strike) a channel (or flow) interacts with a given fold. The specific location where channels cross structures, in turn, is dictated by how deformation is partitioned between structures across-strike, and by the particular distribution of strain rates along-strike. Distribution and architecture are effectively two linked variables which depend on a set of evolving parameters during the growth of a thrust array; the cumulative strain, strain rates and degree of fault linkage.
Version
Open Access
Date Issued
2019-09
Date Awarded
2020-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Mayall, Mike
Lonergan, Lidia
Whittaker, Alexander
Sponsor
Natural Environment Research Council (Great Britain)
Publisher Department
Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)