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The kinematics of intra-salt layers during salt tectonics

Al-Habsi, Hamood 2015. The kinematics of intra-salt layers during salt tectonics. PhD Thesis, Cardiff University.
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The structures and dynamics of intra-salt layers have received limited study in comparison with the external shape of salt structures. Our limited understanding of the behaviour of intra-salt layers generally comes from salt mines, outcrops, analogue, and numerical modelling where the full three-dimensionality of intra-salt layers is barely observed. To understand the internal dynamics of giant salt structures and the response of their intra-salt layers during regional tectonics, this thesis provides detailed interpretation and analysis of intra-salt layers from the Silverpit Basin, in the Southern North Sea Basin, and the Birba Area, in the South Oman Salt Basin. These two locations provide unique natural laboratories where driver mechanisms for salt tectonics are investigated using high-resolution, high-quality three-dimensional (3D) seismic reflection data. The Silverpit Basin is a buckled basin formed during the Mid Eocene to Late Oligocene, while the Birba Basin was affected by massive sediment loading, which generated differential loading from the Early Cambrian to the Late Permian. Differential loading of the basin caused down-building and influenced the growth of diapirs and minibasins, which later led to intense deformation and fragmentation of the intra-salt carbonate stringers. In the Silverpit Basin, regional salt anticlines encapsulated a 23–63 m-thick intra-salt layer known as the Z3 Stringer. Lithologically, the Z3 Stringer is composed of anhydrite, and it represents a strong seismic marker across the Southern North Sea Basin. Relative to regional anticlines and synclines at the Top Salt level, the Z3 Stringer deformed in a ductile manner comparable in geometry and attitude to the regional salt structure. Non-cylindrical stringer folds, which vary from gentle to isoclinal, are related to the intensity of the regional-scale structure, whereby tighter vii stringer folds are observed under well-developed Top Salt anticlines and synclines. Synclines at the Top Salt level include long-wavelength gentle folds. Extreme thinning of the Zechstein by the downward displacement of the Top Salt causes the stringers to extend and finally break laterally in a mode-1 tensile fracture mechanism. This thesis highlights the complexity of intra-salt deformation and forms a good large-scale case study for the analysis of the kinematics and rheology of competent material enclosed within an incompetent medium. Understanding the complexities and attitudes of intra-salt layers and their encasing salt structures has broader implications for regional tectonic history, hydrocarbon prospectivity, and industrial applications.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Earth and Environmental Sciences
Subjects: Q Science > QE Geology
Date of First Compliant Deposit: 11 July 2017
Last Modified: 12 Jun 2019 02:02

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