Use this URL to cite or link to this record in EThOS:
Title: The role of pre-existing intra-basement structures on the structural evolution of rift basins
Author: Lenhart, Antje
ISNI:       0000 0004 8504 4036
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
Availability of Full Text:
Access from EThOS:
Access from Institution:
Rifting of continental crust is likely to be influenced by pre-existing intra-basement structures inherited from previous tectonic events. However, the origin, nature, 3D geometry and the mechanisms controlling the reactivation of these pre-existing structures during later phases of rifting are not well understood. This is mainly due to limitations in borehole penetration, seismic imaging and complex overprinting of multiple phases of deformation. This study investigates how structures related to the Caledonian orogeny and subsequent Devonian extensional tectonics influence the structural evolution and geometry of the North Sea rift basin. In a first step, the lithological composition and three-dimensional structural architecture of crystalline basement is established using borehole, 3D seismic reflection and potential field data, as well as correlations with the Norwegian onshore geology. In addition, synthetic seismogram modelling and 2D forward modelling of gravity and magnetic data are used to constrain the seismic interpretation of the subsurface. Having determined the structural configuration of crystalline basement, this study then investigates the 3D-geometrical and kinematic relationships between intra-basement structures and rift-related normal faults and discusses the relative influence of inherited structures on rift geometry at the local and regional scale. Results show that crystalline basement is highly heterogeneous, comprising various igneous and metamorphic rock types, exhumed metamorphic core complexes, discrete brittle and ductile structures, and pervasive fabrics and structural lineaments. Those intra-basement structures are oriented obliquely to the rift axis and can be correlated with Caledonian and Devonian faults, folds and shear zones onshore. Detailed structural analyses show that both reactivation and non-reactivation of pre-existing structures occurs. The main identified control factors for reactivation are: 1) the scale (i.e. width, length, spacing and depth extent); 2) 3D geometry (i.e. strike and dip); 3) rheology; and 4) the orientation of the pre-existing structure relative to regional stress field. Furthermore, upper-crustal intra-basement structures can influence fault geometries at the local scale, whereas crustal-scale pre-existing weaknesses are more likely to control the overall rift geometry. Results of this study correlate with findings from previous field, subsurface and modelling studies and improve our understanding of the role of structural inheritance on rift evolution.
Supervisor: Jackson, Christopher A.-L. ; Bell, Rebecca E. ; Duffy, Oliver Sponsor: Norges forskningsråd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral