<p>This thesis addresses the spatial distribution of structures and deformation geometry in the southern Sudbury Basin, Ontario, a synclinal fold basin. Major components are low-temperature fabric development in the Sudbury Igneous Complex (SIC), the relation between fabrics and fold structures in Huronian rocks, and kinematic modeling of deformation of the southern Sudbury Basin. These topics lead to a synthetic model of the structural history of the SIC and its host rocks. Analysis of structures in the Norite layer of the SIC shows that this unit deformed under a single deformation regime and variable rheological conditions. This is evident by foliation planes, folded granitoid dikes, brittle shear faults and ductile high-strain zones. Brittle deformation preceded the formation of foliation planes and caused hydrolytic weakening of the Norite. Bulk thinning led to steepening of lithological contacts and igneous layering in the SIC. Structures in Huronian rocks and Sudbury Breccia display components of post-impact deformation that cannot be accounted for by thrusting along a high-strain zone, the so-called South Range Shear Zone, and by large-scale folding of the SIC. Shape change of the SIC from a convex outward to concave inward geometry led to basin-concentric shortening, the formation of a buckle fold of the SIC and axial-planar fabrics in Huronian rocks. Mutually perpendicular fabric orientations compatible with overall NW-SE shortening indicate that discordant foliations can form as a consequence of local strain perturbations near lithological contacts. Kinematic modelling of deformation based on field-based structural data tests the validity of trishear fault propagation folding as a possible deformation mechanism for the southern Sudbury Basin. Trishear deformation of the central South Range accounts for angular discordances between the upper and basal contacts of the SIC, local overturning of southern SIC, steepening of foliation planes, strain gradients in the Sudbury Basin, and thickness variations of SIC layers. Implications are shallowly dipping SIC layers both at greater depths and above the current erosion level, translation of Huronian rocks, and thinning in a section of the trishear zone manifested at surface by the South Range Shear Zone.</p> / Doctor of Philosophy (PhD)

This thesis presents a whole-embryo finite element model of neurulation -- the first of its kind. An advanced, multiscale finite element approach is used to capture the mechanical interactions that occur across cellular, tissue and whole-embryo scales. Cell-based simulations are used to construct a system of constitutive equations for embryonic tissue fabric evolution under different scenarios including bulk deformation, cell annealing, mitosis, and Lamellipodia effect. Experimental data are used to determine the parameters in these equations. Techniques for obtaining images of live embryos, serial sections of fixed embryo fabric parameters, and material properties of embryonic tissues are used. Also a spatial-temporal correlation system is introduced to organize and correlate the data and to construct the finite element model. Biological experiments have been conducted to verify the validity of this constitutive model. A full functional finite element analysis package has been written and is used to conduct computational simulations. A simplified contact algorithm is introduced to address the element permeability issue. Computational simulations of different cases have been conducted to investigate possible causes of neural tube defects. Defect cases including neural plate defect, non-neural epidermis defect, apical constriction defect, and convergent extension defect are compared with the case of normal embryonic development. Corresponding biological experiments are included to support these defect cases. A case with biomechanical feedbacks on non-neural epidermis is also discussed in detail with biological experiments and computational simulations. Its comparison with the normal case indicates that the introduction of biomechanical feedbacks can yield more realistic simulation results.

This thesis presents a whole-embryo finite element model of neurulation -- the first of its kind. An advanced, multiscale finite element approach is used to capture the mechanical interactions that occur across cellular, tissue and whole-embryo scales. Cell-based simulations are used to construct a system of constitutive equations for embryonic tissue fabric evolution under different scenarios including bulk deformation, cell annealing, mitosis, and Lamellipodia effect. Experimental data are used to determine the parameters in these equations. Techniques for obtaining images of live embryos, serial sections of fixed embryo fabric parameters, and material properties of embryonic tissues are used. Also a spatial-temporal correlation system is introduced to organize and correlate the data and to construct the finite element model. Biological experiments have been conducted to verify the validity of this constitutive model. A full functional finite element analysis package has been written and is used to conduct computational simulations. A simplified contact algorithm is introduced to address the element permeability issue. Computational simulations of different cases have been conducted to investigate possible causes of neural tube defects. Defect cases including neural plate defect, non-neural epidermis defect, apical constriction defect, and convergent extension defect are compared with the case of normal embryonic development. Corresponding biological experiments are included to support these defect cases. A case with biomechanical feedbacks on non-neural epidermis is also discussed in detail with biological experiments and computational simulations. Its comparison with the normal case indicates that the introduction of biomechanical feedbacks can yield more realistic simulation results.