Janice Allen

Ph. D. Thesis

Numerical Modeling of Salt Tectonics at Rifted Continental Margins

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This thesis applies finite element numerical modeling to a range of projects investigating salt tectonics at rifted continental margins. Both two-dimensional and fully three-dimensional models are used. The first project demonstrates that incorrect density scaling in physical analogue models of salt tectonics leads to: 1) overestimated buoyancy force and 2) underestimated pressure gradient and sediment strength. Numerical models (2D) show a shift in salt structures, from diapir-minibasin pairs to expulsion rollover, when density scaling errors are corrected. The second and third projects use 2D nested models, which allow for dynamic evolution of the continental margin scale system while providing high resolution visualization of salt basins, to study the interactions among syn-rift salt deposition and deformation, post-salt sedimentation, and ongoing rifting tectonics. This work makes the important advancement of allowing salt basin geometry to evolve dynamically. The second project considers intermediate width margins, and shows that the timing of salt deposition relative to rifting (early syn-rift vs late syn-rift salt) leads to distinct patterns of salt distribution and deformation. Key features of salt tectonics at the Central Red Sea are captured using a layered salt succession deposited in the mid to late syn-rift period. The third project considers wide continental margins, developed from weak continental crust. In addition to studying syn-rift salt tectonics, the impact of sedimentation on the style of rifting is investigated. A comparison is made to the central and northern Nova Scotia margin. The final project presents preliminary results from a fully 3D numerical modeling study of the formation of minibasins through uneven sediment loading over salt. This work compares the evolution of 2D-equivalent and fully 3D model designs, exploring the importance of studying even simple salt tectonic systems using a fully 3D approach.

Keywords: salt, salt tectonics, rifted margin, conjugate margin, numerical modeling
Pages: 334
Supervisor: Chris Beaumont