Ph.D. RESEARCH SEMINAR DEPARTMENT OF EARTH SCIENCES ...

Apr 21, 2015 - 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.
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Ph.D. RESEARCH SEMINAR DEPARTMENT OF EARTH SCIENCES DALHOUSIE UNIVERSITY

Janice Allen Ph.D. Candidate Department of Earth Sciences Dalhousie University “Numerical Modeling of Salt Tectonics at Rifted Continental Margins”

Tuesday, April 21, 2015

11:30 a.m. Milligan Room, 8th Floor Biology-Earth Sciences Wing, Life Sciences Centre, Dalhousie University

COFFEE AND DOUGHNUTS WILL BE AVAILABLE IN THE MILLIGAN ROOM BEFORE THE SEMINAR

Numerical Modeling of Salt Tectonics at Rifted Continental Margins Janice Allen Ph.D. Candidate Department of Earth Sciences Dalhousie University

This work 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. This work also shows that dry physical models with reduced sand density provide a reasonable analogue to submarine natural system. The second project uses 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. Previous work (e.g. Huismans and Beaumont, 2011; Goteti et al, 2013) has largely considered the evolution of rifted margins and the development of salt tectonics separately, though there is growing interest in their interaction (e.g. Rowan, 2014). The first paper in this 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. Crustal thinning in these models is diachronous, and can lead to thick sag basin deposits with active faulting only at the current distal margin. The second paper in this project considers wide (and possibly narrow) continental margins, developed from weak (and strong) continental crust. In addition to studying syn-rift salt tectonics, the impact of sedimentation on the style of rifting, particularly for wide margins, will be investigated. Finally, fully 3D numerical models, accounting for the key features of salt tectonic systems, would represent a significant advancement in this field. The fourth project of this thesis involves the augmentation of existing 3D numerical modeling software to suit the study of salt tectonics, and demonstration of this approach. Salt tectonics in nature has many inherently three-dimensional features, that cannot be captured with 2D models. Currently underway, this project will study the development of 3D minibasins through uneven sedimentation, and will consider the interaction of prograding deltaic sediments and minibasins formation.