Collaborative Research: Effect of Contrasting Structural and Compositional Inheritances on the Development of Rifting Margins

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Throughout Earth's history continents have broken apart and reassembled as part of the fundamental plate tectonic evolution of the planet. How continents break apart by rifting processes is thought to be predefined by inherent structural and compositional variability of Earth's crust and mantle that make up the lithosphere and is likely inherited from previous tectonic events. Understanding the style of continental breakup provides fundamental information for the exploration for energy and mineral resources and to understanding the geologic hazards associated with these processes. Geological observations often support the fact that these inheritances are key parameters in the development of rift structures but the extent to which these inheritances play a role during the rifting process remain unclear. This project investigates how the variable composition of continental lithosphere and the presence of inherited geological structures affect rifting processes. A multi-disciplinary approach will employ geological and geophysical observations to characterize inheritances in the crust and mantle of the lithosphere. These observations will be integrated into numerical models that simulate the deformation of the lithosphere over millions of years by extension. The results of this project will fundamentally advance the understanding of lithospheric scale deformation processes and impact structural geology, computational geosciences and potentially the fossil fuel communities. Under broader impacts the project supports an early career female researcher at Texas State University, a primarily Hispanic-serving institution, and a master student will be recruited to participate directly in the research.Passive margins define about half of the Earth's coastlines and have been the focus of numerous studies in recent decades. While understanding of rifting processes has greatly improved, fundamental questions remain on the effects of inherited conditions on localization processes in extending lithosphere. Multiple studies suggest that structural, compositional and thermal inheritances are key parameters in the development of rift structures. However, the extent to which they play a role during breakup is still unclear. This project will address the hypothesis that inheritances strongly affect rifting processes and can explain: 1) the distribution of strain during the initial phase of deformation, 2) the mechanism of thinning during the rifting process, and 3) the mechanism leading to the exhumation and/or the formation of oceanic crust. To test this hypothesis numerical rifting experiments will be run with both structural and compositional inheritances. Inheritances are parameterized as oriented fabrics obtained from 2D seismic and 3D structural observations. A polymineralic composition is assigned to these heterogeneities in order to account for the natural variation in compositions observed in the continental lithosphere. In order to constrain the models, a multidisciplinary approach will be used that combines: 1) the analysis of geological and geophysical data, 2) a systematic exploration of the effects of numerical modeling experiments using a bimineralic rheology, and 3) a case study of the Northeastern Canadian margin with 2D and 3D numerical models. This approach will allow for a large amount of quantitative information on rift evolution to be acquired by independently varying the composition, distribution and orientation of inheritances. Results will help improve understanding of strain distribution, localization processes and mechanisms of deformation during continental breakup, and visualize the dynamic evolution of rifting processes depending on the type of inheritances.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.