The Evolution of Oceanic Crust in the South Atlantic

• Main Author: Estep, Justin David
• Other Authors: Reeces, Robert S, Carlson, Richard L, Petronotis, Katerina, Sparks, David W
• Format: Thesis
• Language: English
• Published: 2020
• Subjects: Oceanic Crust; South Atlantic; Layer 2A; Rio Grande Rise; South Atlantic Ocean
• Online Access: https://hdl.handle.net/1969.1/191625

Oceanic crust comprises two thirds of the crust on Earth and is the surface manifestation of mantle convection, the driving force behind plate tectonics. The age-progressive nature of oceanic crust away from its origin at mid-ocean ridges inherently works as a time series of changes in the style of accretion and of aging-related effects. The very nature of oceanic crust forming ocean basins and, therefore, residing under hundreds to thousands of meters of water has reduced our ability to broadly sample and measure in situ oceanic crust. Studies of large-scale temporal and spatial processes have thus far relied on scattered data collected in various ocean basins and of crust created at multiple spreading centers. This dissertation takes advantage of a multichannel seismic dataset that surveyed oceanic crust continuously from 0-70 Myrs old created at one spreading segment in the South Atlantic Ocean at spreading half-rates of 12-31 mm/yr. Using this dataset, we find that layer 2A, the uppermost igneous crust, continues to evolve for at least ~48 Myrs and layer 2A thickness is not dependent on crustal age or spreading rate. Furthermore, we find that the accommodation of spreading, the rate of spreading, and the roughness of the crust are all interrelated. We also find differences in subsidence rate between normal crust and thickened crust causes deformation across the transition from normal to thickened crust. Our findings imply that the hydrothermal circulation system in the South Atlantic oceanic crust is active into older crustal ages, that primarily magmatic accommodation of spreading exists in the South Atlantic, and that deformation can occur in areas where no tectonic forcing is expected.