Date of this Version
Liu, M., 2018, Integrated Geophysical Analysis in the Northeastern Gulf of Mexico, [Master thesis], The University of Nebraska-Lincoln.
The formation of the Gulf of Mexico (GoM) relates to the breakup of Pangea and opening of the central Atlantic Ocean. The tectonic history of the basin is still being debated due to lack of geological constraints. This project addresses the crustal architecture in the northeastern GoM from integrative analysis of multiple geophysical datasets to provide constraints for the tectonic reconstruction.
The objectives of this study are: 1) to delineate various tectonic zones (continental and oceanic domains) and map the boundary between them, 2) to derive physical properties of the subsurface rocks, 3) to map the major tectonic structures in the study area, such as the pre-salt basin and the Seaward Dipping Reflectors (SDR) province in continental domain, and segments of an extinct spreading center with associated transform faults in oceanic domain, and 4) to establish the spatial and temporal relations between different tectonic zones and structures.
Three two-dimensional subsurface models were developed in the northeastern GoM by using consistent physical properties for subsurface rocks. Further, spatial analysis was performed on gravity and magnetic grids, which allowed mapping of various tectonic zones and structures.
As a result of this study, two distinct spreading episodes of GoM formation were identified. The first one, presumably from 160 to 150 Ma, was an ultra-slow spreading event (estimated full spreading rate of 0.9 cm/yr) that produced thin (~5 km) and dense (2.95 g/cc) oceanic crust with fast seismic velocities (~7km/s) and high magnetic susceptibility (0.0075 cgs), most likely composed of gabbro. At ~150 Ma, the spreading center jumped to the south due to a change in location of the Euler pole. The second spreading episode was faster (1.1 cm/yr) and produced thicker crust (up to 9 km) composed of two layers – a basaltic layer (2-4 km thick, Vp = 6-6.5 km/s, density 2.65 g/cc and magnetic susceptibility 0.007 cgs) on top of a gabbroic one. The ridge propagation resulted in the asymmetry of the oceanic domain that needs to be accounted for during tectonic reconstruction.
Advisor: Irina Filina