Oceanography
Ph.D. in Geological Oceanography - Seismic Group
Structures of the Eastern Grand Bank/Newfoundland Basin Rifted Margin
Outline:
Divergent motion between two plates causes continental crust to be extended and thinned, which results in the formation of continental rift systems. As extension proceeds towards continental breakup, seafloor spreading begins and oceanic crust is formed. The complexes that border the breakup locations become the modern passive continental margins and pairs of formerly connected margins are known as conjugate margin pairs. Previous studies in the deep structures of the N. Atlantic non-volcanic rifted margins showed a region called the ocean-continent transition (OCT), a zone between thinned continental crust and equivocal oceanic crust. In order to further our understanding of the structures and development history of the N. Atlantic margins, especially the OCT, a study of the Newfoundland Basin-Iberia (NI) rift system, one of the major N. Atlantic non-volcanic rift systems, is proposed. Since studies have been both intensive and extensive on the Iberia margin, it is now a good opportunity for comparable studies to be done on the Newfoundland margin in order to complete the full picture of our knowledge of this rift system.
Therefore, the proposed doctoral thesis will be a detailed study of the structures of the E. Grand Bank/Newfoundland Basin rifted margin. It will center on new data collected on Jul.-Aug., 2000 during the SCREECH (Study of Continental Rifting and Extension on the Eastern Canadian sHelf) program. These include multi-channel seismic reflection (MCS), wide-angle seismic reflection/refraction, gravity and magnetic data. Project objectives are: 1) to use previous data within the Flemish Cap/Grand Bank/Newfoundland Basin Margin to build up a framework for interpreting new data; 2) to describe the crustal structures of the full width of the margin along a selected seismic line in the SCREECH program and to understand their formation in a regional scale; 3) to understand the relationship between the 2-D structures of the selected line in the SCREECH program and those of its conjugate on the Iberia margin and its adjacent seismic lines, and to compare these observations with those of other non-volcanic margins in N. Atlantic. For the second objective, I seek to a) characterize the structures of the rifted basins and the upper and lower thinned crust, relevant for petroleum modeling; b) determine the rock type and geometry of the OCT basement; c) identify the landward limit of the oceanic crust.
I have been re-interpreting and compiling all available previous results within the Newfoundland Basin margin into databases of gridded depths of basement and major sedimentary reflectors. New data will be processed for combined interpretations of the reflection and refraction data on the selected line in the SCREECH program and co-analysis of the seismic, gravity and magnetic interpretation to achieve objective 2. Both the MCS and wide-angle data will be processed by following standard methods such as stacking, filtering, coherence filtering, deconvolution and migration, and using pre-stack depth migrations to help imaging a mid-crustal reflection feature, which is crucial in discriminating among extensional mechanisms. Analyses based on amplitudes and arrival times of the signal will be done on the reflection data for detailed studies of a high amplitude reflection above basement and on the refraction data for deriving a seismic velocity model. The observed structural geometry, seismic velocities (both p- and s-waves), gravity and magnetic signals of the selected line in the SCREECH program will be compared with those of hypothesized crustal origins of the OCT. These interpretations will be synthesized with those of other chosen profiles to achieve objective 3.
Supervisor: Keith Louden
