Geophysics – Geodynamics

Our work examines controls on the tectonic, stratigraphic, and thermal evolution of conjugate rifted margins and oceanic lithosphere during continental rifting. Using geodynamic modeling, we investigate how factors like lithospheric structure, spreading velocities, and initial temperatures influence rifting process, by comparing the simulation results with geophysical observations. In the last years we have been focusing in the following topics:

1) Rifted conjugate margin asymmetry - Observations of conjugate rifted margin along the South Atlantic indicate that margins close to cratons are narrower than those on the conjugate side, that rifted close to ancient fold-belts. In our study published in Geology (Raghuram et al., 2023), we use 2D models of continental rifting to explore how rifting close to a craton can affect conjugate margin asymmetry, and its postrift evolution. We find that rifting close to a craton always results in narrow margins on the craton side. Thermal relaxation under the craton margin is delayed by almost 40 Myrs resulting in less post-rift tectonic subsidence compared to the fold-belt conjugate margin (Figure 1). The difference in thermal evolution under the margins has implications on development of mineral deposits on craton side margin and sag basins, which potentially host hydrocarbons on the fold-belt side. We also show that rifting adjacent to craton can affect the subsequent development of dynamic topography and induce compositional changes in the spreading system.

2) Syn- and post-rift heat-flow evolution of margins - In some margins, like the Norwegian margin, the heat-flow in the post-rift phase is larger than that predicted by classical theories of rifting. Using geodynamic simulations, we reveal that thermal relaxation in the post-rift phase is significantly delayed, likely due to small-scale convection beneath the hyper-extended margin lithosphere. These small scale convection cells sustain elevated heat flow even 60 Myrs after break-up, with key implications for hydrocarbon prospectivity in distal sections of margins and early oceanic crust (Figure 2). This study is published in Geological Society of London Special Publications (Pérez-Gussinyé et al. 2024).

3) Nature of the Lithosphere-Asthenosphere boundary (LAB) during oceanic plate evolution - Seismological observations reveal that shear wave velocity structure deepens with lithosphere age in oceanic basins, yet different proxies for the lithosphere-asthenosphere boundary (LAB) show varied trends. While radial anisotropy observations from seismic tomography lacks an age-related depth increase, azimuthal anisotropy observations suggests age dependence, possibly aligning with sharp discontinuities identified through Scattered wave imaging and SS precursor imaging techniques. These contrasting observations raise questions about how they relate to the mechanical response of the lithosphere to the convecting mantle below and how the base of the oceanic lithosphere can be delineated. Using 2D geodynamic models, we explore the evolution of the thermal and viscosity structure from continental breakup through oceanic formation, seeking correlations of LAB with these seismological signatures.

Dr. Raghu Ram Gudipati, 2019-2025.

Funding from the University of Bremen.