How extensional tectonics and surface processes interact to shape continental plate boundaries
Seismic observations document how substantial amounts of sediments may be transported from the onshore to the offshore during formation of extensional continental margins. Thick sedimentary packages are, for example, found on the margins of Norway, the eastern US coast, and the Gulf of Mexico. In contrast, the Goban Spur, Galicia Bank, and the Red Sea are examples of sediment-starved margins. Such variations in the amount of sediments impact not only the development of offshore sedimentary basins, but the changes in mass balance by erosion and sedimentation can also interact with extensional tectonic processes. In convergent settings, such feedback relationships between erosion and tectonic deformation have long been highlighted: Erosion reduces the elevation and width of mountain belts and in turn tectonic activity and exhumation are focused at regions of enhanced erosion. But what is the role played by surface processes during formation of extensional continental margins? In this lecture, I will discuss geodynamic experiments that explore the response of continental rifts to erosion and sedimentation from initial rifting to continental break-up. These experiments show how the interaction of extensional tectonics and surface processes can fundamentally alter the width and topography of continent-ocean boundaries.