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Shaping slow-spreading seafloor with detachment faults

Jean-Arthur Olive
Fri, April 20, 2018, 10:30am - 11:30am

Video Broadcast

Host: Luc Lavier

While seafloor formed at intermediate- and fast-spreading mid-ocean ridges shows little variability in the along-axis direction, the morphology of slow-spread seafloor is inherently three-dimensional. Within tens of km along a slow ridge segment, the landscape can change from regularly-spaced basaltic hills bounded by short-offset faults to dome-shaped exposures of mantle units capped by a large-offset detachment. Because most previous modeling efforts have been confined to 2-D cross-axis sections, the mechanics of the along-axis transition between these two distinct modes of seafloor spreading is largely unknown. In a broader sense, the link between the sub-seafloor geometry / extent of a detachment fault and its expression at the seafloor remains contentious. I will address these questions through a combination of bathymetric analysis, 3-D thermo-mechanical modeling, and simple mechanical modeling. In the first part of the presentation, I will show that the along-axis extent and overall shape of detachment fault footwalls directly reflect along-axis gradients in the amount of magma supplied to the ridge axis. In the second part of the talk, I will discuss the way seafloor-shaping processes (e.g., mass wasting) continuously rework detachment fault footwalls and complicate the tectonic interpretation of bathymetry. Together, these efforts greatly improve our ability to interpret seafloor morphology in terms of underlying geodynamic processes.