Propagation of hotspot volcanism driven flexure in oceanic crust - 85°E Ridge case study

The study focuses on the flexural down-warping of oceanic crust related to the Early Cretaceous hotspot volcanic chain in offshore East India, drawing from robust reflection seismic coverage of the 85°E Ridge and associated moats and arches. Seismic data image three moat-filling units including the basal pelagic, landslide and ponded units, representing the sedimentary record preceding, coeval and postponing flexure. Their stacking patterns allow one to understand the flexural history of the oceanic crust reacting to the volcanic load, in space and time. The flexural history of the oceanic crust can be divided into four stages. The first stage is the brittle faulting-assisted flexure reacting to the appearance of the load. It has a short wavelength and controls the development of moat undergoing deposition of the landslide unit. Then follows the long-wavelength flexure, when the arch starts to develop. The flexural arch formation prevents the landslide unit from covering it, while the moat keeps subsiding. The third flexure stage is a short-wavelength deformation when the moat and arch subside together. Accordingly, the syn-flexural landslide unit records an initial rapid and a later slower subsidence. The fourth flexure stage is characterized by the passive infill of moat by sediments of ponded unit, although limited isostatic adjustments can occur, accompanied by mass wasting.