The Bathymetrists Seamounts – intraplate volcanic province meets Riedel Shears (eastern Equatorial Atlantic Segment)

The Bathymetrists Seamounts (BSM) form a 900 km long and 200 km wide volcanic chain of about 40 volcanic edifices within the eastern Equatorial Segment of the Atlantic. They are located between the Vema Fracture Zone in the north and the 4°N Fracture zone in the south (both transcurrent faults). Like other submarine chains east of the Mid-Atlantic Ridge, the BSM trend NE-SW. Many of those volcanic chains are intensively studied and attributed to hot spot tracks above mantle plumes. However, the BSM is much broader and strongly associated with faults. Still, it remains unclear if a mantle plume, decompression melting along fracture zones, or small-scale upper mantle convection caused these seamounts. We present new insights to the BSM based on about 80,000 km² high-resolution bathymetric data with 50 m spatial resolution, and 4,000 km of 2D seismic reflection data, collected during expeditions RV Merian MSM70 in 2018 and RV Meteor M152/2 in 2019. Seismic sections across the volcanic edifices allow a simple estimation of their relative age distribution, as it is inferred by the stacking pattern of the volcanic successions. Moreover, the structural pattern includes flower structures and indicates transtension. The single seamounts are arranged along E-W to NE-SW lineaments that can be explained by large-scaling Riedel shears. This Riedel shear pattern reveals a NW-SE orientated extensional local stress field during its generation in the Paleogene. Therefore, deep mantle plumes and shallower tectonics on a lithospheric scale could play an important role in the emplacement of the volcanoes.