Legacy seismic and gravity data in the vicinity of Great Meteor Seamount and its tectonic implications

The Great Meteor seamounts are located in the eastern Atlantic Ocean, about 750 km south of
the Azores. Conjugate to the Corner seamounts in the western Atlantic Ocean, it has been
suggested they formed at the same hotspot that generated the New England Seamount chain.
However, isotopic data suggest the Great Meteor seamounts are genetically linked to the
Azores rather than to the New England hotspot. To test this, we have used seismic, gravity
and bathymetry data acquired onboard M/V Meteor in 1990 to reassess the crustal structure,
elastic thickness, Te, and tectonic setting of the seamounts. The most prominent is Great
Meteor, the largest seamount in the Atlantic Ocean. We show that the guyot comprises a
pelagic, limestone (2.0-4.5 km s-1) and extrusive basaltic lava (5.0-6.0 km s-1) drape that
overlies a relatively high P-wave velocity (6.0 - 6.5 km s-1) intrusive ‘core’ of mafic and
possibly ultramafic rocks. The seismic structure has been verified by gravity modeling
assuming a Gardner and Nafe-Drake relationship between P-wave velocity and density. The
best fit between the observed and calculated gravity anomaly based on a plate flexure model
is for an elastic thickness, Te, of ~20 km which implies an edifice age of ~43 Ma, assuming a
450°C controlling oceanic isotherm. While the edifice age is greater than the sample age (~17
Ma), it explains the subsidence history of Great Meteor and is compatible with dynamic
models of plume-ridge interactions that predict the Azores hotspot has migrated north during
the Cenozoic.