Three‐dimensional gravity and bathymetry analysis of the Mid‐Atlantic Ridge between 20°N and 24°N: Flow geometry and temporal evolution of the segmentation

Abstract

Bathymetry and gravity data covering 10 m.y. on both flanks of the Mid‐Atlantic Ridge south of the Kane Fracture Zone reveal a complex segmentation pattern well correlated with short‐scale temporal variations in crustal production. Segment and paleosegment centers are associated with crustal thickening, while their extremities appear as elongated bands of thin crust. Subsidence rates vary between centers and extremities of a segment, with higher than world average values at segmert midpoints and closer to average values at the edges. This is consistent with segment centers being the site of focused mantle upwellings, with associated thin lithosphere, and with thick crust. A pronounced circular minimum in the long wavelength of the Mantle Bouguer Anomaly, associated to a maximum in the long wavelength of the bathymetry, marks the site of a mantle upwelling, associated with a particularly robust segment located north of a small fracture zone (21°20′N). An offset is often observed between extreme values of topography and crustal thickness, resulting in a lack of isostatic equilibrium for off‐axis short‐wavelength features. An obliquity between maxima of crustal thickening associated with active segments and the topographic axial domain suggests that the shift between topography and crustal structure may arise partly from a decoupling between crust and topography formation processes.