Four-dimensional upper crustal construction at fast-spreading mid-ocean ridges: A perspective from an upper crustal cross-section at the Hess Deep Rift

During spreading and magmatic construction, subaxial subsidence accommodates thickening of the basaltic lava unit. Sub-axial subsidence, faulting, and block rotation result in an upper crust with inward-dipping (toward the axis) lava flows and outward-dipping (away from the axis) dikes. Substantial differences in upper crustal geology may result from segment-scale variations in which vertical magma delivery dominates in areas of robust magma supply (likely over sites of recently recharged melt lenses at segment centers) but lateral magma transport dominates in areas of relatively lower magma supply (possibly toward segment ends).