Disparate crustal thicknesses beneath oceanic transform faults and adjacent fracture zones revealed by gravity anomalies

Plate tectonics describes oceanic transform faults as conservative strike-slip bound-aries, where lithosphere is neither created nor destroyed. Therefore, seafloor accreted at ridge-transform intersections should follow a similar subsidence trend with age as lithosphere that forms away from ridge-transform intersections. Yet, recent compila-tions of high-resolution bathymetry show that the seafloor is significantly deeper along transform faults than at the adjacent fracture zones. We present residual mantle Bouguer anomalies, a proxy for crustal thickness, for 11 transform fault systems across the full range of spreading rates. Our results indicate that the crust is thinner in the transform deformation zone than in either the adjacent fracture zones or the inside corner regions. Consequently, oceanic transform faulting appears not only to thin the transform valley crust but also leads to a secondary phase of magmatic addition at the transition to the passive fracture zones. These observations challenge the concept of transform faults being conservative plate boundaries.

Automated summary

Recent research shows that the crust in oceanic transform faults is thinner than in adjacent fracture zones, challenging the concept of transform faults as conservative plate boundaries. This study also reveals the addition of secondary magmatic material at the transition to passive fracture zones.