Listric faults imaged in oceanic crust

Deep seismic reflection profiling has provided exceptional images of listric faulting in oceanic basement of Jurassic age off the coast of Nova Scotia. The faults dip toward the Mid-Atlantic Ridge and sole near the base of the crust at a common depth of about 4 km, presumably the brittle-ductile transition at the time of deformation. At least five rotated fault blocks, with dips ranging from 0° at the surface to 45° at the base, are observed along a 36 km flow-line segment, suggesting a stretching factor, β, of 1.5-2.5. The faults can be traced upward with small displacement in the overlying sedimentary strata to approximately the middle Cretaceous strata, implying continued movement or consolidation for about 70 m.y. after crustal formation.