Collier, J.S., J.J. Da?obeitia, J.P. Canales, R. Dalwood, S. Gadd, N. Hayward, T. Henstock, S. Krastel, C. Pierce and A. Watts, Evidence for asymmetric accretion and low-angle, planar faults in slow-spreading oceanic crust, Geology, 25, 1075-1078, 1997[PDF]
New seismic reflection data in the eastern Atlantic have enabled two large-scale dipping reflectors imaged within Mesozoic ocean crust to be mapped in three dimensions and placed in their sea-floor-spreading context. One of the reflectors dips to the west and extends from a step in the igneous basement to the Moho. The other reflector dips to the east and extends between 4 and 10 km below basement. Both reflectors are oriented approximately parallel to isochrons, lie just north of a 5-km-offset, third-order discontinuity, are planar in cross section, and dip at 30?. We interpret both these reflectors as lithospheric-scale faults formed within the median valley at the axis. We suggest that the lower part of the eastward-dipping fault was ?captured? from the North American plate, possibly by rapid propagation of an active volcanic rift across the discontinuity.