FAST RIFT PROPAGATION AT A SLOW-SPREADING RIDGE

Bathymetric, magnetic, gravity, and morphologic data from the flank of the slow-spreading Mid-Atlantic Ridge reveal obliquely oriented featu res that offset magnetic isochrons and morphological patterns within i ndividual ridge segments. These features form angles of similar to 10 degrees-40 degrees with the isochrons and are inferred to result from rift propagation at rates several times the spreading rate, representi ng the fastest propagators get observed at a slow-spreading ridge. The se fast propagators appear to have formed as a result of tectonic exte nsion migrating along ridge segments as the segments change from more magmatic to less magmatic periods of spreading.