Multibeam investigation of the active North Atlantic plate boundary reorganization tip

• Revised interpretation of the active North Atlantic reorganization tip location.
• New marine geophysical data reveal the recent Reykjanes Ridge reorganization history.
• Rapid successive transform eliminations before abrupt slowing at the Modred transform.
• Modred transform fault converted to non-transform offset at the reorganization tip.
• Simple thermal and propagating rift models are inadequate to explain the new data.

The previous orthogonal ridge/transform staircase geometry south of Iceland is being progressively changed to the present continuous oblique Reykjanes Ridge spreading geometry as North America–Eurasia transform faults are successively eliminated from north to south. This reorganization is commonly interpreted as a thermal phenomenon, caused by warmer Iceland plume mantle progressively interacting with the ridge, although other diachronous seafloor spreading reorganizations are thought to result from tectonic rift propagation. New marine geophysical data covering our reinterpretation of the reorganization tip near 57°N show successive transform eliminations at a propagation velocity of ∼110 km/Myr, ten times the spreading half rate, followed by abrupt reorganization slowing at the Modred transform as it was converted to a migrating non-transform offset. Neither the simple thermal model nor the simple propagating rift model appears adequate to explain the complicated plate boundary reorganization process.