EVOLUTION OF THE GREENLAND-ICELAND-FAROES RIDGE

Any theory to explain the Greenland-Iceland-Faroes ridge must also account for numerous tectonic complications in the Atlantic ocean to the north and south. These include:

• Plate-boundary reorganizations and rift migrations, e.g., from the Aegir ridge to the Kolbeinsey ridge;
• Continental material of unknown extent, e.g., the Jan Mayen microcontinent, which possibly extends south beneath Iceland;
• Anomalously shallow bathymetry of the Greenland-Iceland-Faroes ridge, coupled with a normal rate of age-related subsidence;
• Propagating and dying ridges, e.g., on the Reykjanes ridge, the Kolbeinsey ridge and in Iceland;
• Instability on the Reykjanes ridge in the form of evolution from boundary normal oblique spreading to ridge-transform staircase morphology and then back to oblique spreading;
• Sagging, flexing and tilting of blocks around Britain;
• Stress and motion reorganizations and variable orientations over short distances, e.g., in Iceland;
• Tectonic reactivations (e.g., of the Vøring Spur);
• Extensions (evidenced by subsidence and/or volcanism) and compressions (evidenced by uplift) at various times and places from 54 Ma to the present;
• Complex plate boundary configurations including multiple triple junctions.

The region has been chronically unstable from the time of continental breakup at ~ 54 Ma and this is still ongoing today. Large-volume magmatism built the volcanic margins of the North Atlantic at the time of breakup, and anomalous volcanism is still widespread in the region, e.g., at Jan Mayen and Iceland. All the above features suggest widespread, long-lived tectonic instability. This was probably inherited from an original piecemeal style of supercontinent breakup influenced by pre-existing structure. The unusual magmatic activity in the region is likely a by-product of this ongoing instability.