EstGroenland

Offshore between Iceland & Ireland

Irminger and Iceland Geographic Basins

The bathymetry map between the South Greenland and the West Ireland illustrates : (i) The Irminger Geographic Basin, which is basically an oceanic basin ; (ii) The Reykjanes Ridges which corresponds to the Mid-Oceanic Ridge between the Charlie Gibbs Fracture zone and the Iceland ; (iii) The Iceland Geographic Basin, which is the oceanic basin between the Reykjanes ridge and the Hatton and Lousy Banks ; (iv) The Hatton / Rockall banks, which correspond to small Pangea micro-continent ; (v) The Rockall Trough, which seems correspond to the first valley rift of the Pangea breakdown, over which the onset of the Atlantic-type divergent margin deposited before the westward shift of mantle upwelling shifted along the Charlie Gibbs Fracture Zone, as illustrated in next plate.

On this schematic geological cross-section between the South Iceland offshore (Mid-Oceanic ridge and Ireland Offshore), passing trough the Rockall Trough, it is easy to understand that the Rockall trough area is an aborted Atlantic-type divergent margin preserving a tectonic evolution similar to that of the breakup of the South Atlantic. In fact, the Pangea lengthened and thinned continental crust (Rockall Through), Jurassic and Cretaceous rift-type basins developed before the the breakup of the lithosphere, which seems, here, to done, exclusively, by sub-aerial expansion centers from which effused mantle material formed lava flows (SDRs) and built lava deltas with seamounts along leaky fault zones. The breakup zone was, later, fossilized by Tertiary sediments forming an aborted divergent margin, because, in the Early Tertiary, the Rockall geographic basin ceased to widen after the mantle upwelling ceased or shifted westward. Nevertheless the basin continued to subside faster than the onlapping deepwater sediments accumulated, forming the present-day Rockall Trough. Since the mantle upwelling shifted westward, a new spreading centers took place westward of the Hatton bank with lava flows overlying Jurassic rift-type basin. The lava flows pass, laterally, to the oceanic crust as the expansion centers become immersed as illustrated on Page 12I.