Figure F15. Tectonic model for the final stages of continental breakup documented on the distal Newfoundland margin at Site 1277, also taking account of evidence from the Iberia margin and the Alps-Apennines. A–C are seen as a continuum of processes that culminated in "normal" seafloor spreading, possibly around the Aptian/Albian boundary. Later (Albian–Cenomanian) intrusion of alkaline sills in the vicinity of Site 1276 (west of Site 1277) was probably associated with the activity of a postbreak-up thermal plume (Hart and Blusztajn, 2006; not shown here). A. Exhumation of subcontinental mantle lithosphere, coupled with submarine erosion of the low-angle extensional detachment and episodic eruption of mid-ocean-ridge basalt (MORB). Seismic reflection evidence indicates strong crustal thinning along the Newfoundland margin, but the westward-dipping detachment beneath continental crust is hypothetical. B. With continued in-plane extension, the exhumed mantle was dissected to form serpentinite ridges and intervening basins. Evidence from the Alps suggests continuing mid-ocean-ridge (MOR)-type volcanism during this stage. C. Final separation of brittle subcontinental mantle lithosphere and massive influx of magma to initiate "normal" seafloor spreading.

Figure F15. Tectonic model for the final stages of continental breakup documented on the distal Newfoundland margin at Site 1277, also taking account of evidence from the Iberia margin and the Alps-Apennines. A–C are seen as a continuum of processes that culminated in "normal" seafloor spreading, possibly around the Aptian/Albian boundary. Later (Albian–Cenomanian) intrusion of alkaline sills in the vicinity of Site 1276 (west of Site 1277) was probably associated with the activity of a postbreak-up thermal plume (Hart and Blusztajn, 2006; not shown here). A. Exhumation of subcontinental mantle lithosphere, coupled with submarine erosion of the low-angle extensional detachment and episodic eruption of mid-ocean-ridge basalt (MORB). Seismic reflection evidence indicates strong crustal thinning along the Newfoundland margin, but the westward-dipping detachment beneath continental crust is hypothetical. B. With continued in-plane extension, the exhumed mantle was dissected to form serpentinite ridges and intervening basins. Evidence from the Alps suggests continuing mid-ocean-ridge (MOR)-type volcanism during this stage. C. Final separation of brittle subcontinental mantle lithosphere and massive influx of magma to initiate "normal" seafloor spreading.