Early Cretaceous motion of Flemish Cap with respect to North America: implications on the formation of Orphan Basin and SE Flemish Cap–Galicia Bank conjugate margins

Abstract

Bouguer gravity anomalies together with deep seismic reflection and magnetic data on both sides of the North Atlantic are used to locate the hinge zones of the Flemish Cap and Galicia Bank within the Iberian and North American plates, regions across which there were abrupt changes in lithospheric extension. The characteristic shape and alignment of these hinge zones suggest that they were conjugate features generated during chrons M25-M0 (Late Jurassic-Early Aptian) around a distally located Euler pole of rotation. Rifting between Iberia and North America involved these two larger plates and the two smaller microplates -the Flemish Cap and Galicia Bank microplates. The motion of the microplates, which were adjacent to Eurasia, was much more complex than those of the larger plates. The motion between the microplates from chron M25 or older to chron M0 was complicated by the fact that they remained attached to each other for most of the time when regions to the south were rifting apart. As a result, con-

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

“…Bathymetric contours are in metres. The locations and lateral extents of the major sedimentary basins are shown in tan colour (Enachescu et al 2004c;Sibuet et al 2007b;Naylor & Shannon 2011). Superimposed structural components on the Newfoundland margin were adapted from the structural map presented by Sibuet et al (2007b) and originally modified from Enachescu et al (2004a,b,c several broad trends can be observed in the depth to basement map across the conjugate margins (Fig.…”

“…There is also seismic evidence that rifting occurred in the Rockall Basin as early as the Permo-Triassic (Shannon et al 1999;Štolfová & Shannon 2009;Tyrrell et al 2010;Naylor & Shannon 2011). However, the Flemish Cap was not affected until the Early Jurassic (Sibuet et al 2007b).…”

“…The latter separation was preceded by, and continued contemporaneously with, the opening and subdivision of Orphan Basin to the NW of Flemish Cap into an interpreted older East Orphan Basin and a younger West Orphan Basin (Enachescu et al 2004c). The anticlockwise progression in orientation from NE-SW to north-south of the faults and basement ridges within the Orphan sub-basins reflects the westward propagation of rifting (Enachescu et al 2004a,c;Enachescu 2006 (Enachescu et al 2004a,b,c;Sibuet et al 2007b) but this conclusion may simply reflect a lack of deep well control in the basin.…”

“…The postulated clockwise rotation of Flemish Cap (43° relative to Iberia) during the Late Triassic to Early Cretaceous, and its 200-300 km southeastward displacement (relative to North America) from Late Jurassic to early Aptian time (Enachescu 2006;Sibuet et al 2007b) is supported by seismic reflection datasets showing the development of arcuate faults and basement ridges in the East Orphan Basin (Gacal-Isler 2009) as well as shear zones along the northeastern margin of the cap (Welford et al 2010c). At present, it is not clear how this transtensional dimension of rift complexity may have affected the conjugate Irish Atlantic margin.…”

“…Although largely extensional in origin, the tectonic evolution of the Orphan Basin-Flemish Cap and Irish Atlantic conjugate continental margins is also postulated to have involved contemporaneous rotation and displacement of Flemish Cap out of the Orphan Basin (Enachescu et al 2005;Sibuet et al 2007b). Owing to this added dimension of complexity, asymmetry in the conjugate pair and regional variations in crustal thinning are expected.…”