Interplay of tectonics and magmatism during post-rift inversion on the central West Iberian Margin (Estremadura Spur)

ABSTRACT: The combined effects of post-rift magma emplacement and tectonic inversion on the hyper-extended West Iberian Margin are unravelled in detail using multichan nel 2D/3D seismic data. The Estremadura Spur, acting as an uplifted crustal block bounded by two first-order transfer zones, shows evidence of four post-rift tectonic events each with a distinctive seismic-stratigraphic response that can be used to dem onstrate the tectono-magmatic interplay, namely: (a) the Campanian onset of mag matism (including the Fontanelas Volcano, the widespread evidence of multiple sill complexes and the detailed description of a >20 km long laccolith, the Estremadura Spur Intrusion; (b) the Campanian-Maastrichtian NE-SW event pervasively affecting the area, resulting in regional uplift, reverse faulting and folding; (c) the Paleocene mid Eocene inversion that resulted in widespread erosion and; (d) the Oligocene-mid Miocene evidence of rejuvenated NW-SE inversion marked by crestal faulting and forced-fault folding establishing the final geometry of the area. The distinct deforma tion styles within each tectonic phase document a case of decoupled deformation be tween Late Cretaceous and Tertiary units, in response to the predominant stress field evolution, revealing that the magnitude of Late Cretaceous inversion is far more sig nificant than the one affecting the latter units. A detailed analysis of the laccolith and its overburden demonstrate the distinct deformation patterns associated both with magma ascent (including extensional faulting, forced-folding and concentric reverse faulting) and its interference as a rigid intrusive body during subsequent transpres sive inversion. This reinforces the role that the combined tectono-magmatic events played on the margin. Also analysed is the wider impact of post-rift magmatism and the associate emplacement of sub-lithospheric magma on the rheology of a thinned continental crust. This takes into account the simultaneous tectonic inversion of the margin, the implied alternative views on characteristic heat flow, and on how these can be incorporated in source rock organic maturity modelling.info:eu-repo/semantics/publishedVersio

Intraoceanic tectonism on the Gorringe Bank: observations by submersible

The Gorringe Bank is a 200 km long structure, oriented NE-SW, located at the eastern end of the Azores-Gibraltar line, at the Europe-Africa boundary. It consists of two mounts, Mount Gettysburg at the SW (−25 m) and Mount Ormond at the NE (−100 m). Previous works have shown that it corresponds to a section in oceanic mantle and crust. A recent expedition of the submersible SP 3000 CYANA (May-June 1981) has allowed us: (i) to confirm that Mount Gettysburg essentially consists of largely serpentinized peridotites. The study of two oriented samples collected in situ allows some inferences about the kinematics of emplacement for these ultramafics; (ii) to show that Mount Ormond is mostly composed of various gabbros corresponding to different stages of differentiation. All the samples are more or less recrystallized and display strong deformation from high-temperature mylonitization to low-temperature brecciation. Such a ubiquitous deformation is not common in ophiolite complexes and may be linked with the location of the bank at the Europe-Africa plate boundary; (iii) to observe two generations of undeformed dykes cutting the Ormond gabbros: the first one of dolerites genetically linked with the gabbros, the second of alkaline rocks, feeders of the more recent alkaline volcanics capping the mount

A multivariate approach to the feeding habits of small fishes in the Guadalquivir Estuary

Publicado