Neogene to recent contraction and basin inversion along the Nubia-Iberia boundary in SW Iberia

Abstract

The SW of Iberia is currently undergoing compression related to the convergence between Nubia and Iberia. Multiple compressive structures, and their related seismic activity, have been documented along the diffuse Nubia‐Iberia plate boundary, including the Gorringe bank west of the Gulf of Cadiz, and the Betic‐Rif orogen to the east. Despite seismic activity indicating a dominant compressive stress along the Algarve margin in the Gulf of Cadiz, the structures at the origin of this seismicity remain elusive. This paper documents the contractional structures that provide linkage across the Gulf of Cadiz and play a major role in defining the present‐day seismicity and bathymetry of this area. The structures described in this paper caused the Neogene inversion of the Jurassic oblique passive margin that formed between the central Atlantic and the Ligurian Tethys. This example of a partially inverted margin provides insights into the factors that condition the inversion of passive margins.

The Tell-Rif orogenic system (Morocco, Algeria, Tunisia) and the structural heritage of the southern Tethys margin

“…Geological data from Iberia and Africa show a set of NE to ENE trending "en echelon" Mesozoic basins, which were more or less subject to tectonic inversion during the Cenozoic. These basins are: the Algarve (Ramos et al, 2016;2017a, 2017b and Subbetic (García-Hernández et al, 1989;Vera, 2001) basins on the Iberian side and the Khemisset-Rif (Favre, 1995;Favre et al, 1991), Middle-Atlas, High-Atlas, Sahara-Atlas and TunisiaAtlas basins on the African side (Frizon de Lamotte et al, 2000, 2009 and references therein; Fig. 5A).…”

“…More precisely, it corresponds to an orogenic climax in the Pyrenees (Vergés and García-Senz, 2001) (the concept of Pyrenean phase), the Iberian Chain (Guimerá et al, 2004), the Catalan Coastal range (López-Blanco et al, 2000) and in Southern Portugal (Algarve region: Ramos et al, 2016, Ramos et al, 2017a. Mirroring the Iberian intra-plate deformations, North Africa also recorded a strong middle-upper Eocene intraplate compressional event, present at the scale of the whole Atlas belt (the concept of "Atlas event" [Frizon de Lamotte et al, 2000, 2009, 2011).…”

Crustal structure of the SW Iberian passive margin: The westernmost remnant of the Ligurian Tethys?

“…N-S to NW-SE directed shortening during the Neogene led to the partial inversion of the passive margin, with the development of southward directed thrusts that have resulted in a stair-stepped topography and bathymetry (Ramos et al, 2017). During compression, most likely during the Tortonian, the Accretionary Wedge of the Gulf of Cadiz (AWGC; chaotic and mélange-like assemblage of Mesozoic to Cenozoic sediments, Fig.…”

“…Roughly N-S directed compression during the Mesozoic caused the partial inversion of the basin (Ramos et al, 2017) resulting in the present-day configuration of the basement of the basin (Fig. 9b).…”

“…12 responsible for inversion are not evident on seismic and have been inferred from multiple criteria, mainly from the tilting and truncation of Mesozoic and Cenozoic units and the geometry of the BFU unconformity (Ramos et al, 2017) (Fig. 10).…”