Structure and evolution of the “Olistostrome” complex of the Gibraltar Arc in the Gulf of Cádiz (eastern Central Atlantic): evidence from two long seismic cross-sections

Abstract

Reflection profiles characterize the structure and the upper Mesozoic to Cenozoic deposits of the Gulf of Ciidiz region. Two long ENE-WSW multichannel seismic lines (ca. 400-500 km long) are analyzed to study the evolution of the area from the continental shelf to the Horseshoe and Seine abyssal plains. The huge allochthonous deposits emplaced in this region (the so called "Olistostrome" of the Gulf of Cadiz) are described in terms of three different domains on the basis of the seismic architecture, the main tectonic features and the nature of the basement, oceanic or continental. The eastern domain extends along the continental shelf and upper and middle slope and corresponds to the offshore extension of the Betic -Rifean external front. It is characterized by salt and shale nappes later affected by extensional collapses. The central domain develops along the lower slope between the Betic-Rifean front and the abyssal plains and is characterized by a change in dip of the allochthonous basal surface and the basement. The allochthonous masses were emplaced by a combined gravitational and tectonic mechanism.The nOlihern boundary of this domain is marked by the occurrence of an outstanding WNW -ESE-trending thrust fault with a strike-slip component, termed here as the Gorringe-Horseshoe fault. The westernmost domain corresponds to the abyssal plains, where the distal emplacement of the allochthonous body takes place; it is characterized by thrust faults affecting both the sedimentary cover and the oceanic basement. The allochthonous masses show a less chaotic character and the thickness decreases notably. These domains represent different evolutionary steps in the mechanisms of emplacement of the allochthonous units. The eastern domain of the allochthonous units was emplaced as part of the pre-Messinian orogenic wedge related to the collision that gave rise to the Betic-Rifean Belt, whereas the allochthonous wedge of the central and western domains were emplaced later as a consequence of the NE-SW late Miocene compression that continues in present times.

The global relevance of the Scotia Arc: An introduction

“…This arc straddles the convergent boundary between Africa and Iberia and is associated with the development of an accretionary prism in the Gulf of Cádiz which is overriding the central eastern Atlantic Plate (Maldonado et al, 1999;Medialdea et al, 2004;Zitellini et al, 2009;Duarte et al, 2013). The Gibraltar Arc occupies the location of the Mesozoic Atlantic-Tethys connection during the Mesozoic and early Cenozoic and of Atlantic-Mediterranean oceanographic interactions during the late Cenozoic (Maldonado and Nelson, 1999;Vergés and Fernández, 2012.).…”

Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): Palaeoenvironmental records of fluid venting and bottom currents

“…The development of the Rifean-Betic orogen is the consequence of the westward drift and collision of the Alboran Domain with the North African and South Iberian margins in the Early to Middle Miocene under the N and NW Africa-Eurasia convergence and the emplacement of huge chaotic masses with a wedge shape (e.g. Medialdea et al, 2004;Platt et al, 2006) (Fig. 1) composed of a chaotic mixture of Triassic, Cretaceous, Palaeogene and Neogene materials .…”

“…Baraza and Ercilla, 1996;Gardner, 2001;Pinheiro et al, 2003;Somoza et al, 2003;Medialdea et al, 2004;León et al, 2007). Detailed information about the location and the geophysical methods used in this work can be found in the Fig.…”

Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

“…Structurally, this 'Gibraltar Arc Foreland Basin' is relatively indistinct due to the accompanying tectonic deformation of the foreland region and the chaotic deposition of the huge Gibraltar Arc Allochthon ( Fig. 1; Torelli et al, 1997;Medialdea et al, 2004). Like the Guadalquivir Allochthon ( Fig.…”