Mauretanian flysch nappe in the northwestern Rif Cordillera (Morocco): deformation chronology and evidence for a complex nappe emplacement

Abstract

This study deals with the Mauretanian flysch nappe in the southern side of the Gibraltar Strait, NW of the Rif belt (Morocco), where it is possible to better appraise the stacking pattern of its two structural components (the Tisirene and Béni Ider nappes), and to decipher the chronology of deformation and its structural relationships with the overlying (Predorsalian and Numidian nappes) and the underlying nappes (Melloussa and Intrarif units). It is found that the main deformations were produced by an intermittent compressional regime, during which north-south- to NW-SE-directed compressional phases alternated with ENE-WSW to east-west-directed compressional ones. Whereas the former were generated by the Africa-Iberia convergence and resulted in small-scale thrusts and a brittle deformation style, the latter were driven by the west-drifting Alboran plate and resulted in paroxysmal fold-thrust deformations. Field evidence shows that the emplacement of the Mauretanian nappe over the Massylian one and the Intrarif units operated by inter-related compressional and gravitational processes, by virtue of which the majority of nappes stacked in an out-of-sequence regime. The precise age of the paroxysmal phases remains uncertain because of paucity or absence of direct stratigraphical data. However, this structural evolution is likely to have started as early as the mid-Burdigalian, when sedimentation synchronously ceased in the flysch trough. Its final phases may be placed precisely between the Langhian (N8) age of the most recent formations overlapped by these nappes and the late Tortonian age of the oldest formations transgressively covering them.

Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation

“…The Nevado-Filabride continental units represent the underthrusted Iberian margin, with the "ophiolites" being derived from the neighboring Piemonte-Ligurian Ocean. To the west and north, the Alboran domain is underlain by a nonmetamorphic, WNW-ESE shortened fold-thrust belt consisting of Triassic to upper Miocene carbonates that thrusted in Miocene time [Platt et al, 2003b;Crespo-Blanc, 2007;Meijninger and Vissers, 2007] Thrusting of the flysch nappes, as well as of the external Betic and Rif fold-thrust belts, ceased in upper Tortonian time, both onshore and offshore [Platt et al, 2003b;Chalouan et al, 2006]. Field evidence from Morocco and from offshore seismic lines demonstrates that the youngest thrust contacts are unconformably covered by upper Tortonian (~8 Ma) and younger sediments [Crespo-Blanc and Juan, 2001;Melialdea et al, 2004;Chalouan et al, 2006;Iribarren et al, 2007].…”

Underpinning tectonic reconstructions of the western Mediterranean region with dynamic slab evolution from 3‐D numerical modeling

“…This led to an additional ~80° clockwise rotation of the northern segment, culminating in an E‐W, southward dipping orientation of the slab below the south Iberian margin. In all reconstructions, the slab arrives near its modern position in the Tortonian, complying with the geological evidence coming from uppermost Tortonian and Messinian sediments unconformably covering the Gibraltar trench, both onshore and offshore [ Crespo‐Blanc and Campos , ; Melialdea et al ., ; Chalouan et al ., ; Iribarren et al ., ; Ammar et al ., ].…”

Tectono‐Stratigraphic and Thermal Evolution of the Western Betic Flysch: Implications for the Geodynamics of South Iberian Margin and Alboran Domain

“…The Betic Cordillera of southern Spain is understood to result from the subduction of the western Tethys since at the last the Eocene and collision of the Alboran domain with the South Iberian paleomargin (Figure 1; Chalouan et al, 2006;Crespo-Blanc & de Lamotte, 2006;Faccenna et al, 2001;Michard et al, 2008;Platt, Allerton, et al, 2003;Rosenbaum et al, 2002). Geodynamic interpretations of the area vary in terms of timing and nature of the deformational events, paleogeography of the tectonic units, and amount and vergence of subduction (Lonergan & White, 1997;Rosenbaum et al, 2002;Vergés & Fernàndez, 2012; see discussion in van Hinsbergen et al, 2014).…”