Active surface deformation and sub-lithospheric processes in the western Mediterranean constrained by numerical models
Summary (1 min read)
INTRODUCTION
- The authors modeling studies demonstrate the need for sub-crustal or sub-lithospheric, southwestward-directed forcing to account for observed southwestward motion of the Rif and Betic domains.
- The authors then discuss the implications of these model results in light of previous geodynamic models of the plate boundary zone.
TECTONIC SETTING OF THE WESTERN MEDITERRANEAN
- In the western Mediterranean, the Alboran Sea is a thinned continental domain (15 km thickness; Lonergan and White 1997) surrounded by the Internal Rif and Internal Betics , which are the westernmost limit of the Alpine mountain belt (Fig. 1).
- Three factors are likely to infl uence the spatial distribution of the interseismic strain 1) lateral plate driving forces due to long term Nubia-Eurasia oblique convergence, 2) low rigidity of the diffuse plate boundary zone, and 3) deep traction beneath the plate boundary due to upper mantle drag or slab traction.
- The RMSs for the entire zone and for the Rif-Betics region are summarized in Table 1.
- Depending on the thermal regime, the effective elastic thickness of continental plates varies from 3 to 80 km (Watts and Burov, 2003).
DISCUSSION AND GEODYNAMIC IMPLICATIONS
- The authors modeling experiments include no a priori information on sub-lithospheric geometry and are designed to determine whether sublithospheric processes are needed to account for observed deformation of the western Mediterranean region.
- Geodynamic models of the zone involving still active westward rollback of the western Mediterra- nean narrow slab (Gutscher et al., 2002) cannot generate such a small coupling zone confi ned to the External Rif. Spakman and Wortel (2004) suggested that the western Mediterranean slab is detached under the Betics.
- The authors further suggest that the horizontal traction patch could represent the remaining coupling zone between the slab and the overlying continental lithosphere.
- According to their delamination model (Fig. 3) the traction zone is expected to move to the south-southwest following propagation of the delamination front.
- During the Pliocene-Quaternary, eastward subduction has died out, as suggested by the accretionary wedge sealed by undeformed sediments (Zitellini et al., 2009).
ACKNOWLEDGMENTS
- The authors thank G. Bokelmann, S. Lallemand and J.L. Bodinier for their fruitful discussions, and to C. Faccenna and fi ve anonymous reviewers for their constructive comments on this manuscript.
- Reilinger benefi ted from a Visiting Researcher Fellowship from the Observatoire de Recherche Méditerranéen en Environnement of Montpellier while engaged in this study.
Did you find this useful? Give us your feedback
Citations
17 citations
16 citations
Cites background from "Active surface deformation and sub-..."
...These processes appear to be related to active subduction (e.g. Gutscher et al., 2002), deep‐seated delamination processes (e.g. Fadil et al., 2006, Pérouse et al., 2010, Petit et al., 2015, May‐Baratin et al., 2016, among others), or slab dragging (Spakman et al., 2018)....
[...]
16 citations
Cites methods from "Active surface deformation and sub-..."
...Pérouse et al. (2010) and Petit et al. (2015) 409 reached a similar conclusion, based respectively in the modeling of GPS data and in the analysis 410 of the degree of isostatic compensation of the Rif topography....
[...]
...To account for those observations, 104 Pérouse et al. (2010) presented a geodynamical model involving dragging from the slab beneath 105 eastern Rif, resulting in a crustal thickening beneath this area....
[...]
15 citations
Cites background or methods from "Active surface deformation and sub-..."
...Dense temporal deployments in the Betic‐Rif region help evaluating subcrustal earthquakes and lithospheric structure....
[...]
...Motion of the Rif has been attributed to slab rollback (Pérouse et al., 2010), although upper mantle anisotropy (Diaz et al., 2010) indicates mantle flow perpendicular to the escape of the Rif....
[...]
...This direction also characterizes compression in NW Morocco, providing support for a deep origin of the emplacement of the Rif mountains in direction perpendicular to current plate motion....
[...]
...The direction of compression is similar to the peculiar SW motion of the Rif block in NW Morocco with respect to the Nubian plate (Fadil et al., 2006; Koulali et al., 2011)....
[...]
...From dynamic modeling of GPS velocities, the SW escape of the Rif has been attributed to horizontal traction applied to the base of the Rif (Pérouse et al., 2010)....
[...]
References
1,609 citations
884 citations
"Active surface deformation and sub-..." refers background or methods in this paper
...…plate boundary in the western Mediterranean and the geometry of the subducted plate are still debated (Calvert et al., 2000; Gutscher et al., 2002; Faccenna et al., 2004; Spakman and Wortel, 2004), we use an elastic plate model approach in order to evaluate the role of basal traction below the…...
[...]
...Tomographic studies (Calvert et al. 2000; Gutscher et al., 2002; Faccenna et al., 2004; Spakman and Wortel, 2004) reveal a narrow east dipping slab (100–200 km wide) located in the Gibraltar Arc....
[...]
...The tectonic evolution of the western Mediterranean and the Alboran Sea has been dominated by the long history of Nubia-Eurasia plate convergence associated with the subduction of the Neotethys Ocean (e.g., Faccenna et al., 2004)....
[...]
...The mechanism responsible for the continental and oceanic nature of the slab (delamination or continental subduction) is still debated (Faccenna et al. 2004; Duggen et al. 2008)....
[...]
...…(1) backarc extension driven by the westward rollback of an eastward subducting slab (Royden, 1993; Lonergan and White, 1997; Gutscher et al., 2002; Faccenna et al., 2004), which passively falls in the mantle driven by its own weight (subduction without convergence, Jolivet et al. 2008) ; (2)…...
[...]
822 citations
"Active surface deformation and sub-..." refers background in this paper
...…1993); (3) crustal extrusion due to forces transmitted across the Eurasia-Africa plate boundary (Rebai et al., 1992); and (4) delamination and convective removal of the lithospheric mantle root beneath the collisional orogen (Platt and Vissers, 1989; Seber et al., 1996; Calvert et al., 2000)....
[...]
818 citations
"Active surface deformation and sub-..." refers background in this paper
...…interaction of plates (i.e., elastic strain and associated faulting, e.g Savage and Burford, 1973), sub-crustal processes (e.g., subduction and slab rollback, mantle delamination, Royden,1993), and/or stresses induced by gravitational potential energy differences (e.g., England and McKenzie 1982)....
[...]
710 citations