Evidence for the eastward migration of the Alboran Sea based on regional subsidence analysis: A case for basin formation by delamination of the subcrustal lithosphere?

Abstract

The paradox of an extensional basin forming at a site of colliding continents is apparent in the evolution of the Neogene Alboran Sea basin of the westernmost Mediterranean. Processes that may be responsible for such basins forming at sites of continental collision include subduction and the removal of subcrustal lithosphere by either convection (extensional collapse) or delamination and have recently been invoked to explain the formation of the Alboran Sea basin. Decoupling of the thermal boundary layer can reverse the stress field from a state of compression to one of extension. The processes of extensional collapse and delamination involve removal of this layer and would have similar consequences in terms of modifying lithosphere geometry: replacement of the detached thermal boundary layer by hot asthenospheric material, which would produce a high geothermal gradient and in turn cause uplift at the surface. With identical effects, it is difficult to distinguish between the two mechanisms. Using the technique of backstripping, a subsidence history which evidences the coexistence of subsided and uplifted areas in the Alboran Sea basin through the Miocene to the Quaternary, has been reconstructed for the basin. While the deformation front of the Alboran Domain migrated westward, subsidence in the Alboran Sea basin propagated in the opposite sense, east/southeastward. This is best explained as the basin forming above a southeastward‐propagating, delaminating subcrustal lithospheric slab.

Scenarios for earthquake-generated tsunamis on a complex tectonic area of diffuse deformation and low velocity: The Alboran Sea, Western Mediterranean

“…3). This shallow lower limit is in agreement with the lithospheric structure obtained from geophysical and rheological modeling (Docherty and Banda, 1995;Tome et al, 2000;Fullea et aI., 2007;Fernandez-lbafiez and Soto, 2008) and from previous seismicity studies (Lapez Casado et al, 2001). This thin crust implies a physical limit to the generation of great earthquakes, although some important events have been described in historical times with intensities of VIII-IX and estimated magnitudes of 6.5-7.0 (Martinez Solares, 2003;IGN, 2008).…”

“…1989;Platt and Vissers, 1989;Vissers et al, 1995). In addition to these hypotheses to explain the shallow tectonics, there are also a number of hypotheses to explain the intermediate and deep focus earthquakes that take place in the area, divided into delamination processes (Garcia-Duefias et al" 1992;Watts et aI., 1993;Docherty and Banda, 1995;Seber et al, 1996;Buforn et al, 1997;Mezcua and Rueda, 1997;Morales et al, 1997) and subducted slab processes (Royden, 1993;Gutscher et aI., 2002;Thiebot and Gutscher, 2006); maybe being both active for deep and intermediate earthquakes respectively (Bufom et aI., 1991;L6pez Dsado et aI., 2001).…”

Role of pre-rift rheology in kinematics of extensional basin formation: constraints from thermomechanical models of Mediterranean and intracratonic basins

“…In addition to the inferred coupling of various stages in their tectonic evolution, a spatial flexural coupling appears to exist between extensional basin formation in the offshore domains and adjacent onshore foreland fold and thrust belts. Such a coupling is supported by data collected in the northern Tyrrhenian Sea/northern Apennines (Keller et al, 1994), Valencia Trough/southern Pyrenean foreland basin (Zoetemeijer et al, 1990;Verges et al, this issue), the Albor~n Sea/Betic System Docherty and Banda, 1995) and the Pannonian/Carpathian system (I-Iorv~ith, 1993). Kinematic modelling studies of the extensional basins in the Gulf of Lion margin (Kooi et al, 1992), the Valencia Trough (Janssen et al, 1993) and the southern part of the Tyrrhenian Sea (Spadini et al, 1995) have provided quantitative estimates for necking depths and other parameters on the pre-rift lithosphere of the western Mediterranean basins.…”

Tertiary-Quaternary subduction processes and related magmatism in the Alpine-Mediterranean region

“…However, the mechanism of this process is highly debated. The competing geodynamic models involve (a) back-arc extension behind the westward retreat of an east-directed subduction zone along the present Gibraltar arc or the Horseshoe seamounts in the eastern Atlantic (Royden 1993;Lonergan & White 1997;Gelabert et al 2002;Gill et al 2004); (b) detachment of the subducted slab (Spakman 1990;Blanco & Spakman 1993;Carminati et al 1998;Zeck 1999;Calvert et al 2000); (c) delamination of the lithospheric mantle (Garcia-Dueňas et al 1992;Docherty & Banda 1995) and (d) convective removal of the lower part of the overthickened lithosphere (Platt & Vissers 1989;Turner et al, 1999). To the east, the presence of a Tethyan oceanic basin enabled the retreat of the ApenninesMaghrebides subduction zone (Carminati et al 1998;Gueguen et al 1998).…”