PICASSO: Program to Investigate Convective Alboran Sea System Overturn: NSF Continental Dynamics EAR 080893.  PICASSO examined subduction and lithospheric delamination under the Gibraltar Arc and Moroccan Atlas Mountains using active and passive seismology, geochemistry, and structural geology.  Rice was the lead US institution (AL, Cin-Ty Lee), with the University of Oregon (Gene Humphreys), University of Southern California (Meghan S. Miller, John Platt, Thorsten Becker), and WHOI (Rob Evans) as US partners, and the Institute of Earth Science “Jaume Almera” (ICTJA), Barcelona (Ramon Carbonell, Josep Gallart),  the University of Salamanca (Puy Ayarza), the Real Instituto y Observatorio de la Armada (ROA; Jose Dávila) as Spanish partners, and the Scientific Institute of Rabat (Ahmed el Hassani, Mimoun Harnafi)  as our Moroccan partner.

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Figure 1a) Tectonic domains of the Gibraltar Arc and Atlas Mountains. The Gibraltar Arc consists of the Internal and External Betics of Spain, the Internal and External Rif of Morocco, and the Alboran Sea extended terrane. TASZ is the Trans-Alboran Shear Zone. Triangles are Cenozoic volcanic fields.  b) Broadband seismograph arrays: Black are PASSCAL and USC stations, red are the IberArray and SIBERIA portable arrays deployed by ICTJA, and pink and dark blue are the Portuguese and Spanish national networks, light blue and yellow are the University of Lisbon Seismic Network, and the Western Mediterranean Seismic Network. In all we used data from ~ 240 broadband seismographs (see Thurner et al, 2014, G3, and Palomeras et al., 2014, G3).

Figure 2: Levander et al., 2014, Nature

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Figure 2: 3D composite seismic image of the lithosphere under the Atlas Mountains, Gibraltar Arc, and Iberian Penninsula.  Blue is the lithosphere (Vs ≥ 4.5 km/s) determined from Rayleigh wave tomography (Palomeras et al., 2014, G3), pink is the Alboran Slab (dVp > 1.5%) determined from teleseismic P-wave tomography (Bezada et al., 2013, EPSL). The lithosphere has been largely removed from beneath the Atlas mountains (Bezada et al., 2014, G3).  The lithosphere is still attached to the crust in parts of the western Rif and Betics. The lower crust and mantle lithosphere are actively delaminating from the central Rif and the eastern Betics (Thurner et al., 2014, G3).

PICASSO publications:

  1. Levander, A., Bezada, M.J., Niu, F., Humphreys, E.D., Palomeras, I., Thurner, S.M., Masy, J., Schmitz, M., Gallart, J., Carbonell, R. and Miller, M.S., 2014. Subduction-driven recycling of continental margin lithosphere. Nature, 515(7526), pp.253-256.
  2. Palomeras, I., Thurner, S., Levander, A., Liu, K., Villaseñor, A., Carbonell, R. and Harnafi, M., 2014. Finite‐frequency Rayleigh wave tomography of the western Mediterranean: Mapping its lithospheric structure. Geochemistry, Geophysics, Geosystems, 15(1), pp.140-160.
  3. Bezada, M.J., Humphreys, E.D., Davila, J.M., Carbonell, R., Harnafi, M., Palomeras, I. and Levander, A., 2014. Piecewise delamination of Moroccan lithosphere from beneath the Atlas Mountains. Geochemistry, Geophysics, Geosystems, 15(4), pp.975-985.
  4. Gil, A., Gallart, J., Diaz, J., Carbonell, R., Torne, M., Levander, A. and Harnafi, M., 2014. Crustal structure beneath the Rif Cordillera, North Morocco, from the RIFSIS wide‐angle reflection seismic experiment. Geochemistry, Geophysics, Geosystems, 15(12), pp.4712-4733.
  5. Thurner, S., Palomeras, I., Levander, A., Carbonell, R. and Lee, C.T., 2014. Ongoing lithospheric removal in the western Mediterranean: evidence from Ps receiver functions and thermobarometry of Neogene basalts (PICASSO project). Geochemistry, Geophysics, Geosystems, 15(4), pp.1113-1127.
  6. Ayarza, P., Carbonell, R., Teixell, A., Palomeras, I., Marti, D., Kchikach, A., Harnafi, M., Levander, A., Gallart, J., Arboleya, M.L. and Alcalde, J., 2014. Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide‐angle reflection seismic data: The SIMA experiment. Geochemistry, Geophysics, Geosystems, 15(5), pp.1698-1717.
  7. Bezada, M.J., Humphreys, E.D., Toomey, D.R., Harnafi, M., Dávila, J.M. and Gallart, J., 2013. Evidence for slab rollback in westernmost Mediterranean from improved upper mantle imaging. Earth Planet. Sci. Lett, 368, pp.51-60.