Tectonics
Supporting Information for
Compressional tectonic inversion of the Algero-Balearic basin: latemost Miocene
to present oblique convergence at the Palomares margin (Western Mediterranean)
Flavio GIACONIA (1), Guillermo BOOTH-REA (1), César R. RANERO (2), Eulàlia
GRÀCIA (3), Rafael BARTOLOME (3), Alcinoe CALAHORRANO (3), Claudio LO
IACONO (4), Montserrat G. VENDRELL (3), Alejandra L. CAMESELLE (3), Sergio
COSTA (3), Laura GÓMEZ DE LA PEÑA (3), Sara MARTÍNEZ-LORIENTE (3), Hector
PEREA (3), Marina VIÑAS (3)
(1) Departamento de Geodinámica, Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Campus
Fuentenueva s/n, 18071, Granada, Spain (flavio@ugr.es)
(2) Barcelona-Center for Subsurface Imaging, ICREA at CSIC, Institut de Ciències del Mar, Passeig Marítim
de la Barceloneta 37-49, 08003, Barcelona, Spain
(3) Barcelona-Center for Subsurface Imaging, Institut de Ciències del Mar - CSIC, Passeig Marítim de la
Barceloneta 37-49, 08003, Barcelona, Spain
(4) Marine Geoscience, National Oceanographic Centre, European Way, SO143ZH Southamton, United
Kingdom
Contents of this file
Text S1
Figures S1
Introduction
The MCS line TM-24 (see the manuscript Figures 7 and 11) does not image any
geological contact at the basal detachment of the Abubacer fault. Thus, to explore the
origin of the basal detachment we provide in the Supporting Information the calculation
of brittle-ductile transition depth at the Palomares margin. With this calculation we aim to
test the possibility that this basal detachment coincides with the brittle-ductile transition
in the crust of the margin.
To obtain a depth range for the brittle-ductile transition in the margin and constrain the
rheological behavior of the rocks we calculated the geotherm and several strength
envelopes using heat-flow data available in the region [Polyak et al., 1996; Soto et al.,
2008]. To determine the frictional deviatoric stress we used the equation given by the
modified Anderson’s theory:
zz-xx =gz(1-)
(1)
Where is a numerical parameter depending on the type of faulting with values of 3.0,
1.2, and 0.75 for thrust, strike-slip and normal faults, respectively; g,z and  are
1
average density, gravity, depth and pore fluid factor [Ranalli, 1995]. For ductile flow we
used the rheological model of dislocation creep proposed by Ranalli [1995]:
zz-xx = (/A)1/nexp(E/nRT)
(2)
Where  is the strain rate, A, n and E are Dorn’s parameter, stress exponent and creep
activation energy, respectively.
Text S1.
Calculation of brittle-ductile transition depth at the Palomares margin
To determine the frictional deviatoric stress we used the equation given by the modified
Anderson’s theory [Ranalli, 1995] employing a  value of 3.0 according to the thrustfaulting regime at the margin offshore. To determine the ductile flow we used the
rheological model of dislocation creep [Ranalli, 1995] employing both hydrostatical and
elevated pore pressures (=0.4 and 0.8, respectively) taking into account the
contribution of pore fluid pressure to frictional sliding. Furthermore, we used a common
strain rate (2.5 *10-14) and several creep parameter sets (A, n, E) to account for a broad
range of rock resistances. We calculated strength envelopes for plagioclase (An75) and
quartz diorite, using creep parameters from Ranalli [1995] (Fig. S1). Using a granodiorite
mineralogical composition (with an amount greater than 20% of quartz by volume where
at least 65% of feldspar is plagioclase, in the QAPF diagram) for the volcanic basement
of the margin [like rocks sampled in the Abubacer ridge by Duggen et al., 2008] we can
adopt a strength envelop intermediate between those of a quartz diorite and a
plagioclase (An75). The strength envelope indicates that currently the brittle-ductile
transition is at a depth of about 12.5 and 14.5 km and a temperature of 370 and 400ºC
approximately, for hydrostatic pressure and elevated pore pressures, respectively (Fig.
S1).
References
Duggen, S., K. Hoernle, A. Klügel, J. Geldmacher, M. Thirlwall, F. Hauff, D. Lowry, and
N. Oates (2008), Geochemical zonation of the Miocene Alborán Basin volcanism
(westernmost Mediterranean): geodynamic implications, Contributions to Mineralogy
and Petrology, 156, 577-593,
Polyak, B. G., M. Fernandez, M. D. Khutorskoy, J. I. Soto, I. A. Basov, M. C. Comas, V.
Y. Khain, B. Alonso, G. V. Agapova, I. S. Mazurova, A. Negredo, V. O. Tochitsky, J.
delaLinde, N. A. Bogdanov, and E. Banda (1996), Heat flow in the Alboran Sea,
western Mediterranean, Tectonophysics, 263(1-4), 191-218,
Ranalli, G. (1995), Rheology of the Earth, Second edition ed., 413 pp., Chapman & Hall.
Soto, J. I., F. Fernández-Ibáñez, M. Fernandez, and A. García-Casco (2008), Thermal
structure of the crust in the Gibraltar Arc: Influence on active tectonics in the western
Mediterranean, Geochem Geophy Geosy, 9, Artn Q10011
Doi 10.1029/2008gc002061.
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Figure S1. Strength envelopes for a granodiorite composition (the intermediate strength
envelop between those of a quartz diorite and a plagioclase An75) for the volcanic
basement of the Palomares margin [rocks sampled at the Abubacer ridge, Duggen et al.,
2008] indicates a brittle-ductile transition at a depth between 12.5 and 14.5 km and at a
temperature between 370 and 400ºC approximately. The frictional deviatoric stress was
obtained using the equation given by the modified Anderson’s theory (zz-xx = z(1)) [Ranalli, 1995] with both hydrostatical and elevated pore pressures (=0.4 and 0.8,
respectively). The ductile rheological behavior of the rocks was obtained using the
rheological model of dislocation creep and creep parameters proposed by [Ranalli,
1995]. The geotherm was obtained using heat flow data by Polyak et al.[1996] and Soto
et al. [2008].
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