The Valencia Trough is an extensional basin which began rifting
during the late Oligocene/early Miocene yet, is located within a
region of compression between the European and African plates.
Seismic reflection, seismic refraction, well, gravity and geoid data
have been used to determine the relative importance of
extensional and compressional processes in controlling the
structure and evolution of the trough. Although the trough
appears symmetric on bathymetric maps, seismic and gravity and
geoid data indicate a fundamental asymmetry in its deep crustal
and upper mantle structure. 2-D flexural backstripping of a
seismic reflection profile along a "transect" of the trough between
the Catalan Coastal Ranges and Mallorca suggest that the crust has
been stretched by up to a factor of 3. There is good agreement
between the predicted depth to the Moho based on a stretching
model and the seismically constrained depth beneath the Catalan
margin but, poor agreement beneath Mallorca. The seismic Moho
beneath Mallorca can be explained by a model in which the crust
was modified by the flexural effects of thrust/fold loading. Geoid
data suggest the differences in the crustal structure between the
two margins extend into the upper mantle. The Catalan margin is
characterized by a thermal and mechanical boundary, which
marks the transition between cold, unstretched, lithosphere and
hot, thin, lithosphere while Mallorca is located above a broad
region of lithospheric thinning. The subsidence history and
amount of crustal thinning in the Catalan margin resembles that of
a typical Atlantic-type non-volcanic margin. However, a narrow
transition zone ( < 60 km), the lack of any evidence for a
"conjugate" margin and, the absence of oceanic crust suggest
fundamental differences in the way that extensional processes
may occur in convergent plate settings.
Watts, A.B. and TornŽ., "Subsidence History, Crustal Structure and
Thermal Evolution of the Valencia Trough: A Young Extensional
Basin in the Western Mediterranean." J. Geophys.Res.,97, 20,021 -
20,041, 1992