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regional kinematics in the Caribbean realm, imposed
by the opening of the Cayman trough and the disruption
between Cuba and Hispaniola.
The youngest tectonic stress field was recon-
structed only in the marls of MAQ Formation (Site
4—C). This tectonic stress field determines the
opening of a sub-vertical system of fractures with
general direction N 30. This is also the general
direction of the galleries of the largest cave system in
the region—El Campanario. It is reflected also by the
rose-diagram from Site 3 (Fig.
2.48
). At the entrance
of El Campanario Cave the rose-diagram of the
fracture orientation is mostly coinciding with the
strike of the system of faults with orientation favor-
able for opening under the conditions of stress field C.
A number of cave entrances are situated along these
faults. Rojas-Agramonte et al. (
2003
) reconstructed
deformation phases D2 and D3 comprising NE-SW to
nearly N-S directed compression.
Sites 6-k, 9-k and 14-k in Fig.
2.48
are the places
of azimuthal vertical electrical sounding. The corre-
sponding graphs are plotted on Table
2.7
.
The graphs show the general tendencies of the
electrical anisotropy on the site of measurements.
Sites 6-k and 14-k are informative for the limestones
of CHR Formation, while site 9-k is on a large neg-
ative karst structure with a tick filling of young,
mostly Quaternary sediments.
The ellipses of anisotropy at point 6-k are for
depths not exceeding 10 m and their general direction
of the long axes N 95 reflects the controlling role on
the fracturing of the nearest fault with the same
direction. But the site was situated exactly over the
known galleries of Campanario Cave and the abrupt
changes of the direction of the anisotropy ellipse to
azimuths between N 5 and 50 is reflecting the
preferential direction of the cave galleries. The situ-
ation is similar for point 9-k where a clear coinci-
dence exists between the long axes of the electrical
anisotropy ellipses (N 50) and the detected linea-
ments with SW-NE direction. The young age of this
direction was discussed above and probably it con-
trols the recent karstification. It can be also assumed
that this is the direction of a satellite fault to the well
expressed regional fault zone of E-W direction.
The E-W direction is well reflected in the ellipses
of anisotropy from point 14-k. Even to depth more
than 100 m, the direction N 90-95 is so stable that it
clearly illustrates the controlling role of the sub-
equatorial fault on the karst structures near the falling
of Guaso River into the underground karst system.
2.3.4
France: Tectonic Stresses
and Their Control on the Karst
Formation in Plateau of Vaucluse
(Alps Maritimes, France)
Plateau of Vaucluse, framed by Mont Ventoux
(1,912 m) from northwest, by the Mountain of Lure
(1,826 m) from northeast, and by the geological
structure, named Syncline of Apt from the south
(Fig.
2.49
), is worldwide known with its karst phe-
nomena. Spring Fontaine de Vaucluse is the most
impressive karst manifestation in this region (vau-
clusian type of spring). The 308 m deep abyss is
draining the underground waters from the plateau.
The coloring test of waters from different places on
the plateau or in the caves has shown a relation
between the caves and the Spring of Vaucluse (Mudry
and Puig
1991
). Among a number of publications
concerning the karst of this area, a study on the
relationship between karst formation and recent tec-
tonics in the context of the tectonic stress fields has
been published (Shanov and Cousset
1993
). More
detailed analyses, including reference on geodetic
records, completed these studies (Shanov and
Georgiev
2001
). The presented analyses follow the
principal results from these two publications.
Southeastern France is also an area of earthquake
activity and this fact allows for a more complete
evaluation of the contemporary tectonic stress field
and the related processes in the karst.
2.3.4.1 Geological Background
Plateau of Vaucluse is formed by limestones and
marl-limestones of Lower Cretaceous-Hauterivian,
Barremian and Bedoulian age, as well as by rocks of
the Urgonian reef facies (after Fage
1981
). The Pro-
vencal tectonic phase at the end of the Eocene has
marked the uplift of Plateau of Vaucluse and the
beginning of the karst processes in the limestones.
The contemporary morphological features were
formed during the Post-Pontian tectonic phase,
expressed by the overthrusts of Mont Ventoux and of
Lure Mountain, when the Provencal tectonic block
