Geoscience Reference
In-Depth Information
good recorders of continental deformation in terms of
brittle structures and seismic features. Tectonics
controls the main directions of karst systems and
determines the mechanical limits to the karst expan-
sion. The exact and brief conclusion resulting from
these studies is: ''No dynamic constraints, no karst !''
(Quinif and Vandycke
2001
).
All these contributions emphasize the new quali-
tative view on the relationships between the geody-
namical processes and karst evolution, as well as the
importance of modern quantitative approaches for
deeper understanding of these relations.
The role of tectonic stress fields as a controlling
factor of karst and caves development is relatively
rarely mentioned in the geological and geomorpho-
logical literature. The importance of the paleostress
fields as a speleogenetic precondition is described
in the works of Jeannin (
1990
), Choppy (
1997
),
Hauselmann et al. (
1999
) for selected karst areas in
Switzerland and France. The papers published in this
period by S. Shanov (Chanov
1988a
,
b
; Shanov and
Cousset
1993
; Chanov and Benderev
1993
; Shanov
1996
; Benderev and Shanov
1997
; Shanov et al.
2001
;
Angelova et al.
1999
; Shanov and Georgiev
2001
)
reveal the important role of tectonic stresses as the
predestination condition for structuring of karst net-
works in different terrains in France, Cuba, Albania,
and Bulgaria.
Of course, fractures and faults are present as
undisputable factors in all works on karst genesis and
evolution. Many natural causes exist for the formation
of fractures and faults. Factors controlling the occur-
rence of natural, open, permeable fractures, are the
nature and intensity of folding, faulting and in situ
stresses acting on rocks with varying in space
porosity, bedding, and lithology. The rock properties
relating to brittleness are most important for varia-
tions in natural fracture density. These properties may
vary from regional to local scale; they may vary
significantly within the rock formations and between
formations. We focus on in situ studies of fracturing
and its relationship to stress, especially in rocks
potentially capable to be karstified (limestones, dol-
omites, marbles, etc.). Unfortunately, in publications
all over the world focused on problems of karst
genesis and development, this very problem is not
sufficiently discussed, or the fracture systems are not
analyzed from the viewpoint of tectonic stress field.
The neotectonic fracturing in karst regions, espe-
cially in regions of recently active karst, is one of the
important parameters that control the movement of
underground water and the development of karst
systems of underground cave passages and potholes.
In principle, the most convenient paths for the
underground water flow in karstifying massifs are
fractures that are oriented perpendicularly to the
minimum principal stress. These could be tensile
fractures in rock volumes close to the surface, as well
as shear joints, formed under conditions of an older
stress field, but found to be perpendicular to the
minimum compression of the younger tectonic stress
field. In such a case, the underground cave passages
with active water flow (draining channels) should be
oriented perpendicularly to the axis r
3
of the youngest
stress field, or under conditions close to the surface—
along the direction of stress r
1
.
The collector underground channel is the main
element of the cave system with its own specific
individuality. It is connected causally with the
lithology, the superimposed tectonic structure, and
hydrogeological conditions. Finally, ''…it is formed
as a result of channel system reorganization, and is a
consequence of the presence of a less permeable and
less stable fault zone perpendicular to the gradient
direction…'' (Šušteršiˇ
2003
). In brief, since the route
of water-penetrating limestone massifs and causing
karst phenomena is controlled by tectonics, it is
possible to use the inverse route: deduce the style of
tectonic movements from the characteristics of karst
phenomena.
1.2
Practical Applications
Our long experience in the karst regions in different
countries has shown that the karst systems might be a
good marker for arranging in the time the recon-
structed tectonic stress fields, in particular for recog-
nition of the Neotectonic and Quaternary stress fields,
and vice versa, the reconstructed and recognized as
young stress fields can help the forecasting of the
preferential directions of the karst galleries formation
and the related dominant flow of the karst waters.
According to Vandycke and Quinif (
2001
)''…karstic
caves are favorable sites for the observation and the
quantification of recent tectonic activity because they
