Geoscience Reference
In-Depth Information
Fig. 3.25
Longitudinal
profile and map of
Varteshkata Cave (after Beron
et al.
2006
)
Table 3.2
Parameters of the investigated stalagmites in Varteshkata Cave (after Paskaleva et al.
2008
)
H
(cm)
a
g
cm/s
2
D
Average
cm
Measured natural
frequency, f
0
Hz
Elastic
modul,
E GPa
Density
gr/cm
3
Tensile
failure stress
MPa
Theoretical natural
frequency, f
0
Hz
Tall
stalagmite
365
11.8
4.5
7.49
2.5 ± 0.08
1.62 ± 0.42
2.15
143.5
Small
stalagmite
140
5.3
10.6
7.49
2.5 ± 0.08
1.62 ± 0.42
6.56
438.1
situated on the right side of the Iskar river, at an
elevation of nearly 105 m above the base level. Some
data about the cave are reported by Ilieva et al. (
1981
)
and Kostov (
1999
) (Fig.
3.27
).
The cave is developed in the massive organogenic
limestones of Aptian age (Bedulian) of the Cherepish
formation, Vratsa Urgonian group (Nikolov et al.
1972
). These carbonates are highly karstified—for
example, in the Cherepish karst area more than 130
caves are currently surveyed within a 4 km
2
area.
From a tectonical point of view, the cave is situated in
the SE wedge-shaped part of the Zgorigrad anticline
(Jordanov et al.
1961
). The latter occupies most part
of the Vratsa Mountain and according to the classical
concept for the tectonic structure of Bulgaria (Yovcev
1971
), it is a structural unit belonging to the Stara
Planina Dislocation Strip.
The morphology of the studied cavity includes a
series of parallel passages striking 140-150 g devel-
oped along a fault and connected via difficult narrow
transversal passages (Fig.
3.2
). The maze-like cave
patterns (the network type of cave—sensu Palmer
1984
) are an indicator of a distinct structural control
on the speleogenesis.
The total length of the cave is 255 m and its ver-
tical extent ranges over 15 m. In some places the
original morphology is concealed by collapse phe-
nomena—gravitational deposits (breakdown blocks of
various sizes). Speleothems were also identified—dry
and weathered dendrites which cover large parts of
the cave walls. The survey was completed on
December 6, 1977 by members of the ''Academic''
speleoclub Sofia (Fig.
3.28
).
According to the results of former investigations
(Ilieva et al.
1981
; Angelova et al.
1995
; Kostov
1999
,
2008
), based on methods of relative geomor-
phology (correlation between caves levels and ter-
races of the Iskar River) it has been inferred that the
relative age of Labirinta Cave is Early Pleistocene.
From the comparatively wide range of neotectonic
speleoindicators
described
in
previous
works
