Geoscience Reference
In-Depth Information
Fig. 2.33
Karst spring
''Jitoliub'', Milanovo Karst
Basin, Lakatnik Karst Region,
Bulgaria
This fact is reflected in the general NE-SW ori-
entation of the karst galleries in the region. Analyzing
the changes of principal stress axes from the Sub-
Hercinian to the Pyrenean Phase, it is possible to
deduce left rotation of the structures. For the most
recent processes such a deformation was not estab-
lished. The karst systems of the area are of precipice
type, actually active, and draining the superficial and
underground waters toward northeast. The contem-
porary configuration of the karst systems is possible
only when the minimum tectonic stress axis r
3
is
nearly vertical.
waters. A study on this problem in the context of the
tectonic control of the underground cave galleries was
published (Benderev et al.
2001
).
Geological and Hydrogeological Background
Milanovo Basin (Fig.
2.34
) with a surface of 101 km
2
is one of the biggest karst basins in Western Balkan
Mountain (Benderev et al.
1987
). Plakalnitsa Fault
separates the basin on the northeast from the karst
basins of Vratsa Karst Region. The rate of total ver-
tical displacement along the fault is 500 m, and it
disturbs the hydrological discontinuity of the karsti-
fied complexes of aquifers. The other borders are the
abrupt slopes from south and southeast toward Iskar
River, from southwest toward Proboynitza River, and
Varshets and Ozirovo valleys from northwest. A flat
plateau with average altitude of about 1,200 m is the
highest part of Milanovo Basin, dominating the Iskar
River valley (altitude 300-350 m).
Milanovo Karst Basin is build of Mesozoic rocks,
overlying different in age Paleozoic basement (dom-
inating granodiorite—granite complex) and Lower
Triassic sediments of Petrohan Terrigenous Group.
The lithological features of the Upper Triassic rocks
determine the existence of one thick complex able to
be karstified (Fig.
2.35
), separated partially by the
carbonate-terrigenous materials of Babino Formation
Lakatnik Karst Region (LAK)
The Lakatnik karst spring ''Jitoliub'' is discharging
waters drained from the southeastern part of the rel-
atively higher karstified zone (LAK in Fig.
2.29
)at
the source neighborhood (Fig.
2.33
)—Milanovo
Basin. One of the biggest caves in Bulgaria—Tem-
nata Dupka (more than 5 km long) is integrating the
old karst levels, as well as the present active galleries
and
their
natural
water
outflow—the
spring
''Jitoliub''.
The necessity to use this water leads to ecological
problems of the water qualities. One of the most
important problems in the area is the correct recog-
nition of the sites of the potential pollutant of the karst
