Geoscience Reference
In-Depth Information
Fig. 2.34
General geological scheme of Milanovo Karst Basin
(after Benderev et al.
2001
) 1—Terrigenous and carbonate-
terrigenous rocks of Komshtitsa formation and Kostina forma-
tion; 2—Upper part of Triassic carbonate complex (Rusinovdel
formation); 3—Intermediate Triassic carbonate-terrigenous
layer (Babino formation); 4—Lower part of Triassic carbonate
complex (Svidol and Mogila formations); 5—Paleozoic rock
basement (granite complex) and Petrohan Terrigenous Group;
6—fault of unknown
type of movement; 7—normal fault;
8—thrust;
9—Karst
springs;
10—Rivers;
Main
faults:
(1)
Plakalnitsa, (2) Pop-Sokolets, and (3) Proboynitsa
in two sub-complexes of limestones and dolomites
(Mogila Formation with thickness of 150-350 m
composed of Opletnia and Lakatnik Members, and
Milanovo and Rusinovdel Formation—mainly dol-
omites). The lowest part of the sequence is most
susceptible toward karstification processes.
The upper part of the Triassic rocks profile is com-
posed of various terrigenous and carbonate-terrigenous
rocks of Komshtitsa Formation and partially by the
locally presented Jurassic terrigenous rocks of Kostina
Formation.
Milanovo Karst Basin contains 103 caves and prec-
ipices, the horizontal or inclined caves being predomi-
nant. The ratio of the total altitude change to the length
of the karst galleries is 0.07, and it presents the domi-
nation of the horizontal karstification. The velocity of
the underground karst hydrological system hollowing is
lower than the erosion on the surface and the
entrenchment of Iskar River. For this reason, the lowest
point of water discharging of Milanovo Karst Basin, the
spring ''Jitoliub'' near Lakatnik Railway Station, is
10 m above the level of Iskar River. Milanovo Basin is
receiving its water from the atmospheric precipitation,
as well from the local rivers. Water losses were detected
at the riverbed of Proboynitza River and some of its
tributaries. The average total discharge of the basin
springs is 1,341 l/s, or presented as a module of the
groundwater flow—13.3 l/s.km
2
. The minimum dis-
charge is 197.5 l/s. The important part of the natural
resources belongs to the spring of ''Jitoliub'' draining
Lakatnik Karst Region. Some quantity of this water is
used for supply of potable water.
The area near the railway station of Lakatnik is
known with the largest quantity of underground karst
