Geoscience Reference
In-Depth Information
Fig. 2.38
Geological map of
the area of Iskrets Karst
Springs (according to Paskalev
et al.
1992
—Reproduced by
permission of Bulletin of
Bulgarian Geological Society)
1—Quaternary alluvium
(gravel and sands);
2—Quaternary colluvium
(rubbles); 3—Lower
Cretaceous (Salash
formation); 4—Tithonian-
Berriasian (Glojene
formation); 5—Lower-Middle
Bajocian (Etropole
Formation); 6—Sinemurian
(Ozirovo formation);
7—Hettangian (Kostino
formation); 8—Ladinian
(Milanovo formation);
9—Upper Anisian (Babino
Formation); 10—Anisian
(Lakatnik Member);
11 —Middle Anisian
(Opletnia Member);
12—Lower Triassic (Petrohan
Terrigenous Group);
13—Ordovician (Grohoten
formation); 14—fault with
unknown movements of the
blocks; 15—normal fault;
16—overthrust; 17—Cave
Dushnika; 18—Iskrets Karst
springs; Faults: (1) Topilia
faults; (2) Sulio fault;
(3) Ejdan-Breze fault;
(4) Tchernovodene fault;
(5) Dushnika fault
geophysical studies have shown that the northern block
subsided (Paskalev et al.
1992
).
Dushnika Fault. It cuts the sediments of Opletnia
Member, to the south of Iskrets Karst Springs. The
advance of Iskrets Overthrust toward north created
conditions for activation of the fault as inverse
structure, and probably it created conditions for bar-
raging the underground water flow and the formation
of the springs.
Tectonic Stress Fields Reconstructions
and Directions of the Karst Galleries
Two methods were applied for the analysis of the
tectonic stress fields—Nikolaev's Method (Nikolaev
1977
) based on the dispersion of the shear joints
density and studies of the electrical anisotropy.
The shear joints analyses are based on data from
three sites in the vicinity of the karst springs and
Dushnika Cave (Fig.
2.39
). The reconstructions gave
