Geology Reference
In-Depth Information
composition and total salinity. The depth discharge occurs mostly by injec-
tion in the Productive Sequence section of genetically foreign low-salinity
hydrocarbonate-sodium waters.
It
is accompanied by the emergence of
alkaline hydrochemical anomalies against the general background of high-
salinity chlorine-calcium waters in the enclosing geologic medium. Their
mixing with the background waters often results in hydrothermal build-
ups. These buildups may be calcite veins and dykes, carbonate filled frac-
ture jointing, secondary cementation of reservoirs in the fault zones, etc.
Depending on geologic conditions, the surface discharge usually occurs
in two modifications. One is eruptions of depth hydrocarbonate-sodium
waters through exposed faults, ascending sources and mud volcanoes.
The result is the formation on the surface of travertines (90% carbon-
ates) (Binagady area, Bibieibat, Kirmaku Valley, Shubany, Cheleken, etc.).
Another is eruptions of hard brines syngenetic with the section serving as
sources feeding numerous lakes, sabkhas, etc.
We will now review in greater detail the genetic nature of the South
Caspian region's lakes. Figure 7.1 and Table 7.2 show that the lakes are
mostly concentrated on the Apsheron Peninsula, which forms as if a geo-
fluid-dynamic system's regional discharge center of the Mesozoic section
on the west flank of the South Caspian Depression. In its area of about
2,000 km
2
, the Peninsula includes over 200 large and small salt lakes with
an area close to 45.5 km
2
. The Peninsula also includes close to 50 sabkhas.
Caspian Sea
1
2
3
4
5
6
7
8
9
Figure 7.1
South Caspian Depression. Zones and areas of ground water discharge on
the Apsheron Peninsula:
1.
Exposures of sediments underlying the Middle Pliocene
Productive Sequence;
2.
Productive Sequence exposures; 3
.
Upper Pliocene exposures;
4.
Oil accumulations;
5.
Gas and condensate accumulations;
6.
Sabkhas;
7.
Major faults;
8.
Reservoir pinch-out lines; 9
.
Mud volcanoes and ascending thermal sources.
