Geology Reference
In-Depth Information
Table 4.1
Geotemperature gradients vs. specific geologic conditions in South
Caspian Depression.
Region
Г =
f
(Нп
п
t
, Нп
kt
)
Г
=
f
(
Н
з
п
)
Apsheron Peninsula
Г = 0.107
Н
0.379
Г = 0.445
Н
0.209
Lower Kura Depression
Г = 0.0004
Н
0.999
Г = 0.161
Н
0.314
Apsheron-Balkhanая zone of
highs
Г = 0.168
Н
0.292
Г = 0.696
Н
0.128
argument increments correspond with the same function increments.
This, in turn, indicates that the curves are not parallel, therefore they
intersect.
Expansion of the area delimited by the described curves at shallow
depths illustrates an increase in relative values of the positive temperature
anomalies caused by the discrete (on the geologic time scale) supply of
hyperthermal (relative to the surrounding medium) alkaline waters and
their discharge in piezominima areas within physically elevated and most
faulted zones of the section. Symptomatically, minimal values of average
geothermal gradients are recorded on the maximum faulted structures
with minimum depth to the lower alkaline waters.
The quoted data suggest that in the South Caspian Depression the effect
of convective component on the formation of geothermal regime in the
Middle Pliocene interval is mostly manifested by the emergence of local
positive thermal anomalies. It consistently decreases with depth and at the
limit, i.e., at the intersection point of the curves Г
=
f
(
Н
base PT
,
Н
base KT
) and
Г =
f
(
Н
tran.zone
) it tends to zero.
The depth to the lower boundary of the total heat flow's convective com-
ponent may be determined as abscissa of the stated functions' intersec-
tion point through joint solution of the equations. By equating their right
portions, we get for the Apsheron Peninsula 4,375 m, for the Lower Kura
depression 5,525 m and for the Apsheron-Balkhan zone of highs 5,807
m. Temperature at these depths is respectively 92°С, 96°С and 107°С. All
these give a reason to assume that at depths below the stated values, the
effect of the convective heat transfer becomes negligible and geothermal
field variations in that sedimentary cover range are mostly determined by
difference in rocks' thermophysical properties.
Practically all over the subject areas, the determined depths are within
the Miocene-Oligocene interval composed mostly of a thick sequence of
