Geology Reference
In-Depth Information
Formation temperature distribution within the depth range of (0)
to
(
−
6,000) m is approximated by the following equations:
The South Caspian Depression:
t
= 13.7 + 0.196
Н
0.725
.
The Padan Depression:
t
= 12.15 + 0.190
Н
0.747
.
The Viennese Depression:
t
= 11.0 + 0.038
Н
0.973
.
The Irrawaddy-Andaman Depression:
t
= 28.0+0.072
Н
0.900
.
The Los Angeles Basin:
t
= 15.6+0.154
Н
0.831
.
The Maracaibo Depression:
t
= 24.5 + 0.177
Н
0.784
.
The Carpathian Trough:
t
= 8.0 + 0.152
Н
0.778
.
The Indolo-Kuban Trough:
t
= 12.9 + 0.069
Н
0.888
.
Tersk-Caspian Trough
t
= 12.5 + 0.629
Н
0.655
.
Zagros Trough
t
= 25.0 + 0.091
Н
0.844
.
Both the figures and their analytical equations show the correlation
t
=
f
(
H
) is qualitatively similar for all regions. This reflects the unity of
their determining factors and conditions. This also suggests that the
following functionality of the geothermal regime in the Alpine folding
regions within the (-500) to (-6,000) m interval:
t
= 0.765
Н
0.616
is legiti-
mate (average geothermal gradient of 2.54°С/100 m). This correlation is
a mathematical form of major temperature trend with depth. Its specific
application is limited to comparisons of temperature conditions for dif-
ferent age tectonic mega-elements (platforms, folded belts, epiplatform
orogens, aulacogens, etc.)
The shape of “temperature vs. depth” and “geothermal gradient vs. depth”
curves (the gradients were determined as
dt
/
dH
) (Figure 4.1) shows that the
mechanisms controlling temperature distribution at depth show up differ-
ently down the section. In all regions in the depth interval about 800-1,500
m the shape of curves
t
=
f
(
H
) change and approach the depth axis.
Under specific geologic conditions in the sediment cover of mobile belt
basins, such phenomenon is believed to be controlled by three factors:
t
Transiency of geothermal field in the recent subsidence and
intense deposition areas.
t
Decrease in the rock density up the section together with the
growth in heat resistance.
t
Effect of heat loss optimization progressing up the section
(heat loss is caused by the increase in temperature gradient
on approaching the surface and cooling effect).
