Geology Reference
In-Depth Information
6. An exception at the present-day knowledge level is the total
inversion of the hydrochemical profile in the South Caspian
Basin and Indolo-Kuban trough. It is expressed as a jump-
like decrease of total salinity on a certain stratigraphic level
and the associated transition from the chlorine-calcium
ground water type to the hydrocarbonate-sodium and is
only manifested at the comparison of large sediment section
components: the Mesozoic regionally saturated with low
salinity alkaline varieties, and the Cenozoic with brines of
the chlorine-calcium background.
7. Local inversion effects recorded in the Cenozoic intervals of
these regions (such as salinity jumps, appearance of «transi-
tional» waters of lower salinity compared to the background)
usually belong with the most areas of the structures. They
are a particular case of cross-flow negative alkaline hydro-
chemical anomalies defined by the hydrodynamic factor;
they disturb the hard regional background manifesting the
direct zoning.
8. Similar occurrences in some intervals in the other regions
are limited vertically and in the area; they are most com-
monly the results of local dehydration of the clay minerals,
thermochemical filtration leaching of the enclosing rocks,
sporadically preserved desalinated paleo-infiltration waters,
exposure of some natural reservoirs, etc.
9. In some regions (the Los Angeles, Maracaibo and Viennese
basins) normal hydrogeochemical zoning is identified in
the areas where the sediment cover was drilled to the base-
ment. This indicates a particular specificity in the formation
of inverted hydrochemical profiles. The major factor in this
phenomenon is apparently the possibility of generation in
the sediment cover or endogenous penetration of the sedi-
ment cover by substantial volumes of CO
2
. hese are super-
posed over the other mandatory accompanying mechanisms
(clay dehydration, thermochemical effects).
