Geology Reference
In-Depth Information
formation temperature as it suppresses activities of the sulphate-reduction
bacteria (Kuznetsov, Ivanov and Lyalikov, 1962; Rachinsky, 1973; Rachinsky
and Aliyev, 1973). Besides, it indicates the presence of vertical cross-flows
of the Mesozoic origin sulphate-enriched waters into the upper intervals
of the sedimentary section, which results in strictly continuous decrease in
the SO
2
−
concentration up the section corresponding with the decrease in
the Cenozoic formation waters of the foreign lower component.
The following conclusions were made regarding the Padan Depression
hydro-chemistry:
t
Vertical hydrochemical zoning of the region is normal: down
the stratigraphic section relatively low-salinity (8.6
23.9 g/l)
hydrocarbonate-sodium (primary alkalinity factor 6.49
−
−
31.14%-equiv.) waters of the clastic Pleistocene-Oligocene
stage are replaced by the chlorine-calcium (secondary salin-
ity factor 25.14
−
34.25%-equiv.) brines (111.6
−
132.6 g/l) of
the carbonate Mesozoic;
t
In hydrocarbonate-sodium water medium their salinity
growth in the vertical direction is accompanied by a decrease
in the primary alkalinity factor values; and in the chlorine-
calciumх brine medium, by an increase in the secondary
salinity factor;
t
In the Cenozoic clastic series maximum ground water salin-
ity values and minimum primary alkalinity factor values
are recorded in the largest hydrocarbon fields where the
Mesozoic stage is also productive (Cortemaggiore, Malossa,
Ravenna-Mare and Porto-Corsine-Mare).
The hydrochemical outlook, geology and manifestation conditions
define carbonate Mesozoic chlorine-calcium brines as a metamorphism
result of ooze water in the marine depositional basin of normal salinity
(Valyashko, 1964; Kapchenko
et al
., 1972; Kapchenko, 1974, 1983).
The low-salinity hydrocarbonate-sodium waters of clastic Cenozoic
complexes in terms of their origin bear a clear footprint of the paleo-
depositional environment, which mostly occurred in a brakish medium
of the basin's neritic area (Rocco and Jaboli, 1961). The alkaline nature of
the ground water appears to be a derivative of lithification at the sedimen-
togenesis and early diagenesis stages. At that time the ooze (pore) waters
were enriched in carbonate- and bicarbonate-ion from the contact with
alkali-containing mineral associations of enclosing rocks formed upon
erosion and redeposition of base magmatites from the framing Alps and
Apennines.
