№ 1,
2006
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Gravitational anomalies of the South Caspian Basin and their nature
Institute of Geology and Geophysics of Azerbaijan National Academy of Sciences, AZ1143, Baku, H.Javid av., 119
Summary
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The South Caspian Basin (SCB) at present attracts increased attention of researchers in connection with its exceptionally rich oil and gas resources. In recent years new data have been obtained and new ideas emerged regarding its structure and geohistory. However, on the whole the question of origin of the basin as a single structure still remains debatable.
In this connection this paper presents an evaluation for predicted gravity anomaly in the SCB that may have formed as a result of the continental plate subsidence at its central part. The structure of the earth crust in the SCB is of suboceanic type and therefore the gravity anomaly formed as a result of subsidence of this plate has been appraised through its comparison with earth crust of the Russian Craton having continental structure. This anomaly has been revealed to be equal to -193 mGal and strongly differs from those observed in the SCB. In fact these 193 mGal appear to be compensated in some way. Such compensation is suggested to be possible due to an action of the strata located beneath the Moho discontinuity with considerably higher density than that of mantle material.
The gravitational action of the excessive masses located in the upper mantle was considered as an action of the horizontal cylinder shaped body and depth interval of the consolidated part of the upper mantle has been evaluated. On creating the geodynamic evolution model for the SCB one needs to take into account an asthenospheric projection which is predicted to occur at 45-135 km interval.
Main Objectives: Estimation of the gravitational anomaly resulting from subsidence of continental type plate and formation of the South Caspian Basin, and revealing nature of the observed gravitational anomalies.
In the SCB gravitational anomaly resulting from subsidence of continental type plate is compensated by action of the strata (mantle diapir, mantle plumes and asthenospheric projection) occurring at 45-135 km interval below the Moho discontinuity with considerably higher density than that of mantle material.