Grigorov downwarp is a large compensated structure located in the southern part of the Dnieper-Donets depression of the Ukraine. Its steep, narrow northern border is at the same time the southern flank of the Sosnov-Belyayev zone of salt domes, and the more gentle southern border passes into the monoclinal border of the depression.
The northwestern border of Grigorov downwarp is complicated by swell-like structures, which are persistent in the modern structure. Up until recently, however, the southeastern border had been represented as relatively undisturbed. Studies now show, however, that similar structures that have lost their closure existed on the southeastern border of this downwarp.
On a basis of correlational analysis of the structural plans of reflecting horizons IVb (top of Lower Permian sediments) and IVg (base of Lower Permian evaporites) there are three zones of maximum angular coefficient of regional regression (K), which trend parallel with the border of the downwarp and correspond with a terrace-like zone of reflecting horizon IVb. This coefficient is a measure of internal stratigraphic and structural discordance. The northern zone of maximum K's contains the most intensive anomalies.
The possibility of existence of inhomogeneities in the Lower Permian sediments between reflecting horizons IVb and IVg is confirmed by the results of correlational analysis of the gravity and magnetic fields, according to which there is a chain of intensive extremes of K along the southeastern border of Grigorov downwarp. These are characteristic of the known local structures of the sedimentary cover of the southern border zone of the Dnieper-Donets depression.
These inhomogeneities in the Lower Permian sediments may be due to salt plugs or biohermal buildups.
Elongate zones of local uplifts appear to be present in the western and southeastern parts of the southern border of Grigorov downwarp. These are particularly well expressed in the Lower Permian complex. In the west where the border is steeper there is a single zone of uplifts, the Oktyabr. In the southeast where the border is more gentle there are three zones of uplifts that have lost their closure.
The existence of these elongate zones of uplifts is of practical as well as scientific interest. The Lower Permian evaporite complex is commercially productive in several gas fields in the southeastern part of the Dnieper-Donets depression. The shallow depth of this play at less than 3000 m makes it more attractive.
Taken from Burakovskiy, 1986; digested in Petroleum
Geology vol. 23, no. 7/8, two structure maps.
Copyright 2003 James Clarke. You are encouraged to print
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