The initial stage in formation of the Dnieper-Donets depression was in the Late Proterozoic, and the final stage was in the Paleozoic. Recent deep seismic sounding profiles along with common depth point seismic surveys and deep drilling have confirmed that periodic floating up of relatively light material was an important factor in the development of this intra-continental depression. Also contributing to this periodic or pulse nature of these processes were super-deep faults, asthenospheric and crust-mantle diapirs, and elevated temperatures in plumes beneath the lithosphere.
The northwest orientation of the Dnieper-Donets paleo-rift was controlled by northwest pre-Devonian super-deep faults. This rift is broken up into segments by transverse super-deep or deep pre-rift faults.
The border faults of the Dnieper-Donets depression are zones of faulting - the Baranovichsko-Astrakhan on the north and the Pripyatsko-Manych on the south. Then toward the middle of the depression are the North (Severo) near-axial rift fault and South (Yuzhno) near-axial rift fault. Finally running down the middle of the depression is the Axial rift fault.
Reconstructions indicate that the crests of the asthenospheric and crust-mantle diapirs coincide with the axis of the Dnieper-Donets depression. Judging from the small but areally persistent thickness of the Middle Devonian deposits (beginning of the economic section) it is supposed that the pre-Middle Devonian deposits were eroded, and that this was favorable to cooling of the asthenospheric and core-mantle diapirs and also to subsidence of the crust not only in the area of the Late Proterozoic rift but also in adjacent areas.
A pyramid high is present on the M-discontinuity in the area of the Srebnen downwarp, which is located in the northwest part of the Dnieper-Donets depression. This downwarp is situated at the site of intersection of several major faults. Amplitude of this Srebnen mantle high exceeds 5 km, and width at its base is almost 50 km. Thickness of the pre-Devonian sedimentary rocks decreases signifi- cantly at this site as well as also that of the Devonian and Lower Carboniferous. These reductions in thickness are explained by pulsating rise of the Srebnen mantle high. Also indicative of this pulsating rise are the erosion and facies changes in the near-shore continental deposits of the upper Visean Stage of the Lower Carboniferous.
At the time of crustal uplift in the Late Devonian all the longitudinal faults (North, South, Axial, and others) were active. Highs associated with these faults were eroded, and volcanic activity was widespread. This explains the negative results of drilling on almost all the fault- associated highs of the northwest and central parts of Dnieper-Donets depression. This may not be true for the southeast part. (Taken from Gavrich (2000); digested in Petroleum Geology, Vol. 35, no. 3, 2001, in preparation, one cross section and one tectonic map.)
Copyright James Clarke, 2001. You are encouraged to print out this News Letter and to forward it to others. Earlier News Letters are available at: http://geocities.com/internetgeology/ This News Letter is distributed without charge in the interest of our science of petroleum geology. To be added to the distribution list please send your e-mail address to: jamesclarke@erols.com Information on the journal Petroleum Geology can be obtained by FAX at 703 759-3754 or by telephone at 703 759-4487.