The Lower Permian salt complex is widespread in the Dnieper-Donets depression. Conditions for formation of these deposits were different from those for the Devonian salt by the fact that accumulation took place not in a rift environment but rather in sineklize (regional low) stage, which lasted from the late Visean to the Anthropogene. This basin of deposition was an embayment hundreds of kilometers long and 100 km wide that connected with the sea on the southeast and northwest. The most complete sections are found in the interior Permian depressions (Srebnen, Koshelev, Monastyrishchen). Distribution of the Permian salt does not coincide with that of the Devonian. In those zones where Devonian salt is well represented and is actively involved in salt tectonics, the Lower Permian salt is absent.
The Permian salt in the study area consists of three formations: Nikitov, Slavyan, and Kramatov. These correspond with the Asselian and Sakmarian Stages. The complex as a whole has a two-member composition. The lower part is composed of rhythmically alternating siltstone, limestone, dolomite, anhydrite and some beds of clay and salt. The upper part is largely salt but carries some thin beds of anhydrite. The section as a whole is 70-80 percent salt, 10-15 percent anhydrite, and 5-10 percent siltstone.
Limestone and dolomite occur in the surrounding shelf zones of the salt basin. Secondary processes there have led to development of reservoirs, which in combination with tectonic and other factors have created conditions for the formation of large pools.
Masses of marine water from the open sea located in the eastern part of the Russian platform in the region of the North Caspian depression contributed to the formation of the Permian salt complex. These waters penetrated into the Dnieper-Donets depression along the north border of the Donets fold system. The Chernigov-Bragin high was a barrier to penetration of these waters farther west into the Pripyat depression. Addirional sources of considerable salt were Devonian diapirs, which penetrated to the surface in the Early Permian salt basins.
The final stage in the formation of the Lower Permian salt complex was marked by accumulation of potassium salts in two horizons 8-12 m thick in several areas. The section there at depths of 1.7-2.3 km contains sylvite, carnallite, kieserite, and other minerals; these have commercial value. At the end of the Ealry Permian conditions of sedimentation leveled off, and Triassic redbeds were deposited on the salt complex.
Of the presently known salt domes forming anticlinal traps, the most favorable are those with a pre-Carboniferous level of penetration. The sedimentary complexes between the Devonian salts and above them are assessed to have considerable undiscovered oil and gas. Using modern geophysical methods structures associated with low levels of salt penetratration can be recognized at depths of 5-7 km in the Carboniferous and Devonian.
Taken from Kurilyuk, Bakarchuk, Slobodyan, and Khmel', 1991;
digested in Petroleum Geology, Vol. 31, No. 3, 1997; one map, two cross
sections.
Copyright 2002 James Clarke. You are encouraged to print out this
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It's a damn poor mind that can think of only one way to spell a word -
Andrew Jackson. This reminds me of the admonishment of
Joseph Barrell to use the Method of Multiple Working Hypotheses.