Cambrian salt is widespread over much of the southwest part of the Siberian craton and is the seal for extensive oil deposits there. Drilling in recent years has supplied much new information on the Middle Paleozoic evaporites, which occur in two separate basins - the Tunguska on the northwest and the Vilyuy on the southeast. Salt was penetrated in eight wells in the Tunguska basin in an area 200 by 200 km immediately east of Dudinka on the Yenisey River. The wells penetrating salt in the Vilyuy basin are in two groups, three wells about 100 km northwest of Vilyuysk and five wells 200 km south of Vilyuysk.
Salt has now been found in the Upper Silurian, in all three divisions of the Devonian, and in the Lower Carboniferous.
Upper Silurian salt-bearing sedimentary rocks have been drilled in the basin of the middle course of Nizhnaya Tunguska River in the section of Turin stratigraphic well. This well is located in the southwest part of the craton hundreds of kilometers from the other wells in which salt was penetrated.
Salt-bearing rocks have been found in Lower Devonian in Noril'sk area in the northwest of the Tunguska basin in rocks of the Yampakhtin and Zabov Formations. In the Yampakhtin (lower Gedinnian Stage) are two main beds 3 and 6 m thick. The salt is gray and has a clearly expressed seasonal layering. Structure and composition indicate deposition in a marine basin. In the Zubov Formation (upper Gedinnian Stage) the salt occurs as two beds of medium- to coarse-grained halite with total thickness of about 10 m.
Salt beds of the Middle Devonian Eifelian Stage are very widespread in their occurrence in both Tunguska and Vilyuy basins. Salt formations of Middle Devonian Givetian and Upper Devonian Frasnian Stages were first established in 1986-87 in the basin of the Imangdy River of the Tunguska basin, where they occur n the Yuktin, Nakokhoz, and Kalargon Formations. The salt of the Yuktin (upper Givetian) occurs as two thick strata separated by brecciated sulfate and carbonate. Total thickness is from 20 to 80 m. In thr lower Frasnian Nakokhoz the salt occurs in 3 to 4 strata, which range in thickness fro 1.5 to 7 m. In the Kalargon of the upper Frasnian-lower Famennian salt beds are present in its lower and upper parts. Middle and Upper Devonian salt beds are widespread in Vilyuy basin.
Lower Carboniferous salt has been found on the Siberian craton only on Kedepchik high, located about 150 km south of Vilyuysk. Three to four salt beds with thickness ranging from 5 to 20 m are present in three wells there.
The salt-bearing units of the north of the Siberian craton appear to haveformed in a single marine basin that has a continuous connection with the Taymyr Sea on the north. Concentration of salt within it repeatedly reached the stahe of sylvite deposition and possibly also that for carnollite.
Taken from Matykhin and Sokolov, 1991; digested in Petroleum
Geology, vol. 32, no. 1, 1998; one map, one stratigraphic correlation
chart, and four geophysical logs.
Copyright 2002 James Clarke. You are encouraged to print out this
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