The fold-thrust belt of the Northern Uals extends some 400 km
from the Perm region on the south to the vicinity of Pechora on the
north. It is 80 km wide. The present structure of the sedimentary
cover formed largely in Carboniferous-Triassic time during the
Uralian orogenesis. Deformation was of the "displicative" type
(combination of disjunctive and plicative deformation). Six main
surfaces of disruption are recognized:
1) In the Permian, salt of the Kungurian and clays of the Artinskian.
2) Carboniferous argillaceous rocks.
3) Upper Devonian Famennian argillaceous rocks.
4) Middle Devonian clastics.
5) Ordovician clastic and sulfate-salt rocks.
6) Upper Proterozoic rocks.
The main structural features here are the Cis-Ural foredeep on the west and the West Ural structural zone on the east.
The main structural feature of the Cis-Ural foredeep is the Upper (Verkhne) Pechora depression with outer (west) and inner (east) zones. Then to its north is the Bol'shesynin depression with the Middle (Sredne) Pechora transverse high between the two. The boundary between the foredeep and the West Ural structural zone has migrated with time in that it runs along the front of a system of large faults known as the Main West Ural overthrust. Horizontal displacement is in the first tens of kilometers, largely in the lower Frasnian section in the Upper Pechora depression and in the Lower Paleozoics in the Bol'shesynin depression.
The West Ural structural zone is separated on the east from the Central Ural zone by a large fault known as the Axial overthrust of the Urals. It has a horizontal displacement of a few tens of kilometers. This West Ural zone consists of three main structural features - Upper (Verkhne) Pechora transverse low on the south, Shchugor transverse low on the north, and Timaiz transverse high between the two.
The Upper Pechora transverse low has the form of a north-south paralellogram that measures 250 by 45 km. Amplitude of folds is from 1000 to 4000 m and more. These folds are grouped in three zones - west, central, and east, which are thrust one upon the other. The thrust planes are in Ordovician and Proterozoic rocks.
The Timaiz transverse high extends north-south 200 km and is about 50 km wide. Intersection of deformation of of north-south and northeast trends is manifest in en echelon disposition of structrues. Degree of folding and faulting here is less than in the adjacent transverse lows, and area of anticlines is substantially greater.
Shchugor transverse low is thrust from the east onto deposits of the Bol'shesynin depression. This low is 10-30 km wide and 150 km long. The fault planes are in Proterozoic rocks.
The information gained from this study should improve the base for petroleum exploration in the fold-thrust belt of the Northern Urals.
Taken from Voinov, Sivkov, and Romanov, 1993; digested in Petroleum
Geology, vol. 28, no. 1/2, p. 62-69, two maps and one cross section.
Copyright 2002 James Clarke. You are encouraged to print out
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