CONDITIONS OF FORMATION OF CARBONATE SEQUENCES IN THE UPPER RIPHAEAN OF THE SOUTHERN URALS

Abstract

Detailed study of the upper Riphaean Min'yara formation of the southern Urals and the fossilized organic matter occurring in it enabled the author to show that the properties of these fossils correlate with several characteristics of present-day cyanobacteria communities. The Min'yara formation is as much as 800 m thick and consists of stratified dolomite and dolomitized limestone, with biostromes and bioherms of platy and columnar stromatolites. It is generally thought that rocks of this type were deposited in shallow seas in the tidal or littoral zone or somewhat below the littoral. Some of them may have been deposited in lagoons. The deposition of Min'yara formation must have occurred under similar conditions. Study methods and results are discussed.