Published online by Cambridge University Press: 01 May 2009
The Silurian and Lower Devonian graptolite-bearing strata are widely distributed in both the platform and geosynclinal areas in the USSR. They are represented by black clay and siliceous shales, marlstones and argillites. In the main area of their distribution the regional zonal standard is established based on graptolites. They serve as the most detailed stratigraphical base for geological mapping and exploration and are used in the regional and inter-regional correlations. Correlation with other countries and continents is carried out by comparison of regional zonal successions with the unified standard of graptolite zones. The latter is compiled from the regional zonal subdivisions of the British, Czechoslovakian and Polish type sections. The zonal stratigraphy based on graptolites allows the establishment of the limits of the Silurian System and Stages/Series in the USSR. The Silurian and Lower Devonian sediments in the USSR are characterized by various geographically widespread graptolite assemblages. The most complete zonal subdivision is worked out for the Lower Silurian. The Upper Silurian and Lower Devonian zonal stratigraphy requires elaboration and precision in the future. The importance of graptolites in solving general geological problems particularly for establishing detailed stratigraphy of regions of industrial explorations considered.