ORDOVICIAN BIOSTRATIGRAPHY AND VOLCANISM OF SALAIR

Litho- and biostratigraphic analysis of a number of Ordovician reference sections has been completed in five different blocks of Salair, including West-Berd’ (Medvedkovo), East-Berd’, Krasnoe, Gurievsk and Eltsovka. Modern data on nine mainly terrigenous and, less often, carbonate-terrigenous sections bearing fossils and composed of carbonate units and volcanic rocks including lavas, as well as tuff and tuff sandstones have been presented. The Ordovician terrigenous sedimentation in the study area was complicated by stages of volcanic sedimentation. Volcanic-sedimentary sequences were documented at four biostratigraphically dated stages in Salair: 1) the Tremadocian, 2) the late Floian, 3) the middle – late Darriwilian, 4) the late Katian – Hirnantian.