ACRITARCHS FROM THE CAMBRIAN-ORDOVICIAN BOUNDARY INTERVAL ON KOLGUEV ISLAND, ARCTIC RUSSIA

Abstract

Abstract New evidence from taxonomically rich and age-diagnostic acritarch assemblages is used to recognize Upper Cambrian and Tremadoc strata in the Bugrino 1 and North-Western 202 boreholes on Kolguev Island, Arctic Russia. The position of the boundary between the Cambrian and Ordovician systems in the sedimentologically continuous successions is inferred, as are stratigraphic intervals equivalent to the Late Cambrian Peltura and Acerocare trilobite zones of Baltica. This is the first paleontological documentation of Cambrian strata on the island and, on a regional scale, within the Pechora Basin and northeastern Europe. The newly established biostratigraphy provides the maximum relative age for the basal portion of the sedimentary cover overlying the Timanian angular unconformity, which separates the sediments from deformed and metamorphosed basement. In turn, it constrains the time-span of the hiatus as pre- Late Cambrian and thus is significant for reconstructing the timing of the major tectonic even...