The Late Riphean Miroedikha microbiota from Siberia. Communication 2: Interpretation in terms of biotic paleosuccession

Changes in the abundance and taxonomic composition of organic-walled microf ossil assemblages of the Late Riphean Miroedikha microbiota, one of most di verse and thriving in the Proterozoic, were analyzed at ten discrete strati graphic levels. The revealed time succession of these assemblages can be co nsidered as an analogue of Phanerozoic coenogenic paleosuccessions characte rizing the evolutionary trend from pioneer to postpioneer and climax commun ities. Some peculiar features of Riphean paleosuccessions and difference in diversity dynamics of morphotypes characteristic of microbiota at the tran sgressive and regressive stages of sedimentation are outlined. It is noted that consecutive taxonomic changes at these stages are comparable with coen ogenic paleosuccessions of the migration and mutation types, and these tran sformations in microbiotas of the Riphean time apparently were related to t he first-order evolutionary cycles of paleobasins. The suggested synoptic m odel of the Miroedikha rnicrobiota "ontogeny" is important for understandin g the progressive complication of the Precambrian microbes.