Boreskov

PP‐43ecosystems of large (up to 600 m in thickness) microbial mounds. They were formed onslopes of shallow‐water carbonate platforms surrounding of starved basins. Massdistribution of the pioneer cyanobacterial communities, non‐skeletal calcimicrobialcarbonates and oolitic sands are the stress indicators in the reef ecosystems. Global falling ofa sea‐level at the Frasnian‐Famennian and Famennian‐Tournaisian boundaries accompaniedby as the biotic extinction and an ocean anoxia were not reflected catastrophically in theecosystem structures of the microbial mounds since metazoan frame‐builders played aninsignificant role in them.The final Late Visean‐Early Permian stage is characterised by an abundance in thebenthic ecosystems by fragile and small метазоа (fenestral bryozoans, sponges,palaeoaplysina, etc.), green phylloid algae. Biologically induced cement made a considerablepart of biogenic frameworks. Prevailing pioneer communities in association with abundantcement formed skeletal, microbial‐algal, and mud mounds from 5 to 330 m in thicknessdeveloping on slopes of deeps of the carbonate platform margin had been deformedbecause of a progradation of the Pre‐Urals Foredeep on the one. During this stage, cardinalreorganisation of the reef ecosystem structures and accordingly of the biogenic frameworkswas defined by mesotrophy of the sea waters in connection with sharp increase of theerosion areas as a result of closing of the Paleo‐Uralian ocean, distribution mainly sessilemetazoan organisms with the aragonite and high‐Mg calcite skeletons, shallow‐water seasand colling as a result of a glaciation of Gondwana in the Late Carboniferous‐Early Permiantime.The allocated stages in evolutions of the Paleozoic reefs in the north of the Urals and anoriginality reef ecosystems ontogeny can be estimated as indicators of periodicity of thelarge biospheric reorganisations which can be used for global correlations of the Paleozoicreef formation.Researches were supported by the Program of the Russian Academy of SciencesPresidium 15/2, № 09‐P‐5‐1008.211