Boreskov

PP‐65Sections of Daldarma formation are in Urik‐Iya graben of Prisayan’e zone of the south ofSiberian craton. The composition of formation includes dark rocks from gravelites up toaleuro‐argillites, limestones, tuffstones and volcanic rocks of the basic and acidcompositions. Rocks were generated in basin of an island arch. Carbonaceous deposit withsulfides, most likely, have been formed in the bent zones of paleobasin with a stagnantenvironment. Granites, breaking through Daldarma formation, have age 1,86 billion years(Levitskii et al., 2002). 8 samples of dark aleuro‐argillites and 1 sample of dark limestonehave been dissolved. The material was studied also in thin sections. Bavlinella (?) Schep.,Eosynechococcus (?) sp., E. cf. giganteus Gol. et Bel., Germinosphaera (?) Mikh.,Leiosphaeridia cf. crassa (Naum.) em. Jank., L. cf. minutissima (Naum.), em. Jank.,Majasphaeridium (?) Herm., Octoedrixium (?) sp., Polysphaeroides (?) sp., Protosphaeridiumdiv. sp. and fragments of carbonaceous films have been certain. Numerous (up to 1000 inone preparation) fragments of carbonaceous "filaments" in the length from 10 up to 800 mare prominent feature of a material. It is supposed, that algae had a benthic way of life onshoaliness and have been taken down in rather fondo and stagnant zone of paleobasin. Finespherical forms (Bavlinella (?) Schep., Protosphaeridium div. sp.) are preliminary comparedwith benthos of chemolithotrophic bacteria, usual for stagnant zones of basins. Dark forms,round or the pear‐shaped form with growths, or some forms in accretions are met indifferent samples. They can be compared to association of forms from phosphate blackslates of the Early Proterozoic Zhdanov formation on the Kola peninsula (Ahmedov et al.,2000) through conformity of morphotypes, preservation of volume and sizes.Forms of the Zhdanov formation have been compared to reproductive and vegetativeorgans of the lowest mushrooms lived in deposits of a stagnant zone of marginal paleobasin.[1]. Ahmedov A.B., Belova M.J., Krupenik V.A., Sidorova I.N. Mikrofossils of the mushroom nature from blackslates of Paleoproterozoic of the Pechengskii complex (Kola peninsula) // Doklady the Russian Academy ofScience, 2000. V. 372. № 5. P. 646‐649. (in Russian).[2]. Levitskii V.I., Mel'nikov A.I., Reznitskii L.Z., Bibikova E.V., Kirnozova T.I., Kozakov I.K., Makarov V.A., andPlotkina Yu.V. Early Proterozoic postcollisional granitoids in southwestern Siberion craton // Russiangeology and geophysics, 2002. V. 43, N 8, P. 717‐731.250