Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Vavrdová

Silicified microbiota from the Bohemian late Proterozoic

Journal of the Czech Geological Society, volume 39 (1994), issue 2-3, 183 - 196

Rich and diverse benthic microbiota has been detected in dark silicites of Precambrian age (Kralupy—Zbraslav Group, Teplá-Barrandian Proterozoic).
The evaluation of in situ preserved cyanobacterial colonies allows to characterize supratidal, intertidal and subtidal fossil sedimentary environment. Bacterial degradation, perinineralization by iron sulphides and early diagenetic silicification were the main factors controlling the preservation of organosedimentary structures and textures such as low-relief bioherms, firm algal mats, fenestral fabrics, bird-eye structures, dessication cracks, plastic deformations and other phenomena.
A Gunflint type of microbiota (Huroniospora psilata - Gunflintia minuta) has been ascertained in the Nižbor anticline. Benthic associations from lydites and siliceous shales from the north of Prague (Kralupy environment) and in the SE part of the basin (Blovice area) resemble in some aspects analogical finds from the Arctic Canada (Dismal Lake Group, Belcher Island Group). Silicified graywackes and stromatolitic iron-rich cherts from the Střibro — Plasy Belt and Svojšín Belt (Siphonophycus - Podolina angulata palaeocommunities) may be well compared with the supratidal fades of the Draken Conglomerate Formation.