Research Summary:

Recent research documents the paucity of exceptionally well-preserved Paleozoic cyanobacteria. Paucity of Paleozoic cyanobacterial assemblages can be attributed to the relative late timing of silicification in examined Paleozoic units (eighteen throughout the United States). The radiation of siliceous sponges and radiolarians during the early Paleozoic likely decreased sea water Si concentrations inhibiting primary inorganic precipitation of silica from sea water. However, recently it has been suggested that very early silicification and preservation of cyanobacterial remains even during the Proterozoic may be rare due to limited primary silicification. Consequently, extremely well-preserved Proterozoic microbiotas like those from the Gunflint and Bitter Springs formations may be the exception and not the rule. Therefore, exceptional preservation of organic-walled microfossils likely requires special geologic circumstances (e.g. hydrothermal system) during any geologic period.

Papers:

Tobin, K.J., In Preparation, Probable cyanobacterial microfossils in chert and the timing of Paleozoic silicification, Sedimentology or Palaios.

Tobin, K.J., 1990, The significance and paleoecology of the Gunflint-like microbiotas from the Frere Formation (Early Proterozoic), Western Australia. Precambrian Research, 47: 71-81.

Strother, P.K. and Tobin, K, 1987, Observations on the genus Huroniospora from the Gunflint Iron Formation. Precambrian Research, 36: 323-333.