M. M. Astafieva

Interesting observations illustrating the process of transformation of some minerals of banded iron formations (BIF) were made while studying the Early Proterozoic jaspilites of the Kursk Magnetic Anomaly (KMA). Examples showing the process of siderite transformation into iron oxides/hydroxides by iron-oxidizing bacteria are given.

This is the first report on the fossilized fibers found in the Archean banded manganese formations of the Chitradurga Greenstone Belt (2.8 Ga, South India), which are similar to the stalk fibers of modern Gallionella ferruginea Ehrenberg, 1838. We have therefore concluded that the intertwined and assembled stalk fibers provide indirect evidence for the presence of bacteria and biogenic mineral formation, but should not be considered as microorganisms.

The earliest finds of probable eukaryotes in the oldest sediments of various regions are reviewed. It is possible that the first eukaryotes could have appeared as early as the Archean.

Various methods for the study of microfossils (AR-PR₁) in macerates, thin sections, and fresh chips have been compared. Each method has its advantages and disadvantages. While working with thin sections, it is often impossible to trace the interrelation between microfossils and host rocks. When preparing macerates, only individual fragments of microorganisms can be observed, as a rule. The overwhelming advantage of the method for the study of rocks in fresh chips has been shown.

The article discusses materials on the Archean (4.0–2.5 Ga) microfossils of the Earth (Greenland, Australia, South Africa, and Fennoscandian Shield). The main emphasis is on the description...

The study of volcanogenic and volcanogenic–sedimentary rocks (Early Proterozoic pillow lava of Karelia and South Africa), where diverse fossilized bacteria (prokaryotes) and probably even...

Nanobacteria, buried in situ, were discovered in the Early Precambrian paraschists (Keivy, Kola Peninsula). It is suggested that occurrence of nanobacteria indicates that a biological factor played a...

Probable microfossils, presumably of bacterial origin, were found in the banded iron formations of Karelia and the Kola Peninsula. The age of these formations is 2.7–2.8 Ga. Based on the organic carbon content and balance estimations it was established that these banded iron formations were deposited in environments rich in organic matter. Comparative analysis of the morphology of Recent and Neoarchean microorganisms suggests a bacterial origin for some magnetite in the studied quartzites.

The assemblages of fossilized microorganisms from volcano-sedimentary material sandwiched between basaltic lava flows in Early Proterozoic (2.0 Ga ago) volcanics of the Sortavala Group of the Sortavala Uplift (northern Lake Ladoga region, near the village of Kharlu) are studied. It is confirmed that volcanogenic and volcano-sedimentary rocks are of significance for bacterial paleontology.

Fossilized cyanobacteria(?) represented by trichomes enclosed in common sheaths were detected in early Proterozoic iron banded formations of the Kursk magnetic anomaly (limonite-martite ores of the Lebedinsky mine and iron banded formations of the Korobkovskoye deposit). These fossils morphologically similar to current representatives of the genus Microcoleus were buried in situ.