M. M. Astafieva

Prasinophyceae (Green Algae) from the Lower Proterozoic of the Kola Peninsula

Eukaryotic organisms discovered from the earliest Lower Proterozoic phosphorites (2.04 Ga) of the Kola Peninsula are described. These are fossil forms Pechengia melezhiki gen. et sp. nov., which are tentatively assigned to green algae of the class Prasinophyceae.

The evolution of the early precambrian geobiological systems

Bacterial paleontology provides vast opportunities for the study of all types of sedimentary and volcanic-sedimentary rocks, at any stage of metamorphism and of any age. Bacteria are shown to play an important role in weathering, transfer, sedimentation, and diagenesis of the sediments and in the formation of many minerals that have previously been thought to be abiogenic.

Fossil Bacteria from the Permotriassic Trappean Strata of Siberia

The strata of the Permotriassic Trappean Complex of Siberia (Ilimpeya River and Kapchan locality) are studied. The water-lava and water-tuff boundaries are shown to be promising for bacterial paleontological studies. The analysis of fossilized microbial communities shows that they vary depending on sedimentation conditions. This example is important for a better understanding of the prospects for the study of similar situations in the Archean and Proterozoic.

Framboidal structures in Earth rocks and in astromaterials

Framboidal structures are common in both Earth rocks and in meteorites - carbonaceous chondrites. The main methods of formation of these structures are discussed. The role of biologic factors in formation of framboids is elevated. Comparison of crystal forms comprising framboids formed in laboratory conditions and in nature is provided. On the basis of investigations of framboidal structures the proposition that pyritoidal form of crystals is typical for the formation of biogenic framboidal structures.

The Early Earth and its environments

The set of discovered Archaean organisms does not indicate anaerobic atmosphere as early as 3.5 Ga. The RNA-world must have existed at least at 3.9 GA and, likely, close to the beginning of degasification and appearance of water on the Earth surface. The earliest cellular organisms (membranes) also appeared before 4.0 Ga. Possibilities of evaluation of conditions on the Earths surface are under the consideration of both geological-geochemical and possibly mainly paleontological data. The important element in the analysis of the Earth conditions is the level of organisms organization presented in the paleontological record, because it is connected with the existence of peculiar abiogenic conditions, such as temperature, amount of oxygen, amount of water etc.

Volcanic Glasses as Habitat for Microfossils: Evidence from the Early Paleoproterozoic Pillow Lavas of Karelia and their Modern Analogues in the Mid-Atlantic Ridge

Microbial complexes were identified in the volcanic glasses from the ancient (2.4-Ga-old basaltic pillowlavas of Karelia) and modern (pillow lavas of Mid-Atlantic ridge) volcanic rocks. It was shown that that their microbial colonization is likely to occur by the same mechanism. Thus, well preserved pillow lavas, which occupy a spacious fields in the Archean and Early Paleoproterozoic greenstone belts, are promising object for search of the earliest traces of life on Earth.

Development of living organisms on the lava-water interface of Palaeoproterozoic Ongeluk lavas of South Africa

An investigation of the Early Proterozoic pillow lavas of South-Africa shows that the lava-water boundary is very interesting from the point of view of bacterial paleontology. In the pillow selvages corresponding to this boundary, forms such as bacteria (including cyanobacteria) developed. Cyanobacterial or bacterial mats formed and probably even such highly organized forms as eukaryotes existed.

Fossil microorganisms in Archaean deposits of Northern Karelia

Newly found biomorphic microstructures from the Upper Archaean (lopian) rocks from Northern Karelia are described. The presence of various microorganisms of a bacterial nature and even cyanobacteria (and possibly eukaryotic forms) is suggested. The necessity of employing methods of electron microscopy, as well as traditional methods, while studying the very early manifestations of life in Archaean and Early Proterozoic is noted.

Prokaryotes in the Early Precambrian

Bacteria and biofilms are frequently preserved in the fossil record, they occur in many sedimentary and volcanogenic-sedimentary rocks. It is highly probable that they always participate in weathering, transfer of matter, sedimentation, and diagenesis of deposits.

Early Proterozoic Pillow Lavas of Suisari As Habitats of the Earliest Microorganisms

Assemblages of fossilized microorganisms from the Paleoproterozoic Suisarian Formation (Ludicovian stratotype of the Karelian Complex) of central Karelia are recognized and investigated. Fossil assemblages of microorganisms confined to different zones of pillow lavas are compared.