Biogenic–Abiogenic Interactions in Stromatolites: Study Possibilities and Outlooks

Abstract

Stromatolites are produced by a complicated interplay of biogenic and abiogenic processes, whose contributions are hard to estimate without applying specialized techniques enabling the researcher to reproduce these processes. Stromatolites are fairly widespread in nature and are found as building organisms of various shape and size. Most researchers classify them into layered and columnar types or subtypes, which comprise complicatedly but systematically branching columns, oncolites, and microstromatolites. In spite of the morphological diversity of stromatolites, stromatolite reefs were formed over significant areas during a certain span of geological time, with only some types of structures found in them. It was determined that the morphological types of stromatolites obviously show a certain spatiotemporal distribution. This fact cannot be explained by the sedimentation conditions alone, and it indicates that biogenic processes and matter played a key role in the origin of stromatolites. However, no stromatolite-forming organisms had long been found. The later transformations of these rocks further complicated the problem in view of the fact that the great majority of stromatolites are of Precambrian age. A recently suggested and tested technique makes it possible to identify the building organisms of stromatolites and estimate their role in forming the structural–textural features of these rocks. This technique involves SEM studies. This publication discusses the potentialities of the techniques and the reliability of results obtained using it, as well as the outlooks in its application to solving specific problems (identification of cyanobacteria) and more general issues concerning the geology of the Precambrian.