ANATOMY AND TAPHONOMY OF A PRECAMBRIAN ALGAL STROMATOLITE

A single specimen of silicified flat algal stromatolite from the late Precambrian Bitter Springs Formation, Australia, contains three distinct microbial communities: (1) an entophysalidacean mat-building community comparable to both modern members of the genus Entophysalis and 2000 Ma old algae from the Belcher Islands, Canada; (2) a filamentous assemblage composed entirely of the Phormidium or Lyngbya-like cyanophyte Eomycetopsis; and (3) a non-stromatolitic assemblage of chroococcoid unicells that may have been associated with small, quickly evaporating ponds or puddles of water. Within each community, fossil preservation varies as a function of preservational microenvironments. Recognition of degradation sequences permits an assessment of taphonomic alterations of the original biological patterns. This, in turn, allows reconstruction of community associations and diversity patterns. The paleoenvironment of this particular Bitter Springs stromatolite is considered to be the lower part of the intertidal zone bordering a shallow, perhaps somewhat restricted sea. Post-mortem degradation has acted to increase apparent diversity through the creation of diagenetic variations in morphology and to decrease the same measure by the selective destruction of less resistant taxa. Three new species are described: Eoentophysalis cumulus, Eosynnechococcus amadeus, and Gloeodiniopsis gregaria. © 1979.