Broadly Branched Digitate Stromatolites from Ordovician Wisconsin

Description: Coming from the Lower Ordovician Oneota Formation, this eminently aesthetic specimen is some 495 million years old, from a time that Prokaryotic life forms no longer had exclusive use of earth's shorelines. Concomitantly, the earth’s coastal habitats had markedly reduced stromatolite reefs, compared with those of the Proterozoic.

By this time in geological history, microbial communities consisted of complex consortia of both prokaryotic and eukaryotic forms with diverse metabolic needs, and competition for resources and differing motility among them made for an intriguing microcosm of interacting life.

The bluish tint seen here interdigiating ioth the ripples in the structure is the result of infilling by glauconite, a biogenically-modified biotite (mica) that is the result marine biogenesis in a nearshore environment, making for an interesting combination of structures formed by living organisms. This remarkable specimen is appropriate for display, teaching or research, representing primitive prokaryotic life responsible for forming the atmosphere that we breathe today. Stromatolites have persisted to the modern day in such places as Shark Bay, Australia where they continue their billions of years old lifestyle.