Conophyton Stromatolites from Base of Ordovician

Coming from the Lower Ordovician Oneota Formation, these stromatolites are some 500 million years old, from a time that Prokaryotic life forms no longer had exclusive use of earth's shorelines. The earth’s coastal habitats had markedly reduced stromatolite reefs, compared with the Proterozoic. The form genera is conophyton, denoting successive laminae with an overall conical shape.

Interestingly, this specimen actually contains some interstitial sand, as a result of its proximity to Cambrian sandstone immediately below the Oneota Formation. Most stromatolites are carbonates with only post-depositional silica replacement. In this case, the carbonate stromatolites grew in a semi-silicastic environment, thus incorporating sand into their growth structure.

By this time in geological history that these stromatolites were formed, 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, some autotrophic, some chemotrophic and some heterotrophic. However, stromatolite reefs are believed to have regained a temporary foothold following the extinctions even that concluded the Cambrian Period. Sine these stromatolites are at the very base of the Ordovician, they may well have been part of the resurgence when predation by other organisms was temporarily, at least, suppressed.