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Fossil Hunter commented on Jack Kallmeyer‘s Fossil #004054 8 years ago
8 years ago8 years agoIs this a type of stromatolite? It is pretty neat. Are there are lot of this type of fossil in this formation? Do you know the depositional environment?
Thanks for your interest and question. It is not a stromatolite nor is it related. Stromatoporoids are currently classified as calcareous sponges. There is internal structure visible in well preserved stromatoporoids. Stromatolites are bacterial in origin and are usually classified as chemical trace fossils by some. They don’t display any internal structures. There is a recent book called Stromatolites that can be bought from Amazon that explains that much better.
The paleoenvironment here in the Cincinnatian was that of a warm shallow tropical sea. These particular examples were preserved in a narrow bed of dark gray shale. In this location they are common and most are small like this one but some other types get much larger. In some sites near here the stromatoporoids form actual reef structures and the individual stromatoporoids can be a few feet across. The example I have posted is silicified which is unusual around here as most fossils are preserved as calcite. Sometimes the internal structure is obliterated by re-crystalization and the big ones sometimes have vugs of calcite crystals inside. I will try to post a couple of other ones.