Sunday, June 3, 2012

Silurian Green Fossil - Bickmorites?

Sometimes when one is searching for fossils in the field, color is important as opposed to just trying to visually match shapes and patterns. In the case of today's posting, the color green is important. The Silurian Period Louisville Limestone found in Jefferson County, Kentucky at times has green blotches that show through. I assume this is a sign of some sort of copper being present. (UPDATE: see comment section as the green material might be glauconite.) My cousin told me this could be a sign of a cephalopod fossil which tend to be difficult to find in this rock layer. Mostly one finds corals (chain or colonial types) and some brachiopods with rare trilobite or graptolite fragments. Years ago, I saw cephalopod fossils found by others but recently I came across the remains shown in these first three pictures. After visiting the Indiana State Museum and seeing some of their Silurian cephalopod specimens, a green color was present in some of those specimens. Their material was from the Wabash Formation if I remember correctly. This formation might not quite match up with the Louisville Limestone.

These next two Bickmorites sp. specimens can be found on the first floor of the Indiana State Museum as of May 2012. They are in the fossil area in the Silurian case.

See a Bickmorites sp. specimen at the Indiana State Museum on-line database.

Last two images are magnified areas of the green fossil I found in the Louisville Limestone. Learn more about these creatures at this web site.

A reader of this blog, avid fossil collector, and chemist Jack Kesling of Pennsylvania sent me a nice fossil find that relates to this posting. He found this unidentified Silurian cephalopod fossil with a lot of greenish material on it. The fossil was found in the Bertie Formation of Herkimer County, New York.

Photo by Jack Kesling


soliussymbiosus said...

The green color is probably from glauconite. It is a phyllosilicate from the mica group that is fairly common in sedimentary rocks.

Kentuckiana Mike said...

Thanks Solius for the information. I need research glauconite. Green shale also can be found from time to time in the Silurian Waldron material.