- Most Popular | Most Recent
Fossiliferous limestone of the Madison Group, collected from talus in Sacagawea Cirque, Bridger Range, Montana. The obverse of this sample, rich in fenestrate bryozoans, can be seen here: gigapan.com/gigapans/185809
The Keyser Limestone is the lowest formation of the late Silurian to early Devonian Helderburg Group. It records stable platform deposits which accumulated in the quiet period between the Taconian and Acadian orogenies. This sample was collected and contributed by Dr. Michael Mengason.