This is an Great Block of a Green River Insect. This is a Fossil Carabidae Beetle trapped in the layers of rock well known from a classic site. The preservation and detail is exquisite.
These Colorado Fossil Insects are Eocene in age, and are 50 Million years old. They come from the Green River Formation.
This formation is known for the insect fossils and leaves coming from that area and this Fossil Carabidae Beetle is in a block of rock and shows outstanding detail. Because the fossilization is exceptional for these small invertebrates you can actually see the eyes but also the ridges on the back of the wing case.. These are not trapped in Amber but they are locked inside rock. This rock is a vert fine grained sediment that preserved these insects beautifully and they display very well. But there are many other organisms buried in the sediment as well.
Because this Fossil Carabidae Beetle was trapped in mud or a mud flow and was buried very quickly it shows quality detail. But it did not completely decay immediately. Because they were preserved in that fine mud and exhibit great detail. The Green River is known for the excellent preservation of fossils but here they are quite small.