Fossil Wasp from the Green River Formation

Here is another insect that I found in the Parachute Creek member of the Green River formation. I believe it is a wasp of the order Hymenoptera based on an image of a similar insect I found on this slide show. You can see the head, eyes, and antennae very clearly and the wings are somewhat visible too. The abdomen is not very detailed  and may not have preserved as well. I also do not see any of the legs and maybe they are preserved under the body.

I collected this fossil near the FAA radar dome in Garfield County, Colorado near Douglass Pass. The Parachute Creek member of the Green River formation is Eocene in age, Lutetian stage (about 46 mya)

Plecia sp. fossil "March Fly" from the Green River Formation

Today I have a couple of specimens of an insect from the family Bibionidae that come from the Parachute Creek member of the Green River formation. I think they can be narrowed down to the genus Plecia but beyond that I am unsure of what species have been described from the Green River formation. The specimens that I identify as Plecia sp. have an abdomen that is at least twice as long as it is wide with wings that are as long or longer than the abdomen. The wings are rounded on the far ends resembling an oval shape.

Specimen #1

Specimen #2

Members of the genus Plecia are still found today and are often called "March Flies" or "Love Bugs" due to their appearance early in the year to mate in large swarms.

I collected these fossils at the FAA radar dome in Garfield County, Colorado near Douglass Pass. The Parachute Creek member of the Green River formation is Eocene in age, Lutetian stage (about 46 mya)

Cricket from the Green River formation

A rare find for me from the Parachute Creek member of the Green River formation is the cricket fossil below.  Crickets belong to the family Gryllidae and generally have long bodies with round heads and six pairs of legs, a pair of which are modified to be longer than the others and are used for jumping. It's those longer legs that lead me to believe the specimen below is a cricket.  I do not know enough about crickets to be able to narrow the ID down to the genera or species, especially as I don't know what species have been described from the Green River formation.

I collected this fossil near the FAA radar dome in Garfield County, Colorado near Douglass Pass. The Parachute Creek member of the Green River formation is Eocene in age, Lutetian stage (about 46 mya)

Fossil Weevil from the Green River formation

Insects from the Green River formation can be difficult to ID down to a species, let alone a generic level. Often you are trying to compare a 2D fossil to 3D pictures of extant insects and all you can do is hope you are correct.  Below is a specimen I purchased because of the good preservation, but also because it had been ID'ed as a Weevil already.  I need to go through my own findings to confirm but I think I have found examples of this same kind of insect on my collecting trips.

I am still trying to find some good resources that list known insect genera from the Green River formation but they are hard to find or expensive to purchase.  At this point I can only say that this fossil is of a member of the Superfamily  Curculionidaea.

A low light shot of the fossil shows some nice details

A direct light shot shows the true color of the fossil better.

This fossil was found in the Parachute Creek shale member of the Green River formation, in Rio Blanco County, Colorado. The Green River formation is dated to the Eocene period, Lutetian stage (about 46 mya).

Check out an older post of mine where I discuss the geology of the Eocene lakes that once existed in SW Wyoming and NW Colorado.

In another one I posted some of my exceptional finds from Douglass Pass.

Parachute Creek member of the Green River Fm.

The Green River formation is an expansive group of rocks which all were lain down by a series of ancient lakes in the Eocene era of the Paleogene period. As you can see by the map below, the deposits that exist today are extensive.



The formation is really four interconnected basins from two major lakes called Lake Unita and Lake Gosiute. The best know parts of the formation are those from Wyoming around Kemmerer where the fossil fish are quarried from the sediments of former Lake Gosiute. To the south in Colorado and Utah, fossil Lake Unita left a similar record but the rock type is a little different. In Wyoming, the fossils are generally preserved in a freshwater limestone while in Colorado and Utah the rocks are oil shale. Both lakes had similar flora and fauna and record a sub tropical ecosystem.

One of the most accessible and well know sites to collect from the Lake Unita oil shales is at an FAA radar dome near Douglas Pass. Here the rocks are considered part of the Piceance Creek basin and the most collectible shales are found in the Parachute Creek member. They are exposed as thick bedded near horizontal layers of light gray shale. The fossil finding process involves taking a piece of the shale and splitting it parallel to the plane of fossilization. The layers are very thin and it's not easy to split the rock completely on a single plane. Often you wind up breaking off a spall and you hope you find something. Unweathered rock is light to dark brown, due to the hydrocarbon content, and the preservation is quite good with thin black carbon films that contrast well against the host rock.

I've had some success collecting at this site over the years and it is a favorite of mine. Here are some pictures of specimens from my collection:

Insects




Plants







I got lucky once and found both halves of a bird feather. The detail is superb and you can see color bands as well as the texture of the feather itself. Bird feather fossils are rare but not uncommon from the Parachute Creek member.






For more info on the Green River formation, check out this page at the Fossil Museum.

Or you can go the the University of California's Museum of Paleontology website and read their page.