Biomphalaria sp. & Goniobasis sp. Gastropods from the Green River Formation

Within the limestone layers of the Green River formation that are exposed in the split fish quarries you will occasionally find some gastropod fossils. The degree of preservation is variable but I have found at least two genera during my trips to Kemmerer, WY.

The most common genus that I have found is Goniobasis sp. which is a high spired, conical shell. Specimen #1 below is fairly well preserved and you can see the aperture on both the positive and negative slab.

Positive and negative slabs followed by close ups of each slab

Specimen #2 - Less well preserved. Positive and negative slabs

The other genus is Biomphalaria sp. and I only have one example. It is a small planispiral shell with no ornamentation and very narrow whorls.

Positive and negative slabs

I used the book "The Lost World of Fossil Lake: Snapshots from Deep Time", Lance Grande, University of Chicago Press, 2013, page 91, figure 40 to identify the above specimens (figure below).

These fossils come from the Fossil Butte member of the Green River formation (Paleogene period, Eocene epoch, Ypresian stage). I found them at the Thompson Ranch split fish quarries which are publicly available to collect in at a number of commercial quarries which lease access.

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.

Salix sp. leaf from the Green River formation

This long, narrow leaf is most likely from a member of the Willow family, Salix sp. and comes from the Parachute Creek member of the Green River formation (Eocene, Lutetian stage).  It was found in Bonanza, Utah and I purchased it because it came with an ID. I am hoping that I can use this and other identified specimens that I purchase to help ID fossils that I have found in the field. There are not many resources easily accessible that show pictures and names for plant and insect fossils from the Green River formation.  I know I have found other examples of Salix sp. that are larger and more recognizable than this specimen but I need to go through my findings and locate it.

Cardiospermum coloradensis leaf from the Green River formation

Soapberry plants are typically found in the tropics and their presence in a northerly latitude like where NE Utah is indicates that the climate used to be much warmer than it is now. Below is a leaf from the Soapberry family,  called Cardiospermum coloradensis, that is also called "Balloon Vine".   Fossils of these leaves are somewhat common in the Parachute Creek member of the Green River formation (Eocene, Lutetian stage), but most of what I have found are smaller. I purchased this piece because of the good preservation and size of the leaf.  I identified it based on this image from James St. John's Flickr page.

Caesalpinites sp. leaf from the Green River formation

Here is another fossil leaf from the Parachute Creek member of the Green River formation (Eocene, Lutetian stage) that I purchased because it came with an ID. It's a leaf called Caesalpinites sp.  The fossil is small and somewhat faint against the rock but you can make out the central vein and overall shape of the leaf.  This specimen comes from a site near Bonanza, Utah.  I'm having a hard time finding any more info about this genus to try and narrow down the species. I've seen other leaves labelled as Caesalpinites falcata from the same area but they look different than my specimen. It could be a different species or maybe the plant had different shaped leaves on different areas. 

Mioplosus labracoides fish head from the Green River Formation

I purchased this fish fossil from a collector just because of it's size and preservation. The collector didn't know what the genus of fish it was but I did a little digging and I think it's a Mioplosus labracoides. The fossil was collected from the Green River formation near Kemmerer, Wyoming (Paleogene, Eocene epoch, Ypresian stage). I have not yet found any Mioplosus fossils myself so this filled a hole in the collection as well as being a cool looking fossil.

 

Fossil bird feathers from the Green River Fm. of Colorado

Bird feathers are somewhat rare in the fossil record but some circumstances allow them to be more easily preserved. Such is the case in the Parachute Creek member of the Green River formation. The Parachute Creek member is an oil shale that was deposited by a series of freshwater lakes in the Eocene located in northwestern Colorado and northeastern Utah. Here are some examples of the feathers that can be found within these fossil lake deposits.

Specimen #1

Specimen #2

Specimen #3

All three of the feathers look to be fairly simple and could just be down feathers. Sometimes color patterns can be preserved but I don't see any on these.

Erismatopterus levatus fossil fish from the Green River Formation

Below are a couple of small plates from the Green River formation in Wyoming with the fry (juvenile) of a trout perch called Erismatopterus levatus. I bought them from a dealer at a local show this spring.

Based on the book "Paleontology of the Green River Formation with a Review of the Fish Fauna", by Lance Grande, Bulletin 63, Geological Survey of Wyoming, pg. 122-124, these fossils are found primarily in fossil lakes Gosiute and Unita. They are uncommon except for mass mortality zones possibly caused by short term lake temperature rises in the summer.

Click over to This Post I wrote two years ago about the Green River formation to see some diagrams of where the various fossil lakes that compose the formation once existed.

Farson Fossil Fish

In 2009 I was able to visit a site that had tantalized me as a youth, the fossil beds near Farson, WY. They were a part of the same Eocene lake system that formed the Green River Formation and contain the same fauna (fish mainly) that can be found at the famous quarries near Kemmerer. The difference is the rock which is a very fine grained shaley limestone as opposed to the pure limestone found farther east in Kemmerer. This is a piece I bought years ago that came from the Farson locality. It features a large number of Knightia sp. fish all grouped together in what is called a mortality plate. The fish were all killed at the same time possibly by water temperature changes or sudden drops in the amount of dissolved oxygen.

Notice how the fish are very finely detailed and stand out from the rock.

The site is out in the vast plains of the Sweetwater Valley north of the town of Green River. As I was driving to the site I was expecting small quarries like those in Kemmerer but what I found was a relatively flat featureless plain spotted with Sage.

It looked to me that things had been confined to small scale digging in the immediate surface layers as evidenced by the large amount of scattered rock slabs. The heyday of this site was in the 50's to 70's before the government came in and put a ban on collecting vertebrate fossils on federal land. The site is in the middle of a vast area of BLM (Bureau of Land Management) jurisdiction so no collecting for me.

I poked around a little in the old, weathered slab piles to see if I could find anything that had been cast off and did find a few bits.

This was probably the best piece that I found. I like the contrast of the rock's patina with the partial fish fossil.

I left the pieces I'd found and had to be content with the pictures I had taken. It's too bad they don't allow collecting here but if it were otherwise it culd be overrun and depleted by commercial collectors very quickly.

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.