Scattered across the upper surface of a hard layer of limestone in the badlands of the Bighorn Basin in Wyoming are the tell-tale signs of dinosaur activity: footprints. Over one thousand footprints have been identified here, most of them on one exposure of rock in a small gully in the Red Gulch region. On our family vacation this summer we spent some time at the main dinosaur tracksite and we also did some fossil hunting in the surrounding hills.
Below I share some pictures of the dinosaur tracksite, fossils that are found there and some of the wildlife we saw on the Red Gulch Back Country Byway.
A few days before we all visited the site I got up before sunrise and drove to the tracksite area to look for fossils and do some photography. The picture above is the view looking north just before sunrise. The dinosaur tracksite is just up the road in a small valley.
A nice boardwalk greats visitors at the main tracksite is maintained by the BLM (Bureau of Land Management). I took this picture just as the first sunlight was hitting the site. The boardwalk takes you right down to the limestone surface where visitors are free talk around and walk in the dinosaur footsteps.
There are several interpretive signs at the Red Gulch Dinosaur Tracksite. The tracksite is maintained by the BLM and free to visit and explore. Removal of dinosaur bones, tracks and other vertebrate fossils is prohibited from federal land without a permit but there are trillions of small shells, crinoids and other fossils in this region and visitors are permitted to collect them.
This sheet of hard rock was formed from fine mud mixed with limy material produced by billions of dissolving shells in the mid-Jurassic period. This was probably a large tidal flat left exposed for prolonged periods in the large shallow inland sea that one lay between the western and central North America. It may be difficult to see but the rock has ripple marks on the surface. There is evidence that the limy mud was covered by a layer of algae when the dinosaurs walked through this area. In the picture above you should be able to find a set of tracks going straight up the picture.
To the left is a theropod dinosaur footprint. To the right the three large depressions are not a footprint but are rather another type of trace fossil. They are the product of large clams that dug down into this layer of sediment from sediments that formed above when the sea level had risen drowning this area. I saw hundreds of these clam trace fossils some of which were right in a dinosaur footprint.
My youngest daughter doing her best theropod interpretation while stepping in the footsteps of a dinosaur.
An interpretive sign at the Red Gulch dinosaur track site provides an explanation for how the dinosaur footprints could have been made and how they were preserved. This shift from hard limestone too much softer shales and claystones above is quite dramatic. This could be explained by rising sea levels and increased erosion from nearby terrestrial landscapes bringing in more course sediments. Evidence for a shallow placid sea above this limestone is found in the tremendous quantity of Gryphaea clamshells (see pictures below) in the rock layers you see in the image below. There are many successive layers that are composed of mostly fossil shells with interspersed sandstones with fewer fossils probably reflecting times of faster sand and silt deposition.
Dinosaur footprints aren’t the only attraction at this site. In fact, although there are hundreds of dinosaur tracks most are not easy to recognize. But the rock above the fossil tracks contains billions of fossil marine bivalve mollusks placed in the genus Gryphaea. This rock erodes far easier than the limestone making this flat surface in the gully possible. As the walls erode countless pieces of these small oyster fossils and the kids spent more time extracting these fossils than looking for dinosaur footprints.
Some of my family searching for Gryphaea fossils that are left on the surface as the softer rock and sediments erode. We are just a couple hundred feet from the dinosaur trackways and are about 20 to 30 feet above the hard limestone rock that contain those dinosaur footprints. In the distance are hills that contain rock that is younger than where we are standing. On the side of those hills I found no Gryphaea fossils but rather saw millions of flat bivalve shells and belemnites which are the remains of an extinct squid-like creature. I will share photos of those fossils and discuss the significance of those fossils, with respect to understanding Earth’s history, in a future post.
A closeup of a complete Gryphaea fossil as it was found on the surface. This bivalve two uneven shells. The larger, seen here, is curled up and a much smaller second shell piece forms the cover over the opening. Usually what is found in just the single large shell and the other half of the bivalve has been separated. The ground here was littered with countless pieces of shells. It does takes some hunting to find a nice complete shell such as this one. This shell is about 1 1/2 inches in diameter.
The surface mostly looks like this in the area above the tracksite. Pieces of fossil shells are everywhere. I will share many more pictures of these fossils when I take a look at other fossil sites in the Bighorn Basin that I was able to explore.
Below are some pictures of the wildlife that we observed in the immediate area of the dinosaur tracksite.
The ever ubiquitous jack-rabbit. Driving on remote dirt roads rabbits are seen darting here and there like swarms of grasshoppers.
This stately pronghorn male pranced up a hill when I came around a bend in the road early in the morning but then stood here quite a while as I slowly crept up closer and closer to get this picture. They are much less skittish than any deer. This could be because they are so much faster than any predator. It is debatable if the pronghorn or the cheetah is the fastest land mammal alive today.
The same pronghorn as the previous picture eventually made its way up the hill. Suddenly I saw a mule deer in my field-of-view through my camera lens. The pronghorn walked toward the deer, looked at it for a moment and then just turn and passed right by as if it weren’t there.
These pronghorn were just a few miles from the Dinosaur tracksite. The first few times I saw pronghorn in Wyoming I took pictures from far away. Little did I realize that we would see pronghorn no fewer than 30 times and many of those encounters were right by the side of the road or on hikes. At some point I stopped taking pictures I had seen them so often. We saw far more pronghorn than we did deer while in Wyoming.
I captured these two pronghorn at a watering hole just after sunrise.
The same morning that I went to the dinosaur tracksite on my way back I spotted a pair of red wolves playing next to their den on the other side of a creek. I stopped and watched them for at least 20 minutes. They were well aware that I was about 100 yards away and would look my way once in a while but they were more interested in playing that anything else. I took more than 100 pictures but unfortunately they were in the shadows of a large hill so this was the best I could do with limited light.
A red fox coming up the road just behind our parked car.
I saw these red foxes on three separate occasions. The time that I had the whole family with me one of the foxes came across the valley right up to our car and then to the top of this hill where it stood and watched us for a while.
With the family later in the day we traveled the entire Red Gulch Back Country Byway. I took this picture about five miles south of the dinosaur tracksite site.
Three days later on a separate fossil-hunting trip I took this picture just after a brief shower which really brought the colors of the hills alive. This was taken just a few miles north of the Red Gulch Dinosaur Tracksite from the same scenic byway road that the whole family traveled a few days before.