Saturday, October 3, 2009

North Dakota Dinosaur Dig: Part 2

Posted by Kirk
Here's post number 2 about my dinosaur hunting trip. (Be sure to read part 1 first!) I present, Tuesday.

Tuesday we headed out to the Triceratops site. This is a site where they were working on a partially complete triceratops. It was very neat to see, though a bit confusing as the skeleton was not complete. I know what a sacrum and ilium are but I'm guessing the kids didn't and had a harder time making sense of the jumble of bones. I wasn't going to include a photo because unless you know what you are looking at it just looks like a shot of the ground and some rocks. I figured what the heck, why not include it. I think it is telling. Take a look at the photo to the left. Can you see the triceratops? This illustrates nicely why this is such slow work. The fossils are hard to locate and often very fragile.

The previous day, a group had made a plaster field jacket for the triceratops femur so we helped haul that out. It was very heavy. I believe this was one of the only pieces taken out as this was the last week of the season and there was not time to remove the entire dinosaur. It would have to be capped for the winter so that it would not degrade now that it was exposed. That's me in the green on the back right getting ready to lower the femur down a small hill. I think the dark blotch on the horizon might be the truck we were carrying it to. We stopped to rest a lot. The field jacket consists of a 2x4 for support, some foil and a lot of plaster strips. The femur was enormous.

While waiting to carry out the femur I did a little prospecting and located a rich trail of bone fragments coming down the hillside maybe 100 feet from the triceratops. I called the rest of the group over and we followed the pieces up to the top of the hill where they stopped. We dug a little but didn't find anything. The two experts with us looked at some of the pieces we found and could tell that they were triceratops frill. It was really cool to follow the trail and start looking for more even though we didn't turn up anything. They hadn't found the head of the triceratops they were excavating 100 feet away so perhaps it disassociated when it died and we were finding pieces of the head of the one they were digging up. Who knows.

Here I am doing a little cleaning up on a different piece of frill. You can see the lines from where the blood vessels were. If you think that triceratops were cold blooded then you think the blood vessels were there to help heat up the dinosaurs via passive solar collection. If you think they were warm blooded then the blood vessels may have helped it cool down. I'll leave that debate to the experts.

FYI: The stylish latex gloves are actually to keep paint and chemicals off my hands as we were making plastic casts of dinosaur teeth and talons on the table in the background.

Later that day we climbed to the top of a butte and felt one of the strongest winds I've ever felt in my life. I took this clip of video but it doesn't do the force of the wind justice. You can get a good view of the basin we are about to descend into as I pan across the landscape. I know it isn't the best video but it also gives you an idea of the landscape.

Atop this bluff we collected some of the K-T boundary. This is the geologic boundary between the Cretaceous and Tertiary periods. This layer of ash comes from the meteorite impact that slammed into the Yucatan peninsula 65 million years ago and almost ended all life on earth. The actual K-T boundary here is very visible, one of the best spots on earth to see it. You can even see yellow ribbons of iridium in the black. Iridium in this concentration generally only comes from meteors.

For reference, check out this satellite photo.

View Larger Map
The marker marks the exact spot we collected the KT boundary. Can you see why they call this the Hell Creek formation? It isn't a real hospitable location. The basin to the south of the butte is where we spent the day hiking and looking for fossils.

We headed down into the basin and scouted out several cool sites. We found many pieces of turtle shell. Most pieces were about the size of a quarter.

The pieces I found are from trionychid turtles such as this one. The complete one in the photo is a replica in the Warner Nature Center collection. For size reference, that is a standard countertop it is sitting on and the fossil takes up the entire depth of the counter. These large turtles are related to the soft shelled turtles that inhabit rivers today. The basic turtle design is evolutionarily very robust and has changed little over time.

At one particularly interesting site after lunch I picked up some broken pieces of fossil that had washed into a small wash coming off a hillside. Since the pieces were found close together (within a five foot stretch) and all appeared similar I put them into their own bag and asked our leader about them. He said they were from a turtle and that I could keep them as they were just broken scrap type pieces. I took them home and to my delight two of the pieces fit together. As I played with them a second piece fell into place and then a third, then a fourth. All in all there were 18 pieces and 9 of them fit together but they don't add up to much.

What I can tell is that it is a portion of the anterior right plastron of a turtle. I have one piece of carapace as well. You can see the curved up portion where the plastron would have connected to the carapace of the turtle. It seems about twice as thick as the trionychid shell pieces we found so I need to do some digging to get and idea of what species I'm dealing with. My impression is that trionychid turtles did not have such solid plastrons.

I had a great time putting all the pieces together. I just wish I had a whole turtle to work with! It was a like a fantastic challenging jigsaw puzzle but in the end, instead of a photo of a basket full of puppies or kittens, you end up with a fossil of an animal that lived 65 million years ago. Pretty damn cool.

We continued on our hike through the basin learning about geology and fossils until our water ran out and we needed to head back. We spotted a badly crumbled hadrosaur femur on the ground and noted it with GPS before turning for home. Maybe another group can look longer at this area next season.

That's all for Today. Come back tomorrow for Part 3!