Wednesday, May 4, 2011

Paleogeography of the Monument in the late Cretaceous (by Matt Selman)

Snow College students and BLM field staff descend to a dig site in Grand Staircase-Escalante National Monument.

The Grand Staircase-Escalante National Monument has, in recent years, become a major national destination for scientists studying the life-forms of the late Cretaceous period. Teams from around Utah and the United States make yearly pilgrimages to the monument to explore its fossilized floodplains, river channels, and coastal lagoons in search of the animals that lived and died in what was an incredibly lush tropical area, now transformed into high desert and badlands topography.
Erosional forms on Horse Mountain.

As different as the climate of the period was from that of the present day, so was the geography markedly dissimilar. Cretaceous North America was the site of a vast, shallow sea known as the Interior Cretaceous Seaway. At its height in the Middle Cretaceous, the seaway’s western boundary devoured the eastern third of what is now Utah. By the Late Cretaceous, the shoreline receded to the east, leaving a damp coastal plain running through the center of present-day Utah.
Top: Dr. Alan Titus discusses the distribution of fossils within the Kaiparowits formation.
Bottom: Scott Richardson of the BLM descends to a dig site in the northern part of the Monument.

At the same time, a significant mountain-building event occurred in the region. The Sevier Orogeny created a chain of mountains running longitudinally from modern-day Mexico up into Canada. As quickly as these mountains were uplifted, the forces of erosion began to work on them, creating great river channels flowing down into the receding interior sea.

Hadrosaur humerus (top) and velociraptor claw (bottom), both deposited in prehistoric floodplain sediments.

This geography, along with the climate of the period--both of which are immensely different from that of today--created the conditions which allowed flora and fauna to flourish, and their remains to be relatively well preserved in the sedimentary deposits of rivers (flowing down and east from the Sevier mountains), floodplains, and the shores of the Interior Cretaceous Seaway.
Returning to camp.

How to recognize a dinosaur fossil? By Candy Chiu

I had a 3 days 2 nights trip in April which took place in Kanab, Utah. This is the geology trip of finding dinosaur fossils. It is a nice and fun trip! Also, this is the first time I ever camped in Utah. Although it was hard to finish this trip, I did it!
I learned how to recognize a dinosaur fossil through this trip. Fossils are unlike usual rocks. Fossils form when the remains of animal that are trapped between rock layers and become a part of the rock sequence. There are two kinds of fossils we found in this trip. We found the tree fossils and the dinosaur fossils.

This is one of the dinosaur fossil that we found.
And this is one of the tree fossil that we found.

From what I see in the cross-section of the fossils, fossils have a higher density than rocks. For the tree fossils, it is in brown color.

This field trip is really a good chance for me to know more about dinosaurs, this extinct creature. This is really a nice trip and I will join it again if I got another chance.

Tuesday, May 3, 2011


I would like to start off by saying that this was the best field trip I have ever been on in my life! Hands down, by far! I wouldn't trade my experience for anything, and I am seriously considering doing it again next year. So, for all you thinking of going, DO!! We spent two nights and three days roughing it in the wilderness with Dr. Alan Titus, the paleontologist for the Grand Staircase - Escalante National Monument and his assistant Scott Richardson. Not only was this trip fun, but I cannot begin to describe all that I learned on this trip. So I have chosen a topic I enjoyed, and I'll do my best.

We spent the second day up there digging for bones! A couple of hours in, Tauni and I were assigned to move a mass of rock on the bottom right section of the quarry. We were given hammers and chisels and told to go layer by layer. I was so excited!! We worked, and worked, and worked....and worked. nothing!! I was feeling pretty down. You see, the movies never show how much work goes into digging out a dinosaur, I felt like I had been tricked ;).

All of the sudden Tauni gasped. My heart sputtered to a stop and I leaned over to see her discovery. "OH MY GOSH! LOOK WHAT YOU FOUND!!" I yelled (I've been known to be a little dramatic). I was so happy all our work was not in vain. Everyone stopped working and ran to see what had been uncovered. There, in her cute little hand was a........GASTROPOD!!! I was so thrilled. Unfortunately, Scott an Alan were less enthusiastic with her great feat. "Just a snail." Scott said and he put it back on the ground. Gosh darn it, no it wasn't 'just a snail'. This was a true, honest to goodness fossil! Millions of years old! And it had just come out of the ground I was digging in! We found half a dozen more similar gastropods, varying in size, in this same layer. It was great.

So, after my excitement subsided, I got to thinking. 'What on earth were snails doing by our Hadrosaur?!' Needless to say, I asked. Not to my dismay I got a fabulous answer. I simply needed to remember the environment of deposition. During the the Cretaceous when the Kaiparowits was being deposited, Utah was a lush, green, tropical place! So what had happened all those millions of years ago was simple. Of coarse there were other animals alive at the same time this Hadrosaur died. Its bones were deposited in a small lake on a floodplain of a river. In this small pond or lake there were snails. So the snail shells were buried in the mud after they died along with the dinosaurs and fossil plants. Our own 'claim to fame', finding gastropods on a Geology trip!