Almost one hundred fifty million years ago, in Late Jurassic east-central Utah, in a lowland basin under a tropical sun, thousands of bones from dozens of dinosaurs collected in a deposit that today is known as the Cleveland-Lloyd Dinosaur Quarry National Natural Landmark — or "the quarry," for short. A century ago, cowboys rounding up cattle in the area were amazed to be stumbling across black dinosaur bones instead of their livestock. But the Cleveland-Lloyd bone deposit wasn't brought to the attention of scientists until 1926 or 1927; the first scientific expedition to collect dinosaur bones here was put together by University of Utah geologists in 1928. They returned in 1929 for additional collection, but after that, the deposit was not studied again until 1939.
At that time, W. Lee Stokes, a native of Cleveland, Utah, was a graduate student in geology at Princeton University in New Jersey. Lee's family ran cattle near Cleveland, so — like many of the local people — he knew about the nearby deposit of dinosaur bones. Although dinosaurs had been recognized as a unique form of life over a hundred years earlier, there was still much that science did not know about them in Stokes's era. So he told his college professors about the place near his hometown where they could collect dinosaur bones to study. The professors thought that that was great in theory. But since they had no money available to finance a research expedition, they encouraged Lee to just focus on his studies at Princeton. Then Malcolm Lloyd, a Philadelphia lawyer and Princeton graduate, stepped forward with a donation of $10,000 to fund just such an expedition. The quarry received its name from a combination of the name of Stokes's hometown — Cleveland — and that of the financial supporter — Lloyd — who made the first excavations possible.
|A femur still embedded in rock within the Cleveland-Lloyd bone deposit.|
According to the scientific method, when you come across a new phenomenon or life form, the first thing to do is gather data (information) about it. Then, you analyze the data you've collected and compare it with what is already known. Next, you propose a hypothesis to explain that data. Then you gather more data, test your hypothesis against the new data, modify the hypothesis as needed, gather even more data, and repeat. Eventually, you choose the hypothesis that best explains all the observations you've made and publish it as your conclusion.
The summer of 1960 saw the beginnings of the University of Utah (U. of U.) Cooperative Dinosaur Dig at Cleveland-Lloyd for the purpose of establishing a research collection of Jurassic dinosaur bones. Gathering data included collecting dinosaur bones — and the U. of U. crew approached the Cleveland-Lloyd deposit quite enthusiastically! In fact, some 8,000 fossilized bones were carefully pulled from the bone bed over the first five years of the project.
|Mike Leschin holding a chunk of femur (thighbone) from a dinosaur, probably a sauropod, or "longneck." This is one of the sights in store for those interested enough — and tough enough — to participate in a "track tour" to view dinosaur tracks.|
As it turned out, most of those bones were identified as belonging to a species called Allosaurus fragilis, a carnivorous dinosaur. Much of what we know today about Allosaurus is derived from the bones taken from Cleveland-Lloyd Dinosaur Quarry during this 1960s dig.
As researchers dug into the bone bed, it became clear that not only was the site a phenomenal source of dinosaur bones, but it was very puzzling as well. Jim Madsen, an expert on the study of Allosaurus bones (osteology), has said, "It was as if someone had dumped a bunch of dinosaur skeletons into a mud pit and then taken a big stick and mixed them up all up." Hardly any of the bones are still articulated (joined together); in other words, with these Allosaurus skeletons, "the ankle bone is no longer connected to the leg bone, the leg bone is no longer connected to the thigh bone," and so on.
Several hypotheses to explain the origin of this deposit have been proposed. Some paleontologists thought the area might have been a muddy place where dinosaurs were trapped, but the most recent study shows that an ordinary flood event was most likely responsible for bringing all the bones here. The orientation of smaller bones, and the presence of a dinosaur egg, show that flood waters were not moving very fast.
So-called "stereo pairs" are photos of an object taken from slightly different locations and angles. Just as our brains resolve the slightly different view from each of our eyes to let us see a third dimension, stereo pairs also allow a computer to "see" a third dimension. At Cleveland-Lloyd, cameras will be attached to special movable mounts suspended from the rafters of the quarry building being worked in. The resulting stereo photo pairs will be processed using modern computer technology, which can then record the positions of the bones in three dimensions instead of just two. The team hopes to achieve a location accuracy of ±5 mm. This approach will also provide an overall photographic record of the deposit as it is being uncovered.
|Mike examines an Allosaurus caudal vertebra (tailbone) in a section of the bone bed that has been overlaid with a portable grid.|
As the old saying goes, sometimes you "can't see the forest for the trees" — meaning that when you're looking at one single tree really closely, you might not notice important things about the forest that contains that tree. In the same way, when a scientist examines the Cleveland-Lloyd bone deposit and the rocks that contain the bones, he or she must also consider the larger setting for both the rocks and the bones. For this reason, BLM has produced a detailed topographic (land feature) map with two-foot (0.6-meter) contour intervals of the quarry area. This map is already in ArcView (a type of GIS software) format and BLM makes it available to qualified researchers for their studies. A recently completed lithologic (rock study) map of the same area will soon join the topographic map in computer space, and will also be available to scientists.