Fruita Paleontological Area, Colorado
The first serious scientific dig I participated in was an Earthwatch
expedition aimed at finding tiny dinosaurs and other
small fossils in the badlands of western Colorado. At the time, I was working as a mechanical engineer for Rockwell International,
and hated my job. I couldn't wait for the opportunity to pursue the interest in paleontology I'd had since I read my first dinosaur book
at age 4. Oh, I'd done some personal collecting of invertebrates over the years, but I'd never done any real science.
The dig was led by Dr. George Callison of California State University at Long Beach. George is a great guy and a lot of fun to
dig with. The dig site is a specially protected area on BLM land just outside Fruita, a small town west of Grand Junction. In the
years since my dig with George, Fruita has been put on the map by the establishment of the Dinosaur Discovery Museum, which is
a small but fascinating museum with fossils and large robotic dinosaurs. However, in July of 1986, Fruita was just one of many
sleepy little towns on Colorado's western slope.
The Fruita Paleontological Area (FPA) is situated in the Grand Valley, an easy walk from the southern bank of the Colorado River.
The Grand Valley is ringed by the Book Cliffs to the north, the Uncompahgre Plateau to the south, and Grand Mesa to the east.
The sediments of the valley floor in the area of the FPA are soft grey shales of the Brushy Basin member of the Jurassic
Morrison Formation, about 144 million years old. The sediments dip to the north, so that as you drive south and up onto the rimrock
where Colorado National Monument is located (our base camp), you go through older rocks. The Book Cliffs on the north consist
of exposures of Tertiary sediments. The Grand Mesa is a high plateau capped by volcanic rocks.
The Morrison Formation is famous for its dinosaurs, but most of them are the familiar giants like
Apatosaurus (Brontosaurus) and
Stegosaurus, the Colorado State Fossil. The formation was named for the tiny town of Morrison, outside Denver, more than
a century ago, when large dinosaur bones were discovered there on what is now known as Dinosaur Ridge.
The Morrison is widely exposed in the western states and consists of a series of sandstones, shales, and lacustrine limestones deposited on a low
coastal plain during late Jurassic time. Once you've seen the Morrison, you can recognize it practically anywhere, by the
distinctive juxtaposition of beds that are purplish-red, grey, and grey-green in color.
The sediments of the Morrison exposed at the FPA are grey bentonitic shales formed from the compaction and weathering
of volcanic ash. It is thought that the volcanic ash was redistributed by streams as fluvial and overbank deposits. The rock
is extremely fine-grained, and is one of the few places in the Morrison (or anywhere) to preserve the delicate bones of tiny
dinosaurs, lizards, and mammals. The shale weathers on the surface to the "popcorn" typical of bentonite, destroying any delicate fossils in
the process; so the overburden needs to be removed first, and the virgin, unweathered rock exposed, before prospecting can begin.
George and his crew had been working the area in previous years, and in the main quarry area, the overburden had been removed
by bulldozer and a grid staked out. When my team was assembled and ready to begin, visqueen laid at the end of the previous
field season to protect the pit over the winter had to be removed first. In addition to the main pit, past surface surveys had
indicated several other promising sites within walking distance, and George assigned some of us to dig at those; I was sent to the top of
a small ridge closer to the river, to a locality designated "Tom's place". I spent the entire two weeks there, digging slowly,
inspecting each piece of rock for bone, and throwing the discards down the hill. A fortnight of excavation by three of us created a ledge
about six feet wide, a dozen feet long, and waist-deep.
George showed us all on the first day what Fruita bones looked like. They resembled pencil leads more than anything else.
The rock was light grey, and the bone was black; bones are so delicate and small that they are not removed from matrix in the field.
When any of us found a piece of rock with something black in it, we called one of George's field assistants over and he or
she inspected it with a hand lens to determine if the discoloration was bone, a manganese stain, a root cast, or something else of
little interest. If it was bone, a preservative was applied and allowed to dry, and then the block was carefully wrapped in toilet
paper, sealed with masking tape, and labeled. Preparation of the tiny bones had to be done later in the lab, using fine tools
and microscopes.
We found numerous "keepers" every day, but most of them didn't look like much in field condition: longbones in
cross-section, things like that. They couldn't be identified as to element let alone animal until after lab preparation was completed.
Nevertheless, each find was exciting, because we could imagine that a splendid fossil might eventually emerge. Digging was tedious, but
fun, despite the hot (90°+) sun and relentless aggravation of biting gnats. At least I did not have as much trouble with gnat bites as some.
For one thing, the gnats took cover during the hottest part of the day, leaving us only the heat to contend with. For another,
they seemed to prefer some people over others. Gordon, in particular, had a "mag-gnat-ic" personality, and the citronella oil he
applied in attempted retaliation seemed to do little other than scent our quarry ledge. And some people had an allergy to the bites; my
tent-mate, Winona, got welts the size of fifty-cent pieces wherever she had been bitten. I was annoyed to have little chunks of my
flesh removed, and to have the beasties dive-bomb my eyes the way gnats always do, but other than that, I didn't have a real problem.
George didn't work us dawn to dusk seven days a week. We did start quite early to avoid the heat, but knocked off by
mid-afternoon. Every few days, we would go on a "field trip" to some interesting location in the area (and there are plenty of
them, geologically and paleontologically speaking). One day we visited Rabbit Valley in the morning -- a dinosaur bone interpretive
area a short hop down the freeway -- and then continued on up to Douglas Pass, where we looked for fossil plants and insects in
the exposures of Eocene Green River Shale right by the roadside. Another day we took a ride to the Dry Mesa quarry west of
Delta, where fluvial Morrison sandstones have yielded the big dinosaur bones, including the remains of "Ultrasaurus". On Sunday
we skipped paleontology completely and went swimming at "the potholes" on the Little Dolores River. The next day it was back
to work, refreshed, at the Fruita quarry.
Aren't the best things always saved for last? On our final day of digging at Tom's place, while we were taking our lunch
break, Rich was half-heartedly knocking away at some unpromising-looking blocks. All of a sudden, one split open to reveal the
complete, articulated skeleton of a small lizard! We couldn't believe our eyes! I rushed to photograph it before it was preserved and
wrapped, something that had to be done quickly since the virgin rock is slightly damp and will crack as it dries if the preservative isn't
applied to bind it together. We ran to tell George, who immediately came to have a look, and declared that this was by far the
best-preserved small lizard from the late Jurassic yet to be found in North America. It made two weeks of finding nothing but pencil
leads worthwhile.
That final afternoon, of course, was anticlimactic. Now that we were sure there really were fossils in those rocks (and didn't have
to take the professionals' word for it that black specks were bone), we kept thinking that where there was one articulated
skeleton, there should be more...but they remained hidden, waiting for the next crew to find.
On the drive back to Boulder, I formulated just how I would tell my husband that I was going to quit my job and go back to
college to study paleontology. To my amazement, he didn't give me a hard time about my announcement; he said he would be glad not
to have to hear me complain about work any more. So, at age 31, that's what I did. It took me 5 years to finish a master's degree
in museum studies with an emphasis on vertebrate paleontology, because I had to start out making up a lot of undergraduate classes
in biology and geology, and I also had a baby along the way (a delightful little girl). But I truly enjoyed school for the first time in
my life, and it was one of the best decisions I've ever made.
