Good Eye Leads to Sharp Find at Sand Arroyo

As is customary, we gathered in a circle for introductions before jumping into our cars and heading out on our Wilderness Walk. The meeting spot for this hike was the Fort Peck Interpretive Center, and our destination was Sand Arroyo, an “Area of Critical Environmental Concern” that’s managed by the Bureau of Land Management (BLM).

What a surprise it was to learn that we would be joined by University of Washington paleontologist Dave DeMar and several of his students, all of whom took time away from a nearby dinosaur dig to join our excursion.

Usually there is someone on the Wilderness Walk who knows quite a bit about something. On this hike it was Doug Smith, a co-leader and our resident paleontology expert from Dagmar, along with Doug Melton, a Bureau of Land Management archeologist, both of whom know a lot about Sand Arroyo. But having Dave and his students along was an added bonus.

Like most of the people who signed up for the hike, Dave and his students were attracted to the area because of the fossils. Sand Arroyo is a hot spot for them, because the exposed bluffs and washouts from the eroding sandstone are always revealing previously unseen fossils. Primarily because of the abundance of fossils, the BLM designated Sand Arroyo (9,052 acres) as an “ACEC,” an administrative designation used to protect paleontological resources and other values.
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All of these fossils are part of a larger story told through layers of rock and sediment, easily seen as you walk through the badlands.

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So while the fossils are an attraction, I also find these rugged badlands stunning. To me, this is a place where you can have a wilderness experience. Driving south from Fort Peck on Highway 24, you’ll see some of the badlands. But you have to walk along the bottoms of the drainages or across the ridge tops to really appreciate the unusual formations, including hoodoos and eroded knife-blade ridges, that make this landscape so extraordinary.

Like most BLM lands in eastern Montana, there are no trails, and for the most part, they’re not needed because hiking generally isn’t difficult on prairie landscapes, even badlands. That said, a trail to guide visitors through the area would be helpful. And that is exactly what Doug Smith is advocating for, albeit a less obtrusive trail. He submitted a proposal to the BLM to create a trail of cairns along an eight mile route.

Following a segment of the trail proposed by Doug, we stopped often to check out each new fossil find. It’s impressive to watch people who can pick out fossils by glancing across the side of ridge, peering into a washout of sediment or somehow feeling them under foot. Then, with a little closer look and touch of the hand, identify the animal it came from. Without the benefit of some experienced and trained eyes, I would have missed a lot.

The rocks almost came alive as we discovered petrified wood, viewed patterns on rocks that at one time were turtle shells, and turned up porous rocks that upon closer examination turned out to be fossilized bones from a Triceratops.

But the real find of the day was two pieces of a large tooth from a T-Rex. Even though it was in two pieces, the tooth was intact and unique enough that Dave recorded the exact location and bagged itto be encased for protection. Some day it might even make its way into a museum, either by itself or as part of an assembled T-Rex. For all we knew, the rest of the T-Rex may have been buried farther up the bluff.

All of these fossils are part of a larger story told through layers of rock and sediment, easily seen as you walk through the badlands. Dave pointed out the layer marking the mass extinction when more than half of the world’s species were obliterated. Above this layer, we found species that survived this event and the beginning of the age of mammals.

After spending most of the day thinking about fossils, observing fossils, and holding fossils in my hands, I was beginning to feel like I too could be a fossil detective. And on the last leg of the hike, I picked up what I thought was a fossilized bone and showed my find to Dave.

He looked at it, held it, and then looked at me and said, “Nope, this is just a rock.”

Oh well. I guess my fossil detective skills aren’t as sharp as I thought, but I now know more than I did and experienced some really interesting and beautiful country. This is a hike I won’t forget.

A word about collecting fossils on BLM lands

Vertebrate fossils are fragile, and because of their rarity and scientific importance, they may only be collected by qualified researchers with a permit. This includes bones and teeth, as well as footprints and other traces of activity. If you find vertebrate fossils, just look, take a photo, and be sure to leave them as they are. They might just provide a clue to a bigger find. If you come across a fossil that you think might be of scientific interest or may be damaged, report your finding at the nearest BLM office.

It is legal to collect small amounts of petrified wood and invertebrate and plant fossils on BLM lands. But consider leaving these too, so that others can experience the fun and excitement of finding a fossil.

– Mark Good, MWA central Montana field director