Flint Hill, South Dakota
Just to show you I'm not the only nut who threw in the towel on a corporate career to go into the unlucrative field of paleontology...my friend Toni quit the phone company after 20 years to pursue her Master's at South Dakota School of Mines. In the summer of '00 she was finishing up the fieldwork for her thesis, and I drove up to the site a little west of Martin, South Dakota to assist her with the digging.
I was a little apprehensive about going, because Angie, who had been there the previous year, had told me that it could get over 100° and that there was nothing bigger than a blade of grass for shade. I don't sweat a lot, and even if I dress lightly, wear a hat, and drink plenty of fluids, being out in the hot sun and getting overheated is a sure trigger for one of my killer migraines, but I decided to go anyway and hope for the best. I hadn't been on a mammal dig in 13 years, and those had been very different experiences -- one a Pleistocene cave deposit, the other collecting microfossils from anthills in the Pawnee Grasslands.
Well, Toni must drive 80 and never make pit stops, because what she told me was a 6 hour drive from Denver took me nine and a half. It was getting dark when I approached the turnoff, only to discover that there was positively no road leading south from mile marker 143. After exploring a couple of long ranch driveways and cowpaths through cornfields in the general vicinity, I decided to look for a motel in Martin and try again in the morning. It even did occur to me that she might have transposed the digits on the directions, but I was too tired to want to deal with it in the dark, especially since the site was several miles in on four wheel drive roads punctuated by those horrible barbed wire ranch gates.
Sure enough, in the morning, right at mile marker 134 were the flags indicating the turnoff, and the landmark windmill a little further on. It was close to lunchtime when I found the Hill (I'm not an early riser) and was greeted by Toni and the rest of the crew.
The site is in the Miocene Batesland Formation, a stream-deposited sandstone/mudstone unit around 15 million years old. The terrain was savannah during the Miocene, and the fauna consisted of a variety of ungulates (hoofed mammals) such as rhinos, gazelle-camels, and entelodonts (nightmarish, predatory pigs), as well as chalicotheres, which look like a cross between a horse and a giraffe, some carnivores and the usual "shadow creatures" like rodents and snakes. As is generally the case with fluvial deposits, you don't find articulated skeletons, because the flowing water disperses the bones. But you do find a lot of single elements, and where the river overfowed onto the floodplain, you can even find small and delicate bones.
Being the tail end of the scheduled digging, most of the gridding and removal of big bones had already been done. Toni and Diane were measuring strat sections and Regina was doing surface surveys, so I chose to sift through the previously-removed sediment in search of small bones that had been missed the first time around. I wanted a task that wasn't too physically strenuous in light of my overheating problem.
Working alone suited me just fine, and I had a beautiful view across the valley of the cottonwoods lining the Little White River. There were a few clouds and a nice breeze to keep it from getting too hot, but not enough wind to blow a lot of my sifting dust into my face. Toni had some pre-built screens but the mesh on all of them was too big for the things I was looking for; so I made do just fine with a plastic tray and a piece of plastic window screen, just scooping up sediment with my trowel and scratching till all the dust went through, then examining what remained on the screen for small bones. Most of what I found was unidentifiable broken sections of long bones, a millimeter or so in diameter and a few long, but I did find a bird femur (thigh bone) and a nice rodent astragalus (ankle bone).
Unfortunately, my digital camera doesn't have a zoom, and even in macro mode, the pictures I took of the small fossils I found don't show much. They do, however, give you an idea of the types of residual material you end up with when you look for fossils by screening sediment. Toni graciously lent me some photos she'd taken earlier of some of the larger bones they'd excavated from the site, so you can get a better idea of the types of fossils that were there.
By noon on Friday the partly cloudy weather had given way to the baking sun that Angie had warned me about. By midday I had that pressurized feeling in my head that lets me know I'd better get out of the sun fast or I'm going to be very sorry real soon, and since it was our last day of fieldwork anyway, I told Toni I thought I'd better pack up my gear and hit the road. Fortunately nowadays there are much better migraine drugs than there were a dozen years ago, and I was able to avoid a repeat of my Hungry Hollow experience. I decided to break the drive home into two days so that I'd have time to swing by Agate Fossil Beds National Monument in western Nebraska and see some good examples of similar, slightly older (20 mya) fossils. It was well worth the detour, as they have a very nice museum with impressive mounted skeletons of an entelodont, a towering chalicothere, and some smaller denizens of the Miocene savannah. I was particularly intrigued by the Daemonelix ("Devil's corkscrew") -- the fossilized burrows of extinct, land-dwelling beavers, something I'd read about but never seen before.
I arrived home just in time to snap a picture of a beautiful sunset behind what we in Boulder call the Flatirons, sandstone massifs that lie against the foothills giving silent testimony to the ancestral Rocky Mountain range that preceded our current one by a quarter billion years -- a fitting postscript to a delightful expedition.
