Ever
since I read about the Idaho Miocene fossil beds, at a place called Fossil
Bowl, decades ago in an essay by Stephen Jay Gould, I have wanted to visit
them. This past summer I finally had the chance. I drove south of Coeur d’Alene
in State Highway 3 for about fifty miles and drove through the little town of
Clarkia, which has no services and which you could almost drive past without
noticing. On the right (west) side of the road was a big open area that had
been converted into a motocross track. Unless you have specific directions or
just happen to see the hand-painted plywood sign set far back from the road,
you will never recognize this as being a famous fossil deposit.
I
drove in and looked for a sign telling me where to go. Because I had called the
Kienbaum family (the owners) before coming, I knew to look for a house on the
hill. So I started driving up what I thought was the driveway and found myself
on the motocross track. I didn’t see it coming. Suddenly I was going up a steep
slope and then my car (a little Scion) launched off into invisible space and
came thumping down on the track. It didn’t make it up the next incline.
Fortunately I found a way to exit the track. I found a van of young adult
bikers who were taking an air conditioning break, and who had been immensely
entertained by the sight of a little car on a motocross track, and they told me
how to find the driveway. I had to knock on every door of the house with
unfinished siding before Mrs. Kienbaum could tell me to look for her husband
and sons in one of the many workshop buildings downhill. The younger son found
me and led me through a crowded storehouse full of wooden furniture that Mr. Kenneth
Kienbaum had made. I paid ten dollars for the privilege of digging fossils and
taking them with me, perhaps the best ten dollars I ever spent. Kenneth told me
of the interest that even major media such as PBS were showing in this site. I
will be posting some YouTube videos [my channel] of my visit and will announce
when I do. I make videos with no budget. If you want to see a video about
Fossil Bowl that was actually produced with a budget, using support from
Bucknell University, the University of Idaho, and the Botanical Society of
America, see Plants Are Cool Too! Episode 2 produced by the very creative Dr. Chris Martine.
The
younger Kienbaum son led me to a place I could park right beside the fossil
deposit. You would never guess what it was. The outcrop is about the size of a
three-car garage.
I
set to work digging and photographing fossil leaves. (Others have found fossil
fishes, but I did not. Leaves are always more abundant than fishes.) I found
many good specimens that had already been excavated and were just lying around
on the ground. One of my best specimens was one I found by stepping on it. I
will provide some details and photos of these specimens in the next essay.
How
did these fossils form? Fifteen million years ago, during the Miocene epoch,
leaves of a lush forest fell into a lake and were preserved in sediments.
Oxygen destroys organic matter, but the water and sediments kept these leaves
away from oxygen. In fact, some of the leaves are not leaf fossils, but are
actually still leaves, complete with tissue and DNA. I believe that these
leaves have provided the oldest DNA specimens ever found, far older than the
30,000-year-old Neanderthal DNA in Europe. The organic molecules from the
70-million-year-old T. rex fossils were collagen, the protein that makes up
cartilage, not DNA.
Once
exposed to oxygen, these leaves quickly turn black. They are still beautiful
fossils, but the organic matter is reduced to a residue. So to find “fresh”
leaves, you have to split intact rocks open, which the older son, Riley
Kienbaum, showed me how to do.
The
leaves, mostly autumn deciduous leaves, are separated by layers of sediments.
The leaves form a slightly weaker layer in the rock, so that you can carefully
split open the rock and expose the leaves. Riley did this for me and I saw some
leaves that still had the same red autumn colors that they had 15 million years
ago!
I
brought back some slabs of rock, which I kept moist, and which I split open in
my laboratory and showed to my students. Unfortunately, in my specimens, the
rocks layers crumbled and I was unable to recover any fresh-looking leaves.
How
do we know the ages of these leaves? Radiometric dating provides the answer.
Radiometric dating can be performed only on volcanic material. But 15 million
years ago the Cascades were just rising up as a series of volcanoes, many of
which remain active today. The volcanic dust layers interspersed with the
leaves and sediments can be dated.
Meanwhile,
motorcyclists did some amazing maneuvers just a few feet away from where I was
digging. Some of them came over to see what I had found. They were genuinely
interested in the fossils and were some of the nicest people I have met
Before
planning your trip, it is good to contact the owners and make sure access is
open when you plan to visit. They are really very
nice people.
In
the next essay, I will tell you about the fossils I found.
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