PETRIFIED WOOD AND FOSSILS (OR NOT)
Most fossils look nothing like the bone above. When I first saw this one, I thought it was modern, washed in from a nearby ranch. I picked it up and it was definitely not bone anymore - too heavy, and the texture was wrong. I still don't understand the clean, smooth break at the right end, as if cleaved off. (Someone left this one on a rock shelf at the base of the Siltstone Wall, described in Hike #1).
Usually, when you spot a fossil, you need to spend some time looking at it before you can guess what it is. And vertebrate fossils are quite rare, even in the Bisti/De-Na-Zin Wilderness. Most common is petrified wood, and most of the petrified wood is in flakes.
It is illegal to remove anything from the Bisti/De-Na-Zin wilderness, whether sand or fossil. I believe it is a crime to remove the vertebrate fossils. These precious things are so scarce, you really ought to leave them for others. Take only photos. They make the best souvenirs, anyway.
Clam Shells and Petrified Wood
The little rise that I mention in the description of Hike #1, located at N 36˚ 15.921', W 108˚ 14.150', is covered with bits of clinker. On its north side, flakes of petrified wood and fragments of ancient, freshwater clam shell are mixed together. They tend all to be about 1/4 square inch. You can feel the difference between rock and clam shells, however. Clam shells do not fossilize and these still feel slick, like little bits of a modern shell. The photo on left shows the field, with many mixed bits. On right, I sorted out a couple of bigger flakes of petrified wood and smaller, whiter chips of clam shell. The petrified wood chips are probably 1-inch square. Shell chips can be found weathering out of most of the darkest lignite mounds.
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Larger Pieces of Petrified Wood
When you do find larger chunks of petrified wood in the Bisti/De-Na-Zin Wilderness, they look quite different from their famous cousins in the Petrified Forest National Park. The petrified wood here usually has not agatized fully - that is, silicon oxide (quartz) crystals have not filled the gaps in the cells. In the Petrified Forest, the wood was entirely filled with quartz and mineral impurities that lend a blue or red color to much of the petrified wood. Agatized wood feels like jasper, smooth and of a piece.
Petrified wood in the Wilderness is usually buff, light gray, or medium brown. Some chunks in the most dense ash piles are almost white. Some looks like plain old wood. The chunks tend to scatter. Most petrified wood in the wilderness has the texture of sandstone.
Petrified wood in the Wilderness is usually buff, light gray, or medium brown. Some chunks in the most dense ash piles are almost white. Some looks like plain old wood. The chunks tend to scatter. Most petrified wood in the wilderness has the texture of sandstone.
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Chips of petrified wood tend to scatter. They are all over Bisti in the forms you see to the left and above. Sometimes, the chips are clearly eroding from a larger piece (above right), and gradually spreading out.
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Big Pieces
Large pieces of petrified wood usually lie on a pedestal of ash. The lower the pedestal, the fresher the petrified wood generally looks. A tall pedestal indicates that it has been exposed longer.
Agatized Petrified Wood
I have never found a big, intact piece of agatized petrified wood in the Bisti/De-Na-Zin Wilderness. I often see little scattered pieces of quartz, centered around a slightly higher spot. They catch your eye when they glitter in the sun. I have associated them with decaying pieces of petrified wood, and I believe the quartz once built up in the petrified wood, then scattered as the object crumbled. It was not present in dense enough quantities to make the intact piece shiny, but glitters now in the shards. Just my guess.
Whatever their source, below left is a picture of the typical scattering of quartz crystals that you might see glinting in the sun in the Wilderness. And I need to admit that big logs of agatized petrified wood do exist in the Wilderness - I just haven't found any. On the right is a large chunk that my wife and her brother found on a hike when I had to be at work.
Whatever their source, below left is a picture of the typical scattering of quartz crystals that you might see glinting in the sun in the Wilderness. And I need to admit that big logs of agatized petrified wood do exist in the Wilderness - I just haven't found any. On the right is a large chunk that my wife and her brother found on a hike when I had to be at work.
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Fossils
Vertebrate fossils are vanishingly rare. I have spotted three in my many trips across the Wilderness. One is quite large and involves many pieces scattered over 150 feet. The best-preserved piece is the large vertebra, below (size 12 shoe for scale). The smaller picture of the wash near the bottom of the "erosive geology" page shows the area that contains this fossil, with the vertebra in the foreground.
A trained person, however, can spot a shark's tooth or fleck of turtle shell just about anywhere along the wash in Bisti. (I guess that technically these are vertebrate fossils, but they are unexciting.) Many fossils were polished by the glacier. The texture of fossil in Bisti/De-Na-Zin varies from waxy to sandy.
Fossil bone is distinguished from other rocks most easily when it is damaged. Where it breaks or erodes, the pattern of capillary beds in the bone usually forms parallel lines and curves with a characteristic texture. You can see the pattern on the lower right quadrant of the vertebra. Those micro-grooves are characteristic of all bone fossils.
A trained person, however, can spot a shark's tooth or fleck of turtle shell just about anywhere along the wash in Bisti. (I guess that technically these are vertebrate fossils, but they are unexciting.) Many fossils were polished by the glacier. The texture of fossil in Bisti/De-Na-Zin varies from waxy to sandy.
Fossil bone is distinguished from other rocks most easily when it is damaged. Where it breaks or erodes, the pattern of capillary beds in the bone usually forms parallel lines and curves with a characteristic texture. You can see the pattern on the lower right quadrant of the vertebra. Those micro-grooves are characteristic of all bone fossils.
Organic Inclusions / Ironstone
In many places, pieces of red-and-black rock are weathering out of the sediment. They vary in size and color, but the larger ones tend to be round like river stone. I once assumed that these were fossils of some kind, but alas, not.
A BLM geologist explained that iron oxide tends to crystalize around organic deposits - usually a fragment of leaf or wood trapped in the sediment. You can see such inclusions studded in the wall of a rise, often in a row. These rocks are unusually brittle - you can break the chunks apart in your hand. One book on Bisti refers to these as "ironstone."
A BLM geologist explained that iron oxide tends to crystalize around organic deposits - usually a fragment of leaf or wood trapped in the sediment. You can see such inclusions studded in the wall of a rise, often in a row. These rocks are unusually brittle - you can break the chunks apart in your hand. One book on Bisti refers to these as "ironstone."
Above, my family points at one of those inclusions among a field of short, flat hoodoos.
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The iron oxide-rich inclusions are crumbling onto the face of the ash, above.
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Here is a dense concentration of small inclusions. The rocks behind us on short pedestals are different. They appeared to be limestone tinged with iron oxide on the surface.
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Okay, some of my fossil pictures.
I am not sure whether it is a bigger tease to show the fossils I have found over the years, or to leave the record incomplete. If we know each other, I'll share my "fishing holes." Call me.
But because it is easy to damage or remove fossils, I am not going to post their GPS coordinates on the Web. If you're curious, here are my best finds. On left is a pair of ribs with a crumbling bone that seems to be a joint of some kind. I expect it is from the same animal that left its vertebra (pictured above) 150 feet away. My baseball cap is in the picture for scale. Between the vertebra and the ribs another pair of ribs appear to be eroding out of the clay (below left). Best find ever, by a factor of 10.
But because it is easy to damage or remove fossils, I am not going to post their GPS coordinates on the Web. If you're curious, here are my best finds. On left is a pair of ribs with a crumbling bone that seems to be a joint of some kind. I expect it is from the same animal that left its vertebra (pictured above) 150 feet away. My baseball cap is in the picture for scale. Between the vertebra and the ribs another pair of ribs appear to be eroding out of the clay (below left). Best find ever, by a factor of 10.
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It's anybody's guess what the thing above is. Its silhouette was evocative of a small dragon when I snapped it in 2011. No doubt the reality is much less exciting. I visit it pretty often, but it's not weathering out any more and the outline is less clear now.
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Another mystery here. The big piece is 13" x 5" You can see it's a fossil because of the capillary beds exposed by the break. There is a round hole in the top right piece. Could it be an eye? A more experienced friend suggested it could have provided a channel for nerves or large blood vessels.
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