The petrified wood in the Circle Cliffs, like that of the Petrified Forest National Monument in Arizona, is found in the red and blue shales of the Chinle formation. The word Chinle (pronouneced Chin-lee) is from the Navajo, and means “at the mouth of the canyon.” The name is taken from the area at the mouth of Canyon de Chelly, in Arizona, where the formation is more than 1,000 feet thick.
The Chinle formation was laid down about 180 million years ago during the Triassic period of the Mesozoic era. The Triassic followed the Permian period of the aleozoic era, a period of hard times for the plants and animals of the world. During the Premian, great glaciers covered large portions of the earth, and the amphibious animals that had managed to crawl up on the sand bars and waddle over the mud flats suffered a general degeneration. Many of them returned to the water completely. Plants that had begun to florish were covered by glaciers, or withered away in the cold.
When the Permian ended and the Trinssic period was ushered in, the climate slowly became less severe The glaciers melted. Warm humid breezes blew over the land. Water was plentiful and the earth was clothed in a mantle of green. Living conditions for the plants and animals of the world were good and they florished.
At that time, a large area in what is now southwestern United States was covered with a shallow arm of the Pacific Ocean that reached as far east as Texas and north into Utah and Colorado. Rivers of silt-laden waters from – the surrounding higher land meandered through wide flood plains and broad sandy beaches to reach the shallow sea. Some of the silt and sand is thought to have come from the ancestral Rocky Mountains which were beginning to rise above the surrounding ground. The blue clay and shale, so characteristic of the Chinle, came from weathering volcanoes that dotted the landscape.
There is a general belief that the shallow sea was surrounded by a sun-baked, arid desert. Many of the fossil plants that have been found in the Chinle formation, however, indicate that the climate at that time was at least sub-tropical. And, that plants such as ferns, reeds, rushes, and cypress-like trees with swollen bases grew in the swamps and along the banks of the slow, meandering streams. On the higher ground, cycads and cycad-like trees grew side-by-side with the ancestors of the conifers found in this region today.
In the slow moving, brackish streams and stagnant waters of the swamps and lakes were strange looking, heavily armored fish that were able to survive the foul water by coming to the surface and gulping mouthfuls of air- Their mortal enemy was the Phytosaur, a large, flat bodied amphibian that swam or crawled about the shallow water and fed on the fish and other animals it was able to catch. Teeth and bones of this strange, crodocile-like animal are often found in the blue shale of the Chinle today.
Most of the trees that grew in those ancient times died, fell to the ground and rotted away. Occasionally, however, flash floods uprotted groves of trees that grew along the drainages, carried them downstream and deposited them in tangled masses on sand bars and in the bays of the shallow sea. Rapid burial by mud and sand prevented their decay, and the deposits in which the trees were buried thickened and hardened into shales and sandstones.
The sediments which buried the logs contained a large amount of silica-rich volcanic ash. And over the years, water seeping through the ground picked up the silica and, as the wood deteriorated, the silica replaced it, a cell at a time, and produced stone replicas of the prehistoric logs. Sometimes, particles of uranium were also carried in the water and logs have been found that were especially rich in the radio-active metal.
Most petrified wood is chalcedony, a non-crystalline form of quartz, which makes beautiful handmade jewelry. It is generally colored by an impurity, and called agate or jasper. The Wolverine Area wood is a type of jasper colored a dark, rich brown by limonite in the silica bearing water. Sections of logs and bits of wood are twisted, gnarled, and pitted with knots and cracks and look as though they might have been hacked from a dead juniper. Sparkling quartz crystals have filled many of the cracks and crevices, and coated broken bits and pieces of the brown stone. Although this wood does not have the color found in the agatized wood in the Petrified Forest in Arizona, it can be cut and polished into gemstones with a deep, warm brown color.
When I was ready to leave the area, I suddenly found that I was at the end of the road and had no place to go. After I followed some tracks up a steep hill and made a couple of false starts, I discovered the road to Boulder made an abrupt turn to the right and went up the bottom of a sandy draw. Recent floods had covered all trace of the tracks, and it was not until I had gone a couple of hundred yards that I was sure I was on the right road.
The Wolverine Petrified Wood Area is located in the wild, rugged country about 30 miles southeast of Boulder, Utah, and you can come in from the east, as I did, or from Boulder. No matter which way you go, you will have 30 or 40 miles of dirt road that is little more than a cow trail, widened and smoothed by a bulldozer. It’s a slow road and you won’t make more than 15 or 20 miles an hour. But, unless the road is washed out from recent floods, you can make it easily in a two-wheel drive pickup. Just be sure to use the stiles to cross the barb-wire fence. If you don’t, you just might leave your jeans, or worse yet a part of you, hanging on the top wire.My Trip to the Petrified Forest National Monument in Arizona,