The Origins of Northern Arizona Petrified Wood
The dominant source of Petrified Wood in Northern Arizona and Southern Utah is the Chinle Formation. The Chinle consists of mudstones with occasional siltstone, sandstone, and other accessory units. Below is a brief summary of the petrified woods geologic origins
Geologists believe this wood was deposited along the banks of a river system while dinosaurs roamed the earth in the Mesozoic era. The river system flower overland a long distance and had mamy systems of ponds, wetlands, and tributaries.
Many of the wood samples found are Ginko trees, which were much more common in that era. When large floods logjammed the river wood blanketed the river floodplains and was sealed in a blanket of sediment before it could decompose. That process results in wood being preserved as stone because mineralization happens slowly and directly replaces the woods cellular structure with mineral. Floodplains are dominanted by fine clay rich sediments that cut off the wood from exposure to atmospheric air once the wood was covered. That is how the wood is preserved at the surface for later fossilization and protected from rotting.
The dominant mineral petrified wood is composed of is chalcedony, pronouned "calsedony". It has the same composition as quartz, making the wood very hard, but chalcedony is microcrystalline, meaning it forms extremely fine crystal grains instead of large plainly visible crystal structures.
Today beautiful specimens of wood erode from the Chinle and find themselves on display in homes, businesses, parks, offices, and more. Note the band of Grey colored Chinle Formation in the image below.
You can typically fine petrified wood from the Chinle Formation for sale at the BJs Spud Ranch store linked below:
Comments
Post a Comment