Arizona State Fossil

Petrified Wood

(Araucarioxylon arizonicum)

Adopted in 1988.

Petrified Wood, (Araucarioxylon arizonicum,) is Arizona State Fossil. It was adopted in 1988. Most of the petrified wood in Arizona can be found in the Petrified Forest in northern Arizona. Remnants of giant trees from ancient forests of the Triassic Period over 200 million years old, these logs turned from wood to rock after the trees were buried under layers of sand and silt. In some cases, the microscopic structure of the wood was preserved during the process.

Arizona State Fossil: Petrified Wood

Petrified wood (from the Greek root petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization. All the organic materials have been replaced with minerals (mostly a silicate, such as quartz), while retaining the original structure of the stem tissue. Unlike other types of fossils which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition. Mineral-laden water flowing through the sediment deposits minerals in the plant's cells; as the plant's lignin and cellulose decay, a stone mould forms in its place. The organic matter needs to become petrified before it decomposes completely. A forest where such material has petrified becomes known as a petrified forest.

Petrified wood can be seen in the Petrified Forest National Monument located north of I-40 east of Holbrook. The famous fossil wood of Petrified Forest National Park, in Arizona, is of Triassic age (about 200 million years). That fossil wood is a colorful agate.

It is illegal to remove petrified wood from the Petrified Forest National Park. Pieces of petrified wood on sale within the Park and elsewhere come from private land outside the Park.

The Arizona Revised Statutes

The law designating the petrified wood as the official Arizona state fossil is found in Arizona Revised Statutes, Title 41 (State Government) Chapter 4.1 (HISTORY, ARCHAEOLOGY AND STATE EMBLEMS) Article 5 (State Emblems) Section 41-853

Title 41 - State Government.
Chapter 4.1 - HISTORY, ARCHAEOLOGY AND STATE EMBLEMS.
Article 5 - State Emblems.
41-853. State fossil

41-853. State fossil
Petrified wood, or araucarioxylon arizonicum, is the official state fossil.

Taxonomic Hierarchy: Petrified Wood

Kingdom: Plantae - Plants
Division: Pteridophyta
Class: Filicopsida -
Order: Coniferales
Family: Uncertain
Genus: Araucarioxylon
Species: Araucarioxylon arizonicum