Name/Title
WoodworthiaEntry/Object ID
07.58.104Description
The Chinle formation of northern Arizona is
famous for the abundance of petrified wood
found in these sedimentary rocks and mudstones.
These sediments we deposited during the Triassic
period more than 200 million years ago. The climate
of Arizona at that time was tropical at that time
so the forests were populated by tropical species
of araucaria and its rarer relative Woodworthia
arizonica.
While not recognized as a distinct
species at first, John Muir noted in
1905 that it differed from the larger
fossil araucaria logs typical of the area.
The trunks of Woodworthia are covered with
distinctive bud scars that suggest this species
was capable of sprouting new branches and
leaves should it be defoliated by browsing
dinosaurs or volcanic ashfall. While the trees
found in the Chinle formation do have growth
bands they don’t form clear rings because of
the lack of seasonality in their tropical habitat
Assemblage Zone: Sedimentary
Chemical Composition: Si O2
Crystal System: Hexagonal
Description: Family: Protopinaceae
Genus: Woodworthia
Species: Arizonica
Common name: Woodworthia
Age: Late Triassic
Location data: Chinle Formation, Arizona USA
Description: Polished cut slab with colors brown, tanish to yellowish, beige and pinks with a crystalline center. The growth rings are apparent and the slab is some what of a complete round Size: 7.00"x 6.500"x 3.500"
Type of Fossils Present: Plants
Fracture: conchoidal
Grain Size: Fine
Hardness: 7 Quartz
Lithofacies: Fluvial System
Luster: Glassy
Occurrence: Silicified wood, which is the fossilization and opalization of organic woody matter by the deposition of SiO2 in a anaerobic environment to prevent decay. This means that the wood must somehow be buried in an oxygen free enviroment, possibly in the silt-laden river or the bottom of a lake or buried by volcanic ash or related volcanic mudflow. The organic material in the wood is then replaced by silica (SiO2), other minerals determined its colors.
Pressure: Low-Moderate
Rock Color: Medium
Rock Origin: Post-depositional
Rock Type: Sedimentary
Specific Gravity: 2.6
Surface Process: Not apparent
Streak: white
Temperature: Low
Texture: Mircrocrystalline
Variety: Petrified woods here are hydrous microcrystalline variety of quartz that can be generally termed as chalcedony.Collection
Petrified Wood CollectionAcquisition
Accession
05.58Source or Donor
Petrified Wood CollectionAcquisition Method
DonationOther Names and Numbers
Other Number
Other Number: 2007.58.104Dimensions
Width
6-1/2 inDepth
3-1/2 inLength
7 inDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
PW-10Room
Petrified Wood RoomBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Jillian Mather KettleyDate
August 1, 2025Notes
location updated while inventorying room
