Roxy Ann Wood

Object/Artifact

-

Crater Rock Museum

Name/Title

Roxy Ann Wood

Entry/Object ID

04.58.16 (A)

Description

Assemblage Zone: volcanic sediments Chemical Composition: Si O2 Crystal System: Hexagonal Description: Age: Oligocene Location data: Dry Creek, Roxy Ann Peak, Jackson County, Oregon, USA Description: Polished face shows brown color rims with woody stirctun, cut faceis a swirl of red and milky white, agate and greenish brown Type of Fossils Present: Plants Fracture: conchoidal Grain Size: Fine Hardness: 7 Quartz Lithofacies: volcaniclastic Luster: Glassy Occurrence: During the Oligcene (23 to 34 million year ago), standing forests were often destroyed by volcanic eruptions and then buried by falling volcanic ash and /or by mudflows of volcanic ash, called lahars. In some cases these destroyed forests were exposed to atmospheric oxygen because the wood was on the surface or because the layer of volcanic material enclosing the wood had dried out, which allowed microbes to attack the decaying wood. Subsequent volcanic eruption covered this material with another thick layer of volcanic ash or mudflow deposits; then silica-rich fluids derived from the surrounding volcanic ash replaced the partially rotted wood with amorphous silica, which later re-crystallized into chalcedony. These layers of volcanic sediment and wood fragments were buried by thousands of feet of additional material and transformed by heat, pressure, and fluids. In the Late Miocene (8 to 10 million years ago), these buried layers were uplifted, which over time allowed erosion to produce the modern landscape. Pressure: Moderate Rock Color: Dark Rock Origin: Post-depositional Rock Type: Sedimentary Specific Gravity: 2.6 Surface Process: Not apparent Streak: white Temperature: Low to moderate Texture: Mircrocrystalline Variety: "Roxy Ann Wood " is composed of a mélange of petrified wood, chalcedony and jasper, with in fillings of volcanic ash and microcrystalline quartz. The specimens show woody texture on their outer surfaces, they are not true limb casts. According to geologist Marty Norris, the conditions necessary formation of limb casts were present, but these specimens were shattered, splintered and then began to decay before their transformation into petrified wood, and so they are "wood cast." Mr. Norris notes that some "Roxy Ann Wood " specimens show compressional deformation and other have fractures in a directional pattern, both of which suggest that there was downward pressure from the weight of overburden and/or lateral pressure from crustal movements before the amorphous silica replaced the wood fragments. The growth of quartz crystals on the outer surfaces of some specimens, which formed after the wood was replaced by silica and fractured, supports the conclusion that there were several episodes of fluid migration through the sediments.

Collection

Petrified Wood Collection

Acquisition

Accession

04.58

Source or Donor

Petrified Wood Collection

Acquisition Method

Donation

Other Names and Numbers

Other Number

Other Number: 2004.58.16 (A)

Dimensions

Depth

1/4 in

Diameter

5 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

top left, top left

Wall

right - south

Room

Wood room

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent

Moved By

Catherine Boyd

Date

March 6, 2008

Location

Shelf

top left, top left

Wall

south

Room

Wood room

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent

Moved By

Catherine Boyd

Date

March 6, 2008

Location

Container

Right

Drawer

Top Shelf

Shelf

Left

Cabinet

Case #100

Wall

South wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent