Tree Fern

Object/Artifact

-

Crater Rock Museum

Name/Title

Tree Fern

Entry/Object ID

05.58.196 (B)

Description

Fossil Tree Fern Osmundacaulis Jonesii . This fossil fern grew in the Jurassic period around 185 million years ago in southern Tasmania . Fern trunk fossils are rare as soft bodied plants normally rot before they survive the fossilisation process. At Lune River the forest was flattened by a pyroclastic flow of volcanic ash . This was covered in a layer of basalt and dolerite a kilometre thick. Hot Silica rich fluids produced by the cooling of the basalt and dolerite replaced the carbon in the plants at a cellular level perfectly preserving a range of ancient ferns and trees in colourful agate ,jasper and quartz. 180 million years later the kilometre thick layer of volcanic rock has weathered away leaving these beautiful fossil plants on or near the surface Chemical Composition: Si O2 Crystal System: Hexagonal Description: Family: Osmundaceae Genus: Osmundacaulis Common name: Manfern Age: Early Cretaceous Location data: Lune River, Tasmania, Australia Description: This specimen is the two sides of a cut piece the polished slabs are colored grey, black, yellow and red. The growth rings are apparent. Type of Fossils Present: Plants Fracture: conchoidal Grain Size: Fine Hardness: 7 Quartz 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 Collection

Acquisition

Accession

05.58

Source or Donor

Petrified Wood Collection

Acquisition Method

Donation

Other Names and Numbers

Other Number

Other Number: 2005.58.196

Dimensions

Width

4-1/2 in

Depth

1-1/2 in

Length

5-1/4 in

Dimension Notes

Dimension taken at widest points

Location

Location

Container

Right

Drawer

2nd Shelf

Shelf

Left

Cabinet

Case #104

Wall

East Wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent