Leaf Fossil

Object/Artifact

-

Crater Rock Museum

Name/Title

Leaf Fossil

Entry/Object ID

78.57.04

Description

Assemblage Zone: sandstone Chemical Composition: Si O2 Crystal System: Subhedral Description: Family: Taxodium Genus: Sequoia Common name: Dawn Redwood Age: Oligocene to Miocene Location data: John Day Formation, Fossil, Oregon Description: Leaf imprint on a beige sandstone. Size: 6.250"x 3.250"x 1.00" Type of Fossils Present: Plants Fracture: conchoidal Grain Size: Fine Hardness: 7 Quartz Lithofacies: sedimentary Luster: Silky Occurrence: The eruptions of the John Day Formation occurred about 36 million years ago generating pyroclasttic ash flows or "ignimbrites". These hot gas charged clouds of ash poured down the flanks of volcanoes then across the landscape of miles destroying everything on the way before settling to the ground and annealing into a solid crystal-studded, glassy mass. This rapid deposition of volcanic ash and mud in every depression on the landscape was optimum to preserving the remains of the semi-tropical vegetation and mammals whicn lived in the John Day Basin. Pressure: Moderate Rock Color: Dark Rock Origin: Marine/Freshwater Rock Type: Sedimentary Specific Gravity: 2.6 Surface Process: Not apparent Temperature: Low Texture: fine grain Variety: Leaf fossils in this case are carbon films that remain on the bedding surfaces of fine-grained sediments. Fossilization happened after the leaves sank to the bottom of a pond or lake and were later buried by additional fine-grained sediments. With burial, the leaves were compressed and the sediment surrounding them solidified. Eventually these fine-grained sediments became sandstone, shale or mudstone. When all the volatile organic material in the living leaf was pressed out, only a thin carbon residue was left in the sediment, marking the outline and veins of the leaf.

Collection

Fossil Collection

Acquisition

Accession

78.57

Source or Donor

Delmar Smith Fossil Collection

Acquisition Method

Donation

Other Names and Numbers

Other Number

Other Number: 1978.57.04

Dimensions

Width

3-1/4 in

Depth

1 in

Length

6-1/4 in

Dimension Notes

Dimensions taken at widest points

Location

Location

Container

Center

Drawer

2nd Shelf

Shelf

Left

Cabinet

Case #105

Wall

North Wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent