Petrified Conifer, longitudinal wood slice from Arizona, Araucaria, petrified wood

A fossilized conifer longitudinal section from Arizona, from the Triassic genus Araucaria. 167 cm in length in a longitudinal cut, which makes the wood fiber structures visible along the growth axis.

Longitudinal sections differ diagnostically from cross-sections: instead of annual rings, the parallel tracheid bundles, i.e., the water-conducting vessels of the tree, are recognizable as striped structures. A different interpretation of wood mineralogy.

Fossilized wood from the Petrified Forest National Park is approximately 220 million years old. Permineralization occurred under oxygen-poor conditions, where silica-rich groundwater replaced the organic material cell by cell with quartz or chalcedony.

The reddish-brown color bands are caused by iron oxides. Longitudinal sections show these bands as parallel lines along the trunk axis, a didactically different reading than with cross-sections.

A paleontological collector's item of museum dimension with a rare longitudinal section presentation.