Photos Courtesy of Dr. Kathleen Pigg
At Promontory Butte, on the Mogollon Rim, near Christopher Creek, AZ. This is a Pennsylvanian/Permian boundary river deposit that has a mixture of wetter coal swamp plants like ferns and horsetails and drier "upland" elements like conifers preserved in a grey shale. It's interesting because it shows this ecological transition that occured around 300 million years ago when the conifers first started to become important with drier conditions.
At Yakima Canyon, central Washington state. Petrified fossils from here are 15 million years old (midle Miocene) and include petrified ferns, conifers, oaks and other hardwood trees, mostly related to modern genera. The difference is that today this area is desert scrub, not hardwood forest. The fossils were preserved by minerals from volcanic eruptions.
This is a middle Miocene site(also around 15 million years old) in the Virgin Valley, northwestern Nevada. By then Nevade had already started climatic changes toward present day dry conditions while the Yakima site in Washington, of the same age, was still a nice forest.
At Fossil Creek, near Strawberry, AZ. Fossils of Pennsylvanian/Permian boundary age (300 million years), similar to the Promonotory Butte fossils at site in fig 1.
These are compressed leaves from the Miocene of the northern Czech Republic that occur along with large coal deposits. On this slab you can see some sweet gum leaves (the ones with the pointy tips) and some bald cypress conifer twigs (the ones with the little needle-like leaves).
Another slab from the Miocene of northern Czech Republic. The plant on the surface with all the little roots is an aquatic floating plant.
Gail Maiorana. (2009, November 12). Working in the Field. ASU - Ask A Biologist. Retrieved March 29, 2020 from https://askabiologist.asu.edu/fr/working-field
Gail Maiorana. "Working in the Field". ASU - Ask A Biologist. 12 November, 2009. https://askabiologist.asu.edu/fr/working-field
Gail Maiorana. "Working in the Field". ASU - Ask A Biologist. 12 Nov 2009. ASU - Ask A Biologist, Web. 29 Mar 2020. https://askabiologist.asu.edu/fr/working-field
Kathleen Pigg with a fossilized plant.