Petrified Tree stump

The shale layers underneath the stump reveal that this tree has moved from its original location. If the tree had grown in this spot, the roots would have disturbed the soil underneath. This stump eroded, or was carried, to its current location. NPS photo by Jack Wood.

Terrestrial Fossil

Today, Chaco Canyon’s arid environment doesn’t support many trees, but petrified wood is the most common fossil in the park. During the Late Cretaceous (85-75 million years ago) the regional climate was much warmer, and flowering plant and tree species were flourishing. This subtropical lowland forest supported species similar to today’s conifer, eucalyptus, ebony palm, cypress, and magnolia. Since plants grow in climates suited to their needs, paleobotanists can paint a picture of ancient landscapes by studying fossilized plants and trees.

3D Petrified Tree stump

Chaco Culture National Historical Park, New Mexico

Alternative Text for the 3D Model

A 3D model. This model shows a fossil tree stump. The model can be rotated and tilted using a computer interface.

Today, the canyons of Chaco Culture National Historical Park are part of an arid landscape with few trees. Petrified wood however is common within the park. During the Late Cretaceous (85-75 million years ago) the regional climate was much warmer and wetter, and flowering plants and tree species flurished. This subtropical lowland forest supported species similar to today’s conifer, ecaluptus, ebony palm, cypress and mangnolia. Since plants grow in climates suited to their needs, paleobiologists can paint a picture of an ancient landscape by studying fossilized plants and trees. Chaco Culture NHP is a special place to study fossiliced wood because angiosperms were just starting to become more dominate arounf the time of the Cretaceous. Currently, angiosperms dominate the flora of most of Earth’s ecosystems.

Footnotes linked to the model:

Scale—This scale bar was used, with several others in the photography to make the 3D photogrammetric model. The circular targets at each end are read by the software. The distance between the two targets is precisely known, and is about 28 cm.

Growth rings—This specimen of petrified wood also preserves the growth rings in the tree. These rings are more pronounced because of differential weathering. By this, some portions of this “rock” stump are less susceptible to erosion; at the top of the specimen, this has highlighted the rings.

In place or transported?—This stump was thought to be inplace, meaning that it is within the rock unit formed from the sediments where the tree once grew. However, in looking closely at the bedding planes of the rock, these are finely bedded silty sandstones and there are no disruptions from roots. This suggests that the rock was transported here. That still leaves the question , whether it rolled downhill from a different rock unit or was carried by people.

Footnotes

Scale—This scale bar was used, with several others in the photography to make the 3D photogrammetric model. The circular targets at each end are read by the software. The distance between the two targets is precisely known, and is about 28 cm.

• Growth rings—This specimen of petrified wood also preserves the growth rings in the tree. These rings are more pronounced because of differential weathering. By this, some portions of this “rock” stump are less susceptible to erosion; at the top of the specimen, this has highlighted the rings.
• In place or transported?—This stump was thought to be inplace, meaning that it is within the rock unit formed from the sediments where the tree once grew. However, in looking closely at the bedding planes of the rock, these are finely bedded silty sandstones and there are no disruptions from roots. This suggests that the rock was transported here. That still leaves the question , whether it rolled downhill from a different rock unit or was carried by people.

Related Links

• NPS—Chaco Culture National Historical Park
• NPS—National Fossil Day
• NPS—Photogrammetry
• NPS—Fossils and Paleontology
• NPS—Geology

Part of a series of articles titled
Chaco Collections—Paleontology.

Previous:
Shark and Vertebrate Fossils

Next:
Inoceramus shells

Where this belongs

• Chaco Culture National Historical Park

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