Ripples and Bivalves

NPS photo.

Inoceramid shells—These extinct relatives of living clams and mussels leave behind casts and molds. Though their shells have deteriorated, their morphology is preserved by infilled sand.

NPS photo.

Geological features and fossils tell the story of an ancient ecosystem. This boulder is a unique example of both. The size and shape of the ripples leave clues about the force and direction of the current, and the shell molds provide examples of who lived in this environment. Located in Chaco Culture National Historical Park, these features were exposed when a massive boulder known as Threatening Rock collapsed on Pueblo Bonito on January 22, 1941.

3D Ripples and Bivalves at Pueblo Bonito
Chaco Culture National Historical Park, New Mexico

Chaco Culture—Ripple Marks and Bivalve Fossils

Left image
Ripple mark model with true color overlay.
Credit: NPS image by Jack Wood.

Right image
Ripple mark model with color ramp overlay.
Credit: NPS image by Jack Wood.

_{Clams and ripples at Pueblo Bonito by National Park Service Geologic Resources Division on Sketchfab}

Alternative Text for the 3D Model

A 3D model. This model shows a block of rock with fossils on the surface. The model can be rotated and tilted using a computer interface.

Geological features and fossils tell the story of an ancient ecosystem. This boulder is a unique example of both. The size and shape of the ripples leave clues about the force and direction of the current, and the shell molds provide examples of what lived in this environment. Located in Chaco Culture National Historical Park, these features were exposed when a massive monolith of sandstone known as Threatening Rock collapsed on Pueblo Bonito on January 22, 1941. If visiting the park, you can learn about this rockfall event and see this boulder, along the trail at the pueblo.

To learn more, visit - https://www.nps.gov/articles/series.htm?id=7B32EA8A-A130-11C3-E755871E8385F30E

Footnotes (labeled on model)

1. Inoceramus—This is the clam-like Inoceramus fossil. It is shown in better detail in one of the other photogrammetry models on a smaller slab of sandstone. Here, it is nestled in with ripple marks, the elongate wave-like patterns seen on this sandstone bedding plain. This shows that Inoceramus was inhabiting near-shore environments, like a beach or sandy-bottomed tide pool.
2. Ripples—This is former, Cretaceous-age beach-front property. Get the sunscreen! ....which is still needed for a visit to Chaco Culture NHP. This slab of the Cliff House Sandstone show ripple marks, which are indications of tidal or wave actions on the sea-floor. This indicates shallow and near-shore environment.
3. More ripple marks—Ripple marks can be preserved in both marine and freshwater environments. If the ripples are symmetrical, it means the current went in both directions, like at a sea shore. If the ripples are asymmetrical, the current went one way, like in a flowing river.
4. Scale bar.
5. Fubar.
   

Related Links

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