Chacarilla Formation facts for kids
Quick facts for kids Chacarilla FormationStratigraphic range: Oxfordian-Aptian ~160–120Ma |
|
|---|---|
| Type | Geological formation |
| Underlies | Cerro Empexa Formation |
| Overlies | not exposed |
| Thickness | min. 1,100 m (3,600 ft) |
| Lithology | |
| Primary | Sandstone, shale |
| Location | |
| Coordinates | 20°36′S 69°06′W / 20.6°S 69.1°W |
| Approximate paleocoordinates | 21°30′S 36°06′W / 21.5°S 36.1°W |
| Region | Tarapacá Region |
| Country |  Chile |
| Extent | Tarapacá Basin |
| Type section | |
| Named for | Quebrada de Chacarilla |
The Chacarilla Formation (which means "Characilla Formation" in Spanish) is a special rock layer found in northern Chile. It formed a very long time ago, from the Oxfordian period (around 160 million years ago) to the Early Cretaceous period (around 120 million years ago). This formation is famous because it holds many dinosaur footprints! Because of these amazing fossils, it was made a Natural Sanctuary (a protected area) in 2004.
What is the Chacarilla Formation?
This rock formation is made up of many layers of red sandstone and shale. These layers are stacked on top of each other and are at least 1,100 meters (about 3,600 feet) thick.
The lower parts of the Chacarilla Formation were formed in the ocean. The upper parts were formed by rivers. These rivers flowed across a wide, flat area called a floodplain. Scientists can tell which way the ancient rivers flowed. They moved towards the west and northwest.
The upper part of the formation contains ichnofossils. These are not bones, but traces left by living things. In this case, they are dinosaur footprints! These footprints are from the Early Cretaceous period. Above these layers are younger volcanic and rock layers. These younger layers belong to the Cerro Empexa Formation.
Amazing Dinosaur Footprints
The Chacarilla Formation is a treasure chest of fossils. Scientists have found tracks from stegosaurs, sauropods, and theropods here. They have also found fossils of ancient plants.
One important spot is called the Chacarilla III tracksite. Here, scientists found 14 different paths of footprints. These paths contain a total of 76 individual dinosaur footprints!
- Two of the paths were made by large ornithopods. These dinosaurs had footprints about 39 centimeters (15 inches) long.
- Two other paths were made by smaller theropods. Their footprints were less than 25 centimeters (10 inches) long.
- The other ten paths were made by large theropods. These footprints were between 31 and 65 centimeters (12 to 26 inches) long. Many of these tracks show claw marks.
Scientists can even estimate how fast these dinosaurs were moving. They think the dinosaurs walked at a speed of about 4 to 7 kilometers per hour (2.5 to 4.3 miles per hour).
Besides dinosaur tracks, the older, Jurassic parts of the formation also have plant fossils. These include ancient plants like Baiera sp., Brachyphyllum sp., Cladophlebis sp., and Equisetites sp..
See also
In Spanish: Formación Chacarilla para niños
- List of dinosaur-bearing rock formations
- List of stratigraphic units with ornithischian tracks
- Stegosaur tracks
- List of stratigraphic units with ornithischian tracks
- Arcabuco Formation, a similar formation with fossils in Colombia
- La Puerta Formation, a similar formation with fossils in Bolivia
- Baños del Flaco Formation, a similar formation with fossils in central Chile
