Cañadón Asfalto Formation, Geological formation in Chubut, Argentina.

The Cañadón Asfalto Formation is a sequence of sedimentary rock layers in northwestern Patagonia, in the Argentine province of Chubut. It is made up of sandstone, limestone, shale, and volcanic deposits stacked in clearly visible layers.

The formation dates back roughly 171 million years, to a time when the ancient supercontinent Pangaea was breaking apart and the present landmasses were beginning to separate. These shifts created the conditions for lakes and rivers to form and deposit the sediment layers visible today.

The formation's name comes from the Asfalto canyon near Cerro Cóndor, where Stipanicic defined the unit in 1968. Its fossil beds yielded Patagosaurus, Piatnitzkysaurus and Volkheimeria, described by Bonaparte in 1979, and the sauropod Bagualia was named from remains found here. The site lies in the Somuncurá-Cañadón Asfalto rift basin, whose Jurassic rocks are among the most extensive exposures of their age in South America.

The formation lies in the middle Chubut River valley, Paso de Indios Department, near the hamlet of Cerro Cóndor; the reference sections are the Sauzal (Lahuincó) and Asfalto canyons. There is no visitor infrastructure, so reach the area with an organized expedition and a local guide. Ground is bare rock and loose sediment; carry water and sun protection, as the Patagonian steppe offers little shade.

Remains of plant species found here are among the oldest of their kind in South America and document a major shift in the plant life of the time. Together with dinosaur bones and traces of ancient lakes, these finds give a rare picture of what the region may have looked like millions of years ago.