NPS Photo by Tom Lyttle
The Lewis Shale is an olive-gray marine shale thinly interbedded with claystone, siltstone and sandstone as well as scattered beds of limestone. It overlies the Cliff House Sandstone and is exposed only near the northern boundary of the park. This unit was deposited at water depths greater than the Cliff House Sandstone and represents the last significant transgression of the Western Interior Seaway into northwestern New Mexico. Few fossils have been found in the Lewis Shale unit within the park.
Did You Know?
A thousand years ago when Chaco was flourishing, you could hear the loud sounds of sea shell trumpets echoing off the canyon walls. The people traded for conch shells with groups along trade routes that stretched deep into present-day Mexico and the Gulf of California. More...