You are looking at the Mesozoic rocks in the far background - these are tilted along the Echo Cliffs monocline as it crosses the river. From a blog I found: A large falling dune is seen on the leeward side of the Echo Peaks. These features form when wind carries sand but drops its load as the wind falls behind a rock obstruction such as a cliff. As the velocity of the wind lessens behind the obstacle, its capacity to carry the sand diminishes and the sand falls to the ground. This is an especially large falling dune.
Note the tilt on the Echo Cliffs monocline as well.

Upstream and surrounding the Ferry itself, magnificent Mesozoic strata rise more than 3,000 feet. From the river up, these include: the Moenkopi, Shinarump Conglomerate and other Chinle (pronounced “schin-lee”) Shale members (with fossils of sharks, turtles, the earliest mammals, and much petrified wood), Kayenta, and a thick exposure of Navajo Sandstone Formations, with several small buttes of Jurassic deposits. Downstream from Lees Ferry, the Kaibab Limestone emerges from the river. The caprock for much of the southern Colorado Plateau, this is the layer on which one stands looking into Grand Canyon from the North or South Rims, 50 miles south of Lees Ferry. Thus, the Kaibab Limestone rises 5,000 feet from Lees Ferry to the North Rim.