Nacimiento Formation Nacimiento Formation The Nacimiento Formation is a sedimentary rock formation found in the San Juan Basin of western New Mexico (United States) and named for the Nacimiento Mountains. It is a heterogeneous nonmarine formation composed of shale, siltstone, and sandstone, deposited in floodplain, fluvial and lacustrine settings, and made up of sediment shed from the San Juan uplift to the north and the Brazos-Sangre de Cristo uplift to the east. It was deposited mostly between ~64.5 and ~61 million years ago, during the early and middle Paleocene. The climate was humid and warm to hot. This unit interbeds with the
Vermilion Cliffs by settlers during the 19th Century. The area was explored by the Mormon pioneer and missionary Jacob Hamblin, who started a ranch at the base of the cliffs in House Rock Valley. Present day U.S. Highway 89A basically follows the old wagon route past the cliffs through House Rock Valley and up the Kaibab Plateau to Jacob Lake. Famous locations in the cliff area include Lee's Ferry, Glen Canyon and the Glen Canyon National Recreational Area, The Wave, Coyote Buttes, and others. Reddish or vermilion-colored cliffs are found along U.S. Highway 89A near Navajo Bridge, and may be seen from