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
Brazos Valley Brazos Valley The Brazos Valley ( ) is a region in the U.S. state of Texas (a subsection of the larger Central Texas region) consisting of the counties of Brazos, Burleson, and Robertson (which collectively comprise the Bryan–College Station metropolitan area), and the neighboring counties of Grimes, Leon, Madison, and Washington. The area is centered on Brazos County, the cities of College Station and Bryan, and Texas A&M University. Although the Brazos River lies at the center of the region, not all areas of the region are a part of the Brazos watershed. The population of the region was estimated