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 Bend State Park river otter. The most noteworthy and popular residents of the park are the relatively large population of American alligators. The park is open year-round, with the exception of several weekends a year during which it is closed for controlled hunts to manage the white-tailed deer population. Brazos Bend State Park occupies land bordering the Brazos River and includes within its boundaries low-lying areas left over from the River's previous meanderings. Pre-Columbian inhabitants included a series of Native American groups, most notably the Karankawa. The land passed through a variety of landowners' hands, resulting in some of the existing structures on