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 River popular recreational activity on the Brazos River with many locations favorable for launching and recovery. The best paddling can be found immediately below Possum Kingdom Lake and Lake Granbury. Sandbar Camping is also permitted since the entire streambed of the river is considered to be state-owned public property. Fishing, camping, and picnicking are legal here, including on the sandbars. Several scout camps are located along the Brazos River and they support a wide range of water and shoreline activities for scouts, youth groups and family groups. The Brazos River Authority maintains several public campsites along the river and at the