Ancient Rocks Boundary

The mountains toward the east are limestone reef beds deposited in the Cretaceous and Permian seas about 135 million years ago and 250 million years ago; respectively. The limestone reefs overlie deformed rocks in the Ouachita Fold Belt, which is visible along the highway to the east, near Marathon. To the south are younger limestone beds deposited about 125 to 135 million year ago. They also rest above the Ouachita Fold Belt (so named for the Ouachita Mountains of Arkansas-Oklahoma, where formation was first studied by geologists). Toward the west, northwest, and southwest are layers of lava and associated volcanic rocks 25 to 35 million years old. These were thrust upward, into and over most of the older sedimentary rock layers. Many of the molten rock masses cooled and hardened underneath, while vast quantities poured over the surface in the form of lava flows and volcanic debris up to a mile in thickness. Subsequent erosion has sculptured these highlands by removing much of the younger volcanic rock, and cutting deeply into the older sea deposits. Out of the lower, ingenuus hills grow yucca and other cacti, contrasting with juniper and pinon on the higher elevations. (1970)

Ancient Rocks Boundary is a historical marker in Alpine, Brewster County, dedicated in 1970. It is one of 30 historical markers documented in Brewster County in the Texas Historical Commission Atlas, among 40 historic sites cataloged across the county.

The site sits at 30.3770, -103.5338 near Alpine. The nearest cataloged historic site is Brewster County (historical marker), about under a tenth of a mile away. Others within a short drive include Ross, General Lawrence "Sul", Burgess' Water Hole, and Nolte-Rooney House.

This record corresponds to Texas Historical Commission Atlas #5043000157. Use the map below for its exact position and turn-by-turn directions.