Black plaque № 13276

Alpine, TX, United States

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 Arkans

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