Geology of the Canadian River Valley - Lake Meredith ...
Due to its hardness, the dolomite resisted erosion. The dolomite acted as a "caprock" and slowed the erosion of the softer red beds, resulting in the rugged mesas around Lake Meredith and Alibates Flint Quarries. When the underlying rock eventually erodes, the dolomite fractures into numerous white boulders found on the sides of mesas.