The Markagunt Plateau, in southwestern Utah, lies at an altitude of about 9,500 feet, largely within Dixie National For- est. The plateau is capped primarily by Tertiary- and Quater- nary-age volcanic rocks that overlie Paleocene- to Eocene-age limestone of the Claron Formation, which forms escarpments on the west and south sides of the plateau. In the southwestern part of the plateau, an extensive area of sinkholes has formed that resulted primarily from dissolution of the underlying limestone and subsequent subsidence and (or) collapse of the basalt, producing sinkholes as large as 1,000 feet across and 100 feet deep. Karst development in the Claron Formation likely has been enhanced by high infiltration rates through the basalt.