A lower paleozoic paleoaquifer; the Kingsport Formation and Mascot dolomite of Tennessee and southwest Virginia

The Kingsport Formation (Lower Ordovician) in one section may be composed of two dominant rock types--limestone and medium to coarsely crystalline dolomite--whereas in an adjacent section, most of the formation may be largely composed of breccia. The breccia bodies, which are interpreted to be solution-collapse features, range in width from 30 feet to several hundred feet, in thickness from a few feet to more than 200 feet, and are hundreds of feet long. Many of the complexities of the Kingsport can be directly related to the development of an unconformity at the top of the overlying Mascot Dolomite. Erosion associated with the unconformity produced a widespread karst topography with an attendant paleoaquifer system. Ground water, apparently reacting to differences in solubility between limestone of the Kingsport and dense dolomite of the Mascot, is thought to be a major contributing factor in regional dolomitization and localization of solution-thinning and collapse features at the contact of the Kingsport and Mascot. Later mineralizing solutions invaded the paleoaquifer, locally depositing commercial quantities of zinc ore.