Heat flow in western Virginia and a model for the origin of thermal springs in the folded Appalachians

Abstract

Five new heat flow values in the Blue Ridge (37°02′N, 80°12′W), Valley and Ridge (38°00′N, 79°50′W; 37°54′N, 79°54′W; 38°14′N, 79°49′W), and Alleghany Plateau (37°12′N, 82°06′W) provinces of Virginia are 36.3±1.3 mW/m2, 317±20 mW/m2, 48.3±0.3 mW/m2, 49.5±1.5 mW/m2, and 55.8±1.7 mW/m2, respectively. The value of 36.3 mW/m2 in the Blue Ridge agrees with values predicted by the contour map of Sass et al. (1976) for this part of the eastern United States; the values of 49.5 and 48.3 mW/m2 in the Valley and Ridge province do not. The high value of 317±20 mW/m2 at Hot Springs, Virginia, is the result of convection along a fault zone and is not regionally representative. The value of 48.3 mW/m2 determined at a site about 8 km southwest of Hot Springs, Virginia, is regionally representative of the heat flux. New data support a model of moderately deep circulation of meteoric water entering near‐vertical sedimentary beds at relatively high topographic elevations and circulating downward via bedding plane permeability and fractures within Silurian quartzites and/or adjacent carbonate units. The moderately deep circulation is then intersected by vertical transverse linear fracture zones along which the water rises. All of the warm springs are located adjacent to topographic gaps which have developed along zones of weakness associated with the transverse fracture zones.