AIR-FILLED CAVES AS AN INDICATOR OF DIRECTIONAL TRANSMISSIVITY IN THE UNCONFINED UPPER FLORIDAN AQUIFER OF WEST CENTRAL FLORIDA
Length-weighted rose diagrams of the orientations of conduits within air-filled caves in the springsheds of Rainbow and Silver Springs reveal preferential orientations in sub-orthogonal azimuth sets. The sets vary regionally but generally trend NE-SW and NW-SE and conform to the directions of photolinears found in preceding studies. The likely association of these conduit orientations with fractures is confirmed by visual inspection and photography in several of the caves. Strikingly, many of the rose diagrams show that lengths are concentrated in one of the two directions, as if dissolution has selected one direction over the other, although the particular selection and its direction vary across the study area. Because the fracture systems that ultimately control the direction of conduits within the cave systems extend below the present water level, we hypothesize that similar patterns apply in the phreatic zone and account for directional transmissivities found in a recent modeling study of the Upper Floridan aquifer in the area.