Geology of Seneca Caverns, Seneca County, Ohio

Abstract

Seneca Caverns were formed along a major fracture which trends N68°W and dips 40°NE in the Columbus and Lucas Formations (Middle Devonian) and possibly the underlying strata. This cavern is a collapse or breakdown-type cavern, probably resulting from deep-seated solution of gypsum in the Bass Islands Group (Upper Silurian). Seven of the 12 known levels or rooms were surveyed and mapped to delineate the elevations, dimensions and unique features of each level. Cavern stratigraphy and paleontology correlated with the stratigraphy of north-central and central Ohio. Fluctuations in the level of the cavern stream (Old Mist'ry River), commonly found in the seventh level approximately 30 m (100 ft) below the surface, appear to be the direct result of rate and duration of precipitation and soil moisture content. Lag times range from five hours to five days, 15 hours, and 10 minutes. Geochemical parameters exhibited by the cavern stream were very similar to those of Castalia Blue Hole. The 1988 drought eliminated a selected dye trace to evaluate the possible connection of these two features.