ABSTRACT
Subrosion of evaporite deposits in the Upper Silurian Salina Group has resulted in subsidence at several locations in the Tully Valley, New York. The resulting subsidence structures typically exhibit vertical displacements of 10 to greater than 50 feet, and areal extents of thousands to tens of thousands of square feet. At several locations, notably the King farm, subsidence has led to the formation of numerous effusion features identified as sand volcanoes and sandboils.
The formation of and discharge produced by the sand volcanoes and sandboils is attributed to subsidence-induced increases in hydrostatic pressure within the aquifer(s) underlying the structure and vicinity. Analyses of water samples collected from randomly-selected effusion features, nearby streams and wells were used to geochemically characterize the water discharged at the King farm subsidence structure.
Of major importance are data concerning chloride and sulfate ion concentrations, water temperature and sediment concentration. Results suggest that the discharge from the effusion features is a mixture of ground water from several aquifers. The sediment discharged is derived from ground-water erosion of the surfaces of subsidence-related fractures that penetrate the subsurface unconsolidated materials underlying the King farm subsidence structure. Analytical results also indicate that the discharge from the effusion feature at the King Farm have impacted water quality in nearby surface-water bodies.
A mechanism for the formation of the subsidence structure and continued discharge of the effusion features is proposed. The mechanism for the formation of the King farm subsidence structure is considered to be similar to that of subsidence structures occurring elsewhere in the Tully Valley, which are clearly attributed to anthropogenic activities.
