Groundwaters were sampled from four research boreholes, a\ud private supply well and a natural karst resurgence in southern County Durham, England. Time series data sets of piezometric levels, groundwater major ions, and fluorescence\ud of dissolved organic matter (DOM) were interpreted in the light of new geological mapping to assess the movement of groundwater and its potential for the dissolution of gypsum.\ud Three distinct groundwater facies were identified representing contact with gypsiferous strata, dolomitic limestone and Quaternary Till. Piezometric data indicated time varying transverse flow across the gypsifeorus strata, which was confirmed from gradational mixing of\ud groundwater types and cation ratios. Fluorescence of dissolved DOM identified variations in protein and\ud fulvic-like acid fluorescence. The former was taken to represent surface derived, short-lived material.\ud Spatial and temporal variations in protein fluorescence offered a means to trace groundwater movement\ud along the regional groundwater gradient and indicated rapid lateral movement of groundwater. It was concluded that gypsum dissolution is occurring beneath the town of Darlington, however, the presence of a thick deposit of Quaternary till effectively confines the small head differences of approximately 1 m, across the gypsum strata beneath the town. Further to the south, the lowering of the ground surface results in a greater upwards flow of water across the gypsum and is used to explain the presence of historic collapse sinkholes
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