HYDROLOGIC SIGNIFICANCE OF VARIABILITY IN STABLE ISOTOPES, OSTRACODES, AND HYDROCHEMISTRY IN APPALACHIAN KARST SPRING SYSTEMS

Sediment and water samples were taken from 10 springs in Berkeley and Morgan Counties in easternmost West Virginia and Huntingdon County, Pennsylvania. Six of these springs had been sampled previously in a survey of springs in 2004 in Berkeley and Morgan Counties, West Virginia. The isotopic signatures of the springs fall on the Maryland LMWL (Kendall and Coplan, 2001), suggesting short flow paths and short residence times. Replicate samples of the six re-sampled springs show a shift in del O-18 and del D between 2004 and 2009. The change for the three springs within the city of Martinsburg shows that the del O-18 values shifted to more positive (heavier) values, varying from +.4 to +.6 per mil, as did the del D values, from + 4 to +5 per mil. Springs further to the west in Berkeley County and Morgan County show changes as well, but to more negative (lighter values) in 2009, with shifts in del O-18 of about - 0.1 per mil, and shifts in del D ranging from - .7 to - 2.6 per mil. Analysis of the rainfall in the region over the period 2000-2009 shows a major wet period prior to the 2004 sampling and a relatively low rainfall prior to the sampling of 2009. The opposing shifts in the isotopic values from the two groups of springs suggest different residence times for the two groups. Ostracode assemblages in each of the springs show little overlap with each other, despite the springs’ similar hydrochemistries. The distinctive assemblages indicate long established local and separate groundwater catchments and flow paths.