Palaeowaters from the Glatt Valley, Switzerland

Isotopic and noble gas data from a confined gravel aquifer in the Swiss Plateau has been investigated. From glaciomorphological studies it is well known that the Glatt Valley was repeatedly ice covered during the last glacial period. Corrected radiocarbon ages range from 0 to >28 ka bp and reveal a gap of between 25 and 17 ka bp, indicating an interruption of groundwater recharge during the last glacial maximum. Based on 39Ar measurements, a contribution of younger water components with residence times of a few hundred years have been identified in some waters. Recharge temperatures, estimated by analysis of noble gas contents, suggest a temperature difference of c. 5°C at the Holocene-Pleistocene transition at 12 ka bp. The long-term temporal δ18O-recharge temperature relation over the last 30 ka has a slope of c. 0.49‰ °C−1, consistent with the modern seasonal relation