© 2010 Taylor & Francis Group, London. Radiocarbon dating of groundwater has been a major tool for assessing the residence time of groundwater. Several models have been proposed to quantify carbonate dissolution in groundwater system in attempts to correct for “dead carbon”. Here I propose using boron isotopes as an additional indirect proxy for evaluating the input of carbonate dissolution. In coastal areas, meteoric boron has a high δ11B signature (≥39‰) and thus recharge water would have a significant different δ11B value relative to solution derived from carbonate dissolution. Preservation of high δ11B rainwater composition in coastal groundwater infers lack of carbonate dissolution and thus an indirect proxy for14C correction. The model is applied for fossil groundwater from the Disi aquifer in Jordan where high δ11B (25–48‰) and B/Cl ratio (>sea water) suggest that the recharge water originated from coastal rainwater of an early stage of air mass evolution with negligible water-rock interactions in the aquifer.