ESR dating of saline sediments using NaHCO3 and NaCl

Age estimates of NaCl and NaHCO₃ in the sediments at Searles Lake, California have been obtained using electron spin resonance (ESR). ESR signals are identified as H⁺Ca²⁺---CO₃³⁻ or H⁺---CO₂⁻ electron type and hole CO₃⁻ type centres, stabilized by impurities in NaHCO₃ and in NaCl. The total dose of natural radiation (TD) and the tentative ESR ages were determined using these signals based on U, Th and K analyses assuming uranium series disequilibrium for a simple infinite medium. Although ESR ages are concordant with the stratigraphy, radiation assessment considering the loss and incorporation of radioactive elements must be made to get reliable absolute ages.