The first known Mazama ash occurrence in Saskatchewan was discovered in eolian sediments at the top of the bluffs on the South Saskatchewan River valley 20 miles (~32 km) west of Leader, Saskatchewan. The chemical composition and the refractive index of the volcanic glass serve for the definite identification of the Mazama ash. The ash layer is a useful horizon marker in the eolian sediments, for it represents a time-break at 6 600 years ago. It is suggested that eolian deposits in similar sedimentary environments be examined for other occurrences of the Mazama ash.