Baksi questions the ages of the various units presented in Hooper et al. (2002) and reiterates his belief that Imnaha basalt flows on the main Columbia Plateau are older than the Steens Basalt. In particular he questions two new 40Ar/39Ar ages of Imnaha basalt flows from R.A. Duncan's laboratory at Oregon State University that are based on multiple step plateaus comprising >50% of gas released, concordant with isochron ages. In support of this position he quotes his own 40Ar/39Ar ages (Baksi and Farmer, 1990). In part this is a disagreement between specialized...

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