A40-K40 dating of igneous rocks and sediments

Absolute age of early Precambrian rocks in the Bighorn Basin of Wyoming and Montana, and southeastern Manitoba

“…Aldrich and others [1955] and Wetherill [1955] have measured some ages on a lepidolite in the Wind River Canyon area. They obtain a rubidiumstrontium age of 2460 m y and a potassium-argon age of 2290 m y using the decay constants adopted in this paper.…”

THE NEED TO UNIFY THE DECAY CONSTANTS OF K40USED IN AGE CALCULATIONS

“…However, Weatherill, et al (29) confirmed that there are systematic discrepancies between the r for cogenetic feldspars and micas (as Gerling had previously shown), so they remeasured the decay constants of K40 and found R = 0.113 for five muscovites of ages from 255 million years to 995 million years (27). The previous value of 0.085 was interpreted as an empirical calibration constant that incorporated the loss of argon from the feldspars.…”

Soils and Sediments

“…After that time, moderate sedimentation rates developed in both coastal and deep-sea basins, which resulted in the disappearance of important modifications of detrital sedimentary components. Introduction Cormier (1956) and Wasserburg et al (1956) initiated many isotopic investigations of sedimentary minerals and whole rocks for stratigraphic purposes. 16).…”