Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

87Rb/86Sr #1

87Rb/86Sr of the first point.

87Sr/86Sr #1

87Sr/86Sr of the first point.

87Rb/86Sr #2

87Rb/86Sr of the second point.

87Sr/86Sr #2

87Sr/86Sr of the second point.

Fit a two-point Rb-Sr isochron and convert its slope to an age using the Rb-87 decay constant. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Slope

Isochron slope in 87Sr/86Sr per unit 87Rb/86Sr.

Initial 87Sr/86Sr

Initial 87Sr/86Sr from the intercept.

Age (yr)

Isochron age in years.

Age (Ma)

Isochron age in millions of years.

• Radiometric ages require the correct decay constants, isotopic ratios, standards, common-component correction, closure interpretation, initial composition, and analytical uncertainties. Disturbance, inheritance, diffusion, alteration, and model choice can make a calculated number differ from the geological event age.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

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