Consistent rubidium–strontium ages, calculated using mineral–whole rock pairs from the Sudbury area, confirm: (1) the Sudbury event (1900 Ma), (2) the Penokean (Hudsonian) Orogeny (1600–1800 Ma), (3) a cryptic (Elsonian) thermal event (1300–1450 Ma) and (4) the Grenville Orogeny (900–1200 Ma). Rubidium–strontium whole rock isochrons independently define these same events, as do other radioactive decay schemes and conventional geologic studies. The presence of the Kenoran Orogeny (2500–2700 Ma) and pre- to syn-Nipissing diabase folding and faulting (2150–2300 Ma) can be inferred from geologic mapping and radiometric studies in adjacent areas.

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