Terrestrial paleoenvironmental effects of a late quaternary-age supernova

A chronology of the γ and X radiation incident upon the Earth from discrete supernova occurences is desirable for two reasons: (1) large but short-lived γ flashes should result in episodically increased atmospheric ¹⁴C production, and thus affect the ¹⁴C dating method, and (2) modeling of the other atmospheric effects to be expected from nearby supernovas indicates their possible importance as independent variables capable of causing climatic or other environmental changes. Presented here is a preliminary chronology of the larger inferred radiation events experienced by the Earth during the past 15, 000 years. This chronology illustrates the possible importance of the Vela optical-, radio-, and X-emitting supernova remnant (G263.9-3.3), and its associated pulsar (PSR-0833-45), which together record an unusually close (d = 500 pc supernova occuring sometime between 11,300 and 8,400 years B.P. The predicted terrestrial effects of a 10⁴⁹?1 10⁵⁰-erg γ- and X-emitting supernova at this distance include short-term increases in ¹⁴C activity (+3 to +6%), increases in aquatic productivity at some localities, and a brief global cooling. Such effects appear to be documented by many late Quaternary paleoenvironmental records dated between 11,000 and 10,000 ¹⁴C yr B.P.