of the Quaternary is set at the top of the Olduvai event at 1.7 my. Four FADs, twelve LADs, two acme datums, and one ratio reversal datum occur above the base of the Quaternary at an average rate of about 1 per 100,000 yr. Five FADs and twelve LADs are recognized
in the 0.8 my interval between the top of the Olduvai event and the Gauss/Matuyama boundary at 2.5 my at an average incidence of about 1 per 50,000 yr.