leg site hole age mnemonic auxiliary age mnemonic top of section depth(m) bottom of section depth(m) special condition age auxiliary age averaged age age top of section(million years) age bottom of section(million years) average age(million years)t data source 31 290 A UPPER OLIGOCENE 108.5 140.0 NO AGE GIVEN NO AGE GIVEN 22.5 30 26.25 DSDP INITIAL REPORTS