206Pb/238U CA-ID-TIMS dating of zircons from volcanic tuffs of the White River Group

206Pb/238U CA-ID-TIMS dating of zircons from volcanic tuffs intercalated in the White River Group, sampled at Flagstaff Rim, Wyoming, and Toadstool Geologic Park, Nebraska. The aim of the study was to establish the timing of environmental change associated with the Chadronian/Orellan transition in N America, relative to the marine record of the Eocene/Oligocene transition, and the onset of early Oligocene Antarctic glaciation.