Supplemental Material: Ibex Hollow Tuff from ca. 12 Ma supereruption, southern Idaho, identified across North America, eastern Pacific Ocean, and Gulf of Mexico

Item S1 (MS Word document): Detailed methods for major, minor, and trace-element analysis; electron-microprobe analysis (EMA); instrumental neutron activation analysis (INAA); laser ablation–inductively coupled–mass spectrometry (LA-ICP-MS); isothermal-plateau fission-track method of age determination; correlation methods; references cited for methods section. Item S2: Table of major– and minor–EMA analyses of individual glass shards of tephra beds correlated to Ibex Hollow Tuff; contains plots of Fe₂O₃ versus CaO for samples. Item S3: Table of major– and minor–EMA analyses of individual glass shards of tephra beds of the Ibex Hollow Tuff, performed at the U.S. Geological Survey, Menlo Park, California. Initial compositions and totals on analysis are presented, with plots of Fe₂O₃ versus CaO. Item S4: Table of major– and minor–EMA analyses of individual glass shards of tephra beds that correlate with the Ibex Hollow Tuff. Initial compositions and totals on analysis are presented, with plots of Fe₂O₃ versus CaO. Item S5: Binary graphic plots of major oxides and elements of the Ibex Hollow Tuff and overlying and underlying tephra layers at Trapper Creek, Idaho, USA.