John Stone¹, Perry E Spector², Trevor Hillebrand¹, Joel H Gombiner¹, James K Feathers³, Joseph Talghader⁴, Jeffrey P Severinghaus⁵, David Pollard⁶, Greg Balco⁷ and L Keith Fifield⁸, (1)University of Washington, Department of Earth and Space Sciences, Seattle, WA, United States, (2)University of California Berkeley, Berkeley, CA, United States, (3)University of Washington, Seattle, WA, United States, (4)University of Minnesota Twin Cities, Electrical & Computer Engineering, Minneapolis, MN, United States, (5)Scripps Institution of Oceanography, La Jolla, CA, United States, (6)Pennsylvania State University, Earth and Environmental Systems Institute, University Park, PA, United States, (7)Berkeley Geochronology Center, Berkeley, CA, United States, (8)The Australian National University, Canberra, Australia