Assessing the relationships of the Hell Creek–Fort Union contact, Cretaceous-Paleogene boundary, and Chicxulub impact ejecta horizon at the Hell Creek Formation lectostratotype, Montana, USA, Wilson Gregory P, Moore Jason R, Sharma Mukul, Hallock Hannah R, Braman Dennis R, and Renne Paul R, Geological Society of America Special Papers, Volume 503, p.123–135, Geological Society of America (2014)