Formal definitions of the Cenomanian-Turonian and lower-middle Turonian boundaries are proposed, following discussions at the Second International Symposium on Cretaceous Stage Boundaries, held in Brussels, 8-16 September 1995. The Global boundary Stratotype Section and Point (GSSP, "golden spike") for the Cenomanian-Turonian boundary should be placed at the base of Bed 86 in a section at Rock Canyon Anticline, west of Pueblo, Colorado, USA, coincident with the first occurrence of the ammonite Watinoceras devonense WRIGHT & KENNEDY, 1981. A GSSP for the lower-middle Turonian boundary is proposed at the level of first occurrence of the ammonite Collignoniceras woollgari (MANTELL, 1822) in the same section (Bed 120). For the middle-upper Turonian boundary no GSSP can be proposed at present.
