“…The excursion in d 13 C is located just below the formational contact of the Middle Dakota with the overlying marine Tropic Shale, a contact that is readily identifiable throughout southern Utah and represents a flooding surface associated with a major sealevel transgression that reached maximum high stand in the early Turonian (Haq et al, 1987;Roberts and Kirschbaum, 1995). This transgression provided the initial framework for correlating the Dakota Formation and Tropic Shale on the Colorado Plateau with the Greenhorn Cycle (Averitt, 1962;Peterson, 1969;Peterson and Kirk, 1977). The correlation from western Utah to the CenomanianeTuronian GSSP in Pueblo, Colorado was improved using bentonite (Kowallis et al, 1989) and limestone marker beds (Elder et al, 1994), coupled with associated ammonite and bivalve index fossils (Cobban and Scott, 1972;Kauffman, 1977;Cobban, 1984;Kauffman and Caldwell, 1993).…”