DEFINITION AND GLOBAL CORRELATION OF THE SANTONIAN CAMPANIAN BOUNDARY

Review of biostratigraphical evidence from different regions shows tha t criteria used by workers on various marine fossil groups to define t he Santonian-Campanian boundary differ considerably in relative age an d position. Probably the most widely recognizable of these criteria is the extinction of the distinctive crinoid Marsupites testudinarius (N orth America, Europe, Asia, north Africa, Australia), which, coincides exactly with two separate definitions of the boundary - appearances o f the ammonite Placenticeras bidousatum and the belemnite Goniateuthis granulataquadrata - and may also coincide with a third - entry of the planktic foraminiferan Globotruncana elevnta. A comparison of evidenc e from upper Santonian and lower Campanian successions in widely separ ated regions allows us to place a series of important biostratigraphic al markers in correct order. Defining the boundary at the extinction o f M. testudinarius corresponds to a Sr-87/Sr-86 of 0.707479, and a sma ll positive excursion in delta(13)C. Th, base of magnetochron 33R, gen erally considered to coincide with, or fall just above the base of the Campanian, is shown to lie within the upper Santonian Uintacrinus soc ialis Zone.