STRONTIUM ISOTOPE STRATIGRAPHY LN THE LATE CRETACEOUS - NUMERICAL CALIBRATION OF THE SR ISOTOPE CURVE AND INTERCONTINENTAL CORRELATION FOR THE CAMPANIAN

The white Chalk exposed in quarries at Lagerdorf and Kronsmoor, northw estern Germany, provides a standard section for the European Upper Cre taceous. The Sr-87/Sr-86 values of nannofossil chalk and belemnite cal cite increase upward through 330 m of section, from less than or equal to 0.70746 in the Upper Santonian to greater than or equal to 0.70777 in the Lower Maastrichtian. The data define three linear trends separ ated by major points of inflection at stratigraphic heights in the sec tion of 162 m (75.5 Ma) in the Upper Campanian Galerites vulgaris zone and at -6 m (82.9 Ma), just above the base of the Campanian in the In oceramus lingua/Goniateuthis quadrata zone. The temporal rate of chang e of Sr-87/Sr-86 was constant through each of the linear segments of o ur isotope ''curve'' when viewed at the resolution of our average samp ling interval (0.15 m.y.). Fine structure, if rear, may record brief ( <100 kyr) excursions of (SrSr)-Sr-87-Sr-86 from values expected from t he overall trends. In Lagerdorf, the boundary between the Santonian an d Campanian stages, taken here as the level of first occurrence of the belemnite Gonioteuthis granulataquadrata, has an Sr-87/Sr-86 Of 0.707 473 +/- 5. This is within error of the values of 0.707457 +/- 16 for t his boundary in the U.S. western interior (base of the Scaphites leei III zone) and 0.707479 +/- 9 for this boundary in the English Chalk (t op of the Marsupites testudinarius zone). In Kronsmoor, the boundary b etween the Campanian and Maastrichtian stages, taken here as the level of first occurrence of the belemnite Belemnella lanceolata, has an Sr -87/Sr-86 of 0.707723 +/- 4. This is within error of the values of 0.7 07725 +/- 20 for this boundary in the U.S. western interior (base of t he Baculites eliasi zone) and 0.707728 +/- 5 for this boundary in the English Chalk (defined as in Germany).