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A preliminary report on this subject was read before the Pacific Section of the Association on October 16, 1941. The present paper incorporates slight revisions based on suggestions from several colleagues, notably John B. Reeside, Jr., and his associates, Gayle Scott and Hans E. Thalmann.
The standard of the Cretaceous system represents a composite time-rock column--a total or complete sequence of strata between the Jurassic and the Cenozoic. This standard has been built up by fitting together continuous sections which are especially well exposed in several areas in Europe. The system is subdivided into Series, Stages and Zones. These divisions are based on paleontologic evidence, with no regard being paid to thicknesses of strata and their lithologic character. Particular attention is drawn to the early work of d'Orbigny in setting up the Stages, and a detailed analysis of a representative Cretaceous Zone is presented to clarify the meaning of the termi zone. The study of the boundaries between the underlying Jurassic and the overlying Cenozoic leads to the conclusion that the lowest Cretaceous stage is the Berriasian and the highest is the Danian.
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