The Upper Cretaceous series is the most widespread and the thickest in the Rocky Mountain area and more work has been done on it and more published than on any other series, but the literature is full of conflicting local names and is very confusing. The Upper Cretaceous sediments were eroded from a western land mass and deposited in a vast marine basin. Thick sandstones on the west side grade eastward into shales and finally even into limestones. In the west five main sandstone units can be differentiated with four intervening shale bodies and these have been given different names in different places. In the eastern area the series is largely shale and has been subdivided by paleontologic methods and by using the few limestones, but the two sets of subdivisions do not match. It is suggested that the entire problem be reviewed, group names given the main western sandstone and shale units for use through the Rocky Mountains, and many names eliminated. A conference of those in authority and those most interested and best informed might well be held to arrange such a simplification of the Upper Cretaceous nomenclature.

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