The name Cretaceous is derived from the Latin word for chalk (Creta), because in England, where the name was early used, the thick masses of chalk are the most conspicuous members of the system. Though first made known in England, the main subdivisions of the Cretaceous, as employed in geological literature, bear French names, which have proved themselves better adapted to general use.

In very marked contrast to the scanty development of the Jura, the Cretaceous strata of North America are displayed on a vast scale, and cover enormous areas of the continent, eloquent witnesses of the great geographical changes in that long period. Continental, estuarine, and marine rocks are all well represented, and, in consequence, our information regarding the life of North America and its seas during Cretaceous times is incomparably more complete than it is for the Triassic and Jurassic.

The Cretaceous rocks of North America are of very different character in the different parts of the continent, and require separate classification.