The term Paleocene has not been used by American geological writers, who have, however, frequently employed the more noncommittal name of post-Cretaceous. It will be an advantage to follow the European usage wherever this can be done to express facts of correspondence between the two continents.

American

Marine formations of this epoch have not yet been distinctly identified in North America, though in the table the Midway of the Gulf region has been provisionally placed in that series. On the other hand, extensive areas in the western interior are referable to it. In the region of the Rocky Mountains and northern plains, the Denver and Livingstone beds may eventually prove to be a part of the Paleocene series, a correlation which is favoured by the plants which they contain. They also contain, remains of Dinosaurs, and though it is not at all impossible that some of these great reptiles should have survived in the earliest Tertiary, they are not yet known to have done so. The oldest known beds which are definitely assignable to the Paleocene are those of the Fort Union, a formation with a maximum thickness of 2000 feet, which covers very large areas in Canada, Montana, North Dakota, and eastern Wyoming, and is composed of sandstones and clay rocks. In Montana it lies conformably on the Livingstone, and in Wyoming there is an apparently unbroken succession from the Laramie into the Fort Union, barren sandstones between the two probably representing the Livingstone-Denver series.

Originally referred to the Tertiary on account of its plants, the position of the Fort Union has been confirmed by the finding of a considerable number of mammals in it. The conditions under which these beds were formed have not been clearly determined. That they may have been partly lacustrine is indicated by the presence of freshwater shells in some localities. Other parts are probably floodplain deposits and others again entirely subaerial. Beds with similar plants have been found in Greenland and Alaska.

A somewhat different facies of the Paleocene occurs in northwestern New Mexico and southwestern Colorado in a formation which also lies in apparent conformity upon the Laramie. In these beds, which are about 800 feet thick and mostly barren of fossils, are two separate horizons, which have yielded numerous fossil mammals, and each of which has its own characteristic fauna. The lower and older of these horizons is the Puerco, and the higher the Torrejon, the Fort Union corresponding to both together.

Foreign

In northern Patagonia is a continental formation, called, from one of its most characteristic fossils, the Notostylops beds, the mammals of which suggest correlation with the Puerco of North America.

In Europe a rapid elevation of the continent had occurred in the latest- phases of the Cretaceous, followed at the beginning of the Tertiary by numerous minor oscillations of level, which occasioned a continual struggle between land and sea and, as a result, "the Paleocene does not consist of purely marine deposits, but of a repeated alternation of marine, brackish, and fresh-water formations." (Kayser.) The sands, marls, and limestones thus produced cover a large area in the north of France, Belgium, and the south of England. The upper portion of the series near Rheims, in France, contains a mammalian fauna so like that of the American Torrejon as to indicate not only a correlation with that horizon, but also the existence of a land bridge between the two continents, which permitted the migration of terrestrial animals from one to the other. Paleocene beds occur also in Denmark and in central Russia and in southern Europe; in the south of France and the Pyrenees, it is represented by fresh-water beds, while in Egypt it is marine.

Climate

The earliest Tertiary floras of Greenland and Alaska show that the equable conditions of the late Cretaceous continued, but those of England indicate merely a temperate climate in that latitude, where in the true Eocene it became tropical.