In recent years it has come to be generally recognized that within the stratigraphic series of both the old and the new world there are a number of deposits which owe their origin and characteristics not so much to the ordinary forces active in marine sedimentation, but rather to the dominance of the influence of water on land. Most noteworthy among these are the deposits formed by rivers, those formed by lakes or other standing water bodies being of secondary and limited significance.
River deposits may be divided into (1) interstream deposits, or those formed along the course of the stream—that is, on its floodplain—and (2) terminal deposits, or those formed at its debouchure either at the foot of the mountains or at its junction with the sea or a lake. Considering only the last type, we find that in the first case a dry delta or . . .