Along the eastern border of the Piedmont plateau, lying for the most part directly on the flanks of its ancient crystallines and constituting the basal element of the Atlantic Coastal plain, is a series of mostly unconsolidated, arenaceous, argillaceous, and often ferruginous sediments of highly varied character. The outcrop constitutes a relatively narrow belt, extending from cape Cod to the Mississippi basin and ranging from a few to 20 miles in width, its landward boundary lying somewhat westward of the so-called Atlantic Fall line.
The general strike of the beds along the Atlantic border is northeast-southwest, the belt being divisible into three districts—northern, middle, and southern—whose strike is progressively more and more southward in passing from the northern district to the southern. The normal dip of the beds within the area of outcrop ranges from 30 to 60 feet per mile, a well marked increase occurring toward the landward . . .