THE PLIOCENE AND PLEISTOCENE 

 DEPOSITS OF MARYLAND. 



BY 



GEORGE BURBANK SHATTUCK. 



INTRODUCTION". 



Geographers have long recognized three physiographic regions within 

 the Middle Atlantic slope. They are known, beginning on the west, as 

 the Appalachian Mountains, the Piedmont Plateau, and the Coastal 

 Plain. While each one of these regions has its own peculiar topographic 

 characteristics, they nevertheless, pass into each other with insensible 

 gradations. The Appalachian Mountain region is composed of flat- 

 topped ridges separated by deep, steep-sided and flat-bottomed valleys. 

 The Piedmont Plateau exhibits a rolling surface which along its eastern 

 margin is dissected by deep river gorges. The Coastal Plain, although 

 built up of terraces, has also developed a rolling topography along its 

 western margin where it blends with the Piedmont Plateau, but through- 

 out most of its eastern half it is as flat and featureless as the noted plain 

 regions of the West. 



The Appalachian region has been carved from folded beds of lime- 

 stone, shale, and sandstone. The Piedmont Plateau consists of metamor- 

 phosed sediments into which have been intercalated great areas of igneous 

 rocks, while the Coastal Plain is made up of unconsolidated sediments 

 composed of clay, marl, sand, and gravel which have been derived in a 

 large measure from the older land surfaces to the west. The Pliocene 

 and Pleistocene deposits are almost exclusively confined to this Coastal 

 Plain region although they lap up on the eastern margin of the Pied- 

 mont Plateau and are represented in the Appalachian Mountain region 

 by accumulations of sand and gravel along the rivers. 



