A- 2 



periods contribute to seasonal variations in salinity throughout the 

 Bay. 



The Chesapeake Bay study area lies entirely within the Atlantic 

 Coastal Plain, and is underlain by a thick, wedge-shaped series of 

 sedimentary formations which strike northeast and dip gently toward the 

 southeast. These "soft" rocks are composed of mostly unconsolidated 

 beds of sands, clays, marls, and gravels, which range from Lower 

 Cretaceous to Recent in age. The base upon which these sedimentary 

 formations rest is composed of very ancient, predominantly pre-Cambrian, 

 crystalline rocks upon which a prolonged pre-Cretaceous erosion cycle 

 produced a peneplained surface. Along the inner westernmost edge of 

 the Coastal Plain, the crystalline rocks emerge from beneath the over- 

 lapping unconsolidated formations along a line of demarcation known as 

 the "Fall Line" which marks the head of navigation on some tributaries 

 to Chesapeake Bay, such as the Patapsco River at Baltimore, the Potomac 

 River at Washington, and the Rappahannock River at Fredericksburg, 

 Virginia. The Fall Line also marks a topographic change westward, from 

 the flat or gently rolling low elevation of the Coastal Plain to the 

 higher elevated, bolder relief of the Piedmont Plateau (Corps, 1970). 



Of the 20,000 square miles of the Chesapeake Bay region, 15,600 

 square miles are land. Table 1 shows the distribution of this land 

 into forests, agricultural land, pasture, urban areas, and marsh wet- 

 lands. 



The forest land covers an area of slightly over 6 million acres 

 or 9450 square miles. Forests include 68 percent of the tidewater 

 counties of Maryland, 60 percent of Virginia and 48 percent of 

 Delaware. The total value of the cut timber (stumpage) is about $13 

 million in Maryland, $13 million in Virginia, and $0.5 million in 

 Delaware. 



The forests of the Chesapeake Bay include the combination of oak, 

 hickory, and pine as the major type, but, in the southern part, the 

 combinations are oak with hickory, oak with pine, loblolly pine with 

 shortleaf pine, and oak with gum and cypress. In many areas with 

 better soils there are a large number of mixed mesophytic deciduous 

 species with maple, tulip tree, beech, gum, various species of oak, 

 flood plain species of ash, elm, maple, sycamore, birch, and many 

 other species. The main timber trees are red and white oak, tulip tree, 

 pine, sweetgum, and various other hardwoods. 



