shelf. Side-scan sonar data were reviewed for information on bed forms 

 and gross textural distribution across the ridges. 



b. Lithology and Textural Analysis . Samples were obtained from the 

 cores at 0.3-meter (1 foot) intervals by either splitting the core or 

 drilling through the side of the plastic liner. Gross lithology of core 

 and boring samples was determined by examination under a binocular micro- 

 scope. Characteristics of the sediment noted include: color, texture, 

 size, sorting, gross mineralogy, and faunal constituents. Particular 

 emphasis was placed on identification of dominant and diagnostic clastic 

 and skeletal particles. Samples from the three boreholes made on central 

 Assateague were analyzed to provide a comparison of the adjacent barrier 

 island with the inner shelf sedimentary record. 



Textural properties of several hundred sand samples were analyzed by 

 sieving at 0.5-phi intervals or by the settling tube method. The latter 

 analysis was made on the CERC Rapid Sediment Analyzer (RSA) which effec- 

 tively monitors grain size by measuring the fall velocity of particles 

 in a column of water. 



5. Regional Setting . 



a. Geologic Setting and Stratigraphy . The Delmarva Peninsula is 

 part of the Atlantic Coastal Plain province of the eastern United States 

 which extends from Florida to Long Island, New York, and is bordered on 

 the west by the Piedmont province. Bounded by Chesapeake Bay and Delaware 

 Bay, Delmarva comprises about 5,400 square kilometers (6,500 square miles) 

 and contains most of Delaware and parts of Maryland and Virginia. 



Underlying the peninsula is a seaward-thickening wedge of unconsoli- 

 dated clastic sediments dating from at least earliest Cretaceous time and 

 possibly earlier (Jurassic) . These sediments thicken in a southeast di- 

 rection from less than 150 meters near Baltimore to more than 2,438 

 meters (8,000 feet) near Ocean City. The basement is pre-Cambrian 

 crystalline rock. Major structural trends in the basement surface are 

 the southeast-trending Salisbury Embayment (beneath the peninsula) and 

 the Baltimore Canyon Trough (beneath the Outer Continental Shelf) . 



Characteristics and stratigraphic relationships of Cretaceous and 

 Tertiary strata underlying eastern Delmarva, reported by Rasmussen and 

 Slaughter (1955), have recently been reviewed by Cushing, Kantrowitz, 

 and Taylor (1973) . Their discussion is summarized below and pertinent 

 information on stratigraphic nomenclature and hydrologic units is tabu- 

 lated in Table 1 . 



Nearly three-fourths of the total sediment column is composed of 

 Lower Cretaceous nonmarine rocks. The upper surface elevation of these 

 rocks ranges from above sea level at the western edge of the Coastal 

 Plain to more than 610 meters (2,000 feet) below sea level along the 

 coastline; total thickness ranges from a few feet to more than 1,830 

 meters (6,000 feet). The sediments directly overlie the crystalline 



