increase in number and thickness toward the east and. are interfingered 

 with fluvial and proglacial outwash deposits (Weigle, 1974). 



Onshore, Holocene deposits vary up to 12 meters (40 feet) in thick- 

 ness, with an average approximate thickness of 1.5 meters (Weigle, 1974). 

 Most of the area of Holocene deposition is restricted to coastal and 

 marsh areas of the Atlantic coast, Delaware Bay, and Chesapeake Bay. 

 In general, these deposits are genetically similar to the Pleistocene 

 littoral and shallow marine sediments. 



c. Hydrologic Units . Much of the available information on subsur- 

 face stratigraphy of eastern Delmarva Peninsula has been obtained through 

 studies of water-bearing strata, the prime source for freshwater in the 

 area. Studies by Rasmussen and Slaughter (1955) , Sinnott and Tibbitts 

 (1955), Cushing, Kantrowitz, and Taylor (1973), and Weigle (1974) have 

 produced maps of major aquifers and aquicludes in the region. Because 



of their ability to transmit or restrict the flow of subsurface waters, 

 these hydrologic units are often reliable indicators of significant 

 lithologic changes. In the vicinity of Ocean City, Maryland, water is 

 supplied by four major hydrologic units: the Pleistocene (or Quaternary) 

 aquifer, the Pocomoke aquifer, the Ocean City aquifer, and the Manokin 

 aquifer. 



The Pleistocene aquifer (Beaverdam sand) is variable in extent and 

 thickness. Beneath Ocean City, it lies at about -16.5 meters (-54 feet) 

 MSL and is 18 to 24 meters (60 to 80 feet) thick, but is generally thinner 

 (7.6 to 15 meters, 25 to 50 feet) elsewhere in the vicinity. Separating 

 the Pleistocene and Pocomoke aquifers is a 4.5- to 6. 1-meter-thick (15 to 

 20 feet) unit of blue-green silt, fine gray sand, and blue-green pebbly 

 clay referred to as the upper confining bed or upper aquiclude. The 

 Pocomoke aquifer, a major water producer for the Eastern Shore, lies at 

 about -49 meters (-160 feet) MSL at Ocean City and is 12 to 18 meters 

 (40 to 60 feet) thick (Weigle, 1974). Rasmussen and Slaughter (1955) 

 reported a southeastward dip for the top of the aquifer at about 1.4 

 meters per kilometer (7.5 feet per mile). Contained within the under- 

 lying lower confining bed is the Ocean City aquifer, a unit of gray sand. 

 This unit, composed chiefly of gray sand lies at about -73 to -61 meters 

 (-240 to -200 feet) MSL in the Ocean City area. The Manokin aquifer, 

 untapped before 1972, is a potentially important source of ground water 

 for the area. At Ocean City the aquifer lies at about -107 to -145 meters 

 (-350 to -475 feet) MSL (Weigle, 1974) and is generally below the depth 

 range of seismic reflection equipment used in this study. 



d. Oceanographic Regime . Only limited data have been obtained on 

 large-scale water circulation patterns off the Delmarva Peninsula (Bumpus 

 and Lauzier, 1965; Harrison and Norcross, 1967). This information is 

 based on results of drift bottles and seabed drifters. Although results 

 of these types of studies are often questionable because of the low 

 recovery rate and bias in favor of shoreward transport, they do provide 



a useful indication of major surface-current circulation. Two aspects 

 of particular interest in Harrison and Norcross (1967) are the apparent 



