closed during prehistorical times. The net effect of the filling is 

 to translate coarser sediments landward. Along Assateague there is 

 sufficient evidence (beach ridge orientation, back-barrier and marsh 

 configuration) indicating a significant role for inlet filling in bar- 

 rier island evolution and also indicating that numerous inlets formerly 

 existed, rather than a single inlet migrating for long distances along 

 the coast (Harrison, 1972) . 



Transport of beach sands (overwash) through the dunes and across the 

 island by storm-generated surge is a major mechanism of modification to 

 barrier islands. As storms pile up water against the coast, the attend- 

 ant storm breakers often breach the dunes and carry sand to the central 

 and back side of the island, and often into the lagoon. The transport 

 mechanics and resulting sedimentary record of overwash are discussed by 

 Godfrey and Godfrey (1973) and Schwartz (1975). Overwash has been a 

 major modifying process along the coastline of the study area. During 

 the March 1962 storm most of the Maryland coast was completely submerged 

 at one time or another (U.S. Army Engineer District, Baltimore, 1972). 

 Washover on Assateague may occur as individual fans, a series of fans, 

 or large coalesced fans. Characteristics of these features are discussed 

 by Field (1976) . The net effect of overwash is to place coarse and medium 

 beach sands immediately over back-barrier fine sand and lagoonal muds. 

 This is a key process in the landward translation of the barrier itself. 



A series of geologic cross sections of the coast by Kraft, Biggs, 

 and Halsey (1973) show that the modern barrier sands vary in thickness 

 between 2.4 and 13.7 meters (8 and 45 feet); depth to Pleistocene between 

 6.1 and 12.2 meters below sea level. The cross sections also show the 

 presence of certain units (e.g., lower Holocene sands) only at certain 

 locations. Both Biggs (1970) and Weigle (1974) present subsurface geolo- 

 gic data for shore-normal transects from the mainland across the lagoon 

 and onto the barrier. These sections show that dip is not uniformly east 

 and that local reversals are common in dip of the Holocene-Pleistocene 

 contact. No distinct vertical sedimentary sequence exists for the whole 

 of the barrier island. Beneath Ocean City, sands overlie silt and clay, 

 which overlie sandy silts over peat. The peat, traceable across the 

 entire zone, lies at about -4.6 to -7.6 meters and has been sampled from 

 several places, including the shoreface, and radiocarbon age-dated; the 

 dates and pollen analysis both indicate at least a mid-Wisconsin age. 

 Except for the northern part of the island, this peat horizon is generally 

 absent beneath Assateague. 



Correlation of onshore borehole data and seismic refraction data with 

 offshore vibratory core and seismic reflection data across the Fox Hills 

 level area on central Assateague Island is shown in Figure 37. Subsurface 

 lithologies are generally correlative between boring and the offshore core. 

 The sequence of clayey silt at -15.2 to -18.3 meters, underlain by fine 

 and very fine sands, is particularly distinctive for the two seaward bor- 

 ings and the offshore core. The contact between the two coincides with a 

 seismic reflection horizon beneath the shoreface. At greater subsurface 

 depths (-22.2 to -25.3 meters or -73 to -83 feet), a layer of gravelly 



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