outside the Bay area. The very shallow shoal tops and apparent occur- 

 rence of this sediment above sea level at Fisherman Island in addition 

 to a microfauna adapted to present conditions in the Bay Entrance 

 (Nelson 1969) , indicate deposition of at least the upper part of this 

 unit at or above existing relative sea level. 



Present sources of sand-size sediment bayward of the deposits in 

 the entrance are largely to be found on the western shore of the Bay 

 area where shore erosion and main-stream drainage are estimated to have 

 produced the bulk of post-transgressive Bay sediments (Ryan 1953) . If 

 type A sand in the Bay Entrance is largely of post-transgressive origin, 

 it is unlikely that the source area is in the western Bay because the 

 western Bay sands grade finer toward 1;he inner bay, and the deep ce'ntral 

 Bay channel is mud-floored (Ryan 1953); thus, no avenue of present large 

 scale transport between the western shore and the entrance area is 

 apparent . 



Transport of sand from the eastern shore of the Bay to the entrance 

 area seems a more feasible route, but sand production on the eastern 

 shore is relatively small and probably inadequate to account for the 

 large volume of Type A sand present around the entrance area. 



Further evidence of a possible seaward origin for the fine gray 

 sand body is a contrast in percentages of some heavy minerals contained 

 in the Bay Entrance area sands to percentages of the same minerals in 

 other Bay areas. Of the 78 samples from the Bay area examined for heavy 

 minerals by Ryan (1953) 13 were in the fine gray sand body south and 

 west of the Cape Charles area. In these 13 samples hornblende ranged 

 between 19% and 52% of the total heavy fraction; hornblende exceeded 19% 

 in only 9 of the 65 samples from elsewhere in the Bay. Chlorite ranged 

 from 4 to 38 percent in samples from south of Cape Charles, but was 

 only 1 percent or less in samples from west of Cape Charles and else- 

 where in the Bay area. Black opaques which are generally 25% to 60% of 

 the total heavy fraction in most Bay samples, are less than 10% in all 

 but 4 of the samples from the gray sand blanket. 



Since the fine sand flats around Cape Charles contain a size range 

 that is not common elsewhere in the Bay, the differences in percentage 

 of hornblende, chlorite and black opaques may be due to a preferential 

 association of these minerals with the dominant size mode of the sand. 

 However, the degree of difference in size with some large areas of sand 

 in the Bay is not great, and the percentage difference in the content of 

 these minerals is substantial. 



Pleistocene and Holocene events have been the dominant influence 

 in shaping the present bottom and shallow subbottom characteristics of 

 the Bay Entrance. Repeated erosion of underlying Miocene strata 

 occurred as a consequence of low sea level stands during Pleistocene 

 glacial epochs. 



3,5 



