Figure 



4. Geological cross section of Chesapeake Bay Entrance along 



the Bridge Tunnel route compiled from engineering borings. 14 



5. Contours on a reflector within the presumed Miocene section 

 underlying the study area 16 



6. Contours on the buried erosion surface underlying the 



study area 18 



7. Surface sediment distribution in the study area based 



on gross characteristics 21 



8. Typical fine gray sand (Unit A) from Chesapeake Bay 



Entrance '. 22 



9. Size distribution for typical samples from the fine gray 



sand (Unit A) 23 



10. Typical samples of the coarse gravelly sand (Unit E) 

 occurring in Thimble Shoals Channel and under Tail 



of the Horseshoe 24 



11. Size distribution for typical samples of Unit E sand ... 25 



12. Photos of typical samples from the coarse, brown, shelly . 27 



13. Size distribution curves for typical samples of the 

 coarse, brown, shelly sand occurring in patches on the 



Cape Charles Terrace 28 



14. Histogram of the phi mean diameter of 95 samples from 



cores in the fine gray sand (Unit) 29 



15. Isopachous map of sediment thickness over the "blue" 

 reflector surface 31 



16. Detailed plan view of the Thimble Shoals outcrop of 

 Type E sand. Crosshatched area outlines the area of 

 outcrop where the most economically recoverable material 



lies. Contours are on the first subbottom reflector ... 39 



IV 



