SECT. 1] 



CONTINUOUS REFLECTION PROFILING 



57 



tures. Later on. deeper parts of the continental shelf were studied, and, at 

 present writing, successful studies have been carried out both in oceanic depths 

 of 5 to 6 km and in the Puerto Rico Trench. During these studies, reflections 

 over 1 km below the bottom have been recorded. 



Even in so young a development it is already difficult to sketch, much less 

 to describe completely, the investigations which have been undertaken. How- 

 ever, the following are representative. 



A. Inland Waters 



Early emphasis was placed both on obtaining sub-bottom echoes and on 

 comparing them with geologic evidence from bore holes and by charting 

 reflecting horizons to outcrops. In 1956 and 1957, J. B. Hersey, D. Fink and 

 Miss E. T. Bunce conducted two surveys in different parts of Narragansett 



CORE 



CORE 7 



CORE 3 



T 



BAY FLOOR 



SEA-LEVEL „ 



~ - 20 





■rf— 'tlili 



r-1 



- 4 -1 



> i "1 ; 



100 



N- 



1 5 MllES 



-^^-s 



LEGEND 



SAND 



ClAY MUD 



■ ' SMEU5 



BEAUMONT ClAV 



Fig. 7. Marine Sonoprobe profile across Corpus Christ i Bay showing buried oyster reefs 

 (see a, b, c and d). (After McClure, Nelson and Huckaby, 1958, fig. 9.) 



Bay, one for the First Naval District Office of Public Works and one for the 

 Army Corps of Engineers. The principal objectives were to map bedrock under 

 glacial deposits in parts of the Bay. Fig. 6 is representative of recordings 

 obtained. Bedrock reflections and other shallower horizons were traceable over 

 most of the areas studied. Beckmann et al. (1959) report surveys in Long 

 Island Sound and Chesapeake Bay. Fig. 4 shows a beautifully clear recording 

 of bedrock obtained at shallow depth with a spark sound source. In these 

 surveys continuous profiles were successfully correlated with core samples and 

 jaenetration tests measured by the number of blows per foot required to drive 

 driUing tools into the sediment. Reflection depths agreed well with abrupt 

 changes in the number of blows per foot. 



