IN SITU INVESTIGATION OF OCEAN SEDIMENTS USING THE 

 DEEP OCEAN SEDIMENT PROBE (DOSP) 



Lloyd Lewis 



Research Associate in Ocean Engineering 



University of Rhode Island 



James Gallagher 



Oceanographer, USNUSC 



New London, Connecticut 



ABSTRACT 



The DOSP was tested and evaluated in shallow water off Ponce, 

 Puerto Rico. Ten stations in depths to 200 feet were occupied 

 by the R/V ADVANCE II. Grab samples, Pheleger cores, DOSP and 

 correlation Ewing gravity cores were taken at each station. 

 In situ acoustic and temperature data were recorded and com- 

 pared to physical properties determined in the laboratory at 

 URI. Grab samples and Pheleger cores taken at stations in the 

 vicinity of the U.S. Virgin Islands indicated a thin surface 

 sediment layer of compacted coral sand and debris. Operations 

 with the DOSP in this region proved impossible. 



INTRODUCTION 



The primary task for the DOSP participation in the TEKTITE II Ocean Survey 

 Program was to contribute to the ocean sediment survey on the Virgin Islands 

 plateau. This effort was undertaken as an aid to extending the detailed geo- 

 logical investigations at Lameshur Bay. Extensive sampling from the R/V 

 ADVANCE II (Phase I) and the AVR VAST (Phase II) resulted in a pattern of 

 coarse sand and shell debris covering and filling shallow pockets among coral 

 reef structures at all sites investigated. As a result, DOSP operations in 

 this area were not possible. A summary of these investigations is given along 

 with other activities during these phases. Phase III studies involved actual 

 DOSP operations off the south coast of Puerto Rico from the R/V ADVANCE II. 

 In situ and laboratory data from this work has served as the basis for a doc- 

 toral dissertation in ocean engineering (Lewis, 1971) and further DOSP sensor 

 development (Rose, 1971; Erchul, 1971). Operations during this phase were 

 quite successful, and the resulting observations have led to positive verifica- 

 tion of the usefulness of in situ investigations. 



INSTRUMENTATION 



The DOSP and its associated components have been described in some detail in 

 Lewis, et.al. (1969 and 1970). Referring to Figure 1, the DOSP should be 

 regarded as a unique, station keeping, bottom mounted platform from which a 

 variety of marine sediment investigations can be undertaken. It has the capa- 

 bility of common, incremental, nonrotating penetration to 5.0 feet of four 

 probe sensors situated at the corners of a 4.2 foot square. A centrally 

 located, thin walled, 3-inch diameter corer can take a relatively undisturbed 

 sample up to 5.0 feet in length with a slow, steady, nonrotating motion. 



VII-18 



