TABLE 3. CLEARANCE AND AREA RATIOS OF SOME SUBMARINE SEDIMENT CORERS 



Corer 



Piston or 



Gravity 



Type 



Clearance Ratios 



Inside 

 (%) 



Outside 

 (%) 



Area 



Ratio 



(%) 



Reference 



Hvorslev -Stetson 



Gravity 



1, 1.6, 2 



1 



35 



USNHO Hydroplastic 



Either 



1.3 



13 



57 



USNHO "Phleger" 



Gravity 



10.2 







62 



USNHO "Ewing" 



Piston 



0.6 



23 



84 



Lament Geol . Obs . 











Ewing 



Piston 



5.3 



18 



87 



USNHO "Kulienberg" 



Either 



1.8 



10 



105 



USNEL Standard 



Either 



2.4 



22 



130 



Kulienberg 



Piston 







25 



373 



Hvorslev & Stetson (1946) 

 Richards & Keller (in press) 

 U.S. Hydro. Off. (1955) 

 U.S. Hydro. Off. (1955) 



Heezen (1952) 

 U.S. Hydro. Off. (1955) 

 Richards h Keller (in press) 

 Kulienberg (1955) 



Hvorslev's recommenda- 

 tions: cohesive sediments 

 and long corers. 



0.75 to 1.5 <3 



<10 Hvorslev (1949) 



Most gravity cores taken by oceanographers appear to have gross recovery ratios 

 much less than 100 percent, with consequent sample disturbance; the magnitude of the 

 ratio appears to be a function of the corer design . Gravity cores with gross recovery 

 ratios of 100 percent, at least in the upper 50 cm or so, can be obtained by better 

 design . 



In this report, the distance below the top of the core is the actual distance meas- 

 ured in the laboratory from the surface of each core. The gross recovery ratio listed in 

 Table 2 is based on the extreme condition that core shortening is the same throughout the 

 length of the core (Fig. 5, II), and that core penetration equals corer penetration. Corer 

 penetration, incidentally, was crudely estimated by the conventional method of measuring 

 the amount of sediment adhering to the outside of the core barrel after the corer had been 

 brought aboard the ship. The other extreme is that the gross recovery ratio Is 100 percent, 

 which has been assumed for all piston cores listed in Table 2. 



After Richards and Keller (in press), with additional computations by Richards. 



16 



