70 



calcium carbonate content and the third quartile diameter for all 27 

 sediments is 0.61 it 0.09, but if the anomalous sample 8 is omitted, it is 

 0.71 ±0.07. This indicates a fairly good relationship and shows that 

 in general the calcium carbonate content increases as the sediments 

 become finer. 



Organic content. — The organic content of recent sediments is con- 

 vientlj^ estimated by multiplying the nitrogen content by 11. This 

 is not an exact procedure, but it is a rapid means of procuring a rough 

 approximation.* Table 5 and Figure 50 show the distribution of 

 nitrogen in the sediments of Davis Strait. Except for sample 20 ad- 

 jacent to the north coast of Labrador, the nitrogen content ranges 

 between 0.05 and 0.09 per cent. This indicates that the deposits 

 contain about 1 per cent organic matter, which compared with tho 

 content of other marine sediments is very low. 



■ As a rule the ignition loss aids the estimation of the organic 

 content of sediments, but the samples from Davis Strait contain so 

 much calcium carbonate that it is not of much assistance for these 

 deposits. HoAvever, it is included in Table 5. 



THE ORIGIN OF THE SEDIMENTS 



Texture. — The sediments of Davis Strait are complex in origin. 

 They contain a considerable quantity of ice-borne debris; the pres- 

 ence of frosted sand grains suggests wdnd transport; the large 

 amount of very fine calcium carbonate particles may possibly (but 

 not probably) be due to chemical precipitation; and the uneven sea 

 floor and differential current action cause great variations in the 

 texture of the deposits. 



The submarine topography is the dominant factor governing the 

 texture of the sediments of Davis Strait. Even though considerable 

 quantities of ice-borne rock fragments are distributed throughout 

 the deposits, the mechanical composition of the sediments is in- 

 fluenced greatly by the bottom configuration. Along the longitudi- 

 nal series of samples adjacent to the Cumberland Peninsula, the 

 sediments are coarsest on the highest point on the section and they 

 become progressively finer as the water deepens on either side. The 

 median decreases from 260 microns in a sample in 418 meters of 

 water to 5 microns in 1,270 meters on the north, and 135 microns 

 in 625 meters on the south. Sample 5, having a median of 163 

 microns lies in 420 meters, but it contains only 12 per cent gravel 

 compared with 26 per cent in adjoining samples, and if the gravel 

 is discounted, the two sediments have aproximately the same texture. 



The samples along the lines eastward from Cape Murchison, 

 similarly, vary in texture with the topography. Deposits that lie in 

 200 meters have medians of about 200 microns; sample 11, in 250 

 meters has 155 microns; sample 14, in 263 meters, 131 microns; 

 sample 8 in 290 meters, 85 microns; and sample 15 in 1,500 meters, 

 21 microns. 



Sample 19, in Hudson Strait in 575 meters, has a median of 208 

 microns. This shows clearly that it is not depth of Avater that is 



*P. D. Trask, Sedimentation of tne Cliannel Islands Region. California. Econ. Geol., 

 vol. 26, pp. 36-42, 1931. 



