70 



Lithology 



Figure 64. Photographs of 

 phosphorite, (a) Nodules (ir- 

 regular masses, such as in up- 

 per center) and detrital cobbles 

 mostly of andesite (such as 

 smooth one in center) imbed- 

 ded in foraminiferal glauco- 

 nitic sand. Fortymile Bank 

 (lat. 32°40', long, 117°58', 588 

 feet). Photograph by Dietz, 

 Kierstad, and Shumway, April 

 15,1952. Bottom edge is about 

 4 feet long, (b ) Phosphorite in 

 two dredgings from ridge west 

 of Tanner Basin. Only five 

 small pieces of nonphosphatic 

 rock, shown in foreground, 

 were included. At station FPS 

 159, on the left (lat. 33° 04', 

 long. 120° 10', 1620 feet), a 

 large number of small nodules 

 were recovered. The large nod- 

 ule on the right (2 feet in di- 

 ameter) is from station FPS 

 162 (lat. 33°08', long. 120°22', 

 780 feet). Note the irregular 

 bumpy surfaces of phosphorite. 

 From Emery and Shepard 

 (1945, PI. 3). 



1955). In shallow water the top, exposed 

 surface is lightly to heavily encrusted with 

 organisms such as bryozoans, worm tubes, 

 sponges, and corals, showing that the nod- 

 ules are rarely if ever rolled about the 

 bottom. 



Internally, the nodules exhibit a wide range 

 of purity (Fig. 65). Some small ones are 

 homogeneous and very fine-grained. Most 

 of the large ones, however, contain some to 



much nonphosphatic material which ranges 

 from cobbles to grains finer than sand and 

 is of the same composition as the nearby bed- 

 rock or sediment mantle. Frequently, older 

 and darker nodules are cemented together 

 as a nodular conglomerate. Especially sig- 

 nificant is the presence of glauconitic fora- 

 miniferal sand both within and surrounding 

 the nodules. Very commonly small pockets 

 of this sand lie atop internal discontinuities 



