458 



PRINCIPLES OF STRATIGRAPHY 



lime-secreting organisms, 1.7 per cent, mineral matter and 40 per 

 cent, of the fine red mud. 



The geographic distribution of this deposit is much less than 

 that of the Foraminifera, the total area covered by it being only- 

 something over 12 million square kilometers, or 3.4 per cent, of the 

 total ocean bottom. It seems to be entirely wanting in the Atlantic, 

 and restricted to the region around the Cocos and Christmas 

 islands in the Indian Ocean. In the Pacific it finds its greatest dis- 

 tribution between 5° and 15° north latitude, and between Central 

 America and 165° west longitude. A few other isolated patches in 

 the Pacific contain this deposit. 



Fig. 108. Radiolarian ooze from the Indian Ocean, x 40. (After Kriim- 

 mel.) I. Tricyrtida; 2. Dicyrtida; 3. Discoidea ; 4. Prunoidea ; 

 5. Larcoidea ; 6. Coronida; 7. Sphaeroida ; 8. Chaetoceras (Dia- 

 tom) ; 9. Sponge-spicules. 



Fossil radiolarian oozes also occur, but in most cases it may be 

 questioned whether they are really deep-sea deposits. An example 

 is the radiolarian rock described by Rtist (75:7(5'/), which has been 

 regarded as of deep-sea origin, but Walther has insisted that the 

 high content of Carbonaceous material and the quantity of littoral 

 sediments oppose this view. The island of Barbados also furnishes 

 a colored clay which contains an abundance of radiolaria (Barbados 

 earth), and this has been regarded as a deep-sea deposit similar 

 to that found in the Pacific at 5,000 m. and now brought to the 

 surface by a local elevation. Limestones similar to the modern 

 Globigerina ooze also occur on this island. 



