668 



PRINCIPLES OF STRATIGRAPHY 



Deposits of the Bathyal District. 



On the whole the deposits of this region, which nominally lie be- 

 tween 200 and 900 meters or between 100 and 500 fathoms, are con- 

 tinuous with those of the neritic zone on the one hand, and with 

 those of the abyssal on the other. The following deposits seem to 

 be most characteristic of this district, though extending into both of 

 the adjoining ones : 



Table SJwzving Kinds and Distribution of Bathyal Deposits. 



Clastic deposits 



Mean depth 



in fathoms 



m meters 



Area covered 

 in square miles 



Blue mud. . . . 



Red mud 



Green mud . , . 

 Green sand . . . 

 Volcanic mud . 

 Volcanic sand . 

 Coral mud . . . 

 Coral sand . . . 



14,500,000 

 100,000 



850,000 

 600,000 



2,556,800 



The table on page 669, taken from Clarke's Data of Geochemistry 

 {2oh:48g), gives the analysis of the terrigenous and volcanic muds 

 and the green sands: i. Blue mud dried at 110° (Brazier); 2, 

 red mud dried at 100° (Hornung) ; 3, green mud dried at 110° 

 (Brazier) ; 4, green sand dried at 110° (Brazier) ; 5, volcanic mud 

 dried at 110° (Brazier). 



Three types of land-derived muds are found in the modern sea 

 away from the shore. These are the blue, the red and green muds. 



The Blue or Slate-Colored Mud. This is the most widely dis- 

 tributed, extending, according to Murray and Renard, over an area 

 of 14,500,000 square miles. It covers the floors of the shallow sea 

 to the edge of the continental shelf, as well as the floor of the entire 

 polar sea. The greatest depth at which it was observed by the 

 Challenger was 5,120 meters. In the Gulf of Naples it begins at 

 a depth of 15 meters, where in contact with the sea water it gen- 



