426 C. SCHUCHERT DIAGENESIS IN SEDIMENTATION 



of the rock materials we know but little in regard to the destructive or 

 katamorphic changes and the constructive or anamorphic alterations of 

 the sedimentary formations. Finally, when the sediments come to rest 

 in their basins of accumulation, they are again subjected not only to the 

 variable chemistry and temperature of the water, or more rarely the air, 

 but also to the physical and chemical work resulting from organic decay. 

 The enormous quantity of chemical work done by the organisms, not only 

 of the land, but even more of the water-bodies and chiefly of the seas, is 

 not at all appreciated by geologists. The paleontologist often sees the 

 resultant diagenetic changes, but he is usually too busy interpreting the 

 fossils gathered from the sediments to study the rocks themselves. The 

 diagenetic changes are therefore rarely studied by any one, but it is the 

 paleontologist who must take up this line of research, which requires 

 also a knowledge of chemistry, physics, and mathematics. 



A good beginning has been made by the staff of the Dry Tortugas Bio- 

 logical Station of the Carnegie Institution of Washington, but their work 

 as yet relates wholly to the calcareous deposits. Then, too, it is in a 

 region of warm waters, so that the diagenesis of cool and cold waters 

 remains almost wholly unstudied. On the other hand, ■ the chemical 

 laboratory of the United States Geological Survey has also done much 

 good work in ascertaining the nature of the hard parts of invertebrates, 

 and whether the calcareous structures are in the form of calcite or ara- 

 gonite. Their results are important to stratigraphers and paleontolo- 

 gists, since it is well known that aragonitic structures are rarely preserved 

 in fossils. Aragonite is the first mineral to change in the diagenesis of 

 marine sediments. 

 ' All life is ceaselessly undergoing chemical change and is constantly 

 throwing off materials that affect other materials, both organic and in- 

 organic; and all life is destined to die, resulting in bacterial decomposi- 

 tion products that are either taken up by the sediments or are trans- 

 formed by them. A great amount of the organic acids is used up on the 

 land, but much is also washed into the seas, where still more is made by 

 the decomposition of the marine organisms. To bring out the stupendous 

 amount of organic material and the chemical changes involved in its 

 death and decay, let me direct your attention to a few figures which will 

 visualize to you the quantities of life. 



It is well known that the kinetic energy of the sun is at the basis of 

 all life. We are told that on an average about 4,000,000 horsepower per 

 square mile is received by that portion of the earth's surface exposed not 

 too obliquely to the sun's rays; and yet Horace Brown has shown that 

 the plants store up less than 2 per cent of the sun's energy received by 



