36 trask. PRINCIPLES OF SEDIMENTATION [Ch. 1 



such as soil erosion, gullying of arable lands, degradation and aggrada- 

 tion of stream valleys below dams, silting in reservoirs, beach erosion, 

 development of harbors and breakwaters, stream channel control, and 

 silting in irrigation canals (Brown, 1948). 



Lastly, sediments are of great use to the geologist interested in de- 

 termining the mode of origin of sediments, or the environmental condi- 

 tions under which they were deposited. For, if the geologist knows the 

 mode of origin and if he understands the distribution of sediments and 

 their attributes in the environment of deposition, he is in a position 

 to predict what the nature of the sediments will be at some place be- 

 neath the surface of the ground. Using information obtained from 

 sediments exposed in some outcrop or drill hole, the geologist is con- 

 stantly being called on to indicate the nature of the sediments at some 

 distance from these exposed points. If the geologist cannot predict, 

 he has to guess. Hence he should endeavor to learn all he can about 

 sediments, so that he can foretell, with desired reliability, the nature 

 of the deposits in the unexposed places. Geologists have a long way to 

 go in this respect, but the goal is clear. It is hoped that this chapter 

 will help some people along toward that goal. 



REFERENCES 



Allen, V. T. (1936). Terminology of medium-grained sediments: Report, Com- 

 mittee on Sedimentation, 1935-1936 (National Research Council), pp. 18-47. 

 Ailing, H. L. (1945). Use of microlithologies as illustrated by some New York 



sedimentary rocks: Bull. Geol. Soc. Amer., vol. 56, pp. 737-755. 

 Andree, K. (1916). Wesen, Ursachen und Art der Schichtung: Geol. Rundschau, 



Bd. 6, pp. 351-397. 

 Antevs, E. (1922). The recession of the last ice sheet in New England: Amer. 



Geogr. Soc, Research Ser. 11, 120 pages. 

 Athy, L. F. (1930). Density, porosity, and compaction of sedimentary rocks: 



Bull. Amer. Assoc. Petroleum Geol., vol. 14, pp. 1-24. 

 Bagnold, R. A. (1941). The physics of blown sand and desert dunes: Methuen 



and Co., Ltd., London, 265 pages. 

 Bailey, E. B. (1936). Sedimentation in relation to tectonics: Bull. Geol. Soc. 



Amer., vol. 47, pp. 1713-1726. 

 Barrell, J. (1917). Rhythms and the measurements of geologic time: Bull. Geol. 



Soc. Amer., vol. 28, pp. 745-904. 

 Baver, L. P. (1948). Soil physics: John Wiley & Sons, New York, 2nd ed., 398 



pages. 

 Beers, R. F., and Goodman, C. (1944). Distribution of radioactivity in ancient 



sediments: Bull. Geol. Soc. Amer., vol. 55, pp. 1229-1253. 

 Blackwelder, W. (1940). The hardness of ice: Amer. Jour. Sci., vol. 238, pp. 



61-62. 

 Boswell, P. G. H. (1933). Mineralogy of sedimentary rocks: Thos. Murby, 



London, 393 pages. 



