THE ELEMENTS OF A PALEOGEOGRAPHIC PROBLEM 5 



SHALLOW-WATER DEPOSITS. 



Following the conglomerate in the advance of the strand and finally 

 covering it are the shallow-water deposits, the finer sands, sandy muds, and 

 pure muds formed in the quieter region beyond the zone of wave-action. 

 Such deposits may result from so many different original conditions and 

 different forms of transportation that the utmost care is necessary in the 

 differentiation and interpretation of the beds. The presence of marine 

 fossils will at once determine the general character of the deposits, and this 

 may be checked, if necessary, by the adjacent formations, both horizontally 

 and vertically. 



Regularity in the bedding with a high degree of purity in the fauna (lack 

 of accidental inclusion of foreign forms, as terrestrial or fresh-water animals 

 or plants) indicate accumulation in large bodies of quiet water. Specimens 

 of land vegetation floated out, waterlogged, and sunk have been obtained 

 by dredgings far from land and in relatively deep water; such sporadic 

 occurrences in beds of great age are not impossible and mean no more than 

 accidents of distribution, but they may give a hint of the proximity of 

 powerful streams upon the land and some idea of the vegetation which 

 covered the land at the time of their deposition. 



By far the larger proportion of the sedimentary beds encountered in 

 geological investigation are marine accumulations in shallow water, and 

 most of the following remarks are applicable to them.^ 



DEEP-WATER AND ABYSSAL DEPOSITS. 



These are most easily detected by the peculiarities of the deposits and 

 fauna and the absence of shore debris. Deep waters are not, however, 

 always remote from the shore, and the proximity of abysses even to mountain 

 lands, as the coast of Japan, may permit the remains of shore and land life 

 and shore debris to be swept out and deposited in unusual surroundings.^ 

 Thus it would not be impossible that on the shores of Japan or the Pacific 

 coast of North America the impetuous streams might carry mountain forms 

 or mountain debris so far out that they would ultimately rest in the depths 

 of the abyss. 



It has been pointed out that the abyssal deposits of to-day are not 

 necessarily the same in character or fauna as those of the remote past. 

 Neither red muds nor oozes may have been formed in the depths of the 



^ Concerning shallow-water deposits and subaerial deposits, the student should read with 

 close attention Barrell, Relative Geological Importance of Continental, Littoral, and 

 Marine Deposits, Journal of Geology, vol. xiv, Nos. 4, 5, and 6, 1906, and Bulletin 

 Geological Society of America, Rhythms and the Measurement of Geological Time, pt. 

 II, p. 776, vol. 28, 1918. While much that the writer points out is not readily seen in 

 limited exposures, the paper is full of suggestive points of view and working hypotheses. 



^ White, David, Value of Floral Evidence in Marine Strata as Indicative of Nearness of 

 Shore Line, Bull. Geol. Soc. Amer., p. 221, vol. 22, 1911. 



