325] G. E. Dorsey 127 



fathoms. Fine particles of mud are, of course, as good indi- 

 cations of clear water as chalk. There seems to be a general 

 unanimity that quiet water is a requisite in the deposition of 

 the glauconite. Goldman (4, p. 178), in speaking of the 

 chemical reactions supposed to take place in the formation 

 of glauconite says, "but whatever the process, the fact may 

 be accepted that in the presence of abundant organic matter 

 in fairly quiet waters, FeS 2 is formed." De Lapparent (19, 

 p. 365), says it is deposited in "green muds which form in 

 depths from 200 to 1300 meters along abrupt coasts, where 

 no important rivers empty as is the case along the south coast 

 of Africa and the coast of Australia." Graoau (20), says the 

 glauconite is formed in shallow water, on the continental 

 shelf, and is usually found as replacements in the fine marine 

 muds. Chamberlin and Salisbury (21, p. 366-68, Vol. i), 

 remark that " Glauconite is, on the whole, most abundant 

 along the edges of the continental shelves, though it is by no 

 means universal in this position. It is not commonly found 

 in deep water, nor very near the shore, but approximately at 

 the mud line." 



But where clear, quiet waters prevail for any time, glau- 

 conite can be deposited, even if the waters are very shallow. 

 Thoulet has found it in the Gulf of Lyons from water of only 

 a few feet. Professor E. W. Berry informs me that he has 

 found glauconite in very near-shore deposits in the eastern 

 Gulf region of the United States. It seems probable, in view 

 of the predominance of sands, that the Cretaceous glauconite 

 was formed at shallower depths than that being formed today 

 near the edge of the continental shelf. 



We are not concerned here with any of the discussions of 

 the chemical origin of glauconite. It may be formed after 

 the consolidation of rocks, as Cayeux has shown, and it may 

 not be due in any way to organic agencies. All we are in- 

 terested in is that the primary glauconite of the " greensands " 

 was deposited, in quiet waters, predominantly clear, sometimes 

 of very shallow depth, sometimes in depths of several hundred 

 feet. 



