August 11, 1922] 



SCIENCE 



173 



the area, in which phosphate is found, above 

 water makes little difference. The essential 

 fact is that the phosphate nodules and most of 

 the materials associated with them probably 

 accumulated mainly in place and not as a result 

 of transportation. 



The length of the period during which the 

 deposits accumulated is deduced from the fol- 

 lowing facts: (1) The wide range of the fossils 

 they contain; (2) The great thickness of the 

 "equivalent" section in other areas. Without 

 the fossils this has no bearing; (3) In modern 

 deposits of similar character the decomposition 

 of associated detrital minerals and evidence of 

 prolonged submarine exposure of other con- 

 stituents; (4) The abundance in the deposits 

 of bore holes made by submarine animals; (5) 

 The evidence of different stages in the forma- 

 tion of the nodules; (6) Differences in the 

 amount of wear on different nodules, indicating 

 formation at different times; (7) The fact that 

 the sand included in the concretions is finer 

 than that in the matrix, indicating a range of 

 conditions; (8) The abundance in the deposits 

 of the teeth of fish without their bones, the 

 bones having been dissolved. 



One of the most convincing arguments 

 involves a consideration of the origin of the 

 deposits and the reason for their association 

 with stratigraphic breaks. This is not the 

 place for attempting a complete discussion of 

 the problem, but one explanation formulated 

 or implied by several of the papers cited is so 

 convincing in its simplicity that I wish to state 

 it briefly as superseding the one which, follow- 

 ing Cayeux, I proposed in my previous papers. 

 This new explanation is based on the peculiar 

 composition of the glauconite and phosphate 

 beds at stratigraphic breaks. A definition of 

 these peculiarities is almost an explanation of 

 them — they are essentially concentrations. The 

 materials concentrated as I have described 

 them and as they are described in part by 

 Fearnsides and others include the glauconite 

 and phosphate grains and nodules themselves, 

 shells or coarse fragments of shells of marine 

 animals, sulphide concretions, etc. These same 

 constituents are found in the overlying bed and 

 in some localities also in the underlying bed. 

 The reason they are concentrated here is ap- 

 parently that no detrital material accumulated 

 to separate them. In Teall's picturesque 



words,^" "The deposition of sediment acts on the 

 zonal succession [of ammonites] and on the 

 distribution of phosphatic matter very much 

 as a prism acts on the rays of light. It sup- 

 plies a kind of dispersive power." So far as 

 my reading goes, Hayes^"^ is the only one who 

 has made the important deduction from this 

 interpretation that the scarcity of calcareous 

 shells must then be accounted for. He attrib- 

 uted it to solution, which accounts also for the 

 dominance of phosphatic skeletons, the lime 

 phosphate being less soluble than the car- 

 bonate. Otherwise the abundance of living 

 phosphatic organisms such as the brachiopods, 

 which usually characterizes these areas of phos- 

 phate deposition, would be hard to explain, 

 seeming to imply a puzzling selective action of 

 the environment on the fauna. Murray and 

 Renard^- noted on the one hand the occui'rence 

 of glauconite and phosphate deposits in areas 

 of slow sedimentation, and on the other hand 

 the presence of glauconite, though in much 

 smaller relative amount, in many types of more 

 rapidly accumulating deposits, such as the 

 Blue Muds. But apparently they did not asso- 

 ciate the abundance of the glauconite and phos- 

 phate with the mere scarcity of the sediment. 



It is perhaps surprising that a fact so long 

 and frequently recognized as this association of 

 phosphate and glauconite with stratigraphic 

 breaks should have failed almost completely to 

 penetrate the text-books. I have found it 

 touched on only in Grabau's "Geology of the 

 Non-metallic Minerals."^^ Nevertheless, though 

 it still requires a great deal of interpretation 

 and qualification, it seems to be established 

 well enough to receive general consideration 

 from stratigi'aphers as a criterion of great pos- 

 sible value in the analysis of stratigraphic 

 sections. 



Marcus I. Goldman 



U. S. Geological Survey 



lOTeall, J. J. H.: "The Natural History of 

 Phosphatic Deposits," Proc. Geologists' Assoc, 

 London, IG, p. 379, 1900 (bibliography of 45 

 titles). 



11 Hayes, C. W., loc. cit., 1895, pp. 621-622. 



12 Murray, John, and Eenard, A. F. : "Deep- 

 sea Deposits, ' ' Report on the Scientific Results 

 of the Voyage of H.M.S. Challenger, pp. 382 

 and 411, 1891. 



IS Vol. 1, p. 306, McGraw-Hill, New Yerk, 1920. 



