BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 31, pp. 425-432 NOVEMBER 30, 1920 



DIAGENESIS IN SEDIMENTATION ^ 



BY CHARLES SCHUCHERT 



{Read before the Society December 31, 1919) 



Doctor Vaughan has asked me to say something of the problems that 

 liave arisen in my studies of sedimentary formations, and the kinds of 

 research that are needed in their solution. I will dwell on but one phase 

 in sedimentation, but this is a most important one, though seldom taken 

 up seriously by students of stratigraphy or by oceanographers. I refer 

 to diagenesis, or the chemical and physical changes that sediments un- 

 dergo during and after their accumulation, but before consolidation takes 

 place. Diagenesis, therefore, has nothing to do with the later metamor- 

 phic alterations superimposed by orogeny and intrusive rocks. It is 

 strange that this subject is so rarely studied, since it was as long ago as 

 1888 that Giimbel directed attention to these changes and coined the 

 word. On the other hand, Walther in 1893 devoted a long chapter to 

 diagenesis in his ^'Einleitung in der Geologic" (pages 693-711), and yet 

 we rarely see the word employed by European or American stratigraphers. 



It is well known that the igneous rocks are the primary sources for all 

 sedimentary formations, and something is known as to the kinds of ma- 

 terial into which they break down under the influence of temperature, 

 water, grade, and climate. The end-results — the muds, sandstones, and 

 limestones — make up the stratified formations, and they may later un- 

 dergo another process of weathering, and so be reworked and redeposited. 

 But in detail we know next to nothing as to what the exact end-products 

 are that develop under the many varying kinds of climate. What is even 

 more important, almost nothing is known in regard to the very decided 

 chemical changes wrought on them directly or indirectly by the organic 

 world. The climate that is impressed on the rock detritals and the or- 

 ganic deposits, as recorded in our geologic formations, is also hardly ever 

 discerned by stratigraphers. In all of this we see that at the very source 



Manuscript received l)y the Secretary of the Society February 9, 1920. 

 This paper Is one of a series composing a symposium on sedimentation. 



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