LITHOGENESIS OF THE SEDIMENTS 163 



THE LITHOGENESIS OF THE SEDIMENTS. 

 FRANCIS M. VAN TUYL. 



There are few lines of investigation in geology which promise 

 more fruitful returns than the lithogenesis of the sediments. 

 The sedimentary rocks have from the first hen sadly neglected 

 although the igneous and metamorphic groups have been sys- 

 tematically and more or less intensively studied both in the held 

 and in the laboratory. Even the megascopic characters of the 

 sediments have for the most part been indefinitely and vaguely 

 described and petrographic examinations have until recently 

 rarely been made. Descriptive terms have been indiscriminate- 

 ly used and such important features as mud cracks and many 

 others equally as significant have in many cases been wholly 

 overlooked. Moreover, until within the last ten years few seri- 

 ous attempts were made to determine the conditions of deposi- 

 tion of the clastic sediments. It is little wonder then that the 

 application of more refined methods of study to these rocks bids 

 fair to revolutionize the fields of physical stratigraphy and 

 paleogeography. 



The importance of careful study of recent sedimentary de- 

 posits of both the continental and marine types as a basis for 

 interpreting the history of the ancient sediments cannot he too 

 strongly emphasized, as was pointed out recently by both An- 

 dree 1 and Goldman.- Indeed some of the greatest contributions 

 to stratigraphy have come through such studies. The im- 

 portance of Drew's recent investigation on the deposition of 

 limestone through the agency of bacteria in the modern seas^ as 

 bearing on the origin of the ancient thick, fine-grained limestones 

 which in themselves furnish no positive clue as to their mode 

 of formation must be admitted by all. 



Witness also the valuable contributions of Grabau and Bar 

 rell, who, working independently, have been able not only to 

 prove beyond a reasonable doubt that many of the thick Pale- 

 ozoic clastic formations of the Appalachian region which were 

 formerly believed by all to be either of marine or estuarine origin 



Tetermann's Mitteilungen Vol. 59, part 2, 1013, p. 117 IT. 



2 Am. Jour. Scl., 4th ser., Vol. 39, p. 287. 



s Carnegie Inst. Washington, Pub. 182, 1914, pp. 9-45. 



