BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 14, pp. 353-368, PLS. 49-53 SEPTEMBER 12, 1903 



CONCRETIONS AND THEIR GEOLOGICAL EFFECTS • 



BY J. E. TODD 



{Read before the Society January 1, 1903) 



CONTENTS 



Page 



Introduction 353 



Concretions defined 354 



Concretions and crystals 354 



Size 355 



Siiape 355 



Location 356 



Chemical composition and conditions of formation 357 



Methods of growth 358 



Accretions 358 



Intercretions 359 



Excretions and incretions 361 



Geological effects 363 



In general 363 



Teepee buttes .' 363 



Bad Land pinnacles 363 



Buttes 364 



Knobs 364 



Natural revetments 365 



Explanation of plates . 366 



Introduction 



Some over thirty years ago the writer's attention was turned to the 

 peculiar cracked concretions abounding in loess, which are known as 

 loess kindchen. Not satisfied with current explanations of their origin 

 and history, he has ever since improved opportunities to note and collect 

 concretions, which abound in vast numbers and of numerous types in 

 tlie Mesozoic and Cenozoic formations of the west. This paper presents 

 some of the more prominent conclusions for consideration and criticism. 

 Some well known facts are briefly recapitulated for the proper setting 

 forth of the more novel conclusions. 



It should be stated at the outset that the author disclaims intimate 

 acquaintance with the chemical aspects of the subject. His data are 



L— Bur.L. Geoi,. Soc. Am., Voi,. 14, 1902 (353) 



