BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 34, pp. 309-380, PL. 4 JUNE 30, 1923 



OUTLINES OF APPALACHIAN STEUCTUEE ^ 



BY ARTHUR KEITH 



{Presented before the Society December 29, 1922) 



CONTENTS 



Page 



Introduction 310 



Definition 311 



Description 313 



Folds 313 



Salients and recesses 313 



Southeastward intensity 314 



Metamorphism 315 



Competency of beds 315 



Effect of load 316 



Bedding slip 316 



Effect in kind of yielding 317 



Border faults 317 



Height and depth of folds 318 



Fan structure 319 



Precambrian divergence 320 



Triassic trend lines 320 



System of batholiths , 321 



Precambrian plateau 322 



Paleozoic geosynclines 328 



Major linear folds 325 



Cross-structures . . . . : 326 



Cross-fold system 328 



Southward convergence 329 



Northward thrust from Llanoria 329 



Relation of cross-folds to salients 330 



Age of axes shown 330 



Periods of folding 331 



Amount of folding 334 



Inferences 336 



Direction of the deforming force 336 



How the deforming force was transmitted 338 



1 Manuscript received by the Secretary of the Society July 5, 1923. 

 Published by permission of the Acting- Director, U. S. Geological Survey. 

 This paper is one of a series composing a "Symposium on the structure and history 

 <)f mountains and the causes of their development." 



(309) 



