BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, pp. 209-224. February i9, 1891 



THE RELATION OF SECULAR ROCK-DISINTEGRATION TO 

 CERTAIN TRANSITIONAL CRYSTALLINE SCHISTS. 



BY RAPHAEL PUMPELLY. 



{Read before the Society December 30, 1891.) 



CONTENTS. 



Page. 



Kesume of former Studies 209 



Evidence of secular Disintegration in ancient Rocks 210 



Derivation of Cambrian basal Conglomerates 210 



Evidence of the Stamford Dike 211 



Evidence from the G-reen Mountains 211 



Corroborative Evidence from the Southern Appalachians 216 



Influence of antecedent Disintegration on Rock Formation 217 



Formation of basal Beds 217 



Formation of detrital Rocks 217 



Accumuhxtion of Ores 219 



Formation of Transition Beds 221 



Bearing of Results on Time-Scale 223 



Discussion 223 



Resume of former Studies. 



Geology had its rise and most of its growth in the glaciated regions of 

 Europe and America. To this circumstance is due the fact that compara- 

 tively little attention has been given to the part played by secular rock- 

 disintegration in various geological processes. 



In a former paper '*' I attempted to show, in some of its bearings, the im- 

 portant part performed by the action of this process through the ages. The 

 central idea expressed was that a land surface exposed during a long period 

 to the influence of a moist climate, and protected by vegetation, Avould be sub- 

 jected to disintegration and decomposition of its rocks. The waters circu- 

 lating in depth, charged with oxygen and carbonic acid, and bearing acids 

 derived from vegetable decay, would set in motion a destroying action which 



*The Relation of Secular Rock-Disintegration to Loess, Glacial Drift and Rocli Basins; Amer. 

 Journ. Sei., 3d ser., vol. XVII, 1879, p. 133. 



XXXII-BuLL. Geol. Soc. Am., Vol. 2, 1890. (209) 



