WORK OF JOSEPH BAEEELL ON SEDIMEXTATIOX 39 



For the interpretation of these he sought similar phenomena which were 

 produced under known conditions, and knowledge of fundamental prin- 

 ciples, and he then returned to the problem that he at first had in mind. 

 Barrell's investigations of a few formations will be briefly reviewed. 



In his first lengthy paper, under the caption '^Illustrative geological 

 application,"" ^-^ he discussed the mud-cracked geologic formations of the 

 Precambrian of Montana and Arizona and concluded that considerable 

 portions of the Belt terrane and the Grand Canyon series are continental 

 deposits. 



The Gila conglomerate of Arizona^® was considered by Barrell as pos- 

 sibly due to climatic causes, for "An examination of the literature showed 

 that the relations of the two divisions of the Gila conglomerate, the vol- 

 umes and relative ages of each, corresponded with the two epochs of 

 glaciation which were pronounced in Utah and Xevada and the two 

 periods of expansion of Lakes Bonneville and Lahontan.'" It appears to 

 have ^'originated from an increase in the ratio of erosion to transporta- 

 tion, due to the severe cold and consequent frost action of the Glacial 

 times, without a correspondingly large increase, in this arid region, of 

 precipitation."'" 



The origin of the ''Orange Sand*^ formation of Hilgard or the "Lafay- 

 ette"'" formation of Hilgard and McGee is discussed and the hypothesis 

 is advanced that it may be due to a climatic cause, by a shift from a semi- 

 arid to a rainy climate, a,s had been indicated on precediag pages of this 

 review.-' 



The Mauch Chunk shale, for the interpretation of which the studies 

 recorded in the article above referred to were made, "'lq the anthracite 

 region, more surely in the southeastern and eastern portions,"" is shown 

 to be, from top to bottom, ''a subaerial delta deposit laid down under a 

 semi-arid climate.^^ 



The Patuxent, Arundel, Patapsco, and Earitan formations of the At- 

 lantic Coastal Plain are interpreted as delta,s which 'Vere confluent as a 

 flat piedmont coastal plain, probably with a highly irregular and shifting 

 shoreline.^' -^ 



Barren's most extensive studies of any set of formations were those of 

 "The Tapper Devonian delta of the Appalachian geosyncline,'' ^^ and 



-^.Tour. Geol.. vol. 14. 1906, pp. .353-568. 



2«.Jour. GeoL. vol. 16, 1908. pp. 173-174. 



2" Op. sup. cit., pp. 373-378. 



^ Bull. Geol. Soc. Am., vol. 18. 19n7. p. 45u. 



»Bull. Geol. Soc. Am., vol. 23. 1912. p. 410. 



3<'Am. .Jour. Sci. (4i. vol. 36, 1913. pp. 429-472: vol. 37, 1914, pp. 87-109. 225-253. 



