WORK OF JOSEPJI BAKRELL OX SEDIMENTATION 35 



". . . climate is a factor comparable to disturbances of the crust or move- 

 ments of tlie shoreline in determining the nature and the variations in the 

 stratified rocks of continental or offshore origin, thus playing a part of large, 

 though ])ut little-appreciated, importance in the making of the stratigraphic 

 record." 



As it is quite impracticable to summarize in this place this excellent 

 study, only the divisions of the subjects will be given and a few general 

 remarks made. Part I is entitled "Relations of sediments to regions of 

 erosion/* and in it are discussed the "character of rocks supplying sedi- 

 ment/' "relations of rainfall and topography to erosion," "relations of 

 temperature and topography to erosion," "separation of the topographic 

 and climatic factors," and "separation of tectonic and climatic oscilla- 

 tions." Part II is entitled "Relations of sediments to regions of deposi- 

 tion," and in it are considered the "influence of nature of surface of 

 deposition" (piedmont slopes and aerial deltas, lower floodplains and 

 aqueous deltas, and criteria for the elimination of local geographic fac- 

 tors), and the "climatic influences in regions of deposition." Under the 

 latter caption attention is paid to the effects of constantly rainy climates, 

 intermittently rainy climates, semi-arid climates, and arid climates, and 

 to the climatic significance of color. Part III is devoted to the "Relations 

 of climate to stream transportation." In this part the topics discussed 

 are "the effects of stream transportation," "relations of stable climates to 

 transportation," and "effects of varying climates upon transportation." 



These topics can only give an idea of the treatment of the subject. 

 One climatic relation of special importance will be mentioned. Barrell 

 describes in the third part of this article how the piedmont slopes built 

 up in the youth of a normal topographic cycle would be trenched and the 

 removal of the component materials commence in a stage of maturity. 

 If there were in topographic maturity a sudden change from semi -arid 

 to pluvial climate, erosion of the piedmont slopes will be accelerated and 

 "the final region of deposit undergo a sudden increase in sedimentation, 

 which may be called a veritable flood of waste, but it will be of phenom- 

 enal coarseness compared to that which preceded and that which will 

 come after." ^^ Conglomerates and sandstones are classified into marine, 

 tectonic, and climatic. He says : 



"Climatic conglomerates and sandstones are here made distinct and inde- 

 pendent from those of tectonic origin by the taxonomic elevation of the shift- 

 ing location of deposits (in space) to coordinate importance with intermittem 

 uplift and resulting pulses of erosion (in time)." " 



Op. cit., pp. 371, 

 Op. cit.. p. 384. 



