CLIMATE AND TERRESTRIAL DEPOSITS 163 



Upper Carboniferous formations of eastern Pennsylvania; forma- 

 tions which had been found by the writer from field investigations 

 to be continental in origin and therefore their contrasted features 

 not to be attributed to changes in the relations of land and sea. 

 As an illustration of the importance of the climatic factor in sedimenta- 

 tion, it may be stated that an application of the conclusions of this 

 paper goes to show on several lines of evidence, which it is hoped to 

 publish in the near future, that the changes from the red beds of the 

 Catskill formation, several thousand feet in thickness, to the gray 

 Pocono sandstones with a maximum thickness of 1,200 to 1,300 feet, 

 then to the sharply contrasted red shales and sandstones of the Mauch 

 Chunck, 3,000 feet in maximum thickness, and back to the massive 

 white conglomerates of the Pottsville conglomerate, 1,200 feet in 

 maximum thickness, followed by the coal measures, are all the result 

 of increasingly wide swings of the climatic pendulum which carried 

 the world from Upper Devonian warmth and semi-aridity to Upper 

 Carboniferous coolness, humidity, and glaciation. 



PART I. RELATIONS OF SEDIMENTS TO REGIONS OF EROSION 



Introduction 



The larger rivers of the world, of which the Missouri and the Nile 

 may be cited as striking examples, frequently rise in a climatic zone 

 entirely distinct from that of the mouth. Such rivers usually flow 

 for some hundreds of miles across low-lying country after escaping 

 from the mountains, and carry nothing coarser than fine sand in 

 their lower reaches, the dominant deposits over the surfaces of the 

 large deltas being a great volume of clay and loam. That the climatic 

 conditions under which the sediment is supplied at the source, has 

 an appreciable influence even in these extreme cases is shown by 

 Walther, who points out that the alluvium of the large tropical rivers 

 is usually red in color while that of the Ganges and Mississippi, 

 brought to the limits of the tropics from temperate regions, is gray 

 instead of red.' 



In shorter river systems, however, not only is the climate of the 

 headwaters more closely related to that of the alluvial plains, but both 

 the climatic and geographic conditions existing over the former region 



I Einleitung in die Geologic, 1894, p. 815. 



