486 STEVENSON— THE FORMATION OF COAL BEDS. l^°y- «. 



and even of carbonaceous matter, were made in very shallow turbu- 

 lent water or on vast tidal beaches. 



Dannenberg,"'" discussing the importance of red beds, refers to 

 activities of changing climatic conditions as perhaps a notable agent 

 in bringing about the contrast between the productive and the barren 

 measures. In the productive measures, one finds constantly dark 

 gray to black as predominating colors, due to impregnation of the 

 whole mass with coaly substance, while the succeeding barren meas- 

 ures are recognizable by the red color. The Rothliegende, succeed- 

 ing the Carboniferous, owes the first half of its name to this 

 condition. But the change in color begins before the close of the 

 Carboniferous, for the red appears as soon as conditions for coal- 

 making end — with the entrance of red, the formation of coal beds 

 ceases. In the Saarbruck region, reds occur in the Upper Carbon- 

 iferous over the productive division. That a luxurious vegetation 

 existed during deposition of this unproductive red shale is proved 

 Ijy the presence of great masses of vegetation in the Rothliegende, 

 such as the petrified forest at Radowenz in Bohemia. Evidently not 

 failure of vegetation but changing climatic conditions, which were 

 unfavorable to the accumulation of plant remains, brought about the 

 new features. The formation of red rocks and weathered products 

 is at present a peculiarity of the torrid zone, where one finds laterite, 

 terra rossa, etc., in which humus is unimportant. Dannenberg is 

 inclined to think that in the Carboniferous, there were moderate, 

 perhaps ocean climates contrasting with the succeeding hot climate 

 of the continental Rothliegende. 



Barrell,''^ who regards the Mauch Chunk (Upper Mississippian) 

 red shales as, for by far the most part, of flood-plain origin, has 

 publi-shed two important memoirs bearing upon the origin of the red 

 color. In the earlier memoir he shows that the Mauch Chunk con- 

 tains some impressions of plants but no trace of the carbon remains. 

 The loss of carbon has not decolorized the shale, so that evidentlv 



07 



"^ A. Dannenberg, " Geologic der Steinkohlenlager," Berlin, 1910, pp. 



30, 31- 



■^J. Barrell, "Origin and Significance of the Mauch Chunk Shale," 

 Bufl. Geo!. Soc. Anier.. \'ol. 18, 1907, pp. 449-476; "Relations between 

 Climate and Terrestrial Deposits," Joiini. of Gcol., \o\. XVL, 1908, pp. 159- 

 190, 255-295, 363-384. 



