410 CARNEGIE INSTITUTION OF WASHINGTON. 



Bioiic Succession in Bad Lands, by F. E. Clements. 



A considerable number of Bad Lands have been visited during the 

 year. The most important of these are the Cretaceous and Eocene 

 areas in southern Wyoming, and the Miocene of the John Day Basin 

 in central Oregon. Other bad-land formations studied were the 

 Barstow and the Painted Canyon of the Mohave Desert, and the 

 Pliocene of Benson in southern Arizona. In all of these special 

 attention was paid to present-day succession, evidences of climatic 

 cycles, the nature and significance of sedimentation, and the utiliza- 

 tion of bad-land areas. Some evidence has been obtained to indicate 

 that the erosion cycles of Bad Lands correspond to climatic cycles, 

 and that it may prove possible to correlate them with other physio- 

 graphic cycles in the West that are directly or indirectly dependent 

 upon rainfall. 



It has become fairly clear that practically all Bad Lands owe their 

 origin or their persistence to aridity, and that they are thus indicators 

 of arid climates. It appears probable that the bad-land areas of the 

 West originated in grassland during the arid phase of a major cli- 

 matic cycle, chiefly in consequence of the effect of drought upon the 

 grass cover. Such a cover once destroyed, increasing aridity would 

 lead to the general production of the bad-land form, such as is typical 

 of the desert ranges of the Southwest. A typical example of this 

 process seems to be afforded by the Mohave Desert, which was almost 

 certainly grassland in the fairly recent past. A study of grassland 

 relicts in and about this desert, together with that of the grass com- 

 munities that border it on the east and west, not only indicates that 

 it was grassland a few thousand years ago, but also furnishes a some- 

 what detailed picture of its dominants and structure. This seems 

 to be in entire agreement with the paleontological knowledge of its 

 fauna, as far back as the Miocene at least. What is true of the 

 Mohave appears to be equally if less strikingly true of other arid 

 regions, and warrants the assumption that the Great Basin was once 

 a vast grassland. 



Researches in Sedimentation, by F. E. Clements and R. W. Chaney. 



The investigation of succession in the dynamic areas of the West, 

 such as bad lands, dunes and sandhills, lakes, swamps, and playas, 

 has necessarily led to the detailed consideration of the processes 

 of erosion and deposition. In the bad lands the evidences of past 

 sedimentation were present in bewildering number alongside the 

 present processes, and this gave promise that the one could be used 

 in the interpretation of the other. It was evident that many of the 

 theories as to the origin of bad-land deposits were not in harmony 

 with the principles of plant succession, and that the latter was of 

 peculiar value in this problem. It was felt, moreover, that the com- 



