356 CARNEGIE INSTITUTION OF WASHINGTON. 



were studied in San Timoteo Canyon and at Del Mar. Further evidence 

 was secured to indicate that the erosion cycles of Bad Lands are an effect of 

 climatic cycles and that they are in accord with other consequences of climatic 

 changes in the West. 



The first studies of succession in Bad Lands were made in 1897, and the 

 investigation has been carried on actively since 1913. It is expected that 

 the field work will be completed in another season, and as a consequence 

 increasing attention is being given to utilizing the results as a further basis 

 for the organization of the new field of paleo-ecology. This has involved the 

 refinement of the plant materials, the elaboration of the concept of climatic 

 cycles, the reconstruction of the climaxes and seres of the past, and a special 

 consideration of present and past processes in sedimentation and their 

 relation to climate and vegetation. 



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



Further studies of present-day deposition and erosion have been made in 

 connection with succession in bad lands, dunes, playas, valleys, etc., and the 

 nature and significance of sedimentation in the past have again received 

 special attention in bad-land and sandhill areas. A large number of suggestive 

 leads were secured and various working hypotheses tested by a reconnais- 

 sance through the Uinta, Bridger, and Green River of Utah and Wyoming, 

 made in company with Dr. W. D. Matthew, and one through the Miocene 

 and Oligocene of western Nebraska, made under the leadership of Mr. 

 Harold J. Cook. These afforded a unique opportunity to compare views and 

 interpretations and to refine the evidence from the various fields of approach. 

 They threw into clear relief the necessity for a cooperative attack upon the 

 problems of paleo-ecology, and emphasized the urgent need of detailed and 

 quantitative studies of sedimentation in different horizons, in close connection 

 with similar work on present sediments. While it is obvious that there is no 

 real distinction between present and past sediments, it has proved helpful at 

 least to distinguish those in the actual process of formation to-day from those 

 formed recently and the latter from deposits laid down in the Pleistocene or 

 earlier. While the actual details of sedimentation can be studied only in the 

 first, their significance for the interpretation of fossil sediments often depends 

 in large measure upon an understanding of the second. In the case of eolian 

 deposit it has proved possible to obtain a complete series from dunes still 

 forming, to sandhills and sand-plains that have become finally stabilized, and 

 to assign these relative dates. Similar results are indicated for playa and 

 stream deposits, though it has come to be recognized that a river system of 

 to-day exhibits practically all types of deposition in semi-arid regions and that 

 this must have been true throughout the Tertiary. 



Because of its relation to playa deposit, a particular study has been made of 

 the formation of caliche in the valley soils of the Southwest. This has been 

 supposed to be due to the upward movement of lime-bearing water in con- 

 sequence of evaporation, but in a number of localities at least the caliche of 

 the upper 5 feet or so was evidently deposited in the pools of a playa. The 

 lime crusts not only follow the contour of the bottom and sides, but they are 

 also fine-grained, almost pure, and polished on the upper surface, while below 

 they grade into the coarse material of the detrital layer brought in during the 

 floods of a wet phase of the climatic cycle. 



