302 



SCIENCE. 



[N. S. Vol. XVII. No. 435. 



Basiii-Bange Structure in the Death Valley 



Region of Southeastern California: M. 



R. Campbell, Washington, D. C. 



Recently attention has been called to the 

 geologic structure of the mountain ranges 

 of Nevada and southeastern California. An 

 attempt has been made to show that they 

 are generally anticlinal in structure, and 

 that the tilted-bloek type which Gilbert has 

 described, and which is generally known as 

 basin-range structure, is of rare occurrence. 



The object of the present paper is to 

 show that, although minor folding was ob- 

 served in the Death Valley region, the 

 mountains are generally composed of huge 

 blocks of strata that have been strongly 

 tilted and then eroded into their present 

 forms. 



The region described is traversed by two 

 systems of structures; one extending in a 

 north-south direction, being the southern 

 extension of the true basin ranges of 

 Nevada, and the other crossing these in a 

 northwest-southeast direction parallel with 

 and presumably an off -shoot from the main 

 line of the Sierra Nevada. The movements 

 which produced these structures seem to 

 have been preceded by an epoch of slight 

 folding in which the Paleozoic strata were 

 somewhat deformed. This was followed 

 presumably in Eocene time by faulting and 

 tilting along northwest-southeast axes 

 which formed parallel mountains and val- 

 leys trending in the same direction as the 

 Sierra Nevada. In the valleys so formed 

 lakes accumulated, probably through a 

 change in climatic conditions, and sedi- 

 ments having a thickness of several thou- 

 sand feet were laid down. In these lake 

 beds are the great deposits of salt, gypsum, 

 soda and borax, which have made the 

 region famous. Following this period of 

 sedimentation came one of movement along 

 north-south axes, which lifted and tilted 

 the surface into immense mountain ranges 

 trending parallel with the new axes. Pana- 



mint, Death and Amargosa valleys were 

 thus formed, and Funeral and Panamint 

 mountains were raised up between them. 

 Lakes formed in the new valleys and re- 

 ceived sediments similar to those of the 

 preceding period. 



The age of the second lake-forming 

 period is vaguely referred to late Tertiary. 

 From structural and stratigraphic evidence 

 the. beds are younger than the lake sedi- 

 ments of Death Valley, and they are cer- 

 tainly older than the gravel deposits which 

 mark the Pleistocene period in this region ; 

 therefore, they are provisionally classed as 

 Miocene and younger. 



The three papers on the Basin Range 

 structure were discussed together. 



C. R. Van Hise raised the question as to 

 whether or not the entire displacement rep- 

 resented in these uplifted or tilted blocks 

 was brought about by a single great fault 

 or by a series of parallel breaks, which 

 series he had termed a distributive fault. 

 He was of the opinion that such a dis- 

 tributive fault was the usual if not neces- 

 sary process in the production of moun- 

 tains of this type. 



W. M. Davis believed that a single great 

 break would account for the phenomena 

 observed by him, although the possible ex- 

 istence of parallel faults was admitted. G. 

 K. Gilbert pointed out that, in some of the 

 cases cited by him, parallel faults were evi- 

 dent, though not apparent in all instances. 



The consensus of opinion as brought out 

 by the discussion was that the evidence in 

 the field did not support the views ad- 

 vanced by Mr. Spurr. 



The presidential address was delivered 

 Tuesday evening as follows: 



Was Man in America in the Glacial 

 Period? N. H. Winchbll, Minneapolis, 

 Minn. 

 A very enjoyable smoker was then tend- 



