1913] Lawson: Designation of Alluvial Fan Formations 320 



waters. Except for the fact that it is thoroughly cemented and 

 indurated, the rock is very similar to the detritus which flanks 

 the margins of the mountain in the form of alluvial fans. There 

 can be little doubt but that the formation is the remnant of 

 an alluvial fan deposit spread over the region in the remote 

 past. The antiquity of the deposit can be indicated only in a 

 general way. The induration itself distinguishes the formation 

 from any of the Quaternary deposits which the writer has 

 observed in many parts of Nevada. Its position as a cap on the 

 residual hills of the degraded mountain mass, perhaps a thousand 

 feet above the floors of the adjacent valleys, indicates that it 

 antedates the uplift which inaugurated the present erosional 

 cycle. It also antedates the invasion of the country by the 

 igneous rocks, since some of the copper bearing dykes cut the 

 deposit. Moreover, it is traversed by several of the numerous 

 faults which have dislocated the formations of Battle Mountain, 

 since it is found at various sharply contrasted levels. This 

 faulting probably belongs to an older period of disturbance 

 which affected the region anterior to the degradation which in 

 turn preceded the late Tertiary faulting concerned in the up- 

 tilting of the Basin Ranges. Relying upon this interpretation 

 of the age of the faulting, which of course requires the con- 

 firmation of more extended field work, this interesting formation 

 appears to have been deposited between the close of the Paleozoic 

 and the period of deformation which occurred at the close of 

 the Jurassic. Leaving the definite determination of its age, 

 however, an open question, the formation is of peculiar interest 

 as revealing a physiographic condition analogous to the present 

 which prevailed in this part of Nevada in the remote past.* 



Term Fanglomerate Proposed. — For the discussion of this 

 formation a petrographical designation is necessary. I hesitate 

 to call the rock a conglomerate because, that does violence to 

 our current definition of this term and suggests an erroneous 

 conception of the mode of deposit and the climatic conditions 

 which determined that mode. I am equally loath to refer to it 

 as a breccia because that term suggests nothing as to its genesis, 

 nor does it as a purely descriptive term differentiate the rock 

 from others similarly designated. To till the gap in our nomen- 



