352 C. R. KEYES OEOGRAPHir ORIGIN OF LAKE BONNEVILLE 



Page 



(ilacial hypothesis of hike's origin 370 



Expressions of arid erosive influences 371 



Mastery of desert erosional agencies 371 



Destruction of ancient lake terraces 371 



I'lanorasion hy winds 372 



Derivation of hilve sediments 372 



Rock-tloors of desert plains 372 



Recapitulation 373 



IXTKODUCTOKY 



In a recent inqniry into the (lerivation of certain dei^ert features of the 

 (ireat hasin, (h'eat Salt Lake, and especially its precursor, the vaster 

 Lake Bonneville, presented some seemingly anomalies which from a pe- 

 rusal of the literature alone could not be readily adjusted to the modern 

 genetic scheme of physiographical development. This circumstance 

 eventually led to several visits to the Utah field and a critical examination 

 on the ground of the published data relating to the geologic history of 

 the old desert lake. Concerning the origin of' Lake Bonneville so many 

 incongruities were found as to compel the abandonment of the prevailing- 

 hypothesis. Instead of a genesis due to conditions of moister climate 

 induced by a Glacial epoch, the facts gathered seem to ])oint not only to 

 a pre-Glacial date of the lake's birth, but to a diastrophic rather than a 

 climatic cause for its existence. 



That the origin of the great Quaternary expanse of interior waters 

 known as Lake Bonneville, of which the present Great Salt Lake of Utah 

 is an all but extinguished remnant, may not be entirely climatic in 

 character, as advanced by Pi'of. G. K. Gilbert,- is not a new thought. 

 The possibility of the ancient lake's derivation through means of oro- 

 graphic movement was incidentally suggested by Prof. W. M. Davis^ so 

 long ago as 1883 in a summaiy review of Gilbert's prelimii^ary account 

 of his Bonneville investigations.^ I am not aware that this suggestion 

 has ever been pursued further. Its consideration now is the result of 

 accidental rather than of premeditative causes. The recent observations 

 indicate that this view not only has much merit in it, but that it has, 

 unexpectedly, an unusual amount of critically supporting evidence that 

 has never been even hinted at in the various discussions on lake subjects. 

 Approach from a direction entirely different fi'om anything jn-eviously 

 attempted is mainly responsible for the present return to Ihe theme. 



2Mon. U. S. Geol. Survey, vol. i, 1802. 



=* Science, vol. i, 1883, p. 570. 



* Second Ann. Kept. U. S. Geol. Survey, 1881, p. 160. 



