ACAD.MY or scienos] BASIN RANGES 247 



It is a loss to science that Gilbert's genius was not applied to the further discussion of the 

 problems thus brought to light. 



By very reason of the abundance of material recorded in the notebooks of 1901, it is sad- 

 dening to look them over. True, they indicate plainly enough that Gilbert enjoyed the summer 

 and had the exhilaration of making many successful searches and many encouraging discoveries, 

 even though the heat of the desert may have sometimes taxed his endurance. And the notes 

 leave no doubt, as the extracts quoted above must suffice to show, that in so far as concerns 

 visited examples, the basin ranges are displaced and eroded fault blocks; but precisely because 

 the search was successful and because the origin of the ranges was so well proved, it is grievous 

 to look over the rich records and to know that GUbert was so disheartened by the calamity 

 which followed their collection that he set them aU aside and turned to other work. Great 

 would have been the profit to American geology had this campaign among the basin ranges led 

 to a report similar in volume to that on the Henry Mountains. Rich as the notebooks are, the 

 report would have been richer still, for Gilbert had the habit of carrying a large part of his 

 results and practically all his argument in his memory. It is not likely that much would have 

 been told regarding the ancient deformation of the region and the resulting Cretaceous topog- 

 raphy, but a clear statement of its modern deformation and of the existing topographic features 

 resulting therefrom would surely have been forthcoming, and with a safety of demonstration 

 and a wealth of illustration that would have convinced all readers. It may be confidently 

 believed that, among the results reached, there would have been a satisfying definition of the 

 two main periods of strong deformation and active erosion, as well as of the long intervening 

 period when deformation essentially ceased and when erosion gradually weakened. While it 

 would then still be in a certain sense true that the existing structures and forms of the Great 

 Basin are the result of "compound earth movements" and "compound erosion" operative since 

 Jurassic times, it would also be true that the replacement of these general, not to say indefinite, 

 terms by more specific terms would constitute an important advance in the knowledge of the 

 basin ranges. 



RANGES IN THE HUMBOLDT REGION, WESTERN NEVADA 



By good fortune it was just at the time when the discussion of the basin-range problem 

 was renewed at Washington that a substantial contribution to its settlement was made by 

 Louderback, of the University of California, in his studies of certain ranges in the Humboldt 

 region of western Nevada; 6 and as Gilbert was asked to present the results thus gained at the 

 St. Louis meeting of the Geological Society in December, 1903, he had the pleasure of reading 

 to his assembled colleagues a very striking demonstration of the correctness of the composite 

 basin-range theory, provided by work entirely independent of his own. Indeed, the verifica- 

 tion for the three essential elements of the composite theory thus afforded was exceptionally 

 complete: Mesozoic formations of marine origin were folded and upheaved, presumably in 

 mountainous disorder, after the close of Jurassic time, as King and others had first demonstrated 

 many years before; the post-Jurassic mountains thus raised were reduced by long-continued 

 relief, as Powell and Dutton had inferred, and in the locality here studied the worn-down 

 surface was unconformably covered by nearly horizontal tuffs and basalts; the compound mass 

 was then, as Gilbert had supposed, faulted and irregularly displaced at a time so recent that 

 but a moderate amount of erosion has subsequently taken place. 



The unconformable volcanic cover, by which both the extinction of the post-Jurassic moun- 

 tains during a period of crustal quiet and the modern upfaulting of the existing ranges were so 

 convincingly proved, was an addition to the basin-range problem as unexpected as it was appo- 

 site ; and Louderback 's timely recognition of its pertinence in this respect constitutes the greatest 

 advance made in the study of the basin ranges since the King, Powell-Dutton, and Gilbert 

 elements of the composite theory were introduced a quarter century or more earlier. The 

 history of the ranges in the Humboldt region probably holds good for many other ranges also; 

 for it can hardly be supposed that the covering basalts selected an exceptional part of the Great 



» G. B. Louderback. Basin range structures of the Humboldt region. Bull. Geol. Soc. Amer., XV, 1904, 289-346. 



