ABSTRACTS OF PAPERS 87 



VOTES OF THAXKS 



At the close of this, the last general session of the meeting, most hearty 

 votes of thanks were passed to President Burton and the Board of Regents 

 of the University of Michigan for the generous hospitality extended to 

 the Society in connection with the thirty-fifth annnal meeting, and to the 

 local committee, particularly to its chairman, Prof. Walter F. Hmit, for 

 the perfection of the arrangements which had made the Ann Arbor meet- 

 ing of the Society memorable for comfort and convenience in all of the 

 requirements of a large and complicated program. 



Saturday Afterxoojs^ Sessioxs 



Two sectional sessions were held simultaneously on Saturday after- 

 noon. 



The papers of Group A, of dynamical, structural, glacial, and physio- 

 graphic nature, were read in the auditorium of the iSTatural Science 

 Building. President Schuchert opened this session, Avith E. 0. Hovey 

 acting as Secretary. 



Papers of Group B, of petrologic, mineralogic, and economic nature, 

 were read in Room G 217, with Vice-President H. S. Washington in the 

 chair and F. E. Wright acting as Secretary. 



titles axd abstracts of papers of group a axd discussioxs thereox 

 physical history of the colorado froxt raxge 



BY F. M. VAN TUYL AND G. W. MACHAMER 



(Abstract) 



The Front Range represents a great anticlinal uplift locally faulted and 

 everywhere profoundly eroded. The Cretaceous and older sedimentaries which 

 once covered the area have been entirely removed over the crest of the struc- 

 ture, thus exposing the Precambrian crystallines. 



The appearance of a large amount of volcanic debris in the Denver and 

 Middle Park beds indicates igneous outbreaks in the range at the time they 

 were deposited. In the present foothills area a few lava flows and dikes were 

 formed at this time. There is evidence that the basaltic flows of North and 

 South Table Mountains at Golden were derived from a volcano on North Table 

 Mountain itself, rather than from a fissure now occupied by a dike several 

 miles to the north. 



The appearance of boulder beds in the upper portion of the Denver forma- 

 tion suggests readjustments in the mountains to the westward, possibly pre- 

 liminary to the great uplift. Subsequent to the deposition of the above-men- 

 tioned continental fans there were profound orogenic movements which de- 



