558 



PROCEEDINGS OF THE ALBUQUERQUE MEETING 



luer, with Dr G. R. Mansfield and Mr H. E. Merwin, a review was made of 

 their physiographic and geologic features, and some three- hundred photo- 

 graphs were obtained, dealing with points of especial intei'est. One small 

 glacier was discovered and visited, and another, not so readily accessible, was 

 noted; the relative age of the granite-diorite stocks and of alkali-syenite was 

 found and minor points determined. After a review of the geology of the 

 mountains and of their special features, the results of last summer's work 

 were described and the whole illustrated by a small selection of lantern slides. 

 The accompanying paper, by Doctor Mansfield, was included in Professor 

 Wolff's presentation : 



GLACIATION IX THE CRAZY MOUNTAJNii OF MUATANA'^ 

 BY GEORGE EOGEES MANSFIELD 



Contents 



Page 



Introduction 558 



Character of glaciation 560 



Number and dimensions of glaciers 500 



Living glaciers _. 561 



Effects of glaciation 562 



Cirques and hanging valleys 562 



Troughs 562 



Striffi and depth of cutting 563 



Moraines and wash deposits 56.S 



Lakelets 56.S 



Relations to previous topography 564 



Peneplanation 564 



Revival 564 



Alternative hypotheses 565 



Advent of ice 565 



Duration of glaciation 565 



Post-Glacial erosion 566 



Summary 566 



Introduction 



The Crazy mountains (figure 1) occupy a somewhat oval area in central 

 Montana, about 40 miles long from north to south, and 1.5 to 20 miles wide. 

 The middle portion is approximately 46 degrees 10 minutes north latitude and 

 110 degrees 20 minutes west longitude. The mountains are divided by the 

 broad basin of the Shields river into two practically separate sections — the 

 north and the south — iilthough there is a narrow connecting ridge along the 

 east side. The two are:is thus determined constitute distinct imits, both topo- 

 graphically and geologically, and each has an approximately radial system of 

 drainage. The northern section rises to a maximum altitude of about 9,200 

 feet, and is marked by gentle outlines in its upper slopes. The southern sec- 

 tion, which occupies a larger territory, reaches a maxinuim height of 11.178 

 feet above the sea, and is very rugged. 



In the summer of 1007 the writer, in conjunction with Professor J. E. Wolff, 

 conducted a geological field party from the Harvard Summer School through 

 these mountains. After the close of the school he assisted Professor Wolff in 



1 Introduced by John E. Wolff, 



