DISCUSSION OF GEOLOGY OF WASATCH MOUNTAINS 767 



NEW LIGHT ON THE GEOLOGY OF THE WASATCH MOUNTAINS, UTAH 

 BY ELIOT BLACKWELDEE 



Published as pages 517-542 of this volume. 



Discussion 



Mr. S. F. Emmons said that he was much gratified in listening to Mr. 

 Blackwelder's paper, for it explained many things that had puzzled him just 

 40 years ago last summer, when, as geologist of the Survey of the 40th Par- 

 allel, he surveyed the region under consideration, and a few years later was 

 called on to outline its geological formations on the map. In those days 

 "overthrust faulting" had not been invented. The range was regarded as a 

 great anticlinal fold, with its axis somewhat warped by a north-south com- 

 pression and its western flank cut off by the great Wahsatch fault. It had 

 been his hope that this great range, which Dana in the last edition of his text 

 book had characterized as the most comprehensive single range in the world, 

 would long before this have been surveyed in detail, as Mr. Blackwelder's 

 work showed that it well deserved. Time was so limited when the 40th 

 Parallel work was done that by no means all of the country could be ade- 

 quately studied, though it was all mapped. For instance, to Ogden Canyon, of 

 which he speaks, only a single day's work could be given ; consequently it was 

 only possible to ride to the head and back. In the summer of 18G9, not only 

 the whole Wahsatch range and the western end of the Uinta Mountains, but 

 also over 5,000 square miles of desert ranges to the west had to be surveyed, 

 and necessarily the ground had to be traversed very rapidly. 



As to the Weber quartzite, Mr. Emmons had observed that it thinned out to 

 the southward as well as at the north, there being less than 2,000 feet in the 

 Park City region, as Mr. Boutwell's detailed work has shown, while at Mount 

 Timpanogos, still farther south, it seems to be represented by an alternating 

 series of limestones and quartzites, called by him the Intercalated series. On 

 the other hand, in the next range to the westward, the survey of the Brigham 

 district shows over 8,000 feet of quartzites in the Weber series. 



HAWAIIAN VOLCANOES 

 BY REGINALD A. DALY 



i Abstract) 



Evidence was given for the view that the vent at Kilauea is an opening in 

 the roof of a large laccolith. This conception offers a tentative explanation of 

 the observed independence of Halemaumau and Mokuaweoweo (Mauna Loa). 

 A small, visible laccolith on Hawaii was described. The paper also included a 

 discussion of (a) the method by which the heat is maintained in Halemau- 

 mau; (6) the differentiation of Mauna Kea alkaline rocks from basaltic 

 magma, and (c) the development of Mauna Kea in its present form. 



