VI CONTENTS. 



Chapter II — Continued. Vage. 



Differentiated sheet southeast of Electric Peak 82 



Gallatin River laccolith 8* 



Dacite-porphyry 84 



Intrusive sheets in Mount Everts 85 



The Bunseu Peak mass 86 



Dacite-porphyry 86 



Chapter III.— The igneous rocks of Electric Peak and Sepulchre Mountain, by J. P. 



Iddings 89 



Geological sketch of the region 89 



The intrusive rocks in Electric Peak 92 



The dike rocks and certain contact forms of the stock 94 



The stock rocks and apophyses 97 



Varieties in which the dark-colored and light-colored minerals are nearly equal 99 



Varieties in which the light-colored minerals are in excess, but in which quartz is 



not excessive 102 



Varieties with an excess of light-colored minerals, in which quartz is abundant 103 



Quartz-mica-diorite-porphyry 103 



General consideration of the mineral and chemical composition of the intrusive rocks 



in Electric Peak 105 



Mineral composition 105 



Chemical composition 115 



The volcanic rocks of Sepulchre Mountain 121 



The lower breccia 121 



The upper breccia 122 



The dike rocks 128 



General consideration of the mineral and chemical composition of the eruptive rocks 



of Sepulchre Mountain 134 



Mineral composition 134 



Chemi cal composition 135 



The extrusive igneous rooks west and southwest of the Gallatin Mountains 137 



Comparison of the rocks from Electric Peak and Sepulchre Mountain 138 



Correlation of the rocks on a chemical basis 142 



Chapter IV.— Descriptive geology of the northern end of the Teton Range, by J. P. 



Iddings and W. H. "Weed 119 



Introduction 149 



Topographic features - 151 



Crystalline axis and region east .' 152 



Region west of the crystalline axis 157 



Chapter V.— Descriptive geology of Huckleberry Mountain and Big Game Ridge, by 



Arnold Hague 165 



General features 165 



Region of Wildcat Peak and Huckleberry Mountain 168 



Region of Snake River gorge 173 



Region between Red and Basin creeks 175 



Snake River Hot Springs 177 



Region of Coulter Creek and Bobcat Ridge 179 



Region of Wolverine Creek 181 



Region of Piny on Peak 184 



Big Game Ridge 188 



Chicken Ridge 191 



