I 
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CONTENTS. 
Page. 
Synopsis of Part 1. 1 
Part I.—General Descriptions, Discussion, and Conclusions. 
Chapter I.—Introduction. 11 
Field work and acknowledgments. 11 
Literature. 15 
Chapter II.—General geology. 18 
Introductory statement. 18 
First geological survey of the district. 18 
Modification of earlier results. 19 
Basement rocks. 19 
Volcanic rocks. 20 
Form of the volcanic neck. 21 
Sedimentary deposits. 22 
Age of the eruptions. 23 
Geological structure of the district. 23 
Crystalline rocks of the prevolcanic plateau. 23 
Form of the volcanic neck. : . 24 
Breccia. 30 
Local bedding. 30 
Carbonaceous material. 31 
Intrusive masses within the volcanic neck. 32 
Outlying intrusive masses. 34 
Dikes of the volcanic period. 35 
Topographic development. 36 
Introduction. 36 
Prevolcanic conditions. 36 
Epoch of construction. 38 
Epoch of destruction. 39 
Chapter III.—Description and petrology of the metamorphic and igneous rocks, by L. C. Graton. 41 
Introduction. 41 
Plan and scope of the investigation. 41 
Outline of the rock formations. 42 
Ancient crystalline rocks. 43 
Granite. 43 
Pikes Peak granite. 43 
Cripple Creek granite. 45 
« Spring Creek granite. 47 
Relative age of the granites. 47 
Pegmatite. 48 
Gneiss. 48 
Womack gneiss. 48 
Other varieties. 50 
hi 
