PRAIRIE PEAK and PLATEAU

A GUIDE TO THE GEOLOGY OF COLORADO

by John and Halka Chronic

COLORADO GEOLOGICAL SURVEY BULLETIN 32 1972

Available from Colorado Geological Survey 1845 Sherman Street Denver, Colorado 80203 Price—$2.00

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ACKNOWLEDGMENTS

This guidebook was written at the request of the Colorado Geological Survey to fulfill a long-felt need for a popular account of the state’s geology and its relationship to Man.

The authors wish to thank those of their colleagues who have assisted at various times in the preparation of this book. John Rold, Colorado State Geologist, and William Weber, of the University of Colorado Museum staff, made many helpful suggestions concerning the manuscript. John Schooland, vice president of the Colorado Historical Society, generously provided several pictures of early mining activities in Colorado. Permission to reproduce drawings and paintings of fossils and reconstructions of past environments was granted by the American Museum of Natural History and the University of Colorado Museum. Drawings, maps, and diagrams are largely the work of Robert Maurer, who also designed the cover and title page.

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Tilted dark red sedimentary rocks of the Pennsylvanian-Permian Maroon Formation are well exposed in the cliffs of Maroon Bells, southwest of Aspen. (Photo courtesy Hydraulic Unlimited Mfg. Co.)

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CONTENTS

Page

Introduction 1

I Colorado’s Three Provinces 3

The Prairies 8

The Peaks 10

Front Range 11

Wet Mountains 16

Sangre de Cristo Range and Spanish Peaks 17

Park Range and Rabbit Ears Range 19

Gore Range 20

Tenmile and Mosquito Ranges 21

Sawatch Range 22

Elk Mountains and West Elk Mountains 24

San Juan Mountains 25

Uinta Mountains 26

The Plateaus 28

II Geologic History of Colorado 32

Precambrian Era 33

Paleozoic Era 38

Cambrian Period 39

Ordovician Period 40

Silurian Period 42

Devonian Period 42

Mississippian Period 43

Pennsylvanian Period 44

Permian Period 48

Mesozoic Era 51

Triassic Period 51

Jurassic Period 52

Cretaceous Period 56

Cenozoic Era 59

Tertiary Period 59

Quaternary Period 68

III Geology and Man in Colorado 74

Gold, Silver, and Other Metals 77

Boulder County 79

Central City and Idaho Springs 80

Georgetown, Empire, and Silver Plume 81

Leadville 82

Breckenridge 83

Fairplay 84

Silverton 85

Ouray 87

Aspen 88

Creede 89

Cripple Creek 90

Climax 91

Radium, Uranium, and Vanadium 93

Oil, Natural Gas, and Oil Shale 94

Coal 96

Construction Materials 97

Sand, Gravel, and Clay 97

Stone 99

Lime and Gypsum 101

Gems 102

Water 103

Surface Water 103

Groundwater 105

Caves 106

Springs 109

Environmental Geology 111

Glossary 114

Suggested Reading 119

Index 121

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ILLUSTRATIONS

Page

Colorado’s three geologic provinces 2

Pikes Peak, seen from the Garden of the Gods 4

Rock classification (chart) 5

Stratigraphic column (chart) 7

Jurassic rocks in Colorado (map) 9

East face of Longs Peak 11

Rocky Mountain National Park (east-west profile) 12

Big Thompson Canyon, west of Loveland 13

Red Rocks Amphitheater, west of Denver 14

Colorado Springs area (map and cross section) 15

Joint systems in Precambrian rocks, Boulder Canyon 15

Spanish Peaks, southwest of Walsenburg 18

Hahn’s Peak, north of Steamboat Springs 19

Gore Range from the east 20

Aspen Mountain geology (map) 23

Mt. Sopris, south of Glenwood Springs 24

Ouray, in the San Juan Mountains 25

Steamboat Rock, Dinosaur National Monument 27

Grand Hogback, near Rifle (block diagram) 28

Mt. Garfield, near Grand Junction 30

Precambrian-Cambrian unconformity south of Ouray 34

Geologic map of Colorado 35

Black Canyon of the Gunnison National Monument 36

Precambrian-Cambrian unconformity, Glenwood Canyon 38

Cambrian fossils 39

Ordovician fossils 41

Devonian fossils 43

Mississippian fossils 44

Pennsylvanian paleogeography (map) 45

Fountain Formation northwest of Denver 45

Pennsylvanian fossils 46

Contorted Pennsylvanian rocks near Gypsum 46

Balanced Rock, Garden of the Gods 48

Permian reptile tracks 49

The Flatirons, near Boulder 50

Colorado National Monument 51

Morrison Formation, west of Denver 53

Dinosaur bones, found near Morrison 54

Dakota Sandstone hogback 56

Cretaceous fossils 57

Wolford Mountain, north of Kremmling 60

Eohippus, the “Dawn Horse” 61

Golden and South Table Mountain 62

Devil’s Staircase, near Spanish Peaks 63

Green River oil shale, west of Rifle 64

Florissant Fossil Beds National Monument 65

Pawnee Buttes, north of Fort Morgan 66

Fossil mammals, northeastern Colorado 67

Glacial lakes in Rocky Mountain National Park 68

Arapaho Glacier, west of Boulder 70

Pleistocene mastodons 72

Great Sand Dunes National Monument 73

Colorado Mineral Belt (map) 78

Sluicebox mining in early Colorado 81

Early-day Leadville 82

Gold dredge, Fairplay 84

Silverton, in the San Juan Mountains 86

Abrams Mountain, south of Ouray 87

Creede and its mines (map) 89

Cripple Creek, near Pikes Peak 90

Climax molybdenum mine (cross section) 91

Rampart Range quarry, near Colorado Springs 98

Yule Marble quarry, near the town of Marble 99

Lyons Sandstone quarry 100

University of Colorado Museum 100

Colorado-Big Thompson Project (cross section) 103

San Luis Valley (cross section) 105

Cave of the Winds, near Manitou 107

Mesa Verde cave and Indian dwellings 108

Glenwood Hot Springs 109

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