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[Illustration: THE GRAND CANYON—1. SCHISTS AND GRANITES (ARCHEAN ERA):
2. SANDSTONES, LIMESTONES, SHALES (ALGONKIAN ERA): 3. TONTO FORMATIONS
(CAMBRIAN PERIOD): 4. REDWALL LIMESTONE (MISSISSIPPIAN PERIOD): 5. SUPAI
SANDSTONE AND SHALE (PERMIAN PERIOD): 6. HERMIT SHALE (PERMIAN PERIOD):
7. COCONINO SANDSTONE (PERMIAN PERIOD): 8. TOROWEAP AND KAIBAB
FORMATIONS (PERMIAN PERIOD).
NATIONAL PARK SERVICE]
ANCIENT LANDSCAPES OF THE GRAND CANYON REGION
The Geology of Grand Canyon, Zion, Bryce, Petrified Forest & Painted
Desert
by
EDWIN D. McKEE, Asst. Director
Museum of Northern Arizona
Sketches and Charts by Louis Schellbach 3rd Park Naturalist, Grand
Canyon National Park, and Russell Hastings
Published by
Edwin D. McKee
1931
Copyright 1931
Edwin D. McKee
Thirteenth Edition, 1952
Printed by
Coconino Sun Co.
Flagstaff, Arizona
TABLE OF CONTENTS
PAGE
Introduction ix
Chapter I—The Archean Era 1
The Earth’s Oldest Rocks, Grand Canyon 2
Granite in Grand Canyon 4
Chapter II—The Algonkian Era 5
Algonkian Rocks in Grand Canyon 5
Formation of Mountains 6
Early Climates 6
Oldest Known Life 7
Chapter III—The Paleozoic Era 9
First Animal Life—The Tonto Rocks 9
The Missing Periods of the Third Era 11
The Age of Fish 12
Sea Life From the North—Redwall Limestone 12
Tracks in the Supai Sandstone 14
Landscapes of the Hermit Shale 15
Wind-blown Sand—The Coconino Sandstone 17
Warm Seas from the West—The Toroweap and Kaibab Formations 18
Chapter IV—The Mesozoic Era 21
Remnants of Younger Strata—Red Butte and Cedar Mountain 21
The Petrified Forest 22
Dinosaur Tracks—The Painted Desert 24
The Rocks of Zion Canyon and Rainbow Natural Bridge 26
From Seashells to Coalbeds 27
Chapter V—The Cenozoic Era 29
Bryce Canyon Formation 30
A Great Erosion Surface 32
Crustal Movement at Grand Canyon 33
Cutting the Grand Canyon 34
The Forming of Zion Canyon 37
Glaciers 38
San Francisco Mountain Volcanic Field 39
Elephants and Camels 41
Advent of Man in the Southwest 42
Bibliography 45
ILLUSTRATIONS
PAGE
The Grand Canyon Frontispiece
Diagrammatic Sections of Grand Canyon Region x
Rocks of First Era, Inner Gorge of Grand Canyon 1
Block Diagrams of Events of First Era 3
Tilted Rocks of the Second Era, Grand Canyon 5
Diagrammatic Section of Third Era Formations, Grand Canyon 8
Scene on Cambrian Sea Floor in Grand Canyon Region 10
Trilobites Preserved in Green Shale of Grand Canyon Walls 11
A Fresh-water Fish of Devonian Age (Sketch) 12
Sea Life from the Redwall, Grand Canyon (Sketches) 12
Havasu Falls in Redwall Limestone, Grand Canyon 13
Tracks of Short-legged, Prehistoric Animal, Supai Formation, Grand
Canyon 14
Landscape at Time Hermit Shale was Forming 15
Fossil Fern From the Hermit Shale, Grand Canyon 15
Wind-blown Sand, Coconino Formation, Grand Canyon 17
Tracks of Primitive Four-footed Animals, Coconino Sandstone, Grand
Canyon 17
Marine Life From the Kaibab Limestone, Grand Canyon (Sketches) 18, 19
Diagrammatic Section of Fourth Era Formations, Southern Utah and
Painted Desert Regions 20
Cedar Mountain 22
Red Butte 22
Petrified Forest, Arizona 23
Petrified Logs of Triassic Age 23
Dinosaur Tracks, Painted Desert 24
The Painted Desert 25
Zion Canyon, Navajo Sandstone 26
Rainbow Natural Bridge, Navajo Sandstone 26
Cretaceous Shells From Southern Utah (Sketches) 27
Coal Canyon, Painted Desert Country 28
Bryce Canyon 30
Map of Colorado River 31
A Great Erosion Surface 32
Diagrammatic Cross Sections of Grand Canyon 35
The Grand Canyon 36
Zion Canyon 37
Chart of San Francisco Mountains 39
San Francisco Mountain—Past and Present (Sketch) 40
Map of San Francisco Mountain Volcanic Field 40
San Francisco Mountain 41
Elephant and Camel Remains 42
Ancient Indian Petroglyphs, Head of Bright Angel Trail, Grand
Canyon 43
INTRODUCTION
Probably no place in the world of similar area has recorded a more
complete or a more interesting resume of the earth’s history than has
the high plateau country of northern Arizona and southern Utah. Although
many great events and some long intervals of time are not represented by
the formations of this region, yet of the five major chapters or eras
into which all of time has been divided by geologists, at least some
parts of each have left their traces in this area.
Whether on the brink of the mighty Grand Canyon, among beautiful logs of
the Petrified Forest, or beneath the lofty walls of Zion—the “Rainbow of
the Desert”—one looks upon rocks which are not alone curious or
colorful, but which are also records of the past inscribed and
illustrated in an intensely interesting manner. In one place is seen the
sand of ancient dunes, in another the border of an early sea, or perhaps
the floodplain of mighty rivers, and in all of these remain the
unmistakable evidences of life—plants and animals preserved to make a
reality of the living, moving past. Everywhere are found the evidences
of those great processes of nature—erosion of the high country, land
formation in the low country, and mighty crustal movements slowly
raising or lowering the land in both.
From the rim of Grand Canyon one not only looks down through tremendous
space, but also through time, glimpsing the record of vast ages,
measurable not in centuries but in millions and even hundreds of
millions of years. There in the bottom of that mighty chasm are found
rocks formed during the first and oldest era—rocks in which the original
structure has been entirely modified by great heat and pressure and in
which no evidence of life has been found. There in the Grand Canyon are
also seen two other great series of rocks, those of the second era which
are partially altered and which contain earliest traces of plants, and
those of the succeeding era in which are preserved primitive animals of
many types.
[Illustration: NORTH-SOUTH CROSS-SECTION OF THE GRAND CANYON REGION;
EAST-WEST CROSS-SECTION OF THE GRAND CANYON REGION]
Rocks of the fourth great era—the age of dinosaurs—lend color to the
Painted Desert, and to the sheer walls of Zion Canyon. Beautiful little
Bryce Canyon to the north boasts of some of the most recently formed
rocks in the region—those of the fifth and last era, the age of mammals.
The great volcanic mountains and the marvelous features of erosion, such
as the canyons and the desert cliffs, are also developments of this most
recent chapter. In brief, the Grand Canyon region affords some
wonderfully interesting glimpses of ancient landscapes during many
different parts of the earth’s history, and these make the past a
moving, living thing.
CHAPTER I
THE ARCHEAN ERA
[Illustration: ROCKS OF FIRST ERA. INNER GORGE OF GRAND CANYON]
THE EARTH’S OLDEST ROCKS
(THE ARCHEAN ERA)
Looking into the depths of Grand Canyon from any point within the Bright
Angel section, one is immediately impressed by the narrow V-shaped gorge
cut in the black rocks at the bottom. This is popularly termed the
Granite or Inner Gorge. Within its walls one is in another world, both
scenically and geologically. Their steep, bare sides, whose surfaces are
chaotic in the extreme, have a history—long and complex. The rocks of
which they are formed—some of the oldest known today on the surface of
the earth—partially tell the story of the first great era in geologic
history.
Other rocks of this, the Archean age, are found in the Rockies, in the
Adirondacks of New York, and to a very great extent in eastern Canada.
In the last named place they contain valuable deposits of iron, nickel,
cobalt, and copper. Rocks which probably also correspond in age occur in
Scandinavia, Brazil, China, India, and central Africa.
At the Grand Canyon, although we are impressed by the depth of the dark
Archean rocks, beneath the plateau surface approximately a mile, yet we
marvel even more when we contemplate their great age and the important
series of events whose history they partially record. Built up
originally as great horizontal deposits of sand and mud, they were bent
by mighty crustal movements until high mountains, probably comparable to
the present Alps, were formed. Pressures from the northwest and
southeast apparently folded them. The rocks themselves were greatly
compressed and heated, with the result that complete recrystallization
and the development of a banded structure were brought about. The
present vertical attitude of these ancient beds, together with their
dense crystalline character, is evidence of the great depth at which
they were formed and of the extreme pressures to which they were
subjected. In brief, the rocks that we see today in the Canyon bottom
represent merely the roots of once lofty mountains, and the flat surface
cut on these rocks is an old plain that resulted from the wearing down
of high country in this region.
[Illustration: BLOCK DIAGRAMS OF EVENTS OF FIRST ERA]
1 Sands and Muds accumulated to form rock strata.
2 The strata were folded into high mountains. Heat and pressure changed
both structure and composition of the lower rocks during the folding.
3 Molten masses were forced up into cracks from below. Upon cooling they
formed lavas on the surface and granites beneath.
4 During a tremendously long period of time the rivers and rains slowly
widened the valleys and wore down the ancient mountains to a great plain
near sea level.
As yet no definite traces of either plant or animal life have been found
in rocks of the Archean age in Grand Canyon. Though various forms of
life may have existed then, and may have been preserved in the original
rocks, their record has since been entirely removed by those extreme
pressures which altered even the composition and structure of the rocks
themselves.
GRANITE IN GRAND CANYON
(THE ARCHEAN ERA)
Within the black, crystalline rocks of the Inner Gorge may be seen many
large streaks, bands or irregular masses of a lighter color. From the
Canyon rim these appear white, but from nearby they are usually pink.
These light colored rocks are granites with a coarse crystalline
texture.
Granites derive their name from their granular texture. They are formed
by the slow cooling of molten masses that have been forced into older
rocks from the earth’s interior. From a similar source are formed lavas
and volcanic ash, but these flow out or are ejected on the surface of
the earth where they cool so rapidly that no crystals form.
Exceptionally fast cooling or chilling of molten masses, moreover, forms
volcanic glass or obsidian. It is by the application of this same
principle that crystal forming is prevented in the manufacture of common
glass.
The large size of the crystals forming the granite that fills cracks and
fissures of the Inner Gorge at Grand Canyon indicates the considerable
depth at which it was formed and is further evidence of the great
mountains that existed in this region during the first era in geologic
history.