The Tectonics of North America A Discussion to Accompany the Tectonic Map of North America ...

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The Tectonics of North America
A Discussion to Accompany the
Tectonic Map of North America
Scale 1:5,000,000
GEOLOGICAL SURVEY PROFESSIONAL PAPER 628

The Tectonics of North America
A Discussion to Accompany the
Tectonic Map of North America
Scale 1:5,000,000
By PHILIP B. KING
GEOLOGICAL SURVEY PROFESSIONAL PAPER 628
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR
JAMES G. WATT, Secretary
GEOLOGICAL SURVEY
Dallas L. Peck, Director
First printing 1969
Second printing 1970
Third printing 1970
Fourth printing 1978
Fifth printing 1981
For sale by the Distribution Branch, U.S. Geological Survey,
604 South Pickett Street, Alexandria, VA 22304
CONTENTS
Page "The Tectonic Map of North America" Continued Pw
Abstract..._______________________________________ 1 Phanerozoic foldbelts Continued
Introduction __ ___ __ ____ ___________ 1 Sedimentary units______________ ________ 4C
Tectonic maps defined ___________________________ 1 Geosynclinal deposits.... __ 46
Historical sketch __ ______ _____________ 2 Eugeosynclinal deposits _ _ 47
Appraisal of existing tectonic maps ________________ 7 Miogeosynclinal deposits. _____________ 47
Representation of platform areas_________________ 8 Metamorphism of geosynclinal deposits..__ 4P
Representation of foldbelts_____________________ 8 Deposits of successor basins....__________ 4P
"Tectonic Map of United States"_____ ^_ 8 Younger basinal deposits.__ ______ 50
"Tectonic Map of Australia".________________ 9 Thick deposits in structurally negative
"Tectonic Map of U.S.S.R. and Adjacent Areas," areas._________________ ____________ 50
and "Tectonic Map of Europe"_________ 9 Volcanic units_______________ _ 50
"Tectonic Map of Canada"___________ 11 Plutonic units____________ ______ 51
"Tectonic Map of Mexico" and "Tectonic Map Granitic rocks.______ _ __ 51
of U.S.S.R."___________________________ 15 Mafic plutonic rocks_____ 5?
Representation of subsea areas.______________ 17 Ultramafic rocks______________________ 5?
"The Tectonic Map of North America".-_____________ 18 Description of foldbelts____________________ 5f
Compilation of the map_________________________ 18 (K) Innuitian foldbelt____________
Specifications of the map____________________ 19 (J) East Greenland foldbelt_________
Platform areas.______________________________ 21 (L) Appalachian foldbelt..______________ 56
(A) Platform areas within the Precambrian. ___ 21 Northern Appalachians.__________ 56
(B) Platform deposits on Precambrian base Southern Appalachians.____________ 5f
ment _________________________________ 22 (M) Ouachita foldbelt____________ 61
(C) Platform deposits on Paleozoic basement. _ 24 Structural systems related to Ouachita
(D) Platform deposits on Mesozoic basement. _ 27 foldbelt-..._____________. 64
(E) Volcanic rocks and associated sediments of (O) Cordilleran foldbelt____________ 64
North Atlantic province.________________ 27 Northern Cordillera___________ 65
(F) Icecaps________________________________ 29 Central Cordillera. __ __________ 6r
Foldbelts of Precambrian age_________________ 30 Southern Cordillera_______.___ 7?
Stratigrapbic classification._________________ 30 (P) Pacific foldbelt______________ 74
Tectonic classification. ______________________ 32 Alaska. ____________________ 7ft
Foldbelts of Canadian Shield_________________ 33 Washington and Oregon. 7ft
Foldbelts of Greenland________________ 36 California and Baja California.__... 76
Foldbelts south of Canadian Shield. __________ 37 (Q) Antillean foldbelt_____________ 77
Precambrian of northern South America______ 42 (N) Andean foldbelt______________ 7f
Phanerozoic foldbelts ___________________ 43 Subsea areas______________________ 80
The tectonic cycle_______________ 43 Fault zones______________________ 81
Terminology _________________________ 44 Glossary.____________________________ 8f
Geosyncline___________.._____________ 44 References cited______________________ 87
Orogeny______________________ 44 Index of units on "Tectonic Map of North America"
Names of orogenies..._____________ 45 which are referred to in text_______________ 9f
m
IV CONTENTS
ILLUSTRATIONS
Page
FIQTJRE 1. Structural map of Bighorn Mountains uplift, Wyoming and Montana, by N. H. Darton___________________ 2
2. Structural maps of the Jura Mountains, Switzerland, after Albert Heim____________________________ 3
3. Tectonic map of the Alps, by Rudolf Staub____--_-____- __ _______________________________________ 4
4. Tectonic sketch map showing the chief belts of folding in the American Cordilleran system, by Hans StillS__ 6
5. Maps of eastern Tennessee and western North Carolina showing three methods of representing the geology.__ 13
6. Tectonic map of north-central Nevada showing "structural stages" in an area of complex superposed rocks and
structures.-_____-_--__-_-_-_-------_---------------------_------- _____ __ ___ 14
7. Map of Gulf Coastal Plain in Texas, Louisiana, and Mississippi showing structure contours on two horizons in the
strata of the platform cover_________________-________-__-_-_____-_--__-___________ ____________ 26
8. Map of North Atlantic Ocean and adjacent lands showing plateau basalts of North Atlantic province. ______ 28
9. Map of the Canadian Shield showing provinces that contain Precambrian rocks of different ages.______________ 34
10. Map of North America showing inferred extent of exposed and buried provinces of Precambrian rocks__ 39
11. Map of northeastern Greenland showing inferred extent of the late Precambrian Carolinidian foldbelt._______ 55
12. Tectonic maps of the two larger areas of exposure of the Ouachita foldbelt_________________________________ 62
13. Map of northern Nevada showing extent of Antler orogenic belt of middle Paleozoic time___________________ 71
14. Map showing transverse structural features in the southern part of the area of the "Tectonic Map of North
America," and in adjacent regions_______________-_-_---_---_--__-_____________________________ 82
TABLES
Page
TABLE 1. Comparison of various classifications of the Precambrian-__.__________________________ ___________ __ 31
2. Classification of orogenies in Canadian Shield_______-_____--_--_-_-___---_-__-__-_- __ ___ 33
3. Summary of Precambrian rocks and events south of Canadian Shield______________ , ______________._ 40
THE TECTONICS OF NORTH AMERICA A DISCUSSION TO ACCOMPANY THE TECTONIC
MAP OF NORTH AMERICA, SCALE 1:5,000,000
By PHILIP B. KING
ABSTRACT use and understanding of the map, by providing expla
The "Tectonic Map of North America," on a scale of nations more lengthy than could be included in th^
1: 5,000,000, has been compiled by the United States Geologi
legend of the map itself. Such a discussion is the mor>
cal Survey in collaboration with other national geological sur
desirable because the map embodies innovations derived-
veys, and with the assistance of various individuals. The
compilers made use of tectonic maps of some of the countries partly from techniques of tectonic mapping that hav
maps that have been published or are in process of publication. been developed during the last few decades by geologists
In addition, many other basic maps and reports were consulted. in other countries, and that may not as yet be well
North America is divided technically into foldbelts of dif
known, or be well understood in North America.
ferent ages and platform areas where flat-lying or gently tilted
rocks lie upon basements of earlier foldbelts. The two most
TECTONIC MAPS DEFINED
extensive platform areas are those with Precambrian basement
in the central craton, and those with Paleozoic basement in the A tectonic map portrays the architecture of the up
Atlantic and Gulf Coastal Plains. Configuration of the upper
per part of the earth's crust that is, the features prc -
surface of the basement beneath the platforms is shown by
duced by deformation and other earth forces and rep
contours on a 500-meter interval.
resents this architecture by means of symbols, pattern1"
The foldbelts include three of Precambrian age whose principal
exposures are in the Canadian Shield, but which also emerge and colors. Such a map differs from the more familir.r
in various outlying areas. The foldbelts of younger ages lie areal geologic map, whose primary aim is to represent
nearer the edges of the continent, and include four that are the surface distribution of rocks of various kinds and
mainly of Paleozoic age, two that are mainly of Mesozoic age,
ages. Nevertheless, most tectonic maps contain some in
and two that are mainly of Cenozoic age. Each foldbelt was
dication of the ages and kinds of rocks from which th^
formed during a geotectonic cycle many geologic periods in
length, beginning with a geosynclinal phase, passing through structures were made, and areal geologic maps contain
a time of orogeny, and ending with a postorogenic phase. some indication of the structures of the rocks repre
On the "Tectonic Map of North America" the foldbelts are sented, so that distinctions between the two kinds of
distinguished by different colors according to age; where several
maps are not absolute. Tectonic maps are nearly synony
significant times of deformation occurred within them, these
mous with structural maps, just as the subject of teu
are represented by tints of the prevailing colors. The different
kinds of rocks which make up the foldbelts are shown by pat tonics is nearly synonymous with that of structural
terns of these colors. geology. Nevertheless, geologists commonly make a
In the foldbelts, the principal sedimentary rock units on vague distinction between structural geology and struc
the map are those which formed in the eugeosynclinal and tural maps, which deal primarily with the description,
miogeosynclinal areas. In some foldbelts, deposits are preserved
representation, and analysis of structures, mostly on a
which were laid down in successor basins during or shortly
restricted scale, and tectonics and tectonic maps, which
after the main orogenies. In the foldbelts of western North
America various subdivisions are also shown in the Cenozoic synthesize these data over greater areas, inevitably with
sedimentary rocks and terrestrial volcanic rocks. a larger amount of interpretation.
Among the plutonic rocks of the foldbelts, granitic rocks Many other kinds of maps are being made which
are most extensive; they form large to small masses mainly
show earth features, some of which resemble and some
in the eugeosynclinal areas. More mafic and more alkalic vari
of which differ from tectonic maps as here defined:
eties are separately indicated. Ultramafic rocks are important
in places, especially near the Pacific Coast and in tine Caribbean 1. Paleotectonic maps show geologic and tectonic
region; most of these were emplaced in their present positions features as they existed at various times durir^r
by tectonic rather than by magmatic processes. the geologic past, rather than the sum of the tev
tonics as it exists today. Most of the paleotectonic
INTRODUCTION
maps that nave been made portray in much detail
This discussion is a companion to the "Tectonic Map the sedimentary facies and the thickness of strata
of North America," which is being published separately in the cratonic areas, but show few of these details
by the U.S. Geological Survey. It is intended to aid the in the more intensely deformed areas.
THE TECTONICS OF NORTH AMERICA
2. Neotectonic maps are a kind of paleotectonic map in in the "Bulletin of the American Association of Pe
that they represent the tectonic features produced troleum Geologists." A parallel evolution of structural
during one part of geologic time, in this case the and tectonic maps occurred in Europe, where notable
Quaternary or at most the Quaternary and latest maps have portrayed, for example, the folds and faults
Tertiary. Because of the epeirogenic nature of of the Jura Mountains (fig. 2), and the superposed
much of this latest deformation, neotectonic maps nappes and structural layers in the Alps (fig. 3).
emphasize the broad upwarps and downwarps of
the crust.
3. Paleogeographic maps show the probable extent of
lands and seas as they existed at various times dur
ing the geologic past. They thus resemble paleotec
tonic maps, but involve a much greater element of
interpretation.
4. Paleogeologic maps show the areal geology of a sur
face of unconformity that has been covered by a
younger body of strata. This buried areal geology
has tectonic significance, but it is generally not
feasible to represent it on a tectonic map; tectonic
maps and paleogeologic maps should supplement
rather than duplicate each other.
5. Geophysical maps show the instrumentally deter
mined values of gravity, magnetic intensity, or
other physical properties of the earth, generally
by means of contours. The contours express nu
merical values produced by the summation of many
earth processes, not all of which are known. The
data are not themselves tectonic, although many
of them have ultimate tectonic causes. Interpreta
tions of these geophysical data are frequently
helpful in making tectonic maps.
HISTORICAL SKETCH
Geologists have been making structural and tectonic
maps since the early days of the science. Even some of
the early structural maps showed folds, faults, and
structure contours in much detail, but most of them
dealt with rather small areas on large scales. On the
other hand, the earlier tectonic maps, covering larger
areas such as whole countries, continents, or the world,
were on small scales and were primarily intended to por
tray the tectonic or the historical-geological predilec
tions of their authors. Only in recent decades have tec
tonic maps approached the scope and refinement of
areal geologic maps.
In the United States, many excellent structural maps
appeared during the first part of the century in the
FIGURE 1. Structural map of Bighorn Mounts ins uplift,
folios and professional papers of the U.S. Geological
Wyoming and Montana, by N. H. Darton (Darton and
Survey; among these, the structural maps by N. H. Salisbury, 1906, p. 13). Configuration of uplift shown by
Barton of various areas in the Western States are contours on base of Madison Limestone. Dashed lines show
approximate configuration where all sedimentary rocks
classic (fig. 1). Since 1916, many excellent structural
have been removed by erosion. Heavy lines are faults.
maps of small to large areas have also been published
Stippled, areas are covered by Tertiary deposits.
HISTORICAL SKETCH
FIGURE 2. Structural maps of the Jura Mountains, Switzerland, showing folds and faults: A. Part of a
detailed map. B, Generalized map of the whole area. Copied from Albert Heim (1919, pi. 20 and fig. 103).
Longitude is in degrees east of Paris.
THE TECTONICS OF NORTH AMERICA
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