The tectonics of North America — A discussion to accompany the tectonic map of North America, Scale 1:5,000,000
Year: 1969
Type: report
Abstract: The "Tectonic Map of North America," on a scale of 1: 5,000,000, has been compiled by the United States Geological Survey in collaboration with other national geological surveys, and with the assistance of various individuals.The compilers made use of tectonic maps of some of the countries maps that have been published or are in process of publication.In addition, many other basic maps and reports were consulted.North America is divided technically into foldbelts of different ages and platform areas where flat-lying or gently tilted rocks lie upon basements of earlier foldbelts.The two most extensive platform areas are those with Precambrian basement in the central craton, and those with Paleozoic basement in the Atlantic and Gulf Coastal Plains.Configuration of the upper surface of the basement beneath the platforms is shown by contours on a 500-meter interval.The foldbelts include three of Precambrian age whose principal exposures are in the Canadian Shield, but which also emerge in various outlying areas.The foldbelts of younger ages lie nearer the edges of the continent, and include four that are mainly of Paleozoic age, two that are mainly of Mesozoic age, and two that are mainly of Cenozoic age.Each foldbelt was formed during a geotectonic cycle many geologic periods in length, beginning with a geosynclinal phase, passing through a time of orogeny, and ending with a postorogenic phase.On the "Tectonic Map of North America" the foldbelts are distinguished by different colors according to age; where several significant times of deformation occurred within them, these are represented by tints of the prevailing colors.The different kinds of rocks which make up the foldbelts are shown by patterns of these colors.In the foldbelts, the principal sedimentary rock units on the map are those which formed in the eugeosynclinal and miogeosynclinal areas.In some foldbelts, deposits are preserved which were laid down in successor basins during or shortly after the main orogenies.In the foldbelts of western North America various subdivisions are also shown in the Cenozoic sedimentary rocks and terrestrial volcanic rocks.Among the plutonic rocks of the foldbelts, granitic rocks are most extensive; they form large to small masses mainly in the eugeosynclinal areas.More mafic and more alkalic varieties are separately indicated.Ultramafic rocks are important in places, especially near the Pacific Coast and in tine Caribbean region; most of these were emplaced in their present positions by tectonic rather than by magmatic processes.THE TECTONICS OF NORTH AMERICA 26.Upper structural stage, regional depressions ( Ural foreland, OarboniferouSj-Triassici; Kuznets, Carboniferous-Triassic Taimyr foreland, Permian-Triassic; Donetz, Carboniferous-Permian). Intrusive igneous rocks: Ultramafic intrusives, Caledonian granitoids, granitoids undivided, late Hercynian granitoids, and alkalic intrusives."TECTONIC MAP OF EUROPE" Region* of Variacan or Hercynian folding KV.Reworked massifs of Karelian and older folding (Sudetes, Armorica, Bohemia).BV.Reworked massifs of Baikalian folding.CV.Reworked massifs of Caledonian folding.VB, etc. Ancient cores reworked by Variscan folding (various ages indicated by second index letter).Migmatized older Paleozoic and Precambrian of Ural*.Bugeosynclinal (interior) zones eV.Undivided.eVl.Lower structural stage (western Europe, Cambrian-Silurian ; Great Caucasus, Riphean-Paleozoic i; Ural, Paleozoic i-Devonian a) .eV2.Middle structural stage (western Europe and Or eat Caucasus, Devonian-Carboniferousi; Balkans and Anatolia, Silurian-Carboniferousi; Ural, Devonian»-Carbonif er-OUSl).Miogeosynclinal (exterior) zones mV.Undivided (south Ireland and Trans-Caspian region, Devonian-Carboniferous). mVl.Lower structural stage (western Europe, Cambrian-Devonian; Armorica
Source: USGS professional paper
DOI: 10.3133/pp628
Author: P. B. King
Language: English
Subfield: Geology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1908442502