Continental-Crust Structures on the Continental Margin of Western North America

1996 ◽  
Keyword(s):  
North America ◽  
Continental Crust ◽  
Continental Margin ◽  
Western North America

Sedimentary basins developed during evolution of Mesozoic–Cenozoic arc–trench system in western North America

1976 ◽  
Vol 13 (9) ◽  
pp. 1268-1287 ◽  
Author(s):  
William R. Dickinson
Keyword(s):  
North America ◽  
Continental Margin ◽  
Active Continental Margin ◽  
Foreland Basin ◽  
Sedimentary Basins ◽  
Western North America ◽  
Late Mesozoic ◽  
Continental Block ◽  
Forearc Basins ◽  
Tectonic System

Development of Mesozoic and Cenozoic sedimentary basins in western North America was linked to the overall geodynamics of an active continental margin. The Cordilleran margin, now largely of Californian-type with a bounding transform, was Atlantic-type from late Precambrian to early Paleozoic, Japanese-type from late Paleozoic to early Mesozoic, and Andean-type from late Mesozoic to early Tertiary, when a continental-margin arc–trench system included the following tectonic elements from west to east: (a) the subduction complex at the main subduction zone; (b) forearc basins within the arc–trench gap; (c) the magmatic arc of generally andesitic volcanics and subjacent granitic plutons; (d) a backarc fold-thrust belt, commonly with an associated metamorphic infrastructure; and (e) the retroarc foreland basin adjacent to the craton. Progressive broadening of this tectonic system was achieved by tectonic accretion of oceanic elements to the edge of the continental block and by peeling of cover off rigid basement underthrust behind the arc along the edge of a zone of ductile lithosphere formed thermally beneath the arc. An initial Jurassic island arc evolved through the Cretaceous into a terrestrial Tertiary arc as subsiding forearc and retroarc basins were filled with sediment.

Synthesis and Future Directions

2007 ◽  
Author(s):  
Earl B. Alexander ◽  
Roger G. Coleman ◽  
Todd Keeler-Wolfe ◽  
Susan P. Harrison
Keyword(s):  
North America ◽  
Continental Crust ◽  
Ultramafic Rocks ◽  
Western North America ◽  
Ocean Crust ◽  
The Earth ◽  
History Of ◽  
Serpentine Vegetation ◽  
Oceanic Plates ◽  
Eukaryotic Organisms

Ultramafic rocks come from deep within the earth. Most rocks on the surface of the earth are quite different from them. Unique rocks make unique soils and support special plants. Exploring the links and interactions among these unique rocks, soils, and vegetation is an interdisciplinary endeavor that has been accomplished by experts in three areas. It has helped elucidate serpentine rock–soil–plant relationships and provide a rationale for the unusual soil properties and vegetation associated with ultramafic rocks. Examples from arctic tundra to temperate rainforest and hot desert in western North America provide a framework for the investigation of serpentine geoecosystems around the world. The unusual character of most serpentine vegetation is readily apparent even to an untrained eye. Although a vast number of rock and soil types make up the earth’s surface, few have as dramatic and visible effects on ecosystems as do ultramafic, or serpentine materials. Most ultramafic rocks in western North America have been derived from the mantle of earth via ocean crust. Magnesium is highly concentrated in the mantle and calcium, potassium, and phosphorous are relatively low. Calcium and potassium are further depleted from peridotite in the partial melting of ultramafic rock at the base of the ocean crust. As oceanic plates drift from spreading centers, most of the ocean crust is subducted and returns to the mantle (chapter 2). Only relatively small fragments of ocean crust are added to the continents. Because eukaryotic organisms, from protozoa to plants and animals, have evolved on continental crust, they are adapted to soils with higher concentrations of calcium, potassium, and phosphorus (elements with higher concentrations in continental crust than in ultramafic rocks from the base of the ocean crust) and much lower concentrations of magnesium. Having evolved on continents, plants depend on relatively high ratios of calcium and potassium to magnesium, elements that they use for a wide range of physiological functions. Although there has been a long history of evolutionary adaptation to the chemistry of the continental crust, special adaptations have allowed some plants to colonize the atypical conditions of serpentine.

Nitrogen cycling within suboxic and anoxic sediments from the continental margin of Western North America

2012 ◽  
Vol 128-129 ◽  
pp. 13-25 ◽  
Author(s):  
Lauren S. Chong ◽  
Maria G. Prokopenko ◽  
William M. Berelson ◽  
Amy Townsend-Small ◽  
James McManus
Keyword(s):  
North America ◽  
Nitrogen Cycling ◽  
Continental Margin ◽  
Western North America ◽  
Anoxic Sediments
Sign in / Sign up

Export Citation Format

Share Document