geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a

tectonic plate Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

(or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from the surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault. A

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

deposit that buries the contact of the terrane with adjacent rock is called an overlap formation. An

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a stitching pluton. There is also an older usage of the term ''terrane'', which described a series of related rock formations or an area with a preponderance of a particular rock or rock group.

Overview

A tectonostratigraphic terrane did not necessarily originate as an independent microplate, since it may not contain the full thickness of the

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...

. It is a piece of crust that has been transported laterally, usually as part of a larger plate, and is relatively buoyant due to thickness or low density. When the plate of which it was a part subducted under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. Therefore, the terrane transferred from one plate to the other. Typically, accreting terranes are portions of

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

which have

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben ...

ed off another continental mass and been transported surrounded by oceanic crust, or they are old

island arc Island arcs are long archipelago, chains of active volcanoes with intense earthquake, seismic activity found along convergent boundary, convergent plate tectonics, tectonic plate boundaries. Most island arcs originate on oceanic crust and have re ...

s formed at some distant subduction zones. A tectonostratigraphic terrane is a fault-bounded package of rocks of at least regional extent characterized by a geologic history that differs from that of neighboring terranes. The essential characteristic of these terranes is that the present spatial relations are incompatible with the inferred geologic histories. Where terranes that lie next to each other possess strata of the same age, they are considered separate terranes only if it can be demonstrated that the geologic evolutions are different and incompatible. There must be an absence of intermediate lithofacies that could link the strata. The concept of ''tectonostratigraphic terrane '' developed from studies in the 1970s of the complicated Pacific Cordilleran orogenic margin of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, a complex and diverse geological potpourri that was difficult to explain until the new science of plate tectonics illuminated the ability of crustal fragments to "drift" thousands of miles from their origin and attach themselves, crumpled, to an exotic shore. Such terranes were dubbed " accreted terranes" by

geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...

s. Geologist J. N. Carney writes: When terranes are composed of repeated accretionary events, and hence are composed of subunits with distinct history and structure, they may be called superterranes.

List of tectonostratigraphic terranes

Africa * Alkapeca * Birminian terrane * Kahiltna terrane * Likasi terrane * Mozambique Belt Asia * Aldan terrane * Birekte terrane * Bargusin terrane * Daldyn terrane * Magan terrane * Markha terrane * Midyan terrane * Shan–Thai terrane * Tungus terrane * Tynda terrane * Uchur terrane Taiwan * Coastal Range terrane * Longitudinal Valley terrane * Eastern Central Range terrane * Western Central Range terrane * Hsuehshan Range terrane * Western Foothills terrane * Coastal Plain terrane Tibet * Lhasa terraneAitchison, J. C., Ali, J. R., and Davis, A. M. (2007) "When and where did India and Asia collide?" ''

Journal of Geophysical Research The ''Journal of Geophysical Research'' is a peer-reviewed scientific journal. It is the flagship journal of the American Geophysical Union. It contains original research on the physical, chemical, and biological processes that contribute to the u ...

'', v.112, pp.1–19 * Qiangtang terrane * Xigaze terrane * Bainang terrane * Zedong terrane * Dazhuqu terrane Australasia * Brook Street terrane * Buller terrane * Caples terrane * East Tasmanian terrane * Glenburgh terrane * Dun Mountain-Maitai terrane * Molong—Monaro terrane * Murihiku terrane * Narryer Gneiss terrane * Takaka terrane * Torlesse Composite terrane * Waipapa Composite terrane * West Tasmanian terrane Europe * Alkapeca * Armorican terrane *

Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent are terranes in parts of the eastern coast of North America: Atlantic Canada, and parts of the East Coast of the United States, East Coast of the ...

* Avalon Composite terrane * Balearic terrane * Briançonnais terrane * Central Highlands terrane * Central Southern Uplands terrane * Charnwood terrane * Hebridean terrane * Leinster—Lakesman terrane * Midland Valley terrane * North Armorican Composite terrane * Northern Highlands terrane * Rosslare—Monian Terranes * Southern North Sea terrane * Tregor—La Hague terrane * Wrekin terrane Fennoscandia * Bamble terrane * Idefjorden terrane * Kongsberg terrane * Telemarkia terrane * Western Gneiss Region North America * Avalonia terrane * Bancroft terrane * Buffalo Head terrane * Cache Creek terrane * Carolina terrane * Cassiar terrane * Crescent terrane * Elzevir terrane * Frontenac terrane *

Franciscan Complex The Franciscan Complex or Franciscan Assemblage is a geology, geologic term for a late Mesozoic terrane of heterogeneous rock (geology), rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was n ...

* Ganderia terrane * Hottah terrane * Insular Superterrane * Intermontane Plate and

Intermontane Belt The Intermontane Belt is a physical geology, physiogeological region in the Pacific Northwest of North America, stretching from northern Washington (U.S. state), Washington into British Columbia, Yukon, and Alaska. It comprises rolling hills, hig ...

* Meguma terrane * Occidentalia terrane * Pacific Rim terrane * Pearya terrane * Quesnellia * Salinian Block * Slide Mountain terrane * Smartville Block * Sonomia terrane * Steel Mountain terrane * Stikinia * Wrangellia terrane * Yakutat Block * Yukon–Tanana terrane South America * Arequipa-Antofalla * Chaitenia * Chilenia * Chiloé Block *Cuchilla Dionisio Terrane * Cuyania * Fitz Roy terrane * Madre de Dios terrane * Mejillonía * Nico Pérez terrane * Pampia * Paranapanema block * Piedra Alta terrane * Tandilia terrane

References

Citations

General bibliography

* McPhee, John (1981). ''Basin and Range''. New York: Farrar, Straus and Giroux. * McPhee, John (1983). ''In Suspect Terrain''. New York: Farrar, Straus and Giroux. * McPhee, John (1993). ''Assembling California''. New York: Farrar, Straus and Giroux.

External links

West Antarctica terrane analysis

{{Structural geology